reference-Core.rst
Author: Arvid Norberg, arvid@libtorrent.org

| libtorrent

Author: | Arvid Norberg, arvid@libtorrent.org
Version: | 1.2.9

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# Core

Table of contents

- Core
  - peer_class_info
  - peer_connection_handle
  - bt_peer_connection_handle
  - torrent_status
  - announce_endpoint
  - announce_entry
  - open_file_state
  - peer_class_type_filter
  - block_info
  - partial_piece_info
  - torrent_handle
  - cache_status
  - web_seed_entry
  - load_torrent_limits
  - torrent_info
  - add_torrent_params
  - peer_info
  - peer_request
  - write_resume_data() write_resume_data_buf()
  - make_magnet_uri()
  - parse_magnet_uri()
  - version()
  - generate_fingerprint()
  - hash_value()
  - is_utp_stream_logging()
  - set_utp_stream_logging()
  - read_resume_data()
  - enum connection_type
  - enum portmap_transport
  - enum portmap_protocol
  - torrent_flags_t
  - download_priority_t
  - pex_flags_t
  - file_open_mode_t
  - open_mode_t

[report issue]

## peer_class_info

Declared in "libtorrent/peer_class.hpp"

holds settings for a peer class. Used in set_peer_class() and get_peer_class() calls.

    struct peer_class_info
    {
       bool ignore_unchoke_slots;
       int connection_limit_factor;
       std::string label;
       int upload_limit;
       int download_limit;
       int upload_priority;
       int download_priority;
    };

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ignore_unchoke_slots
  `ignore_unchoke_slots` determines whether peers should always unchoke a peer, regardless of the choking algorithm, or if it should honor the unchoke slot limits. It's used for local peers by default. If any of the peer classes a peer belongs to has this set to true, that peer will be unchoked at all times.

[report issue]

connection_limit_factor
  adjusts the connection limit (global and per torrent) that applies to this peer class. By default, local peers are allowed to exceed the normal connection limit for instance. This is specified as a percent factor. 100 makes the peer class apply normally to the limit. 200 means as long as there are fewer connections than twice the limit, we accept this peer. This factor applies both to the global connection limit and the per-torrent limit. Note that if not used carefully one peer class can potentially completely starve out all other over time.

[report issue]

label
  not used by libtorrent. It's intended as a potentially user-facing identifier of this peer class.

[report issue]

upload_limit download_limit
  transfer rates limits for the whole peer class. They are specified in bytes per second and apply to the sum of all peers that are members of this class.

[report issue]

upload_priority download_priority
  relative priorities used by the bandwidth allocator in the rate limiter. If no rate limits are in use, the priority is not used either. Priorities start at 1 (0 is not a valid priority) and may not exceed 255.

[report issue]

## peer_connection_handle

Declared in "libtorrent/peer_connection_handle.hpp"

the peer_connection_handle class provides a handle to the internal peer connection object, to be used by plugins. This is a low level interface that may not be stable across libtorrent versions

    struct peer_connection_handle
    {
       explicit peer_connection_handle (std::weak_ptr<peer_connection> impl);
       connection_type type () const;
       void add_extension (std::shared_ptr<peer_plugin>);
       peer_plugin const* find_plugin (string_view type) const;
       bool is_seed () const;
       bool upload_only () const;
       bool has_piece (piece_index_t i) const;
       peer_id const& pid () const;
       bool is_interesting () const;
       bool is_choked () const;
       bool has_peer_choked () const;
       bool is_peer_interested () const;
       void choke_this_peer ();
       void maybe_unchoke_this_peer ();
       void get_peer_info (peer_info& p) const;
       torrent_handle associated_torrent () const;
       tcp::endpoint local_endpoint () const;
       tcp::endpoint const& remote () const;
       bool is_connecting () const;
       void disconnect (error_code const& ec, operation_t op
          , disconnect_severity_t = peer_connection_interface::normal);
       bool is_outgoing () const;
       bool is_disconnecting () const;
       bool on_local_network () const;
       bool ignore_unchoke_slots () const;
       bool failed () const;
       bool should_log (peer_log_alert::direction_t direction) const;
       void peer_log (peer_log_alert::direction_t direction
          , char const* event, char const* fmt = "", ...) const TORRENT_FORMAT(4,5);
       bool can_disconnect (error_code const& ec) const;
       bool has_metadata () const;
       bool in_handshake () const;
       void send_buffer (char const* begin, int size);
       std::time_t last_seen_complete () const;
       time_point time_of_last_unchoke () const;
       bool operator== (peer_connection_handle const& o) const;
       bool operator!= (peer_connection_handle const& o) const;
       bool operator< (peer_connection_handle const& o) const;
       std::shared_ptr<peer_connection> native_handle () const;
    };

[report issue]

## bt_peer_connection_handle

Declared in "libtorrent/peer_connection_handle.hpp"

The bt_peer_connection_handle provides a handle to the internal bittorrent peer connection object to plugins. It's low level and may not be a stable API across libtorrent versions.

    struct bt_peer_connection_handle : peer_connection_handle
    {
       explicit bt_peer_connection_handle (peer_connection_handle pc);
       bool support_extensions () const;
       bool packet_finished () const;
       bool supports_encryption () const;
       void switch_recv_crypto (std::shared_ptr<crypto_plugin> crypto);
       void switch_send_crypto (std::shared_ptr<crypto_plugin> crypto);
       std::shared_ptr<bt_peer_connection> native_handle () const;
    };

[report issue]

## torrent_status

Declared in "libtorrent/torrent_status.hpp"

holds a snapshot of the status of a torrent, as queried by torrent_handle::status().

    struct torrent_status
    {
       bool operator== (torrent_status const& st) const;
       time_duration next_announce = seconds (0);

       enum state_t
       {
          checking_files,
          downloading_metadata,
          downloading,
          finished,
          seeding,
          allocating,
          checking_resume_data,
       };

       torrent_handle handle;
       error_code errc;
       file_index_t error_file  = torrent_status::error_file_none;
       static constexpr file_index_t error_file_none {-1};
       static constexpr file_index_t error_file_ssl_ctx {-3};
       static constexpr file_index_t error_file_metadata {-4};
       static constexpr file_index_t error_file_exception {-5};
       static constexpr file_index_t error_file_partfile {-6};
       std::string save_path;
       std::string name;
       std::weak_ptr<const torrent_info> torrent_file;
       std::string current_tracker;
       std::int64_t total_download  = 0;
       std::int64_t total_upload  = 0;
       std::int64_t total_payload_download  = 0;
       std::int64_t total_payload_upload  = 0;
       std::int64_t total_failed_bytes  = 0;
       std::int64_t total_redundant_bytes  = 0;
       typed_bitfield<piece_index_t> pieces;
       typed_bitfield<piece_index_t> verified_pieces;
       std::int64_t total_done  = 0;
       std::int64_t total  = 0;
       std::int64_t total_wanted_done  = 0;
       std::int64_t total_wanted  = 0;
       std::int64_t all_time_upload  = 0;
       std::int64_t all_time_download  = 0;
       std::time_t added_time  = 0;
       std::time_t completed_time  = 0;
       std::time_t last_seen_complete  = 0;
       storage_mode_t storage_mode  = storage_mode_sparse;
       float progress  = 0.f;
       int progress_ppm  = 0;
       queue_position_t queue_position {};
       int download_rate  = 0;
       int upload_rate  = 0;
       int download_payload_rate  = 0;
       int upload_payload_rate  = 0;
       int num_seeds  = 0;
       int num_peers  = 0;
       int num_complete  = -1;
       int num_incomplete  = -1;
       int list_seeds  = 0;
       int list_peers  = 0;
       int connect_candidates  = 0;
       int num_pieces  = 0;
       int distributed_full_copies  = 0;
       int distributed_fraction  = 0;
       float distributed_copies  = 0.f;
       int block_size  = 0;
       int num_uploads  = 0;
       int num_connections  = 0;
       int uploads_limit  = 0;
       int connections_limit  = 0;
       int up_bandwidth_queue  = 0;
       int down_bandwidth_queue  = 0;
       int seed_rank  = 0;
       state_t state  = checking_resume_data;
       bool need_save_resume  = false;
       bool is_seeding  = false;
       bool is_finished  = false;
       bool has_metadata  = false;
       bool has_incoming  = false;
       bool moving_storage  = false;
       bool announcing_to_trackers  = false;
       bool announcing_to_lsd  = false;
       bool announcing_to_dht  = false;
       sha1_hash info_hash;
       time_point last_upload;
       time_point last_download;
       seconds active_duration;
       seconds finished_duration;
       seconds seeding_duration;
       torrent_flags_t flags {};
    };

[report issue]

### operator==()

    bool operator== (torrent_status const& st) const;

compares if the torrent status objects come from the same torrent. i.e. only the torrent_handle field is compared.

[report issue]

### seconds()

    time_duration next_announce = seconds (0);

the time until the torrent will announce itself to the tracker.

[report issue]

### enum state_t

Declared in "libtorrent/torrent_status.hpp"

name | value | description
--- | --- | ---
checking_files | 1 | The torrent has not started its download yet, and is currently checking existing files.
downloading_metadata | 2 | The torrent is trying to download metadata from peers. This implies the ut_metadata extension is in use.
downloading | 3 | The torrent is being downloaded. This is the state most torrents will be in most of the time. The progress meter will tell how much of the files that has been downloaded.
finished | 4 | In this state the torrent has finished downloading but still doesn't have the entire torrent. i.e. some pieces are filtered and won't get downloaded.
seeding | 5 | In this state the torrent has finished downloading and is a pure seeder.
allocating | 6 | If the torrent was started in full allocation mode, this indicates that the (disk) storage for the torrent is allocated.
checking_resume_data | 7 | The torrent is currently checking the fast resume data and comparing it to the files on disk. This is typically completed in a fraction of a second, but if you add a large number of torrents at once, they will queue up.

[report issue]

handle
  a handle to the torrent whose status the object represents.

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errc
  may be set to an error code describing why the torrent was paused, in case it was paused by an error. If the torrent is not paused or if it's paused but not because of an error, this error_code is not set. if the error is attributed specifically to a file, error_file is set to the index of that file in the .torrent file.

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error_file
  if the torrent is stopped because of an disk I/O error, this field contains the index of the file in the torrent that encountered the error. If the error did not originate in a file in the torrent, there are a few special values this can be set to: error_file_none, error_file_ssl_ctx, error_file_exception, error_file_partfile or error_file_metadata;

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error_file_none
  special values for error_file to describe which file or component encountered the error (`errc`). the error did not occur on a file

[report issue]

error_file_ssl_ctx
  the error occurred setting up the SSL context

[report issue]

error_file_metadata
  the error occurred while loading the .torrent file via the user supplied load function

[report issue]

error_file_exception
  there was a serious error reported in this torrent. The error code or a torrent log alert may provide more information.

[report issue]

error_file_partfile
  the error occurred with the partfile

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save_path
  the path to the directory where this torrent's files are stored. It's typically the path as was given to async_add_torrent() or add_torrent() when this torrent was started. This field is only included if the torrent status is queried with `torrent_handle::query_save_path`.

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name
  the name of the torrent. Typically this is derived from the .torrent file. In case the torrent was started without metadata, and hasn't completely received it yet, it returns the name given to it when added to the session. See `session::add_torrent`. This field is only included if the torrent status is queried with `torrent_handle::query_name`.

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torrent_file
  set to point to the `torrent_info` object for this torrent. It's only included if the torrent status is queried with `torrent_handle::query_torrent_file`.

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current_tracker
  the URL of the last working tracker. If no tracker request has been successful yet, it's set to an empty string.

[report issue]

total_download total_upload
  the number of bytes downloaded and uploaded to all peers, accumulated, this session only. The session is considered to restart when a torrent is paused and restarted again. When a torrent is paused, these counters are reset to 0. If you want complete, persistent, stats, see `all_time_upload` and `all_time_download`.

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total_payload_download total_payload_upload
  counts the amount of bytes send and received this session, but only the actual payload data (i.e the interesting data), these counters ignore any protocol overhead. The session is considered to restart when a torrent is paused and restarted again. When a torrent is paused, these counters are reset to 0.

[report issue]

total_failed_bytes
  the number of bytes that has been downloaded and that has failed the piece hash test. In other words, this is just how much crap that has been downloaded since the torrent was last started. If a torrent is paused and then restarted again, this counter will be reset.

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total_redundant_bytes
  the number of bytes that has been downloaded even though that data already was downloaded. The reason for this is that in some situations the same data can be downloaded by mistake. When libtorrent sends requests to a peer, and the peer doesn't send a response within a certain timeout, libtorrent will re-request that block. Another situation when libtorrent may re-request blocks is when the requests it sends out are not replied in FIFO-order (it will re-request blocks that are skipped by an out of order block). This is supposed to be as low as possible. This only counts bytes since the torrent was last started. If a torrent is paused and then restarted again, this counter will be reset.

[report issue]

pieces
  a bitmask that represents which pieces we have (set to true) and the pieces we don't have. It's a pointer and may be set to 0 if the torrent isn't downloading or seeding.

[report issue]

verified_pieces
  a bitmask representing which pieces has had their hash checked. This only applies to torrents in seed mode. If the torrent is not in seed mode, this bitmask may be empty.

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total_done
  the total number of bytes of the file(s) that we have. All this does not necessarily has to be downloaded during this session (that's `total_payload_download`).

[report issue]

total
  the total number of bytes to download for this torrent. This may be less than the size of the torrent in case there are pad files. This number only counts bytes that will actually be requested from peers.

[report issue]

total_wanted_done
  the number of bytes we have downloaded, only counting the pieces that we actually want to download. i.e. excluding any pieces that we have but have priority 0 (i.e. not wanted).

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total_wanted
  The total number of bytes we want to download. This may be smaller than the total torrent size in case any pieces are prioritized to 0, i.e. not wanted

[report issue]

all_time_upload all_time_download
  are accumulated upload and download payload byte counters. They are saved in and restored from resume data to keep totals across sessions.

[report issue]

added_time
  the posix-time when this torrent was added. i.e. what `time(nullptr)` returned at the time.

[report issue]

completed_time
  the posix-time when this torrent was finished. If the torrent is not yet finished, this is 0.

[report issue]

last_seen_complete
  the time when we, or one of our peers, last saw a complete copy of this torrent.

[report issue]

storage_mode
  The allocation mode for the torrent. See storage_mode_t for the options. For more information, see storage allocation.

[report issue]

progress
  a value in the range [0, 1], that represents the progress of the torrent's current task. It may be checking files or downloading.

[report issue]

progress_ppm

  progress parts per million (progress * 1000000) when disabling floating point operations, this is the only option to query progress

  reflects the same value as `progress`, but instead in a range [0, 1000000] (ppm = parts per million). When floating point operations are disabled, this is the only alternative to the floating point value in progress.

[report issue]

queue_position
  the position this torrent has in the download queue. If the torrent is a seed or finished, this is -1.

[report issue]

download_rate upload_rate
  the total rates for all peers for this torrent. These will usually have better precision than summing the rates from all peers. The rates are given as the number of bytes per second.

