NAIIOProvider

## NAIIOProvider NAIIOProvider — The I/O Provider Interface |

## Synopsis

    #include <caja-actions/na-iio-provider.h>

    #define             NA_TYPE_IIO_PROVIDER
    #define             NA_IIO_PROVIDER                     (instance)
    #define             NA_IS_IIO_PROVIDER                  (instance)
    #define             NA_IIO_PROVIDER_GET_INTERFACE       (instance)
                        NAIIOProvider;
                        NAIIOProviderInterface;
    enum                NAIIOProviderWritabilityStatus;
    enum                NAIIOProviderOperationStatus;
    void                na_iio_provider_item_changed        (const NAIIOProvider *instance);

## Object Hierarchy

      GInterface
       +----NAIIOProvider

## Prerequisites

NAIIOProvider requires GObject.

## Signals

      "io-provider-item-changed"                       : Action

## Description

The NAIIOProvider interface is defined in order to let both Caja-Actions™ internal and user-provided external plugins provide read and write accesses to their own private storage subsystem.

Caja-Actions™ core does not provide by itself input/output code. Instead, we entirely relies on input/output facilities provided by implementations of this interface.

Caja-Actions™ is bundled with several I/O providers. Since version 3, the `na-desktop` I/O provider, which implements the DES-EMA specification, is the preferred way of storing (and sharing) items.

The NAIIOProvider interface provides three types of services:

- loading items . Loading items is used both by the Caja™ plugin, by the Caja-Actions Configuration Tool™ program, and by the command-line utilities.

- creating, updating or deleting items . Updating items is a feature only used by the Caja-Actions Configuration Tool™ program and by some command-line utilities.

- informing Caja-Actions™ of extern modifications . The I/O provider should inform Caja-Actions™ when an item happens to have been modified in the underlying storage subsystem.

  This feature is only used by the Caja™ plugin and by the Caja-Actions Configuration Tool™ program.

  The NAIIOProvider interface does not define specific monitoring methods (but you can also take a glance at NATimeout object). Instead, it is waited that the I/O provider module takes care itself of managing its own monitoring services at load/unload time, calling the `na_iio_provider_item_changed()` function when appropriate.

These services may be fully implemented by the I/O provider itself. Or, the I/O provider may also prefer to take advantage of the data factory management (see NAIFactoryObject and NAIFactoryProvider interfaces) services.

### I/O provider identifier

For its own internal needs, Caja-Actions™ requires that each I/O provider have its own identifier, as an ASCII string.

In order to avoid any collision, this I/O provider identifier is allocated by the Caja-Actions™ maintainers team. If you wish develop yourself a new I/O provider, and so need a new provider identifier, please contact the maintainers (see caja-actions.doap at the root of the source tree).

Below is a list of currently allocated I/O provider identifiers. This list has been last updated on 2010, Feb. 14th.

Table 2. Currently allocated I/O provider identifiers

Identifier | Name | Holder | Allocated on
--- | --- | --- | ---
`all` | Reserved for Caja-Actions™ internal needs | Caja-Actions™ | 2010-01-28
`na-desktop` | NA Desktop I/O Provider | Caja-Actions™ | 2009-12-16
`na-mateconf` | NA MateConf I/O Provider | Caja-Actions™ | 2009-12-16
`na-xml` | NA XML module | Caja-Actions™ | 2010-02-14

### Versions historic

Table 3. Historic of the versions of the NAIIOProvider interface

Caja-Actions™ version | NAIIOProvider interface version |
--- | --- | ---
since 2.30 | 1 | current version

## Details

### NA_TYPE_IIO_PROVIDER

    #define NA_TYPE_IIO_PROVIDER                      ( na_iio_provider_get_type())

### NA_IIO_PROVIDER()

    #define NA_IIO_PROVIDER( instance )               ( G_TYPE_CHECK_INSTANCE_CAST( instance, NA_TYPE_IIO_PROVIDER, NAIIOProvider ))

### NA_IS_IIO_PROVIDER()

    #define NA_IS_IIO_PROVIDER( instance )            ( G_TYPE_CHECK_INSTANCE_TYPE( instance, NA_TYPE_IIO_PROVIDER ))

### NA_IIO_PROVIDER_GET_INTERFACE()

    #define NA_IIO_PROVIDER_GET_INTERFACE( instance ) ( G_TYPE_INSTANCE_GET_INTERFACE(( instance ), NA_TYPE_IIO_PROVIDER, NAIIOProviderInterface ))

### NAIIOProvider

    typedef struct _NAIIOProvider NAIIOProvider;

