DcmInputStream Class Reference

abstract base class for input streams. More...

Inheritance diagram for DcmInputStream:

Public Member Functions
virtual	~DcmInputStream ()
	destructor
virtual OFBool	good () const
	returns the status of the stream.
virtual OFCondition	status () const
	returns the status of the stream as an OFCondition object.
virtual OFBool	eos ()
	returns true if the producer is at the end of stream.
virtual offile_off_t	avail ()
	returns the minimum number of bytes that can be read with the next call to read().
virtual offile_off_t	read (void *buf, offile_off_t buflen)
	reads as many bytes as possible into the given block.
virtual offile_off_t	skip (offile_off_t skiplen)
	skips over the given number of bytes (or less)
virtual offile_off_t	tell () const
	returns the total number of bytes read from the stream so far
virtual OFCondition	installCompressionFilter (E_StreamCompression filterType)
	installs a compression filter for the given stream compression type, which should be neither ESC_none nor ESC_unsupported.
virtual DcmInputStreamFactory *	newFactory () const =0
	creates a new factory object for the current stream and stream position.
Uint32	nestingDepth () const
	returns the current sequence nesting depth.
Uint32	incrementNestingDepth ()
	increments the sequence nesting depth counter.
void	decrementNestingDepth ()
	decrements the sequence nesting depth counter.
Sint32	maxNestingDepth () const
	returns the maximum permitted sequence nesting depth for this stream.
void	setMaxNestingDepth (Sint32 maxDepth)
	sets the maximum permitted sequence nesting depth for this stream.
virtual void	mark ()
	marks the current stream position for a later putback operation, overwriting a possibly existing prior putback mark.
virtual void	putback ()
	resets the stream to the position previously marked with setPutbackMark().

Protected Member Functions
	DcmInputStream (DcmProducer *initial)
	protected constructor, to be called from derived class constructor
const DcmProducer *	currentProducer () const
	returns pointer to current producer object

Private Member Functions
	DcmInputStream (const DcmInputStream &)
	private unimplemented copy constructor
DcmInputStream &	operator= (const DcmInputStream &)
	private unimplemented copy assignment operator

Private Attributes
DcmProducer *	current_
	pointer to first node in filter chain
DcmInputFilter *	compressionFilter_
	pointer to compression filter, NULL if no compression
offile_off_t	tell_
	counter for number of bytes read so far
offile_off_t	mark_
	putback marker
Uint32	nestingDepth_
	current sequence nesting depth (for stack overflow protection)
Sint32	maxNestingDepth_
	maximum permitted sequence nesting depth (0 = default 64, -1 = unlimited)

Detailed Description

abstract base class for input streams.

Constructor & Destructor Documentation

DcmInputStream()

DcmInputStream::DcmInputStream ( DcmProducer * initial )

protected

protected constructor, to be called from derived class constructor

Parameters

initial

initial pointer to first node in filter chain The pointer is not dereferenced in the constructor, so the object pointed to may be initialized later in the subclass constructor.

Referenced by DcmInputStream(), and operator=().

Member Function Documentation

avail()

virtual offile_off_t DcmInputStream::avail ( )

virtual

returns the minimum number of bytes that can be read with the next call to read().

The DcmObject read methods rely on avail to return a value > 0 if there is no I/O suspension since certain data such as tag and length are only read "en bloc", i.e. all or nothing.

Returns

minimum of data available in producer

decrementNestingDepth()

void DcmInputStream::decrementNestingDepth

(

)

decrements the sequence nesting depth counter.

Does nothing if the counter is already zero.

eos()

virtual OFBool DcmInputStream::eos ( )

virtual

returns true if the producer is at the end of stream.

Returns

true if end of stream, false otherwise

good()

virtual OFBool DcmInputStream::good ( ) const

virtual

returns the status of the stream.

Unless the status is good, the stream will not permit any operation.

Returns

status, true if good

incrementNestingDepth()

Uint32 DcmInputStream::incrementNestingDepth

(

)

increments the sequence nesting depth counter.

Returns

the new nesting depth after incrementing

installCompressionFilter()

virtual OFCondition DcmInputStream::installCompressionFilter ( E_StreamCompression filterType )

virtual

installs a compression filter for the given stream compression type, which should be neither ESC_none nor ESC_unsupported.

Once a compression filter is active, it cannot be deactivated or replaced during the lifetime of the stream.

Parameters

filterType

type of compression filter

Returns

EC_Normal if successful, an error code otherwise

mark()

virtual void DcmInputStream::mark ( )

virtual

marks the current stream position for a later putback operation, overwriting a possibly existing prior putback mark.

The DcmObject read methods rely on the possibility to putback up to 132 bytes for transfer syntax detection, parse error recovery etc. Implementations of this class should guarantee a putback capability of at least 1 kbyte.

maxNestingDepth()

Sint32 DcmInputStream::maxNestingDepth

(

)

const

returns the maximum permitted sequence nesting depth for this stream.

A value of 0 means the compile-time default (DCMTK_MAX_SEQUENCE_NESTING) applies. A value of -1 means the check is disabled (unlimited nesting).

Returns

maximum nesting depth setting

nestingDepth()

Uint32 DcmInputStream::nestingDepth

(

)

const

returns the current sequence nesting depth.

This counter is used to prevent stack overflow from deeply nested DICOM sequences in malicious input files.

Returns

current nesting depth

newFactory()

virtual DcmInputStreamFactory * DcmInputStream::newFactory ( ) const

pure virtual

creates a new factory object for the current stream and stream position.

When activated, the factory will be able to create new DcmInputStream delivering the same data as the current stream. Used to defer loading of value fields until accessed. If no factory object can be created (e.g. because the stream is not seekable), returns NULL.

Returns

pointer to new factory object if successful, NULL otherwise.

Implemented in DcmInputBufferStream, DcmInputFileStream, and DcmStdinStream.

putback()

virtual void DcmInputStream::putback ( )

virtual

resets the stream to the position previously marked with setPutbackMark().

If the putback operation fails (no putback mark set or putback buffer exceeded), status of the producer switches to bad.

read()

virtual offile_off_t DcmInputStream::read ( void * buf, offile_off_t buflen )

virtual

reads as many bytes as possible into the given block.

Parameters

buf	pointer to memory block, must not be NULL
buflen	length of memory block

Returns

number of bytes actually read.

setMaxNestingDepth()

void DcmInputStream::setMaxNestingDepth

(

Sint32

maxDepth

)

sets the maximum permitted sequence nesting depth for this stream.

Must be called before parsing begins.

• Value 0 (default): apply the compile-time default (DCMTK_MAX_SEQUENCE_NESTING, default is 64)
• Value -1: disable the check (allow unlimited nesting)
• Value > 0: use this value as the maximum permitted nesting depth

  Parameters

  maxDepth

  maximum nesting depth setting

skip()

virtual offile_off_t DcmInputStream::skip ( offile_off_t skiplen )

virtual

skips over the given number of bytes (or less)

Parameters

skiplen

number of bytes to skip

Returns

number of bytes actually skipped.

status()

virtual OFCondition DcmInputStream::status ( ) const

virtual

returns the status of the stream as an OFCondition object.

Unless the status is good, the stream will not permit any operation.

Returns

status, EC_Normal if good

tell()

virtual offile_off_t DcmInputStream::tell ( ) const

virtual

returns the total number of bytes read from the stream so far

Returns

total number of bytes read from the stream

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The documentation for this class was generated from the following file:

• dcmdata/include/dcmtk/dcmdata/dcistrma.h