[report issue]

download_payload_rate upload_payload_rate
  the total transfer rate of payload only, not counting protocol chatter. This might be slightly smaller than the other rates, but if projected over a long time (e.g. when calculating ETA:s) the difference may be noticeable.

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num_seeds
  the number of peers that are seeding that this client is currently connected to.

[report issue]

num_peers
  the number of peers this torrent currently is connected to. Peer connections that are in the half-open state (is attempting to connect) or are queued for later connection attempt do not count. Although they are visible in the peer list when you call get_peer_info().

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num_complete num_incomplete
  if the tracker sends scrape info in its announce reply, these fields will be set to the total number of peers that have the whole file and the total number of peers that are still downloading. set to -1 if the tracker did not send any scrape data in its announce reply.

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list_seeds list_peers
  the number of seeds in our peer list and the total number of peers (including seeds). We are not necessarily connected to all the peers in our peer list. This is the number of peers we know of in total, including banned peers and peers that we have failed to connect to.

[report issue]

connect_candidates
  the number of peers in this torrent's peer list that is a candidate to be connected to. i.e. It has fewer connect attempts than the max fail count, it is not a seed if we are a seed, it is not banned etc. If this is 0, it means we don't know of any more peers that we can try.

[report issue]

num_pieces
  the number of pieces that has been downloaded. It is equivalent to: `std::accumulate(pieces->begin(), pieces->end())`. So you don't have to count yourself. This can be used to see if anything has updated since last time if you want to keep a graph of the pieces up to date.

[report issue]

distributed_full_copies
  the number of distributed copies of the torrent. Note that one copy may be spread out among many peers. It tells how many copies there are currently of the rarest piece(s) among the peers this client is connected to.

[report issue]

distributed_fraction

  tells the share of pieces that have more copies than the rarest piece(s). Divide this number by 1000 to get the fraction.

  For example, if `distributed_full_copies` is 2 and `distributed_fraction` is 500, it means that the rarest pieces have only 2 copies among the peers this torrent is connected to, and that 50% of all the pieces have more than two copies.

  If we are a seed, the piece picker is deallocated as an optimization, and piece availability is no longer tracked. In this case the distributed copies members are set to -1.

[report issue]

distributed_copies

  the number of distributed copies of the file. note that one copy may be spread out among many peers. This is a floating point representation of the distributed copies.

  the integer part tells how many copies
    there are of the rarest piece(s)
  the fractional part tells the fraction of pieces that
    have more copies than the rarest piece(s).

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block_size
  the size of a block, in bytes. A block is a sub piece, it is the number of bytes that each piece request asks for and the number of bytes that each bit in the `partial_piece_info`'s bitset represents, see get_download_queue(). This is typically 16 kB, but it may be smaller, if the pieces are smaller.

[report issue]

num_uploads
  the number of unchoked peers in this torrent.

[report issue]

num_connections
  the number of peer connections this torrent has, including half-open connections that hasn't completed the bittorrent handshake yet. This is always >= `num_peers`.

[report issue]

uploads_limit
  the set limit of upload slots (unchoked peers) for this torrent.

[report issue]

connections_limit
  the set limit of number of connections for this torrent.

[report issue]

up_bandwidth_queue down_bandwidth_queue
  the number of peers in this torrent that are waiting for more bandwidth quota from the torrent rate limiter. This can determine if the rate you get from this torrent is bound by the torrents limit or not. If there is no limit set on this torrent, the peers might still be waiting for bandwidth quota from the global limiter, but then they are counted in the `session_status` object.

[report issue]

seed_rank
  A rank of how important it is to seed the torrent, it is used to determine which torrents to seed and which to queue. It is based on the peer to seed ratio from the tracker scrape. For more information, see queuing. Higher value means more important to seed

[report issue]

state
  the main state the torrent is in. See torrent_status::state_t.

[report issue]

need_save_resume
  true if this torrent has unsaved changes to its download state and statistics since the last resume data was saved.

[report issue]

is_seeding
  true if all pieces have been downloaded.

[report issue]

is_finished
  true if all pieces that have a priority > 0 are downloaded. There is only a distinction between finished and seeding if some pieces or files have been set to priority 0, i.e. are not downloaded.

[report issue]

has_metadata
  true if this torrent has metadata (either it was started from a .torrent file or the metadata has been downloaded). The only scenario where this can be false is when the torrent was started torrent-less (i.e. with just an info-hash and tracker ip, a magnet link for instance).

[report issue]

has_incoming
  true if there has ever been an incoming connection attempt to this torrent.

[report issue]

moving_storage
  this is true if this torrent's storage is currently being moved from one location to another. This may potentially be a long operation if a large file ends up being copied from one drive to another.

[report issue]

announcing_to_trackers announcing_to_lsd announcing_to_dht
  these are set to true if this torrent is allowed to announce to the respective peer source. Whether they are true or false is determined by the queue logic/auto manager. Torrents that are not auto managed will always be allowed to announce to all peer sources.

[report issue]

info_hash
  the info-hash for this torrent

[report issue]

last_upload last_download
  the timestamps of the last time this torrent uploaded or downloaded payload to any peer.

[report issue]

active_duration finished_duration seeding_duration
  these are cumulative counters of for how long the torrent has been in different states. active means not paused and added to session. Whether it has found any peers or not is not relevant. finished means all selected files/pieces were downloaded and available to other peers (this is always a subset of active time). seeding means all files/pieces were downloaded and available to peers. Being available to peers does not imply there are other peers asking for the payload.

[report issue]

flags
  reflects several of the torrent's flags. For more information, see `torrent_handle::flags()`.

[report issue]

## announce_endpoint

Declared in "libtorrent/announce_entry.hpp"

announces are sent to each tracker using every listen socket this class holds information about one listen socket for one tracker

    struct announce_endpoint
    {
       void reset ();
       void failed (int backoff_ratio, seconds32 retry_interval = seconds32(0));
       bool can_announce (time_point now, bool is_seed, std::uint8_t fail_limit) const;
       bool is_working () const;

       std::string message;
       error_code last_error;
       tcp::endpoint local_endpoint;
       int scrape_incomplete  = -1;
       int scrape_complete  = -1;
       int scrape_downloaded  = -1;
       std::uint8_t fails : 7;
       bool updating : 1;
       bool start_sent : 1;
       bool complete_sent : 1;
       bool enabled : 1;
    };

[report issue]

### reset()

    void reset ();

reset announce counters and clears the started sent flag. The announce_endpoint will look like we've never talked to the tracker.

[report issue]

### failed()

    void failed (int backoff_ratio, seconds32 retry_interval = seconds32(0));

updates the failure counter and time-outs for re-trying. This is called when the tracker announce fails.

[report issue]

### can_announce()

    bool can_announce (time_point now, bool is_seed, std::uint8_t fail_limit) const;

returns true if we can announce to this tracker now. The current time is passed in as `now`. The `is_seed` argument is necessary because once we become a seed, we need to announce right away, even if the re-announce timer hasn't expired yet.

[report issue]

### is_working()

    bool is_working () const;

returns true if the last time we tried to announce to this tracker succeeded, or if we haven't tried yet.

[report issue]

message
  if this tracker has returned an error or warning message that message is stored here

[report issue]

last_error
  if this tracker failed the last time it was contacted this error code specifies what error occurred

[report issue]

local_endpoint
  the local endpoint of the listen interface associated with this endpoint

[report issue]

scrape_incomplete scrape_complete scrape_downloaded
  if this tracker has returned scrape data, these fields are filled in with valid numbers. Otherwise they are set to -1. `incomplete` counts the number of current downloaders. `complete` counts the number of current peers completed the download, or "seeds". `downloaded` is the cumulative number of completed downloads.

[report issue]

fails
  the number of times in a row we have failed to announce to this tracker.

[report issue]

updating
  true while we're waiting for a response from the tracker.

[report issue]

start_sent
  set to true when we get a valid response from an announce with event=started. If it is set, we won't send start in the subsequent announces.

[report issue]

complete_sent
  set to true when we send a event=completed.

[report issue]

enabled
  set to false to not announce from this endpoint

[report issue]

## announce_entry

Declared in "libtorrent/announce_entry.hpp"

this class holds information about one bittorrent tracker, as it relates to a specific torrent.

    struct announce_entry
    {
       explicit announce_entry (string_view u);
       announce_entry (announce_entry const&);
       announce_entry ();
       announce_entry& operator= (announce_entry const&);
       ~announce_entry ();
       void reset ();
       void trim ();

       enum tracker_source
       {
          source_torrent,
          source_client,
          source_magnet_link,
          source_tex,
       };

       std::string url;
       std::string trackerid;
       std::vector<announce_endpoint> endpoints;
       std::uint8_t tier  = 0;
       std::uint8_t fail_limit  = 0;
       std::uint8_t source:4;
       bool verified:1;
    };

[report issue]

### ~announce_entry() operator=() announce_entry()

    explicit announce_entry (string_view u);
    announce_entry (announce_entry const&);
    announce_entry ();
    announce_entry& operator= (announce_entry const&);
    ~announce_entry ();

constructs a tracker announce entry with `u` as the URL.

[report issue]

### reset()

    void reset ();

reset announce counters and clears the started sent flag. The announce_entry will look like we've never talked to the tracker.

[report issue]

### trim()

    void trim ();

trims whitespace characters from the beginning of the URL.

[report issue]

### enum tracker_source

Declared in "libtorrent/announce_entry.hpp"

name | value | description
--- | --- | ---
source_torrent | 1 | the tracker was part of the .torrent file
source_client | 2 | the tracker was added programmatically via the add_tracker() function
source_magnet_link | 4 | the tracker was part of a magnet link
source_tex | 8 | the tracker was received from the swarm via tracker exchange

[report issue]

url
  tracker URL as it appeared in the torrent file

[report issue]

trackerid
  the current `&trackerid=` argument passed to the tracker. this is optional and is normally empty (in which case no trackerid is sent).

[report issue]

endpoints
  each local listen socket (endpoint) will announce to the tracker. This list contains state per endpoint.

[report issue]

tier
  the tier this tracker belongs to

[report issue]

fail_limit
  the max number of failures to announce to this tracker in a row, before this tracker is not used anymore. 0 means unlimited

[report issue]

source
  a bitmask specifying which sources we got this tracker from.

[report issue]

verified
  set to true the first time we receive a valid response from this tracker.

[report issue]

## open_file_state

Declared in "libtorrent/disk_interface.hpp"

this contains information about a file that's currently open by the libtorrent disk I/O subsystem. It's associated with a single torrent.

    struct open_file_state
    {
       file_index_t file_index;
       file_open_mode_t open_mode;
       time_point last_use;
    };

[report issue]

file_index
  the index of the file this entry refers to into the `file_storage` file list of this torrent. This starts indexing at 0.

[report issue]

open_mode

  `open_mode` is a bitmask of the file flags this file is currently opened with. These are the flags used in the `file::open()` function. For possible flags, see file_open_mode_t.

  Note that the read/write mode is not a bitmask. The two least significant bits are used to represent the read/write mode. Those bits can be masked out using the `rw_mask` constant.

[report issue]

last_use
  a (high precision) timestamp of when the file was last used.

[report issue]

## peer_class_type_filter

Declared in "libtorrent/peer_class_type_filter.hpp"

`peer_class_type_filter` is a simple container for rules for adding and subtracting peer-classes from peers. It is applied after the peer class filter is applied (which is based on the peer's IP address).

    struct peer_class_type_filter
    {
       void remove (socket_type_t const st, peer_class_t const peer_class);
       void add (socket_type_t const st, peer_class_t const peer_class);
       void disallow (socket_type_t const st, peer_class_t const peer_class);
       void allow (socket_type_t const st, peer_class_t const peer_class);
       std::uint32_t apply (socket_type_t const st, std::uint32_t peer_class_mask);

       enum socket_type_t
       {
          tcp_socket,
          utp_socket,
          ssl_tcp_socket,
          ssl_utp_socket,
          i2p_socket,
          num_socket_types,
       };
    };

[report issue]

### add() remove()

    void remove (socket_type_t const st, peer_class_t const peer_class);
    void add (socket_type_t const st, peer_class_t const peer_class);

`add()` and `remove()` adds and removes a peer class to be added to new peers based on socket type.

[report issue]

### disallow() allow()

    void disallow (socket_type_t const st, peer_class_t const peer_class);
    void allow (socket_type_t const st, peer_class_t const peer_class);

`disallow()` and `allow()` adds and removes a peer class to be removed from new peers based on socket type.

The `peer_class` argument cannot be greater than 31. The bitmasks representing peer classes in the `peer_class_type_filter` are 32 bits.

[report issue]

### apply()

    std::uint32_t apply (socket_type_t const st, std::uint32_t peer_class_mask);

takes a bitmask of peer classes and returns a new bitmask of peer classes after the rules have been applied, based on the socket type argument (`st`).

[report issue]

### enum socket_type_t

Declared in "libtorrent/peer_class_type_filter.hpp"

name | value | description
--- | --- | ---
tcp_socket | 0 | these match the socket types from socket_type.hpp shifted one down
utp_socket | 1 |
ssl_tcp_socket | 2 |
ssl_utp_socket | 3 |
i2p_socket | 4 |
num_socket_types | 5 |

[report issue]

## block_info

Declared in "libtorrent/torrent_handle.hpp"

holds the state of a block in a piece. Who we requested it from and how far along we are at downloading it.

    struct block_info
    {
       void set_peer (tcp::endpoint const& ep);
       tcp::endpoint peer () const;

       enum block_state_t
       {
          none,
          requested,
          writing,
          finished,
       };

       unsigned bytes_progress:15;
       unsigned block_size:15;
       unsigned state:2;
       unsigned num_peers:14;
    };

[report issue]

### peer() set_peer()

    void set_peer (tcp::endpoint const& ep);
    tcp::endpoint peer () const;

The peer is the ip address of the peer this block was downloaded from.

[report issue]

### enum block_state_t

Declared in "libtorrent/torrent_handle.hpp"

name | value | description
--- | --- | ---
none | 0 | This block has not been downloaded or requested form any peer.
requested | 1 | The block has been requested, but not completely downloaded yet.
writing | 2 | The block has been downloaded and is currently queued for being written to disk.
finished | 3 | The block has been written to disk.

[report issue]

bytes_progress
  the number of bytes that have been received for this block

[report issue]

block_size
  the total number of bytes in this block.

[report issue]

state
  the state this block is in (see block_state_t)

[report issue]

num_peers
  the number of peers that is currently requesting this block. Typically this is 0 or 1, but at the end of the torrent blocks may be requested by more peers in parallel to speed things up.

[report issue]

## partial_piece_info

Declared in "libtorrent/torrent_handle.hpp"

This class holds information about pieces that have outstanding requests or outstanding writes

    struct partial_piece_info
    {
       piece_index_t piece_index;
       int blocks_in_piece;
       int finished;
       int writing;
       int requested;
       block_info* blocks;
    };

[report issue]

piece_index
  the index of the piece in question. `blocks_in_piece` is the number of blocks in this particular piece. This number will be the same for most pieces, but the last piece may have fewer blocks than the standard pieces.

