DCMTK: DcmZLibInputFilter Class Reference

DCMTK Version 3.6.9 OFFIS DICOM Toolkit

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Public Member Functions | Private Member Functions | Private Attributes | List of all members
DcmZLibInputFilter Class Reference

zlib compression filter for input streams More...

Inheritance diagram for DcmZLibInputFilter:

## Public Member Functions
| DcmZLibInputFilter ()
| default constructor
virtual | ~DcmZLibInputFilter ()
| destructor
virtual OFBool | good () const
| returns the status of the producer.
virtual OFCondition | status () const
| returns the status of the producer 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 void | putback (offile_off_t num)
| resets the stream to the position by the given number of bytes.
virtual void | append (DcmProducer &producer)
| determines the producer from which the filter is supposed to read it's input.
Public Member Functions inherited from DcmInputFilter
virtual | ~DcmInputFilter ()
| destructor
Public Member Functions inherited from DcmProducer
virtual | ~DcmProducer ()
| destructor

## Private Member Functions
| DcmZLibInputFilter (const DcmZLibInputFilter &)
| private unimplemented copy constructor
DcmZLibInputFilter & | operator= (const DcmZLibInputFilter &)
| private unimplemented copy assignment operator
offile_off_t | fillInputBuffer ()
| reads data from the producer into the input ring buffer until the input ring buffer becomes full or the producer suspends
offile_off_t | decompress (const void *buf, offile_off_t buflen)
| decompress data into the given output block until complete or no more input is available in the input ring buffer.
void | fillOutputBuffer ()
| reads and decompresses data from the producer until the producer suspends or the output ring buffer becomes full.
void | flushOutputBuffer ()
| writes the content of the output ring buffer to the next filter stage until the output ring buffer becomes empty or the next filter stage becomes full
offile_off_t | fillInputBuffer (const void *buf, offile_off_t buflen)
| copies as much of the given block of data as possible in the input ring buffer
void | compressInputBuffer (OFBool finalize)
| feed data from the input ring buffer to the compression codec until complete or the output ring buffer becomes full.

## Private Attributes
DcmProducer * | current_
| pointer to producer from which compressed input is read
z_streamp | zstream_
| pointer to struct z_stream object containing the zlib status
OFCondition | status_
| status
OFBool | eos_
| true if the zlib object has reported Z_STREAM_END
unsigned char * | inputBuf_
| input ring buffer
offile_off_t | inputBufStart_
| offset of first byte in input ring buffer
offile_off_t | inputBufCount_
| number of bytes in input ring buffer
unsigned char * | outputBuf_
| output ring buffer
offile_off_t | outputBufStart_
| offset of first byte in output ring buffer
offile_off_t | outputBufCount_
| number of bytes available for read in output ring buffer
offile_off_t | outputBufPutback_
| number of putback bytes in output ring buffer
OFBool | padded_
| flag indicating whether or not a pad byte has been appended to the input stream

## Detailed Description

zlib compression filter for input streams

Remarks
  this class is only available if DCMTK is compiled with ZLIB support enabled.

## Member Function Documentation

## ◆ append()

virtual void DcmZLibInputFilter::append | ( | DcmProducer & | producer | ) |
| virtual

determines the producer from which the filter is supposed to read it's input.

Once a producer for the input filter has been defined, it cannot be changed anymore during the lifetime of the object.

Parameters

  producer | reference to producer, must not be circular chain

Implements DcmInputFilter.

## ◆ avail()

virtual offile_off_t DcmZLibInputFilter::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

Implements DcmProducer.

## ◆ compressInputBuffer()

void DcmZLibInputFilter::compressInputBuffer | ( | OFBool | finalize | ) |
| private

feed data from the input ring buffer to the compression codec until complete or the output ring buffer becomes full.

Does not flush the output ring buffer.

Parameters

  finalize | true if the content of the input ring buffer constitutes the end of the input stream, i.e. the compression codec should be forced to flush its internal state.

## ◆ decompress()

offile_off_t DcmZLibInputFilter::decompress | ( | const void * | buf,
|  | offile_off_t | buflen )
| private

decompress data into the given output block until complete or no more input is available in the input ring buffer.

does not re-fill the input ring buffer from the producer.

Parameters

  buf | pointer to input data
  buflen | number of bytes in buf

Returns
  number of bytes processed

## ◆ eos()

virtual OFBool DcmZLibInputFilter::eos | ( |  | ) |
| virtual

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

Returns
  true if end of stream, false otherwise

Implements DcmProducer.

## ◆ fillInputBuffer() [1/2]

offile_off_t DcmZLibInputFilter::fillInputBuffer | ( |  | ) |
| private

reads data from the producer into the input ring buffer until the input ring buffer becomes full or the producer suspends

Returns
  number of bytes added to input buffer

## ◆ fillInputBuffer() [2/2]

offile_off_t DcmZLibInputFilter::fillInputBuffer | ( | const void * | buf,
|  | offile_off_t | buflen )
| private

copies as much of the given block of data as possible in the input ring buffer

Parameters

  buf | pointer to input data
  buflen | number of bytes in buf

Returns
  number of bytes copied to input ring buffer

## ◆ good()

virtual OFBool DcmZLibInputFilter::good | ( |  | ) | const
| virtual

returns the status of the producer.

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

Returns
  status, true if good

Implements DcmProducer.

## ◆ putback()

virtual void DcmZLibInputFilter::putback | ( | offile_off_t | num | ) |
| virtual

resets the stream to the position by the given number of bytes.

Parameters

  num | number of bytes to putback. If the putback operation fails, the producer status becomes bad.

Implements DcmProducer.

## ◆ read()

virtual offile_off_t DcmZLibInputFilter::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.

Implements DcmProducer.

## ◆ skip()

virtual offile_off_t DcmZLibInputFilter::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.

Implements DcmProducer.

## ◆ status()

virtual OFCondition DcmZLibInputFilter::status | ( |  | ) | const
| virtual

returns the status of the producer as an OFCondition object.

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

Returns
  status, EC_Normal if good

Implements DcmProducer.

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

- dcmdata/include/dcmtk/dcmdata/dcistrmz.h

Generated on Wed Apr 30 2025 for DCMTK Version 3.6.9 by Doxygen 1.13.2