### NAIIOProviderInterface

    typedef struct {
    	/**
    	 * get_version:
    	 * @instance: the NAIIOProvider provider.
    	 *
    	 * Caja-Actions calls this method each time it needs to know
    	 * which version of this interface the plugin implements.
    	 *
    	 * If this method is not implemented by the plugin,
    	 * Caja-Actions considers that the plugin only implements
    	 * the version 1 of the NAIIOProvider interface.
    	 *
    	 * Return value: if implemented, this method must return the version
    	 * number of this interface the I/O provider is supporting.
    	 *
    	 * Defaults to 1.
    	 *
    	 * Since: 2.30
    	 */
    	guint    ( *get_version )        ( const NAIIOProvider *instance );

    	/**
    	 * get_id:
    	 * @instance: the NAIIOProvider provider.
    	 *
    	 * The I/O provider must implement this method.
    	 *
    	 * Return value: the implementation must return the internal identifier
    	 * of the I/O provider, as a newly allocated string which will be g_free()
    	 * by the caller.
    	 *
    	 * Since: 2.30
    	 */
    	gchar *  ( *get_id )             ( const NAIIOProvider *instance );

    	/**
    	 * get_name:
    	 * @instance: the NAIIOProvider provider.
    	 *
    	 * Return value: if implemented, this method must return the display
    	 * name of the I/O provider, as a newly allocated string which will be
    	 * g_free() by the caller.
    	 *
    	 * This may be the name of the module itself, but this also may be a
    	 * special name the modules gives to this interface.
    	 *
    	 * Defaults to an empty string.
    	 *
    	 * Since: 2.30
    	 */
    	gchar *  ( *get_name )           ( const NAIIOProvider *instance );

    	/**
    	 * read_items:
    	 * @instance: the NAIIOProvider provider.
    	 * @messages: a pointer to a GSList list of strings; the provider
    	 *  may append messages to this list, but shouldn't reinitialize it.
    	 *
    	 * Reads the whole items list from the specified I/O provider.
    	 *
    	 * The I/O provider should implement this method, but if it doesn't,
    	 * then this greatly lowerize the interest of this I/O provider (!).
    	 *
    	 * Return value: if implemented, this method must return a unordered
    	 * flat GList of NAObjectItem-derived objects (menus or actions);
    	 * the actions embed their own profiles.
    	 *
    	 * Defaults to NULL list.
    	 *
    	 * Since: 2.30
    	 */
    	GList *  ( *read_items )         ( const NAIIOProvider *instance, GSList **messages );

    	/**
    	 * is_willing_to_write:
    	 * @instance: the NAIIOProvider provider.
    	 *
    	 * The 'willing_to_write' property is intrinsic to the I/O provider.
    	 * It is not supposed to make any assumption on the environment it is
    	 * currently running on.
    	 * This property just says that the developer/maintainer has released
    	 * the needed code in order to update/create/delete NAObjectItem-derived
    	 * objects.
    	 *
    	 * Note that even if this property is TRUE, there is yet many
    	 * reasons for not being able to update/delete existing items or
    	 * create new ones (see e.g. is_able_to_write() method below).
    	 *
    	 * Return value: if implemented, this method must return a boolean
    	 * value, whose purpose is to let know to Caja-Actions whether
    	 * this I/O provider is, or not, willing to write.
    	 *
    	 * Defaults to FALSE.
    	 *
    	 * Since: 2.30
    	 */
    	gboolean ( *is_willing_to_write )( const NAIIOProvider *instance );

    	/**
    	 * is_able_to_write:
    	 * @instance: the NAIIOProvider provider.
    	 *
    	 * The 'able_to_write' property is a runtime one.
    	 * When returning TRUE, the I/O provider insures that it has
    	 * successfully checked that it was able to write some things
    	 * down to its storage subsystem(s).
    	 *
    	 * The 'able_to_write' property is independent of the
    	 * 'willing_to_write' above, though it is only checked if the
    	 * I/O provider is actually willing to write.
    	 *
    	 * This condition is only relevant when trying to define new items,
    	 * to see if a willing_to provider is actually able to do write
    	 * operations. It it not relevant for updating/deleting already
    	 * existing items as they have already checked their own runtime
    	 * writability status when read from the storage subsystems.
    	 *
    	 * Note that even if this property is TRUE, there is yet many
    	 * reasons for not being able to update/delete existing items or
    	 * create new ones (see e.g. 'locked' user preference key).
    	 *
    	 * Return value: if implemented, this method must return a boolean
    	 * value, whose purpose is to let know to Caja-Actions whether
    	 * this I/O provider is eventually able to write.
    	 *
    	 * Defaults to FALSE.
    	 *
    	 * Since: 2.30
    	 */
    	gboolean ( *is_able_to_write )   ( const NAIIOProvider *instance );