[report issue]

blocks_in_piece
  the number of blocks in this piece

[report issue]

finished
  the number of blocks that are in the finished state

[report issue]

writing
  the number of blocks that are in the writing state

[report issue]

requested
  the number of blocks that are in the requested state

[report issue]

blocks

  this is an array of `blocks_in_piece` number of items. One for each block in the piece.

  Warning

  This is a pointer that points to an array that's owned by the session object. The next time get_download_queue() is called, it will be invalidated.

[report issue]

## torrent_handle

Declared in "libtorrent/torrent_handle.hpp"

You will usually have to store your torrent handles somewhere, since it's the object through which you retrieve information about the torrent and aborts the torrent.

Warning

Any member function that returns a value or fills in a value has to be made synchronously. This means it has to wait for the main thread to complete the query before it can return. This might potentially be expensive if done from within a GUI thread that needs to stay responsive. Try to avoid querying for information you don't need, and try to do it in as few calls as possible. You can get most of the interesting information about a torrent from the torrent_handle::status() call.

The default constructor will initialize the handle to an invalid state. Which means you cannot perform any operation on it, unless you first assign it a valid handle. If you try to perform any operation on an uninitialized handle, it will throw `invalid_handle`.

Warning

All operations on a torrent_handle may throw system_error exception, in case the handle is no longer referring to a torrent. There is one exception is_valid() will never throw. Since the torrents are processed by a background thread, there is no guarantee that a handle will remain valid between two calls.

    struct torrent_handle
    {
       torrent_handle () noexcept = default;
       void add_piece (piece_index_t piece, char const* data, add_piece_flags_t flags = {}) const;
       void read_piece (piece_index_t piece) const;
       bool have_piece (piece_index_t piece) const;
       void get_peer_info (std::vector<peer_info>& v) const;
       torrent_status status (status_flags_t flags = status_flags_t::all()) const;
       void get_download_queue (std::vector<partial_piece_info>& queue) const;
       void set_piece_deadline (piece_index_t index, int deadline, deadline_flags_t flags = {}) const;
       void reset_piece_deadline (piece_index_t index) const;
       void clear_piece_deadlines () const;
       void file_progress (std::vector<std::int64_t>& progress, int flags = 0) const;
       std::vector<open_file_state> file_status () const;
       void clear_error () const;
       void replace_trackers (std::vector<announce_entry> const&) const;
       std::vector<announce_entry> trackers () const;
       void add_tracker (announce_entry const&) const;
       std::set<std::string> url_seeds () const;
       void add_url_seed (std::string const& url) const;
       void remove_url_seed (std::string const& url) const;
       void add_http_seed (std::string const& url) const;
       void remove_http_seed (std::string const& url) const;
       std::set<std::string> http_seeds () const;
       void add_extension (
          std::function<std::shared_ptr<torrent_plugin>(torrent_handle const&, void*)> const& ext
          , void* userdata = nullptr);
       bool set_metadata (span<char const> metadata) const;
       bool is_valid () const;
       void resume () const;
       void pause (pause_flags_t flags = {}) const;
       void unset_flags (torrent_flags_t flags) const;
       void set_flags (torrent_flags_t flags) const;
       torrent_flags_t flags () const;
       void set_flags (torrent_flags_t flags, torrent_flags_t mask) const;
       void flush_cache () const;
       void force_recheck () const;
       void save_resume_data (resume_data_flags_t flags = {}) const;
       bool need_save_resume_data () const;
       queue_position_t queue_position () const;
       void queue_position_down () const;
       void queue_position_up () const;
       void queue_position_top () const;
       void queue_position_bottom () const;
       void queue_position_set (queue_position_t p) const;
       void set_ssl_certificate (std::string const& certificate
          , std::string const& private_key
          , std::string const& dh_params
          , std::string const& passphrase = "");
       void set_ssl_certificate_buffer (std::string const& certificate
          , std::string const& private_key
          , std::string const& dh_params);
       storage_interface* get_storage_impl () const;
       std::shared_ptr<const torrent_info> torrent_file () const;
       void piece_availability (std::vector<int>& avail) const;
       download_priority_t piece_priority (piece_index_t index) const;
       void prioritize_pieces (std::vector<std::pair<piece_index_t, download_priority_t>> const& pieces) const;
       std::vector<download_priority_t> get_piece_priorities () const;
       void piece_priority (piece_index_t index, download_priority_t priority) const;
       void prioritize_pieces (std::vector<download_priority_t> const& pieces) const;
       std::vector<download_priority_t> get_file_priorities () const;
       void file_priority (file_index_t index, download_priority_t priority) const;
       download_priority_t file_priority (file_index_t index) const;
       void prioritize_files (std::vector<download_priority_t> const& files) const;
       void force_dht_announce () const;
       void force_reannounce (int seconds = 0, int tracker_index = -1, reannounce_flags_t = {}) const;
       void scrape_tracker (int idx = -1) const;
       void set_download_limit (int limit) const;
       int download_limit () const;
       void set_upload_limit (int limit) const;
       int upload_limit () const;
       void connect_peer (tcp::endpoint const& adr, peer_source_flags_t source = {}
          , pex_flags_t flags = pex_encryption | pex_utp | pex_holepunch) const;
       void clear_peers ();
       void set_max_uploads (int max_uploads) const;
       int max_uploads () const;
       void set_max_connections (int max_connections) const;
       int max_connections () const;
       void move_storage (std::string const& save_path
          , move_flags_t flags = move_flags_t::always_replace_files
          ) const;
       void rename_file (file_index_t index, std::string const& new_name) const;
       sha1_hash info_hash () const;
       bool operator== (const torrent_handle& h) const;
       bool operator!= (const torrent_handle& h) const;
       bool operator< (const torrent_handle& h) const;
       std::uint32_t id () const;
       std::shared_ptr<torrent> native_handle () const;

       enum file_progress_flags_t
       {
          piece_granularity,
       };

       static constexpr add_piece_flags_t overwrite_existing  = 0_bit;
       static constexpr status_flags_t query_distributed_copies  = 0_bit;
       static constexpr status_flags_t query_accurate_download_counters  = 1_bit;
       static constexpr status_flags_t query_last_seen_complete  = 2_bit;
       static constexpr status_flags_t query_pieces  = 3_bit;
       static constexpr status_flags_t query_verified_pieces  = 4_bit;
       static constexpr status_flags_t query_torrent_file  = 5_bit;
       static constexpr status_flags_t query_name  = 6_bit;
       static constexpr status_flags_t query_save_path  = 7_bit;
       static constexpr deadline_flags_t alert_when_available  = 0_bit;
       static constexpr pause_flags_t graceful_pause  = 0_bit;
       static constexpr pause_flags_t clear_disk_cache  = 1_bit;
       static constexpr resume_data_flags_t flush_disk_cache  = 0_bit;
       static constexpr resume_data_flags_t save_info_dict  = 1_bit;
       static constexpr resume_data_flags_t only_if_modified  = 2_bit;
       static constexpr reannounce_flags_t ignore_min_interval  = 0_bit;
    };

[report issue]

### torrent_handle()

    torrent_handle () noexcept = default;

constructs a torrent handle that does not refer to a torrent. i.e. is_valid() will return false.

[report issue]

### add_piece()

    void add_piece (piece_index_t piece, char const* data, add_piece_flags_t flags = {}) const;

This function will write `data` to the storage as piece `piece`, as if it had been downloaded from a peer. `data` is expected to point to a buffer of as many bytes as the size of the specified piece. The data in the buffer is copied and passed on to the disk IO thread to be written at a later point.

By default, data that's already been downloaded is not overwritten by this buffer. If you trust this data to be correct (and pass the piece hash check) you may pass the overwrite_existing flag. This will instruct libtorrent to overwrite any data that may already have been downloaded with this data.

Since the data is written asynchronously, you may know that is passed or failed the hash check by waiting for piece_finished_alert or hash_failed_alert.

Adding pieces while the torrent is being checked (i.e. in torrent_status::checking_files state) is not supported.

[report issue]

### read_piece()

    void read_piece (piece_index_t piece) const;

This function starts an asynchronous read operation of the specified piece from this torrent. You must have completed the download of the specified piece before calling this function.

When the read operation is completed, it is passed back through an alert, read_piece_alert. Since this alert is a response to an explicit call, it will always be posted, regardless of the alert mask.

Note that if you read multiple pieces, the read operations are not guaranteed to finish in the same order as you initiated them.

[report issue]

### have_piece()

    bool have_piece (piece_index_t piece) const;

Returns true if this piece has been completely downloaded and written to disk, and false otherwise.

[report issue]

### get_peer_info()

    void get_peer_info (std::vector<peer_info>& v) const;

takes a reference to a vector that will be cleared and filled with one entry for each peer connected to this torrent, given the handle is valid. If the torrent_handle is invalid, it will throw system_error exception. Each entry in the vector contains information about that particular peer. See peer_info.

[report issue]

### status()

    torrent_status status (status_flags_t flags = status_flags_t::all()) const;

`status()` will return a structure with information about the status of this torrent. If the torrent_handle is invalid, it will throw system_error exception. See torrent_status. The `flags` argument filters what information is returned in the torrent_status. Some information in there is relatively expensive to calculate, and if you're not interested in it (and see performance issues), you can filter them out.

By default everything is included. The flags you can use to decide what to include are defined in this class.

[report issue]

### get_download_queue()

    void get_download_queue (std::vector<partial_piece_info>& queue) const;

`get_download_queue()` takes a non-const reference to a vector which it will fill with information about pieces that are partially downloaded or not downloaded at all but partially requested. See partial_piece_info for the fields in the returned vector.

[report issue]

### reset_piece_deadline() clear_piece_deadlines() set_piece_deadline()

    void set_piece_deadline (piece_index_t index, int deadline, deadline_flags_t flags = {}) const;
    void reset_piece_deadline (piece_index_t index) const;
    void clear_piece_deadlines () const;

This function sets or resets the deadline associated with a specific piece index (`index`). libtorrent will attempt to download this entire piece before the deadline expires. This is not necessarily possible, but pieces with a more recent deadline will always be prioritized over pieces with a deadline further ahead in time. The deadline (and flags) of a piece can be changed by calling this function again.

If the piece is already downloaded when this call is made, nothing happens, unless the alert_when_available flag is set, in which case it will have the same effect as calling read_piece() for `index`.

`deadline` is the number of milliseconds until this piece should be completed.

`reset_piece_deadline` removes the deadline from the piece. If it hasn't already been downloaded, it will no longer be considered a priority.

`clear_piece_deadlines()` removes deadlines on all pieces in the torrent. As if reset_piece_deadline() was called on all pieces.

[report issue]

### file_progress()

    void file_progress (std::vector<std::int64_t>& progress, int flags = 0) const;

This function fills in the supplied vector with the number of bytes downloaded of each file in this torrent. The progress values are ordered the same as the files in the torrent_info. This operation is not very cheap. Its complexity is O(n + mj). Where n is the number of files, m is the number of downloading pieces and j is the number of blocks in a piece.

The `flags` parameter can be used to specify the granularity of the file progress. If left at the default value of 0, the progress will be as accurate as possible, but also more expensive to calculate. If `torrent_handle::piece_granularity` is specified, the progress will be specified in piece granularity. i.e. only pieces that have been fully downloaded and passed the hash check count. When specifying piece granularity, the operation is a lot cheaper, since libtorrent already keeps track of this internally and no calculation is required.

[report issue]

### file_status()

    std::vector<open_file_state> file_status () const;

This function returns a vector with status about files that are open for this torrent. Any file that is not open will not be reported in the vector, i.e. it's possible that the vector is empty when returning, if none of the files in the torrent are currently open.

See open_file_state

[report issue]

### clear_error()

    void clear_error () const;

If the torrent is in an error state (i.e. `torrent_status::error` is non-empty), this will clear the error and start the torrent again.

[report issue]

### add_tracker() replace_trackers() trackers()

    void replace_trackers (std::vector<announce_entry> const&) const;
    std::vector<announce_entry> trackers () const;
    void add_tracker (announce_entry const&) const;

`trackers()` will return the list of trackers for this torrent. The announce entry contains both a string `url` which specify the announce url for the tracker as well as an int `tier`, which is specifies the order in which this tracker is tried. If you want libtorrent to use another list of trackers for this torrent, you can use `replace_trackers()` which takes a list of the same form as the one returned from `trackers()` and will replace it. If you want an immediate effect, you have to call force_reannounce(). See announce_entry.

`add_tracker()` will look if the specified tracker is already in the set. If it is, it doesn't do anything. If it's not in the current set of trackers, it will insert it in the tier specified in the announce_entry.

The updated set of trackers will be saved in the resume data, and when a torrent is started with resume data, the trackers from the resume data will replace the original ones.

[report issue]

### url_seeds() remove_url_seed() add_url_seed()

    std::set<std::string> url_seeds () const;
    void add_url_seed (std::string const& url) const;
    void remove_url_seed (std::string const& url) const;

`add_url_seed()` adds another url to the torrent's list of url seeds. If the given url already exists in that list, the call has no effect. The torrent will connect to the server and try to download pieces from it, unless it's paused, queued, checking or seeding. `remove_url_seed()` removes the given url if it exists already. `url_seeds()` return a set of the url seeds currently in this torrent. Note that URLs that fails may be removed automatically from the list.

See http seeding for more information.

[report issue]

### add_http_seed() remove_http_seed() http_seeds()

    void add_http_seed (std::string const& url) const;
    void remove_http_seed (std::string const& url) const;
    std::set<std::string> http_seeds () const;

These functions are identical as the `*_url_seed()` variants, but they operate on BEP 17 web seeds instead of BEP 19.

See http seeding for more information.

[report issue]

### add_extension()

    void add_extension (
          std::function<std::shared_ptr<torrent_plugin>(torrent_handle const&, void*)> const& ext
          , void* userdata = nullptr);

add the specified extension to this torrent. The `ext` argument is a function that will be called from within libtorrent's context passing in the internal torrent object and the specified userdata pointer. The function is expected to return a shared pointer to a torrent_plugin instance.

[report issue]

### set_metadata()

    bool set_metadata (span<char const> metadata) const;

`set_metadata` expects the info section of metadata. i.e. The buffer passed in will be hashed and verified against the info-hash. If it fails, a `metadata_failed_alert` will be generated. If it passes, a `metadata_received_alert` is generated. The function returns true if the metadata is successfully set on the torrent, and false otherwise. If the torrent already has metadata, this function will not affect the torrent, and false will be returned.

[report issue]

### is_valid()

    bool is_valid () const;

Returns true if this handle refers to a valid torrent and false if it hasn't been initialized or if the torrent it refers to has been aborted. Note that a handle may become invalid after it has been added to the session. Usually this is because the storage for the torrent is somehow invalid or if the filenames are not allowed (and hence cannot be opened/created) on your filesystem. If such an error occurs, a file_error_alert is generated and all handles that refers to that torrent will become invalid.

[report issue]

### pause() resume()

    void resume () const;
    void pause (pause_flags_t flags = {}) const;

`pause()`, and `resume()` will disconnect all peers and reconnect all peers respectively. When a torrent is paused, it will however remember all share ratios to all peers and remember all potential (not connected) peers. Torrents may be paused automatically if there is a file error (e.g. disk full) or something similar. See file_error_alert.

To know if a torrent is paused or not, call `torrent_handle::status()` and inspect `torrent_status::paused`.

Note

Torrents that are auto-managed may be automatically resumed again. It does not make sense to pause an auto-managed torrent without making it not auto-managed first. Torrents are auto-managed by default when added to the session. For more information, see queuing.

[report issue]

### flags() set_flags() unset_flags()

    void unset_flags (torrent_flags_t flags) const;
    void set_flags (torrent_flags_t flags) const;
    torrent_flags_t flags () const;
    void set_flags (torrent_flags_t flags, torrent_flags_t mask) const;

sets and gets the torrent state flags. See torrent_flags_t. The `set_flags` overload that take a mask will affect all flags part of the mask, and set their values to what the `flags` argument is set to. This allows clearing and setting flags in a single function call. The `set_flags` overload that just takes flags, sets all the specified flags and leave any other flags unchanged. `unset_flags` clears the specified flags, while leaving any other flags unchanged.

The seed_mode flag is special, it can only be cleared once the torrent has been added, and it can only be set as part of the add_torrent_params flags, when adding the torrent.

[report issue]

### flush_cache()

    void flush_cache () const;

Instructs libtorrent to flush all the disk caches for this torrent and close all file handles. This is done asynchronously and you will be notified that it's complete through cache_flushed_alert.

Note that by the time you get the alert, libtorrent may have cached more data for the torrent, but you are guaranteed that whatever cached data libtorrent had by the time you called `torrent_handle::flush_cache()` has been written to disk.

[report issue]

### force_recheck()

    void force_recheck () const;

`force_recheck` puts the torrent back in a state where it assumes to have no resume data. All peers will be disconnected and the torrent will stop announcing to the tracker. The torrent will be added to the checking queue, and will be checked (all the files will be read and compared to the piece hashes). Once the check is complete, the torrent will start connecting to peers again, as normal. The torrent will be placed last in queue, i.e. its queue position will be the highest of all torrents in the session.

[report issue]

### save_resume_data()

    void save_resume_data (resume_data_flags_t flags = {}) const;

`save_resume_data()` asks libtorrent to generate fast-resume data for this torrent.

This operation is asynchronous, `save_resume_data` will return immediately. The resume data is delivered when it's done through an save_resume_data_alert.

The fast resume data will be empty in the following cases:

> 1. The torrent handle is invalid.
> 2. The torrent hasn't received valid metadata and was started without metadata (see libtorrent's metadata from peers extension)

Note that by the time you receive the fast resume data, it may already be invalid if the torrent is still downloading! The recommended practice is to first pause the session, then generate the fast resume data, and then close it down. Make sure to not remove_torrent() before you receive the save_resume_data_alert though. There's no need to pause when saving intermittent resume data.

Warning

If you pause every torrent individually instead of pausing the session, every torrent will have its paused state saved in the resume data!

Note

It is typically a good idea to save resume data whenever a torrent is completed or paused. In those cases you don't need to pause the torrent or the session, since the torrent will do no more writing to its files. If you save resume data for torrents when they are paused, you can accelerate the shutdown process by not saving resume data again for paused torrents. Completed torrents should have their resume data saved when they complete and on exit, since their statistics might be updated.

> In full allocation mode the resume data is never invalidated by subsequent writes to the files, since pieces won't move around. This means that you don't need to pause before writing resume data in full or sparse mode. If you don't, however, any data written to disk after you saved resume data and before the session closed is lost.

It also means that if the resume data is out dated, libtorrent will not re-check the files, but assume that it is fairly recent. The assumption is that it's better to loose a little bit than to re-check the entire file.

It is still a good idea to save resume data periodically during download as well as when closing down.

Example code to pause and save resume data for all torrents and wait for the alerts:

    extern int outstanding_resume_data; // global counter of outstanding resume data
    std::vector<torrent_handle> handles = ses.get_torrents();
    ses.pause();
    for (torrent_handle const& h : handles)
    {
            if (!h.is_valid()) continue;
            torrent_status s = h.status();
            if (!s.has_metadata || !s.need_save_resume_data()) continue;

            h.save_resume_data();
            ++outstanding_resume_data;
    }

    while (outstanding_resume_data > 0)
    {
            alert const* a = ses.wait_for_alert(seconds(10));

            // if we don't get an alert within 10 seconds, abort
            if (a == nullptr) break;

            std::vector<alert*> alerts;
            ses.pop_alerts(&alerts);

            for (alert* i : alerts)
            {
                    if (alert_cast<save_resume_data_failed_alert>(i))
                    {
                            process_alert(i);
                            --outstanding_resume_data;
                            continue;
                    }

                    save_resume_data_alert const* rd = alert_cast<save_resume_data_alert>(i);
                    if (rd == nullptr)
                    {
                            process_alert(i);
                            continue;
                    }

                    torrent_handle h = rd->handle;
                    torrent_status st = h.status(torrent_handle::query_save_path
                            | torrent_handle::query_name);
                    std::ofstream out((st.save_path
                            + "/" + st.name + ".fastresume").c_str()
                            , std::ios_base::binary);
                    std::vector<char> buf = write_resume_data_buf(rd->params);
                    out.write(buf.data(), buf.size());
                    --outstanding_resume_data;
            }
    }

Note

Note how `outstanding_resume_data` is a global counter in this example. This is deliberate, otherwise there is a race condition for torrents that was just asked to save their resume data, they posted the alert, but it has not been received yet. Those torrents would report that they don't need to save resume data again, and skipped by the initial loop, and thwart the counter otherwise.

[report issue]

### need_save_resume_data()

    bool need_save_resume_data () const;

This function returns true if any whole chunk has been downloaded since the torrent was first loaded or since the last time the resume data was saved. When saving resume data periodically, it makes sense to skip any torrent which hasn't downloaded anything since the last time.

Note

A torrent's resume data is considered saved as soon as the save_resume_data_alert is posted. It is important to make sure this alert is received and handled in order for this function to be meaningful.

[report issue]

### queue_position_top() queue_position_bottom() queue_position() queue_position_down() queue_position_up()

    queue_position_t queue_position () const;
    void queue_position_down () const;
    void queue_position_up () const;
    void queue_position_top () const;
    void queue_position_bottom () const;

Every torrent that is added is assigned a queue position exactly one greater than the greatest queue position of all existing torrents. Torrents that are being seeded have -1 as their queue position, since they're no longer in line to be downloaded.

When a torrent is removed or turns into a seed, all torrents with greater queue positions have their positions decreased to fill in the space in the sequence.

`queue_position()` returns the torrent's position in the download queue. The torrents with the smallest numbers are the ones that are being downloaded. The smaller number, the closer the torrent is to the front of the line to be started.

The queue position is also available in the torrent_status.

The `queue_position_*()` functions adjust the torrents position in the queue. Up means closer to the front and down means closer to the back of the queue. Top and bottom refers to the front and the back of the queue respectively.

[report issue]

### queue_position_set()

    void queue_position_set (queue_position_t p) const;

updates the position in the queue for this torrent. The relative order of all other torrents remain intact but their numerical queue position shifts to make space for this torrent's new position

[report issue]

### set_ssl_certificate() set_ssl_certificate_buffer()

    void set_ssl_certificate (std::string const& certificate
          , std::string const& private_key
          , std::string const& dh_params
          , std::string const& passphrase = "");
    void set_ssl_certificate_buffer (std::string const& certificate
          , std::string const& private_key
          , std::string const& dh_params);

For SSL torrents, use this to specify a path to a .pem file to use as this client's certificate. The certificate must be signed by the certificate in the .torrent file to be valid.

The set_ssl_certificate_buffer() overload takes the actual certificate, private key and DH params as strings, rather than paths to files.

`cert` is a path to the (signed) certificate in .pem format corresponding to this torrent.

`private_key` is a path to the private key for the specified certificate. This must be in .pem format.

`dh_params` is a path to the Diffie-Hellman parameter file, which needs to be in .pem format. You can generate this file using the openssl command like this: `openssl dhparam -outform PEM -out dhparams.pem 512`.

`passphrase` may be specified if the private key is encrypted and requires a passphrase to be decrypted.

Note that when a torrent first starts up, and it needs a certificate, it will suspend connecting to any peers until it has one. It's typically desirable to resume the torrent after setting the SSL certificate.

If you receive a torrent_need_cert_alert, you need to call this to provide a valid cert. If you don't have a cert you won't be allowed to connect to any peers.

[report issue]

### get_storage_impl()

    storage_interface* get_storage_impl () const;

Returns the storage implementation for this torrent. This depends on the storage constructor function that was passed to add_torrent.

[report issue]

### torrent_file()

    std::shared_ptr<const torrent_info> torrent_file () const;

Returns a pointer to the torrent_info object associated with this torrent. The torrent_info object may be a copy of the internal object. If the torrent doesn't have metadata, the pointer will not be initialized (i.e. a nullptr). The torrent may be in a state without metadata only if it was started without a .torrent file, e.g. by being added by magnet link

[report issue]

### piece_availability()

    void piece_availability (std::vector<int>& avail) const;

Fills the specified `std::vector<int>` with the availability for each piece in this torrent. libtorrent does not keep track of availability for seeds, so if the torrent is seeding the availability for all pieces is reported as 0.

The piece availability is the number of peers that we are connected that has advertised having a particular piece. This is the information that libtorrent uses in order to prefer picking rare pieces.

[report issue]

### prioritize_pieces() get_piece_priorities() piece_priority()

    download_priority_t piece_priority (piece_index_t index) const;
    void prioritize_pieces (std::vector<std::pair<piece_index_t, download_priority_t>> const& pieces) const;
    std::vector<download_priority_t> get_piece_priorities () const;
    void piece_priority (piece_index_t index, download_priority_t priority) const;
    void prioritize_pieces (std::vector<download_priority_t> const& pieces) const;

These functions are used to set and get the priority of individual pieces. By default all pieces have priority 4. That means that the random rarest first algorithm is effectively active for all pieces. You may however change the priority of individual pieces. There are 8 priority levels. 0 means not to download the piece at all. Otherwise, lower priority values means less likely to be picked. Piece priority takes precedence over piece availability. Every piece with priority 7 will be attempted to be picked before a priority 6 piece and so on.

The default priority of pieces is 4.

Piece priorities can not be changed for torrents that have not downloaded the metadata yet. Magnet links won't have metadata immediately. see the metadata_received_alert.

`piece_priority` sets or gets the priority for an individual piece, specified by `index`.

`prioritize_pieces` takes a vector of integers, one integer per piece in the torrent. All the piece priorities will be updated with the priorities in the vector. The second overload of `prioritize_pieces` that takes a vector of pairs will update the priorities of only select pieces, and leave all other unaffected. Each pair is (piece, priority). That is, the first item is the piece index and the second item is the priority of that piece. Invalid entries, where the piece index or priority is out of range, are not allowed.

`get_piece_priorities` returns a vector with one element for each piece in the torrent. Each element is the current priority of that piece.

It's possible to cancel the effect of file priorities by setting the priorities for the affected pieces. Care has to be taken when mixing usage of file- and piece priorities.

[report issue]

### file_priority() prioritize_files() get_file_priorities()

    std::vector<download_priority_t> get_file_priorities () const;
    void file_priority (file_index_t index, download_priority_t priority) const;
    download_priority_t file_priority (file_index_t index) const;
    void prioritize_files (std::vector<download_priority_t> const& files) const;

`index` must be in the range [0, number_of_files).

`file_priority()` queries or sets the priority of file `index`.

`prioritize_files()` takes a vector that has at as many elements as there are files in the torrent. Each entry is the priority of that file. The function sets the priorities of all the pieces in the torrent based on the vector.

`get_file_priorities()` returns a vector with the priorities of all files.

The priority values are the same as for piece_priority(). See download_priority_t.

Whenever a file priority is changed, all other piece priorities are reset to match the file priorities. In order to maintain special priorities for particular pieces, piece_priority() has to be called again for those pieces.

You cannot set the file priorities on a torrent that does not yet have metadata or a torrent that is a seed. `file_priority(int, int)` and prioritize_files() are both no-ops for such torrents.

Since changing file priorities may involve disk operations (of moving files in- and out of the part file), the internal accounting of file priorities happen asynchronously. i.e. setting file priorities and then immediately querying them may not yield the same priorities just set. However, the piece priorities are updated immediately.

when combining file- and piece priorities, the resume file will record both. When loading the resume data, the file priorities will be applied first, then the piece priorities.

[report issue]

### force_reannounce() force_dht_announce()

    void force_dht_announce () const;
    void force_reannounce (int seconds = 0, int tracker_index = -1, reannounce_flags_t = {}) const;

`force_reannounce()` will force this torrent to do another tracker request, to receive new peers. The `seconds` argument specifies how many seconds from now to issue the tracker announces.

If the tracker's `min_interval` has not passed since the last announce, the forced announce will be scheduled to happen immediately as the `min_interval` expires. This is to honor trackers minimum re-announce interval settings.

The `tracker_index` argument specifies which tracker to re-announce. If set to -1 (which is the default), all trackers are re-announce.

The `flags` argument can be used to affect the re-announce. See ignore_min_interval.

`force_dht_announce` will announce the torrent to the DHT immediately.

[report issue]

### scrape_tracker()

    void scrape_tracker (int idx = -1) const;

`scrape_tracker()` will send a scrape request to a tracker. By default (`idx` = -1) it will scrape the last working tracker. If `idx` is >= 0, the tracker with the specified index will scraped.

A scrape request queries the tracker for statistics such as total number of incomplete peers, complete peers, number of downloads etc.

This request will specifically update the `num_complete` and `num_incomplete` fields in the torrent_status struct once it completes. When it completes, it will generate a scrape_reply_alert. If it fails, it will generate a scrape_failed_alert.

[report issue]

### set_download_limit() upload_limit() download_limit() set_upload_limit()

    void set_download_limit (int limit) const;
    int download_limit () const;
    void set_upload_limit (int limit) const;
    int upload_limit () const;

`set_upload_limit` will limit the upload bandwidth used by this particular torrent to the limit you set. It is given as the number of bytes per second the torrent is allowed to upload. `set_download_limit` works the same way but for download bandwidth instead of upload bandwidth. Note that setting a higher limit on a torrent then the global limit (`settings_pack::upload_rate_limit`) will not override the global rate limit. The torrent can never upload more than the global rate limit.

`upload_limit` and `download_limit` will return the current limit setting, for upload and download, respectively.

Local peers are not rate limited by default. see peer classes.

[report issue]

### connect_peer()

    void connect_peer (tcp::endpoint const& adr, peer_source_flags_t source = {}
          , pex_flags_t flags = pex_encryption | pex_utp | pex_holepunch) const;

`connect_peer()` is a way to manually connect to peers that one believe is a part of the torrent. If the peer does not respond, or is not a member of this torrent, it will simply be disconnected. No harm can be done by using this other than an unnecessary connection attempt is made. If the torrent is uninitialized or in queued or checking mode, this will throw system_error. The second (optional) argument will be bitwise ORed into the source mask of this peer. Typically this is one of the source flags in peer_info. i.e. `tracker`, `pex`, `dht` etc.