    	/**
    	 * write_item:
    	 * @instance: the NAIIOProvider provider.
    	 * @item: a NAObjectItem-derived item, menu or action.
    	 * @messages: a pointer to a GSList list of strings; the provider
    	 *  may append messages to this list, but shouldn't reinitialize it.
    	 *
    	 * Writes a new @item down to the privat underlying storage subsystem
    	 * which happens to be managed by the I/O provider.
    	 *
    	 * There is no update_item function; it is the responsibility
    	 * of the provider to delete the previous version of an item before
    	 * actually writing the new one.
    	 *
    	 * The I/O provider should implement this method, or return
    	 * FALSE in is_willing_to_write() method above.
    	 *
    	 * Return value: NA_IIO_PROVIDER_CODE_OK if the write operation
    	 * was successful, or another code depending of the detected error.
    	 *
    	 * Since: 2.30
    	 */
    	guint    ( *write_item )         ( const NAIIOProvider *instance, const NAObjectItem *item, GSList **messages );

    	/**
    	 * delete_item:
    	 * @instance: the NAIIOProvider provider.
    	 * @item: a NAObjectItem-derived item, menu or action.
    	 * @messages: a pointer to a GSList list of strings; the provider
    	 *  may append messages to this list, but shouldn't reinitialize it.
    	 *
    	 * Deletes an existing @item from the I/O subsystem.
    	 *
    	 * The I/O provider should implement this method, or return
    	 * FALSE in is_willing_to_write() method above.
    	 *
    	 * Return value: NA_IIO_PROVIDER_CODE_OK if the delete operation was
    	 * successful, or another code depending of the detected error.
    	 *
    	 * Since: 2.30
    	 */
    	guint    ( *delete_item )        ( const NAIIOProvider *instance, const NAObjectItem *item, GSList **messages );

    	/**
    	 * duplicate_data:
    	 * @instance: the NAIIOProvider provider.
    	 * @dest: a NAObjectItem-derived item, menu or action.
    	 * @source: a NAObjectItem-derived item, menu or action.
    	 * @messages: a pointer to a GSList list of strings; the provider
    	 *  may append messages to this list, but shouldn't reinitialize it.
    	 *
    	 * Caja-Actions typically calls this method while duplicating
    	 * a NAObjectItem-derived object, in order to let the I/O provider
    	 * duplicates itself specific data (if any) it may have set on
    	 * @source object.
    	 *
    	 * Note that this does not duplicate in any way any
    	 * NAObjectItem-derived object. We are just dealing here with
    	 * the provider-specific data which may have been attached to
    	 * the NAObjectItem-derived object.
    	 *
    	 * Return value: NA_IIO_PROVIDER_CODE_OK if the duplicate operation
    	 * was successful, or another code depending of the detected error.
    	 *
    	 * Since: 2.30
    	 */
    	guint    ( *duplicate_data )     ( const NAIIOProvider *instance, NAObjectItem *dest, const NAObjectItem *source, GSList **messages );
    } NAIIOProviderInterface;

This defines the methods that a NAIIOProvider may, should, or must implement.

`get_version` () | [should] returns the version of this interface that the plugin implements.
`get_id` () | [must] returns the internal id of the plugin.
`get_name` () | [should] returns the public name of the plugin.
`read_items` () | [should] reads items.
`is_willing_to_write` () | [should] asks the plugin whether it is willing to write.
`is_able_to_write` () | [should] asks the plugin whether it is able to write.
`write_item` () | [should] writes an item.
`delete_item` () | [should] deletes an item.
`duplicate_data` () | [may] let the I/O provider duplicates its specific data.

### enum NAIIOProviderWritabilityStatus

    typedef enum {
    	NA_IIO_PROVIDER_STATUS_WRITABLE = 0,
    	NA_IIO_PROVIDER_STATUS_UNAVAILABLE,
    	NA_IIO_PROVIDER_STATUS_INCOMPLETE_API,
    	NA_IIO_PROVIDER_STATUS_NOT_WILLING_TO,
    	NA_IIO_PROVIDER_STATUS_NOT_ABLE_TO,
    	NA_IIO_PROVIDER_STATUS_LOCKED_BY_ADMIN,
    	NA_IIO_PROVIDER_STATUS_LOCKED_BY_USER,
    	NA_IIO_PROVIDER_STATUS_ITEM_READONLY,
    	NA_IIO_PROVIDER_STATUS_NO_PROVIDER_FOUND,
    	NA_IIO_PROVIDER_STATUS_LEVEL_ZERO,
    	NA_IIO_PROVIDER_STATUS_UNDETERMINED,
    } NAIIOProviderWritabilityStatus;

The reasons for which an item may not be writable.