For possible values of `flags`, see pex_flags_t.

[report issue]

### clear_peers()

    void clear_peers ();

This will disconnect all peers and clear the peer list for this torrent. New peers will have to be acquired before resuming, from trackers, DHT or local service discovery, for example.

[report issue]

### set_max_uploads() max_uploads()

    void set_max_uploads (int max_uploads) const;
    int max_uploads () const;

`set_max_uploads()` sets the maximum number of peers that's unchoked at the same time on this torrent. If you set this to -1, there will be no limit. This defaults to infinite. The primary setting controlling this is the global unchoke slots limit, set by unchoke_slots_limit in settings_pack.

`max_uploads()` returns the current settings.

[report issue]

### max_connections() set_max_connections()

    void set_max_connections (int max_connections) const;
    int max_connections () const;

`set_max_connections()` sets the maximum number of connection this torrent will open. If all connections are used up, incoming connections may be refused or poor connections may be closed. This must be at least 2. The default is unlimited number of connections. If -1 is given to the function, it means unlimited. There is also a global limit of the number of connections, set by `connections_limit` in settings_pack.

`max_connections()` returns the current settings.

[report issue]

### move_storage()

    void move_storage (std::string const& save_path
          , move_flags_t flags = move_flags_t::always_replace_files
          ) const;

Moves the file(s) that this torrent are currently seeding from or downloading to. If the given `save_path` is not located on the same drive as the original save path, the files will be copied to the new drive and removed from their original location. This will block all other disk IO, and other torrents download and upload rates may drop while copying the file.

Since disk IO is performed in a separate thread, this operation is also asynchronous. Once the operation completes, the `storage_moved_alert` is generated, with the new path as the message. If the move fails for some reason, `storage_moved_failed_alert` is generated instead, containing the error message.

The `flags` argument determines the behavior of the copying/moving of the files in the torrent. see move_flags_t.

`always_replace_files` is the default and replaces any file that exist in both the source directory and the target directory.

`fail_if_exist` first check to see that none of the copy operations would cause an overwrite. If it would, it will fail. Otherwise it will proceed as if it was in `always_replace_files` mode. Note that there is an inherent race condition here. If the files in the target directory appear after the check but before the copy or move completes, they will be overwritten. When failing because of files already existing in the target path, the `error` of `move_storage_failed_alert` is set to `boost::system::errc::file_exists`.

The intention is that a client may use this as a probe, and if it fails, ask the user which mode to use. The client may then re-issue the `move_storage` call with one of the other modes.

`dont_replace` always keeps the existing file in the target directory, if there is one. The source files will still be removed in that case. Note that it won't automatically re-check files. If an incomplete torrent is moved into a directory with the complete files, pause, move, force-recheck and resume. Without the re-checking, the torrent will keep downloading and files in the new download directory will be overwritten.

Files that have been renamed to have absolute paths are not moved by this function. Keep in mind that files that don't belong to the torrent but are stored in the torrent's directory may be moved as well. This goes for files that have been renamed to absolute paths that still end up inside the save path.

[report issue]

### rename_file()

    void rename_file (file_index_t index, std::string const& new_name) const;

Renames the file with the given index asynchronously. The rename operation is complete when either a file_renamed_alert or file_rename_failed_alert is posted.

[report issue]

### info_hash()

    sha1_hash info_hash () const;

`info_hash()` returns the info-hash of the torrent. If this handle is to a torrent that hasn't loaded yet (for instance by being added) by a URL, the returned value is undefined.

[report issue]

### operator==() operator!=() operator<()

    bool operator== (const torrent_handle& h) const;
    bool operator!= (const torrent_handle& h) const;
    bool operator< (const torrent_handle& h) const;

comparison operators. The order of the torrents is unspecified but stable.

[report issue]

### id()

    std::uint32_t id () const;

returns a unique identifier for this torrent. It's not a dense index. It's not preserved across sessions.

[report issue]

### native_handle()

    std::shared_ptr<torrent> native_handle () const;

This function is intended only for use by plugins and the alert dispatch function. This type does not have a stable ABI and should be relied on as little as possible. Accessing the handle returned by this function is not thread safe outside of libtorrent's internal thread (which is used to invoke plugin callbacks). The `torrent` class is not only eligible for changing ABI across minor versions of libtorrent, its layout is also dependent on build configuration. This adds additional requirements on a client to be built with the exact same build configuration as libtorrent itself. i.e. the `TORRENT_` macros must match between libtorrent and the client builds.

[report issue]

### enum file_progress_flags_t

Declared in "libtorrent/torrent_handle.hpp"

name | value | description
--- | --- | ---
piece_granularity | 1 | only calculate file progress at piece granularity. This makes the file_progress() call cheaper and also only takes bytes that have passed the hash check into account, so progress cannot regress in this mode.

[report issue]

overwrite_existing
  instruct libtorrent to overwrite any data that may already have been downloaded with the data of the new piece being added.

[report issue]

query_distributed_copies
  calculates `distributed_copies`, `distributed_full_copies` and `distributed_fraction`.

[report issue]

query_accurate_download_counters
  includes partial downloaded blocks in `total_done` and `total_wanted_done`.

[report issue]

query_last_seen_complete
  includes `last_seen_complete`.

[report issue]

query_pieces
  populate the `pieces` field in torrent_status.

[report issue]

query_verified_pieces
  includes `verified_pieces` (only applies to torrents in seed mode).

[report issue]

query_torrent_file
  includes `torrent_file`, which is all the static information from the .torrent file.

[report issue]

query_name
  includes `name`, the name of the torrent. This is either derived from the .torrent file, or from the `&dn=` magnet link argument or possibly some other source. If the name of the torrent is not known, this is an empty string.

[report issue]

query_save_path
  includes `save_path`, the path to the directory the files of the torrent are saved to.

[report issue]

alert_when_available
  used to ask libtorrent to send an alert once the piece has been downloaded, by passing alert_when_available. When set, the read_piece_alert alert will be delivered, with the piece data, when it's downloaded.

[report issue]

graceful_pause clear_disk_cache
  will delay the disconnect of peers that we're still downloading outstanding requests from. The torrent will not accept any more requests and will disconnect all idle peers. As soon as a peer is done transferring the blocks that were requested from it, it is disconnected. This is a graceful shut down of the torrent in the sense that no downloaded bytes are wasted.

[report issue]

flush_disk_cache
  the disk cache will be flushed before creating the resume data. This avoids a problem with file timestamps in the resume data in case the cache hasn't been flushed yet.

[report issue]

save_info_dict
  the resume data will contain the metadata from the torrent file as well. This is default for any torrent that's added without a torrent file (such as a magnet link or a URL).

[report issue]

only_if_modified
  if nothing significant has changed in the torrent since the last time resume data was saved, fail this attempt. Significant changes primarily include more data having been downloaded, file or piece priorities having changed etc. If the resume data doesn't need saving, a save_resume_data_failed_alert is posted with the error resume_data_not_modified.

[report issue]

ignore_min_interval
  by default, force-reannounce will still honor the min-interval published by the tracker. If this flag is set, it will be ignored and the tracker is announced immediately.

[report issue]

## cache_status

Declared in "libtorrent/disk_io_thread.hpp"

this struct holds a number of statistics counters relevant for the disk io thread and disk cache.

    struct cache_status
    {
       cache_status ();

       std::vector<cached_piece_info> pieces;
    };

[report issue]

### cache_status()

    cache_status ();

initializes all counters to 0

[report issue]

## web_seed_entry

Declared in "libtorrent/torrent_info.hpp"

the web_seed_entry holds information about a web seed (also known as URL seed or HTTP seed). It is essentially a URL with some state associated with it. For more information, see BEP 17 and BEP 19.

    struct web_seed_entry
    {
       bool operator== (web_seed_entry const& e) const;
       bool operator< (web_seed_entry const& e) const;

       enum type_t
       {
          url_seed,
          http_seed,
       };

       std::string url;
       std::string auth;
       headers_t extra_headers;
       std::uint8_t type;
    };

[report issue]

### operator==()

    bool operator== (web_seed_entry const& e) const;

URL and type comparison

[report issue]

### operator<()

    bool operator< (web_seed_entry const& e) const;

URL and type less-than comparison

[report issue]

### enum type_t

Declared in "libtorrent/torrent_info.hpp"

name | value | description
--- | --- | ---
url_seed | 0 |
http_seed | 1 |

[report issue]

url
  The URL of the web seed

[report issue]

auth
  Optional authentication. If this is set, it's passed in as HTTP basic auth to the web seed. The format is: username:password.

[report issue]

extra_headers
  Any extra HTTP headers that need to be passed to the web seed

[report issue]

type
  The type of web seed (see type_t)

[report issue]

## load_torrent_limits

Declared in "libtorrent/torrent_info.hpp"

this object holds configuration options for limits to use when loading torrents. They are meant to prevent loading potentially malicious torrents that cause excessive memory allocations.

    struct load_torrent_limits
    {
       int max_buffer_size  = 10000000;
       int max_pieces  = 0x200000;
       int max_decode_depth  = 100;
       int max_decode_tokens  = 3000000;
    };

[report issue]

max_buffer_size
  the max size of a .torrent file to load into RAM

[report issue]

max_pieces
  the max number of pieces allowed in the torrent

[report issue]

max_decode_depth
  the max recursion depth in the bdecoded structure

[report issue]

max_decode_tokens
  the max number of bdecode tokens

[report issue]

## torrent_info

Declared in "libtorrent/torrent_info.hpp"

the torrent_info class holds the information found in a .torrent file.

    class torrent_info
    {
       torrent_info (std::string const& filename, load_torrent_limits const& cfg);
       explicit torrent_info (bdecode_node const& torrent_file);
       torrent_info (torrent_info const& t);
       explicit torrent_info (span<char const> buffer, from_span_t);
       torrent_info (span<char const> buffer, load_torrent_limits const& cfg, from_span_t);
       explicit torrent_info (sha1_hash const& info_hash);
       torrent_info (char const* buffer, int size, error_code& ec);
       torrent_info (std::string const& filename, error_code& ec);
       torrent_info (bdecode_node const& torrent_file, error_code& ec);
       torrent_info (char const* buffer, int size);
       explicit torrent_info (std::string const& filename);
       torrent_info (bdecode_node const& torrent_file, load_torrent_limits const& cfg);
       torrent_info (span<char const> buffer, error_code& ec, from_span_t);
       ~torrent_info ();
       file_storage const& files () const;
       file_storage const& orig_files () const;
       void rename_file (file_index_t index, std::string const& new_filename);
       void remap_files (file_storage const& f);
       void add_tracker (std::string const& url, int tier
          , announce_entry::tracker_source source);
       void add_tracker (std::string const& url, int tier = 0);
       std::vector<announce_entry> const& trackers () const;
       std::vector<std::string> collections () const;
       std::vector<sha1_hash> similar_torrents () const;
       std::vector<web_seed_entry> const& web_seeds () const;
       void add_url_seed (std::string const& url
          , std::string const& extern_auth = std::string()
          , web_seed_entry::headers_t const& extra_headers = web_seed_entry::headers_t());
       void add_http_seed (std::string const& url
          , std::string const& extern_auth = std::string()
          , web_seed_entry::headers_t const& extra_headers = web_seed_entry::headers_t());
       void set_web_seeds (std::vector<web_seed_entry> seeds);
       std::int64_t total_size () const;
       int piece_length () const;
       int num_pieces () const;
       piece_index_t end_piece () const;
       piece_index_t last_piece () const;
       index_range<piece_index_t> piece_range () const;
       const sha1_hash& info_hash () const;
       int num_files () const;
       std::vector<file_slice> map_block (piece_index_t const piece
          , std::int64_t offset, int size) const;
       peer_request map_file (file_index_t const file, std::int64_t offset, int size) const;
       string_view ssl_cert () const;
       bool is_valid () const;
       bool priv () const;
       bool is_i2p () const;
       int piece_size (piece_index_t index) const;
       char const* hash_for_piece_ptr (piece_index_t const index) const;
       sha1_hash hash_for_piece (piece_index_t index) const;
       bool is_loaded () const;
       std::vector<sha1_hash> const& merkle_tree () const;
       void set_merkle_tree (std::vector<sha1_hash>& h);
       const std::string& name () const;
       std::time_t creation_date () const;
       const std::string& creator () const;
       const std::string& comment () const;
       std::vector<std::pair<std::string, int>> const& nodes () const;
       void add_node (std::pair<std::string, int> const& node);
       bool parse_info_section (bdecode_node const& e, error_code& ec);
       bool parse_info_section (bdecode_node const& e, error_code& ec, int piece_limit);
       bdecode_node info (char const* key) const;
       void swap (torrent_info& ti);
       boost::shared_array<char> metadata () const;
       int metadata_size () const;
       bool is_merkle_torrent () const;
    };

[report issue]

### torrent_info()

    torrent_info (std::string const& filename, load_torrent_limits const& cfg);
    explicit torrent_info (bdecode_node const& torrent_file);
    torrent_info (torrent_info const& t);
    explicit torrent_info (span<char const> buffer, from_span_t);
    torrent_info (span<char const> buffer, load_torrent_limits const& cfg, from_span_t);
    explicit torrent_info (sha1_hash const& info_hash);
    torrent_info (char const* buffer, int size, error_code& ec);
    torrent_info (std::string const& filename, error_code& ec);
    torrent_info (bdecode_node const& torrent_file, error_code& ec);
    torrent_info (char const* buffer, int size);
    explicit torrent_info (std::string const& filename);
    torrent_info (bdecode_node const& torrent_file, load_torrent_limits const& cfg);
    torrent_info (span<char const> buffer, error_code& ec, from_span_t);

The constructor that takes an info-hash will initialize the info-hash to the given value, but leave all other fields empty. This is used internally when downloading torrents without the metadata. The metadata will be created by libtorrent as soon as it has been downloaded from the swarm.

The constructor that takes a bdecode_node will create a torrent_info object from the information found in the given torrent_file. The bdecode_node represents a tree node in an bencoded file. To load an ordinary .torrent file into a bdecode_node, use bdecode().

The version that takes a buffer pointer and a size will decode it as a .torrent file and initialize the torrent_info object for you.

The version that takes a filename will simply load the torrent file and decode it inside the constructor, for convenience. This might not be the most suitable for applications that want to be able to report detailed errors on what might go wrong.

There is an upper limit on the size of the torrent file that will be loaded by the overload taking a filename. If it's important that even very large torrent files are loaded, use one of the other overloads.

The overloads that takes an `error_code const&` never throws if an error occur, they will simply set the error code to describe what went wrong and not fully initialize the torrent_info object. The overloads that do not take the extra error_code parameter will always throw if an error occurs. These overloads are not available when building without exception support.

The overload that takes a `span` also needs an extra parameter of type `from_span_t` to disambiguate the `std::string` overload for string literals. There is an object in the libtorrent namespace of this type called `from_span`.

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### ~torrent_info()

    ~torrent_info ();

frees all storage associated with this torrent_info object

[report issue]

### files() orig_files()

    file_storage const& files () const;
    file_storage const& orig_files () const;

The file_storage object contains the information on how to map the pieces to files. It is separated from the torrent_info object because when creating torrents a storage object needs to be created without having a torrent file. When renaming files in a storage, the storage needs to make its own copy of the file_storage in order to make its mapping differ from the one in the torrent file.

`orig_files()` returns the original (unmodified) file storage for this torrent. This is used by the web server connection, which needs to request files with the original names. Filename may be changed using `torrent_info::rename_file()`.

For more information on the file_storage object, see the separate document on how to create torrents.

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### rename_file()

    void rename_file (file_index_t index, std::string const& new_filename);

Renames the file with the specified index to the new name. The new filename is reflected by the `file_storage` returned by `files()` but not by the one returned by `orig_files()`.

If you want to rename the base name of the torrent (for a multi file torrent), you can copy the `file_storage` (see files() and orig_files() ), change the name, and then use remap_files().

The `new_filename` can both be a relative path, in which case the file name is relative to the `save_path` of the torrent. If the `new_filename` is an absolute path (i.e. `is_complete(new_filename) == true`), then the file is detached from the `save_path` of the torrent. In this case the file is not moved when move_storage() is invoked.

[report issue]

### remap_files()

    void remap_files (file_storage const& f);

Remaps the file storage to a new file layout. This can be used to, for instance, download all data in a torrent to a single file, or to a number of fixed size sector aligned files, regardless of the number and sizes of the files in the torrent.

The new specified `file_storage` must have the exact same size as the current one.

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### add_tracker() trackers()

    void add_tracker (std::string const& url, int tier
          , announce_entry::tracker_source source);
    void add_tracker (std::string const& url, int tier = 0);
    std::vector<announce_entry> const& trackers () const;

`add_tracker()` adds a tracker to the announce-list. The `tier` determines the order in which the trackers are to be tried. The `trackers()` function will return a sorted vector of `announce_entry`. Each announce entry contains a string, which is the tracker url, and a tier index. The tier index is the high-level priority. No matter which trackers that works or not, the ones with lower tier will always be tried before the one with higher tier number. For more information, see announce_entry.

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### similar_torrents() collections()

    std::vector<std::string> collections () const;
    std::vector<sha1_hash> similar_torrents () const;

These two functions are related to BEP 38 (mutable torrents). The vectors returned from these correspond to the "similar" and "collections" keys in the .torrent file. Both info-hashes and collections from within the info-dict and from outside of it are included.

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### add_http_seed() web_seeds() set_web_seeds() add_url_seed()

    std::vector<web_seed_entry> const& web_seeds () const;
    void add_url_seed (std::string const& url
          , std::string const& extern_auth = std::string()
          , web_seed_entry::headers_t const& extra_headers = web_seed_entry::headers_t());
    void add_http_seed (std::string const& url
          , std::string const& extern_auth = std::string()
          , web_seed_entry::headers_t const& extra_headers = web_seed_entry::headers_t());
    void set_web_seeds (std::vector<web_seed_entry> seeds);

`web_seeds()` returns all url seeds and http seeds in the torrent. Each entry is a `web_seed_entry` and may refer to either a url seed or http seed.

`add_url_seed()` and `add_http_seed()` adds one url to the list of url/http seeds. Currently, the only transport protocol supported for the url is http.

`set_web_seeds()` replaces all web seeds with the ones specified in the `seeds` vector.

The `extern_auth` argument can be used for other authorization schemes than basic HTTP authorization. If set, it will override any username and password found in the URL itself. The string will be sent as the HTTP authorization header's value (without specifying "Basic").

The `extra_headers` argument defaults to an empty list, but can be used to insert custom HTTP headers in the requests to a specific web seed.

See http seeding for more information.

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### num_pieces() total_size() piece_length()

    std::int64_t total_size () const;
    int piece_length () const;
    int num_pieces () const;

`total_size()`, `piece_length()` and `num_pieces()` returns the total number of bytes the torrent-file represents (all the files in it), the number of byte for each piece and the total number of pieces, respectively. The difference between `piece_size()` and `piece_length()` is that `piece_size()` takes the piece index as argument and gives you the exact size of that piece. It will always be the same as `piece_length()` except in the case of the last piece, which may be smaller.

[report issue]

### end_piece() last_piece() piece_range()

    piece_index_t end_piece () const;
    piece_index_t last_piece () const;
    index_range<piece_index_t> piece_range () const;

`last_piece()` returns the index to the last piece in the torrent and `end_piece()` returns the index to the one-past-end piece in the torrent `piece_range()` returns an implementation-defined type that can be used as the container in a range-for loop. Where the values are the indices of all pieces in the file_storage.

[report issue]

### info_hash()

    const sha1_hash& info_hash () const;

returns the info-hash of the torrent

[report issue]

### num_files()

    int num_files () const;

If you need index-access to files you can use the `num_files()` along with the `file_path()`, `file_size()`-family of functions to access files using indices.

[report issue]

### map_block()

    std::vector<file_slice> map_block (piece_index_t const piece
          , std::int64_t offset, int size) const;

This function will map a piece index, a byte offset within that piece and a size (in bytes) into the corresponding files with offsets where that data for that piece is supposed to be stored. See file_slice.

[report issue]

### map_file()

    peer_request map_file (file_index_t const file, std::int64_t offset, int size) const;

This function will map a range in a specific file into a range in the torrent. The `file_offset` parameter is the offset in the file, given in bytes, where 0 is the start of the file. See peer_request.

The input range is assumed to be valid within the torrent. `file_offset` + `size` is not allowed to be greater than the file size. `file_index` must refer to a valid file, i.e. it cannot be >= `num_files()`.

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### ssl_cert()

    string_view ssl_cert () const;

Returns the SSL root certificate for the torrent, if it is an SSL torrent. Otherwise returns an empty string. The certificate is the public certificate in x509 format.

[report issue]

### is_valid()

    bool is_valid () const;

returns true if this torrent_info object has a torrent loaded. This is primarily used to determine if a magnet link has had its metadata resolved yet or not.

[report issue]

### priv()

    bool priv () const;

returns true if this torrent is private. i.e., the client should not advertise itself on the trackerless network (the Kademlia DHT) for this torrent.

[report issue]

### is_i2p()

    bool is_i2p () const;

returns true if this is an i2p torrent. This is determined by whether or not it has a tracker whose URL domain name ends with ".i2p". i2p torrents disable the DHT and local peer discovery as well as talking to peers over anything other than the i2p network.

[report issue]

### piece_size()

    int piece_size (piece_index_t index) const;

returns the piece size of file with `index`. This will be the same as piece_length(), except for the last piece, which may be shorter.

[report issue]

### hash_for_piece_ptr() hash_for_piece()

    char const* hash_for_piece_ptr (piece_index_t const index) const;
    sha1_hash hash_for_piece (piece_index_t index) const;

`hash_for_piece()` takes a piece-index and returns the 20-bytes sha1-hash for that piece and `info_hash()` returns the 20-bytes sha1-hash for the info-section of the torrent file. `hash_for_piece_ptr()` returns a pointer to the 20 byte sha1 digest for the piece. Note that the string is not 0-terminated.

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### merkle_tree() set_merkle_tree()

    std::vector<sha1_hash> const& merkle_tree () const;
    void set_merkle_tree (std::vector<sha1_hash>& h);

`merkle_tree()` returns a reference to the merkle tree for this torrent, if any. `set_merkle_tree()` moves the passed in merkle tree into the torrent_info object. i.e. `h` will not be identical after the call. You need to set the merkle tree for a torrent that you've just created (as a merkle torrent). The merkle tree is retrieved from the `create_torrent::merkle_tree()` function, and need to be saved separately from the torrent file itself. Once it's added to libtorrent, the merkle tree will be persisted in the resume data.

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### name()

    const std::string& name () const;

`name()` returns the name of the torrent. name contains UTF-8 encoded string.

[report issue]

### creation_date()

    std::time_t creation_date () const;

`creation_date()` returns the creation date of the torrent as time_t (posix time). If there's no time stamp in the torrent file, the optional object will be uninitialized. .. posix time: http://www.opengroup.org/onlinepubs/009695399/functions/time.html

[report issue]

### creator()

    const std::string& creator () const;

`creator()` returns the creator string in the torrent. If there is no creator string it will return an empty string.

[report issue]

### comment()

    const std::string& comment () const;

`comment()` returns the comment associated with the torrent. If there's no comment, it will return an empty string. comment contains UTF-8 encoded string.

[report issue]

### nodes()

    std::vector<std::pair<std::string, int>> const& nodes () const;

If this torrent contains any DHT nodes, they are put in this vector in their original form (host name and port number).

[report issue]

### add_node()

    void add_node (std::pair<std::string, int> const& node);

This is used when creating torrent. Use this to add a known DHT node. It may be used, by the client, to bootstrap into the DHT network.

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### parse_info_section()

    bool parse_info_section (bdecode_node const& e, error_code& ec);
    bool parse_info_section (bdecode_node const& e, error_code& ec, int piece_limit);

populates the torrent_info by providing just the info-dict buffer. This is used when loading a torrent from a magnet link for instance, where we only have the info-dict. The bdecode_node `e` points to a parsed info-dictionary. `ec` returns an error code if something fails (typically if the info dictionary is malformed). the piece_limit parameter allows limiting the amount of memory dedicated to loading the torrent, and fails for torrents that exceed the limit

[report issue]

### info()

    bdecode_node info (char const* key) const;

This function looks up keys from the info-dictionary of the loaded torrent file. It can be used to access extension values put in the .torrent file. If the specified key cannot be found, it returns nullptr.

[report issue]

### swap()

    void swap (torrent_info& ti);

swap the content of this and `ti`.

[report issue]

### metadata() metadata_size()

    boost::shared_array<char> metadata () const;
    int metadata_size () const;

`metadata()` returns a the raw info section of the torrent file. The size of the metadata is returned by `metadata_size()`.

[report issue]

### is_merkle_torrent()

    bool is_merkle_torrent () const;

returns whether or not this is a merkle torrent. see BEP 30.

[report issue]

## add_torrent_params

Declared in "libtorrent/add_torrent_params.hpp"

The add_torrent_params is a parameter pack for adding torrents to a session. The key fields when adding a torrent are:

- ti - when you have loaded a .torrent file into a torrent_info object
- info_hash - when you don't have the metadata (.torrent file) but. This is set when adding a magnet link.

one of those fields must be set. Another mandatory field is `save_path`. The add_torrent_params object is passed into one of the `session::add_torrent()` overloads or `session::async_add_torrent()`.

If you only specify the info-hash, the torrent file will be downloaded from peers, which requires them to support the metadata extension. For the metadata extension to work, libtorrent must be built with extensions enabled (`TORRENT_DISABLE_EXTENSIONS` must not be defined). It also takes an optional `name` argument. This may be left empty in case no name should be assigned to the torrent. In case it's not, the name is used for the torrent as long as it doesn't have metadata. See `torrent_handle::name`.

The `add_torrent_params` is also used when requesting resume data for a torrent. It can be saved to and restored from a file and added back to a new session. For serialization and de-serialization of `add_torrent_params` objects, see read_resume_data() and write_resume_data().

    struct add_torrent_params
    {
       add_torrent_params (add_torrent_params&&) noexcept;
       add_torrent_params& operator= (add_torrent_params&&) = default;
       add_torrent_params& operator= (add_torrent_params const&);
       explicit add_torrent_params (storage_constructor_type sc = default_storage_constructor);
       add_torrent_params (add_torrent_params const&);

       int version  = LIBTORRENT_VERSION_NUM;
       std::shared_ptr<torrent_info> ti;
       aux::noexcept_movable<std::vector<std::string>> trackers;
       aux::noexcept_movable<std::vector<int>> tracker_tiers;
       aux::noexcept_movable<std::vector<std::pair<std::string, int>>> dht_nodes;
       std::string name;
       std::string save_path;
       storage_mode_t storage_mode  = storage_mode_sparse;
       aux::noexcept_movable<storage_constructor_type> storage;
       void* userdata  = nullptr;
       aux::noexcept_movable<std::vector<download_priority_t>> file_priorities;
       std::string trackerid;
       torrent_flags_t flags  = torrent_flags::default_flags;
       sha1_hash info_hash;
       int max_uploads  = -1;
       int max_connections  = -1;
       int upload_limit  = -1;
       int download_limit  = -1;
       std::int64_t total_uploaded  = 0;
       std::int64_t total_downloaded  = 0;
       int active_time  = 0;
       int finished_time  = 0;
       int seeding_time  = 0;
       std::time_t added_time  = 0;
       std::time_t completed_time  = 0;
       std::time_t last_seen_complete  = 0;
       int num_complete  = -1;
       int num_incomplete  = -1;
       int num_downloaded  = -1;
       aux::noexcept_movable<std::vector<std::string>> http_seeds;
       aux::noexcept_movable<std::vector<std::string>> url_seeds;
       aux::noexcept_movable<std::vector<tcp::endpoint>> peers;
       aux::noexcept_movable<std::vector<tcp::endpoint>> banned_peers;
       aux::noexcept_movable<std::map<piece_index_t, bitfield>> unfinished_pieces;
       typed_bitfield<piece_index_t> have_pieces;
       typed_bitfield<piece_index_t> verified_pieces;
       aux::noexcept_movable<std::vector<download_priority_t>> piece_priorities;
       aux::noexcept_movable<std::vector<sha1_hash>> merkle_tree;
       aux::noexcept_movable<std::map<file_index_t, std::string>> renamed_files;
       std::time_t last_download  = 0;
       std::time_t last_upload  = 0;
    };

[report issue]

### add_torrent_params() operator=()

    add_torrent_params (add_torrent_params&&) noexcept;
    add_torrent_params& operator= (add_torrent_params&&) = default;
    add_torrent_params& operator= (add_torrent_params const&);
    explicit add_torrent_params (storage_constructor_type sc = default_storage_constructor);
    add_torrent_params (add_torrent_params const&);

The constructor can be used to initialize the storage constructor, which determines the storage mechanism for the downloaded or seeding data for the torrent. For more information, see the `storage` field.

[report issue]

version
  filled in by the constructor and should be left untouched. It is used for forward binary compatibility.

[report issue]

ti
  torrent_info object with the torrent to add. Unless the info_hash is set, this is required to be initialized.

[report issue]

trackers
  If the torrent doesn't have a tracker, but relies on the DHT to find peers, the `trackers` can specify tracker URLs for the torrent.

[report issue]

tracker_tiers
  the tiers the URLs in `trackers` belong to. Trackers belonging to different tiers may be treated differently, as defined by the multi tracker extension. This is optional, if not specified trackers are assumed to be part of tier 0, or whichever the last tier was as iterating over the trackers.

[report issue]

dht_nodes
  a list of hostname and port pairs, representing DHT nodes to be added to the session (if DHT is enabled). The hostname may be an IP address.

[report issue]

name
  in case there's no other name in this torrent, this name will be used. The name out of the torrent_info object takes precedence if available.

[report issue]

save_path

  the path where the torrent is or will be stored.

  Note

  On windows this path (and other paths) are interpreted as UNC paths. This means they must use backslashes as directory separators and may not contain the special directories "." or "..".

  Setting this to an absolute path performs slightly better than a relative path.