Not all reasons are to be managed at the I/O provider level. Some are to be used only internally from Caja-Actions™ programs.

`NA_IIO_PROVIDER_STATUS_WRITABLE` | item and i/o provider are writable.
`NA_IIO_PROVIDER_STATUS_UNAVAILABLE` | unavailable i/o provider.
`NA_IIO_PROVIDER_STATUS_INCOMPLETE_API` | i/o provider has an incomplete write api.
`NA_IIO_PROVIDER_STATUS_NOT_WILLING_TO` | i/o provider is not willing to write.
`NA_IIO_PROVIDER_STATUS_NOT_ABLE_TO` | i/o provider is not able to write.
`NA_IIO_PROVIDER_STATUS_LOCKED_BY_ADMIN` | i/o provider has been locked by the administrator.
`NA_IIO_PROVIDER_STATUS_LOCKED_BY_USER` | i/o provider has been locked by the user.
`NA_IIO_PROVIDER_STATUS_ITEM_READONLY` | item is read-only.
`NA_IIO_PROVIDER_STATUS_NO_PROVIDER_FOUND` | no writable i/o provider found.
`NA_IIO_PROVIDER_STATUS_LEVEL_ZERO` | level zero is not writable.
`NA_IIO_PROVIDER_STATUS_UNDETERMINED` | unknwon reason (and probably a bug).

### enum NAIIOProviderOperationStatus

    typedef enum {
    	NA_IIO_PROVIDER_CODE_OK = 0,
    	NA_IIO_PROVIDER_CODE_PROGRAM_ERROR = 1 + NA_IIO_PROVIDER_STATUS_LAST,
    	NA_IIO_PROVIDER_CODE_NOT_WILLING_TO_RUN,
    	NA_IIO_PROVIDER_CODE_WRITE_ERROR,
    	NA_IIO_PROVIDER_CODE_DELETE_SCHEMAS_ERROR,
    	NA_IIO_PROVIDER_CODE_DELETE_CONFIG_ERROR,
    } NAIIOProviderOperationStatus;

The return code of operations.

`NA_IIO_PROVIDER_CODE_OK` | the requested operation has been successful.
`NA_IIO_PROVIDER_CODE_PROGRAM_ERROR` | a program error has been detected; you should open a bug in Bugzilla.
`NA_IIO_PROVIDER_CODE_NOT_WILLING_TO_RUN` | the provider is not willing to do the requested action.
`NA_IIO_PROVIDER_CODE_WRITE_ERROR` | a write error has been detected.
`NA_IIO_PROVIDER_CODE_DELETE_SCHEMAS_ERROR` | the schemas could not be deleted.
`NA_IIO_PROVIDER_CODE_DELETE_CONFIG_ERROR` | the configuration could not be deleted.

### na_iio_provider_item_changed ()

    void                na_iio_provider_item_changed        (const NAIIOProvider *instance);

Informs Caja-Actions™ that this NAIIOProvider `instance` has detected a modification in (at least) one of its items (menu or action).

This function may be triggered for each and every NAObjectItem -derived modified object, and should, at least, be triggered once for a coherent set of updates.

When receiving this signal, the currently running program may just want to immediately reload the current list of items, menus and actions (this is for example what Caja™ plugin does); it may also choose to ask the user if he is willing to reload such a current list (and this is the way Caja-Actions Configuration Tool™ has chosen to deal with this message).

Note that application NAPivot/NAUpdater pivot is typically the only object connected to this signal. It acts so as a filtering proxy, re-emitting its own 'items-changed' signal for a whole set of detected underlying modifications.

`instance` : | the calling NAIIOProvider.

Since 2.30

## Signal Details

### The `"io-provider-item-changed"` signal

    void                user_function                      (NAIIOProvider *provider,
                                                            gpointer       user_data)      : Action

This signal is registered without any default handler.

This signal is not meant to be directly sent by a plugin. Instead, the plugin should call the `na_iio_provider_item_changed()` function.

See also `na_iio_provider_item_changed()`.

`provider` : | the NAIIOProvider which has called the `na_iio_provider_item_changed()` function.
`user_data` : | user data set when the signal handler was connected.