[report issue]

storage_mode
  One of the values from storage_mode_t. For more information, see storage allocation.

[report issue]

storage
  can be used to customize how the data is stored. The default storage will simply write the data to the files it belongs to, but it could be overridden to save everything to a single file at a specific location or encrypt the content on disk for instance. For more information about the storage_interface that needs to be implemented for a custom storage, see storage_interface.

[report issue]

userdata
  The `userdata` parameter is optional and will be passed on to the extension constructor functions, if any (see torrent_handle::add_extension()).

[report issue]

file_priorities
  can be set to control the initial file priorities when adding a torrent. The semantics are the same as for `torrent_handle::prioritize_files()`. The file priorities specified in here take precedence over those specified in the resume data, if any.

[report issue]

trackerid
  the default tracker id to be used when announcing to trackers. By default this is empty, and no tracker ID is used, since this is an optional argument. If a tracker returns a tracker ID, that ID is used instead of this.

[report issue]

flags

  flags controlling aspects of this torrent and how it's added. See torrent_flags_t for details.

  Note

  The `flags` field is initialized with default flags by the constructor. In order to preserve default behavior when clearing or setting other flags, make sure to bitwise OR or in a flag or bitwise AND the inverse of a flag to clear it.

[report issue]

info_hash
  set this to the info hash of the torrent to add in case the info-hash is the only known property of the torrent. i.e. you don't have a .torrent file nor a magnet link. To add a magnet link, use parse_magnet_uri() to populate fields in the add_torrent_params object.

[report issue]

max_uploads max_connections

  `max_uploads`, `max_connections`, `upload_limit`, `download_limit` correspond to the `set_max_uploads()`, `set_max_connections()`, `set_upload_limit()` and `set_download_limit()` functions on torrent_handle. These values let you initialize these settings when the torrent is added, instead of calling these functions immediately following adding it.

  -1 means unlimited on these settings just like their counterpart functions on torrent_handle

  For fine grained control over rate limits, including making them apply to local peers, see peer classes.

[report issue]

upload_limit download_limit
  the upload and download rate limits for this torrent, specified in bytes per second. -1 means unlimited.

[report issue]

total_uploaded total_downloaded
  the total number of bytes uploaded and downloaded by this torrent so far.

[report issue]

active_time finished_time seeding_time
  the number of seconds this torrent has spent in started, finished and seeding state so far, respectively.

[report issue]

added_time completed_time
  if set to a non-zero value, this is the posix time of when this torrent was first added, including previous runs/sessions. If set to zero, the internal added_time will be set to the time of when add_torrent() is called.

[report issue]

last_seen_complete
  if set to non-zero, initializes the time (expressed in posix time) when we last saw a seed or peers that together formed a complete copy of the torrent. If left set to zero, the internal counterpart to this field will be updated when we see a seed or a distributed copies >= 1.0.

[report issue]

num_complete num_incomplete num_downloaded

  these field can be used to initialize the torrent's cached scrape data. The scrape data is high level metadata about the current state of the swarm, as returned by the tracker (either when announcing to it or by sending a specific scrape request). `num_complete` is the number of peers in the swarm that are seeds, or have every piece in the torrent. `num_incomplete` is the number of peers in the swarm that do not have every piece. `num_downloaded` is the number of times the torrent has been downloaded (not initiated, but the number of times a download has completed).

  Leaving any of these values set to -1 indicates we don't know, or we have not received any scrape data.

[report issue]

http_seeds url_seeds

  URLs can be added to these two lists to specify additional web seeds to be used by the torrent. If the `flag_override_web_seeds` is set, these will be the _only_ ones to be used. i.e. any web seeds found in the .torrent file will be overridden.

  http_seeds expects URLs to web servers implementing the original HTTP seed specification BEP 17.

  url_seeds expects URLs to regular web servers, aka "get right" style, specified in BEP 19.

[report issue]

peers
  peers to add to the torrent, to be tried to be connected to as bittorrent peers.

[report issue]

banned_peers
  peers banned from this torrent. The will not be connected to

[report issue]

unfinished_pieces
  this is a map of partially downloaded piece. The key is the piece index and the value is a bitfield where each bit represents a 16 kiB block. A set bit means we have that block.

[report issue]

have_pieces
  this is a bitfield indicating which pieces we already have of this torrent.

[report issue]

verified_pieces
  when in seed_mode, pieces with a set bit in this bitfield have been verified to be valid. Other pieces will be verified the first time a peer requests it.

[report issue]

piece_priorities
  this sets the priorities for each individual piece in the torrent. Each element in the vector represent the piece with the same index. If you set both file- and piece priorities, file priorities will take precedence.

[report issue]

merkle_tree
  if this is a merkle tree torrent, and you're seeding, this field must be set. It is all the hashes in the binary tree, with the root as the first entry. See torrent_info::set_merkle_tree() for more info.

[report issue]

renamed_files
  this is a map of file indices in the torrent and new filenames to be applied before the torrent is added.

[report issue]

last_download last_upload
  the posix time of the last time payload was received or sent for this torrent, respectively.

[report issue]

## peer_info

Declared in "libtorrent/peer_info.hpp"

holds information and statistics about one peer that libtorrent is connected to

    struct peer_info
    {
       enum connection_type_t
       {
          standard_bittorrent,
          web_seed,
          http_seed,
       };

       std::string client;
       typed_bitfield<piece_index_t> pieces;
       std::int64_t total_download;
       std::int64_t total_upload;
       time_duration last_request;
       time_duration last_active;
       time_duration download_queue_time;
       static constexpr peer_flags_t interesting  = 0_bit;
       static constexpr peer_flags_t choked  = 1_bit;
       static constexpr peer_flags_t remote_interested  = 2_bit;
       static constexpr peer_flags_t remote_choked  = 3_bit;
       static constexpr peer_flags_t supports_extensions  = 4_bit;
       static constexpr peer_flags_t local_connection  = 5_bit;
       static constexpr peer_flags_t handshake  = 6_bit;
       static constexpr peer_flags_t connecting  = 7_bit;
       static constexpr peer_flags_t on_parole  = 9_bit;
       static constexpr peer_flags_t seed  = 10_bit;
       static constexpr peer_flags_t optimistic_unchoke  = 11_bit;
       static constexpr peer_flags_t snubbed  = 12_bit;
       static constexpr peer_flags_t upload_only  = 13_bit;
       static constexpr peer_flags_t endgame_mode  = 14_bit;
       static constexpr peer_flags_t holepunched  = 15_bit;
       static constexpr peer_flags_t i2p_socket  = 16_bit;
       static constexpr peer_flags_t utp_socket  = 17_bit;
       static constexpr peer_flags_t ssl_socket  = 18_bit;
       static constexpr peer_flags_t rc4_encrypted  = 19_bit;
       static constexpr peer_flags_t plaintext_encrypted  = 20_bit;
       peer_flags_t flags;
       static constexpr peer_source_flags_t tracker  = 0_bit;
       static constexpr peer_source_flags_t dht  = 1_bit;
       static constexpr peer_source_flags_t pex  = 2_bit;
       static constexpr peer_source_flags_t lsd  = 3_bit;
       static constexpr peer_source_flags_t resume_data  = 4_bit;
       static constexpr peer_source_flags_t incoming  = 5_bit;
       peer_source_flags_t source;
       int up_speed;
       int down_speed;
       int payload_up_speed;
       int payload_down_speed;
       peer_id pid;
       int queue_bytes;
       int request_timeout;
       int send_buffer_size;
       int used_send_buffer;
       int receive_buffer_size;
       int used_receive_buffer;
       int receive_buffer_watermark;
       int num_hashfails;
       int download_queue_length;
       int timed_out_requests;
       int busy_requests;
       int requests_in_buffer;
       int target_dl_queue_length;
       int upload_queue_length;
       int failcount;
       piece_index_t downloading_piece_index;
       int downloading_block_index;
       int downloading_progress;
       int downloading_total;
       int connection_type;
       int pending_disk_bytes;
       int pending_disk_read_bytes;
       int send_quota;
       int receive_quota;
       int rtt;
       int num_pieces;
       int download_rate_peak;
       int upload_rate_peak;
       float progress;
       int progress_ppm;
       int deprecated_estimated_reciprocation_rate;
       tcp::endpoint ip;
       tcp::endpoint local_endpoint;
       static constexpr bandwidth_state_flags_t bw_idle  = 0_bit;
       static constexpr bandwidth_state_flags_t bw_limit  = 1_bit;
       static constexpr bandwidth_state_flags_t bw_network  = 2_bit;
       static constexpr bandwidth_state_flags_t bw_disk  = 4_bit;
       bandwidth_state_flags_t read_state;
       bandwidth_state_flags_t write_state;
    };

[report issue]

### enum connection_type_t

Declared in "libtorrent/peer_info.hpp"

name | value | description
--- | --- | ---
standard_bittorrent | 0 | Regular bittorrent connection
web_seed | 1 | HTTP connection using the BEP 19 protocol
http_seed | 2 | HTTP connection using the BEP 17 protocol

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client
  a string describing the software at the other end of the connection. In some cases this information is not available, then it will contain a string that may give away something about which software is running in the other end. In the case of a web seed, the server type and version will be a part of this string.

[report issue]

pieces
  a bitfield, with one bit per piece in the torrent. Each bit tells you if the peer has that piece (if it's set to 1) or if the peer miss that piece (set to 0).

[report issue]

total_download total_upload
  the total number of bytes downloaded from and uploaded to this peer. These numbers do not include the protocol chatter, but only the payload data.

[report issue]

last_request last_active
  the time since we last sent a request to this peer and since any transfer occurred with this peer

[report issue]

download_queue_time
  the time until all blocks in the request queue will be downloaded

[report issue]

interesting
  we are interested in pieces from this peer.

[report issue]

choked
  we have choked this peer.

[report issue]

remote_interested
  the peer is interested in us

[report issue]

remote_choked
  the peer has choked us.

[report issue]

supports_extensions
  means that this peer supports the extension protocol.

[report issue]

local_connection
  The connection was initiated by us, the peer has a listen port open, and that port is the same as in the address of this peer. If this flag is not set, this peer connection was opened by this peer connecting to us.

[report issue]

handshake
  The connection is opened, and waiting for the handshake. Until the handshake is done, the peer cannot be identified.

[report issue]

connecting
  The connection is in a half-open state (i.e. it is being connected).

[report issue]

on_parole
  The peer has participated in a piece that failed the hash check, and is now "on parole", which means we're only requesting whole pieces from this peer until it either fails that piece or proves that it doesn't send bad data.

[report issue]

seed
  This peer is a seed (it has all the pieces).

[report issue]

optimistic_unchoke
  This peer is subject to an optimistic unchoke. It has been unchoked for a while to see if it might unchoke us in return an earn an upload/unchoke slot. If it doesn't within some period of time, it will be choked and another peer will be optimistically unchoked.

[report issue]

snubbed
  This peer has recently failed to send a block within the request timeout from when the request was sent. We're currently picking one block at a time from this peer.

[report issue]

upload_only
  This peer has either explicitly (with an extension) or implicitly (by becoming a seed) told us that it will not downloading anything more, regardless of which pieces we have.

[report issue]

endgame_mode
  This means the last time this peer picket a piece, it could not pick as many as it wanted because there were not enough free ones. i.e. all pieces this peer has were already requested from other peers.

[report issue]

holepunched
  This flag is set if the peer was in holepunch mode when the connection succeeded. This typically only happens if both peers are behind a NAT and the peers connect via the NAT holepunch mechanism.

[report issue]

i2p_socket
  indicates that this socket is running on top of the I2P transport.

[report issue]

utp_socket
  indicates that this socket is a uTP socket

[report issue]

ssl_socket
  indicates that this socket is running on top of an SSL (TLS) channel

[report issue]

rc4_encrypted
  this connection is obfuscated with RC4

[report issue]

plaintext_encrypted
  the handshake of this connection was obfuscated with a Diffie-Hellman exchange

[report issue]

flags
  tells you in which state the peer is in. It is set to any combination of the peer_flags_t flags above.

[report issue]

tracker
  The peer was received from the tracker.

[report issue]

dht
  The peer was received from the kademlia DHT.

[report issue]

pex
  The peer was received from the peer exchange extension.

[report issue]

lsd
  The peer was received from the local service discovery (The peer is on the local network).

[report issue]

resume_data
  The peer was added from the fast resume data.

[report issue]

incoming
  we received an incoming connection from this peer

[report issue]

source
  a combination of flags describing from which sources this peer was received. A combination of the peer_source_flags_t above.

[report issue]

up_speed down_speed
  the current upload and download speed we have to and from this peer (including any protocol messages). updated about once per second

[report issue]

payload_up_speed payload_down_speed
  The transfer rates of payload data only updated about once per second

[report issue]

pid
  the peer's id as used in the bit torrent protocol. This id can be used to extract 'fingerprints' from the peer. Sometimes it can tell you which client the peer is using. See identify_client()_

[report issue]

queue_bytes
  the number of bytes we have requested from this peer, but not yet received.

[report issue]

request_timeout
  the number of seconds until the current front piece request will time out. This timeout can be adjusted through `settings_pack::request_timeout`. -1 means that there is not outstanding request.

[report issue]

send_buffer_size used_send_buffer
  the number of bytes allocated and used for the peer's send buffer, respectively.

[report issue]

receive_buffer_size used_receive_buffer receive_buffer_watermark
  the number of bytes allocated and used as receive buffer, respectively.

[report issue]

num_hashfails
  the number of pieces this peer has participated in sending us that turned out to fail the hash check.

[report issue]

download_queue_length
  this is the number of requests we have sent to this peer that we haven't got a response for yet

[report issue]

timed_out_requests
  the number of block requests that have timed out, and are still in the download queue

[report issue]

busy_requests
  the number of busy requests in the download queue. A busy request is a request for a block we've also requested from a different peer

[report issue]

requests_in_buffer
  the number of requests messages that are currently in the send buffer waiting to be sent.

[report issue]

target_dl_queue_length
  the number of requests that is tried to be maintained (this is typically a function of download speed)

[report issue]

upload_queue_length
  the number of piece-requests we have received from this peer that we haven't answered with a piece yet.

[report issue]

failcount
  the number of times this peer has "failed". i.e. failed to connect or disconnected us. The failcount is decremented when we see this peer in a tracker response or peer exchange message.

[report issue]

downloading_piece_index downloading_block_index downloading_progress downloading_total
  You can know which piece, and which part of that piece, that is currently being downloaded from a specific peer by looking at these four members. `downloading_piece_index` is the index of the piece that is currently being downloaded. This may be set to -1 if there's currently no piece downloading from this peer. If it is >= 0, the other three members are valid. `downloading_block_index` is the index of the block (or sub-piece) that is being downloaded. `downloading_progress` is the number of bytes of this block we have received from the peer, and `downloading_total` is the total number of bytes in this block.

[report issue]

connection_type
  the kind of connection this peer uses. See connection_type_t.

[report issue]

pending_disk_bytes
  the number of bytes this peer has pending in the disk-io thread. Downloaded and waiting to be written to disk. This is what is capped by `settings_pack::max_queued_disk_bytes`.

[report issue]

pending_disk_read_bytes
  number of outstanding bytes to read from disk

[report issue]

send_quota receive_quota
  the number of bytes this peer has been assigned to be allowed to send and receive until it has to request more quota from the bandwidth manager.

[report issue]

rtt
  an estimated round trip time to this peer, in milliseconds. It is estimated by timing the TCP `connect()`. It may be 0 for incoming connections.

[report issue]

num_pieces
  the number of pieces this peer has.

[report issue]

download_rate_peak upload_rate_peak
  the highest download and upload rates seen on this connection. They are given in bytes per second. This number is reset to 0 on reconnect.

[report issue]

progress
  the progress of the peer in the range [0, 1]. This is always 0 when floating point operations are disabled, instead use `progress_ppm`.

[report issue]

progress_ppm
  indicates the download progress of the peer in the range [0, 1000000] (parts per million).

[report issue]

ip
  the IP-address to this peer. The type is an asio endpoint. For more info, see the asio documentation.

[report issue]

local_endpoint
  the IP and port pair the socket is bound to locally. i.e. the IP address of the interface it's going out over. This may be useful for multi-homed clients with multiple interfaces to the internet.

[report issue]

bw_idle
  The peer is not waiting for any external events to send or receive data.

[report issue]

bw_limit
  The peer is waiting for the rate limiter.

[report issue]

bw_network
  The peer has quota and is currently waiting for a network read or write operation to complete. This is the state all peers are in if there are no bandwidth limits.

[report issue]

bw_disk
  The peer is waiting for the disk I/O thread to catch up writing buffers to disk before downloading more.

[report issue]

read_state write_state
  bitmasks indicating what state this peer is in with regards to sending and receiving data. The states are defined as independent flags of type bandwidth_state_flags_t, in this class.

[report issue]

## peer_request

Declared in "libtorrent/peer_request.hpp"

represents a byte range within a piece. Internally this is is used for incoming piece requests.

    struct peer_request
    {
       bool operator== (peer_request const& r) const;

       piece_index_t piece;
       int start;
       int length;
    };

[report issue]

### operator==()

    bool operator== (peer_request const& r) const;

returns true if the right hand side peer_request refers to the same range as this does.

[report issue]

piece
  the index of the piece in which the range starts.

[report issue]

start
  the offset within that piece where the range starts.

[report issue]

length
  the size of the range, in bytes.

[report issue]

## write_resume_data() write_resume_data_buf()

Declared in "libtorrent/write_resume_data.hpp"

    std::vector<char> write_resume_data_buf (add_torrent_params const& atp);
    entry write_resume_data (add_torrent_params const& atp);

this function turns the resume data in an `add_torrent_params` object into a bencoded structure

[report issue]

## make_magnet_uri()

Declared in "libtorrent/magnet_uri.hpp"

    std::string make_magnet_uri (torrent_info const& info);
    std::string make_magnet_uri (torrent_handle const& handle);

Generates a magnet URI from the specified torrent. If the torrent handle is invalid, an empty string is returned.

For more information about magnet links, see magnet links.

[report issue]

## parse_magnet_uri()

Declared in "libtorrent/magnet_uri.hpp"

    void parse_magnet_uri (string_view uri, add_torrent_params& p, error_code& ec);
    add_torrent_params parse_magnet_uri (string_view uri);
    add_torrent_params parse_magnet_uri (string_view uri, error_code& ec);

This function parses out information from the magnet link and populates the add_torrent_params object. The overload that does not take an `error_code` reference will throw a system_error on error The overload taking an `add_torrent_params` reference will fill in the fields specified in the magnet URI.

[report issue]

## version()

Declared in "libtorrent/version.hpp"

    char const* version ();

returns the libtorrent version as string form in this format: "<major>.<minor>.<tiny>.<tag>"

[report issue]

## generate_fingerprint()

Declared in "libtorrent/fingerprint.hpp"

    std::string generate_fingerprint (std::string name
       , int major, int minor = 0, int revision = 0, int tag = 0);

This is a utility function to produce a client ID fingerprint formatted to the most common convention. The fingerprint can be set via the `peer_fingerprint` setting, in settings_pack.

The name string should contain exactly two characters. These are the characters unique to your client, used to identify it. Make sure not to clash with anybody else. Here are some taken id's:

id chars | client
--- | ---
LT | libtorrent (default)
UT | uTorrent
UM | uTorrent Mac
qB | qBittorrent
BP | BitTorrent Pro
BT | BitTorrent
DE | Deluge
AZ | Azureus
TL | Tribler

There's an informal directory of client id's here.

The `major`, `minor`, `revision` and `tag` parameters are used to identify the version of your client.

[report issue]

## hash_value()

Declared in "libtorrent/torrent_handle.hpp"

    std::size_t hash_value (torrent_handle const& h);

for std::hash (and to support using this type in unordered_map etc.)

[report issue]

## is_utp_stream_logging()

Declared in "libtorrent/utp_stream.hpp"

    bool is_utp_stream_logging ();

[report issue]

## set_utp_stream_logging()

Declared in "libtorrent/utp_stream.hpp"

    void set_utp_stream_logging (bool enable);

This function should be used at the very beginning and very end of your program.

[report issue]

## read_resume_data()

Declared in "libtorrent/read_resume_data.hpp"

    add_torrent_params read_resume_data (span<char const> buffer);
    add_torrent_params read_resume_data (span<char const> buffer
       , error_code& ec);
    add_torrent_params read_resume_data (bdecode_node const& rd
       , error_code& ec);
    add_torrent_params read_resume_data (bdecode_node const& rd);

these functions are used to parse resume data and populate the appropriate fields in an add_torrent_params object. This object can then be used to add the actual torrent_info object to and pass to session::add_torrent() or session::async_add_torrent().

If the client wants to override any field that was loaded from the resume data, e.g. save_path, those fields must be changed after loading resume data but before adding the torrent.

[report issue]

## enum connection_type

Declared in "libtorrent/peer_connection.hpp"

name | value | description
--- | --- | ---
bittorrent | 0 |
url_seed | 1 |
http_seed | 2 |

[report issue]

## enum portmap_transport

Declared in "libtorrent/portmap.hpp"

name | value | description
--- | --- | ---
natpmp | 0 | natpmp can be NAT-PMP or PCP
upnp | 1 |

[report issue]

## enum portmap_protocol

Declared in "libtorrent/portmap.hpp"

name | value | description
--- | --- | ---
none | 0 |
tcp | 1 |
udp | 2 |

[report issue]

## torrent_flags_t

Declared in "libtorrent/torrent_flags.hpp"

seed_mode

  If `seed_mode` is set, libtorrent will assume that all files are present for this torrent and that they all match the hashes in the torrent file. Each time a peer requests to download a block, the piece is verified against the hash, unless it has been verified already. If a hash fails, the torrent will automatically leave the seed mode and recheck all the files. The use case for this mode is if a torrent is created and seeded, or if the user already know that the files are complete, this is a way to avoid the initial file checks, and significantly reduce the startup time.

  Setting `seed_mode` on a torrent without metadata (a .torrent file) is a no-op and will be ignored.

  It is not possible to set the `seed_mode` flag on a torrent after it has been added to a session. It is possible to clear it though.

upload_mode

  If `upload_mode` is set, the torrent will be initialized in upload-mode, which means it will not make any piece requests. This state is typically entered on disk I/O errors, and if the torrent is also auto managed, it will be taken out of this state periodically (see `settings_pack::optimistic_disk_retry`).

  This mode can be used to avoid race conditions when adjusting priorities of pieces before allowing the torrent to start downloading.

  If the torrent is auto-managed (`auto_managed`), the torrent will eventually be taken out of upload-mode, regardless of how it got there. If it's important to manually control when the torrent leaves upload mode, don't make it auto managed.

share_mode

  determines if the torrent should be added in share mode or not. Share mode indicates that we are not interested in downloading the torrent, but merely want to improve our share ratio (i.e. increase it). A torrent started in share mode will do its best to never download more than it uploads to the swarm. If the swarm does not have enough demand for upload capacity, the torrent will not download anything. This mode is intended to be safe to add any number of torrents to, without manual screening, without the risk of downloading more than is uploaded.

  A torrent in share mode sets the priority to all pieces to 0, except for the pieces that are downloaded, when pieces are decided to be downloaded. This affects the progress bar, which might be set to "100% finished" most of the time. Do not change file or piece priorities for torrents in share mode, it will make it not work.

  The share mode has one setting, the share ratio target, see `settings_pack::share_mode_target` for more info.

apply_ip_filter
  determines if the IP filter should apply to this torrent or not. By default all torrents are subject to filtering by the IP filter (i.e. this flag is set by default). This is useful if certain torrents needs to be exempt for some reason, being an auto-update torrent for instance.

paused
  specifies whether or not the torrent is paused. i.e. it won't connect to the tracker or any of the peers until it's resumed. Note that a paused torrent that also has the auto_managed flag set can be started at any time by libtorrent's queuing logic. See queuing.

auto_managed

  If the torrent is auto-managed (`auto_managed`), the torrent may be resumed at any point, regardless of how it paused. If it's important to manually control when the torrent is paused and resumed, don't make it auto managed.

  If `auto_managed` is set, the torrent will be queued, started and seeded automatically by libtorrent. When this is set, the torrent should also be started as paused. The default queue order is the order the torrents were added. They are all downloaded in that order. For more details, see queuing.

duplicate_is_error
  used in add_torrent_params to indicate that it's an error to attempt to add a torrent that's already in the session. If it's not considered an error, a handle to the existing torrent is returned. This flag is not saved by write_resume_data(), since it is only meant for adding torrents.

update_subscribe
  on by default and means that this torrent will be part of state updates when calling post_torrent_updates(). This flag is not saved by write_resume_data().

super_seeding
  sets the torrent into super seeding/initial seeding mode. If the torrent is not a seed, this flag has no effect.

sequential_download
  sets the sequential download state for the torrent. In this mode the piece picker will pick pieces with low index numbers before pieces with high indices. The actual pieces that are picked depend on other factors still, such as which pieces a peer has and whether it is in parole mode or "prefer whole pieces"-mode. Sequential mode is not ideal for streaming media. For that, see set_piece_deadline() instead.

stop_when_ready

  When this flag is set, the torrent will force stop whenever it transitions from a non-data-transferring state into a data-transferring state (referred to as being ready to download or seed). This is useful for torrents that should not start downloading or seeding yet, but want to be made ready to do so. A torrent may need to have its files checked for instance, so it needs to be started and possibly queued for checking (auto-managed and started) but as soon as it's done, it should be stopped.

  Force stopped means auto-managed is set to false and it's paused. As if the auto_manages flag is cleared and the paused flag is set on the torrent.

  Note that the torrent may transition into a downloading state while setting this flag, and since the logic is edge triggered you may miss the edge. To avoid this race, if the torrent already is in a downloading state when this call is made, it will trigger the stop-when-ready immediately.

  When the stop-when-ready logic fires, the flag is cleared. Any subsequent transitions between downloading and non-downloading states will not be affected, until this flag is set again.

  The behavior is more robust when setting this flag as part of adding the torrent. See add_torrent_params.

  The stop-when-ready flag fixes the inherent race condition of waiting for the state_changed_alert and then call pause(). The download/seeding will most likely start in between posting the alert and receiving the call to pause.

  A downloading state is one where peers are being connected. Which means just downloading the metadata via the `ut_metadata` extension counts as a downloading state. In order to stop a torrent once the metadata has been downloaded, instead set all file priorities to dont_download

override_trackers
  when this flag is set, the tracker list in the add_torrent_params object override any trackers from the torrent file. If the flag is not set, the trackers from the add_torrent_params object will be added to the list of trackers used by the torrent. This flag is set by read_resume_data() if there are trackers present in the resume data file. This effectively makes the trackers saved in the resume data take precedence over the original trackers. This includes if there's an empty list of trackers, to support the case where they were explicitly removed in the previous session. This flag is not saved by write_resume_data()

override_web_seeds
  If this flag is set, the web seeds from the add_torrent_params object will override any web seeds in the torrent file. If it's not set, web seeds in the add_torrent_params object will be added to the list of web seeds used by the torrent. This flag is set by read_resume_data() if there are web seeds present in the resume data file. This effectively makes the web seeds saved in the resume data take precedence over the original ones. This includes if there's an empty list of web seeds, to support the case where they were explicitly removed in the previous session. This flag is not saved by write_resume_data()

need_save_resume
  if this flag is set (which it is by default) the torrent will be considered needing to save its resume data immediately as it's added. New torrents that don't have any resume data should do that. This flag is cleared by a successful call to save_resume_data() This flag is not saved by write_resume_data(), since it represents an ephemeral state of a running torrent.

disable_dht
  set this flag to disable DHT for this torrent. This lets you have the DHT enabled for the whole client, and still have specific torrents not participating in it. i.e. not announcing to the DHT nor picking up peers from it.

disable_lsd
  set this flag to disable local service discovery for this torrent.

disable_pex
  set this flag to disable peer exchange for this torrent.

all
  all torrent flags combined. Can conveniently be used when creating masks for flags

[report issue]

## download_priority_t

Declared in "libtorrent/download_priority.hpp"

dont_download
  Don't download the file or piece. Partial pieces may still be downloaded when setting file priorities.

default_priority
  The default priority for files and pieces.

low_priority
  The lowest priority for files and pieces.

top_priority
  The highest priority for files and pieces.

[report issue]

## pex_flags_t

Declared in "libtorrent/pex_flags.hpp"

pex_encryption
  the peer supports protocol encryption

pex_seed
  the peer is a seed

pex_utp
  the peer supports the uTP, transport protocol over UDP.

pex_holepunch
  the peer supports the holepunch extension If this flag is received from a peer, it can be used as a rendezvous point in case direct connections to the peer fail

[report issue]

## file_open_mode_t

Declared in "libtorrent/disk_interface.hpp"

read_only
  open the file for reading only

write_only
  open the file for writing only

read_write
  open the file for reading and writing

rw_mask
  the mask for the bits determining read or write mode

sparse
  open the file in sparse mode (if supported by the filesystem).

no_atime
  don't update the access timestamps on the file (if supported by the operating system and filesystem). this generally improves disk performance.

random_access
  open the file for random access. This disables read-ahead logic

[report issue]

## open_mode_t

Declared in "libtorrent/file.hpp"

read_only
  open the file for reading only

write_only
  open the file for writing only

read_write
  open the file for reading and writing

rw_mask
  the mask for the bits making up the read-write mode.

sparse
  open the file in sparse mode (if supported by the filesystem).

no_atime
  don't update the access timestamps on the file (if supported by the operating system and filesystem). this generally improves disk performance.

random_access
  open the file for random access. This disables read-ahead logic

no_cache
  don't put any pressure on the OS disk cache because of access to this file. We expect our files to be fairly large, and there is already a cache at the bittorrent block level. This may improve overall system performance by leaving running applications in the page cache

coalesce_buffers
  this is only used for readv/writev flags

attribute_hidden
  when creating a file, set the hidden attribute (windows only)

attribute_executable
  when creating a file, set the executable attribute

attribute_mask
  the mask of all attribute bits