OFFIS DCMTK  Version 3.6.0
Public Member Functions | Private Member Functions | Private Attributes | List of all members
DcmRLEEncoder Class Reference

this class implements an RLE compressor conforming to the DICOM standard. More...

Collaboration diagram for DcmRLEEncoder:
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Public Member Functions

 DcmRLEEncoder (int doPad)
 default constructor
 
 ~DcmRLEEncoder ()
 destructor
 
void add (unsigned char ch)
 this method adds one byte to the byte stream to be compressed with the RLE compressor.
 
void add (const unsigned char *buf, size_t bufcount)
 this method adds a block of bytes to the byte stream to be compressed with the RLE compressor.
 
void flush ()
 this method finalizes the compressed RLE stream, i.e.
 
size_t size () const
 returns the size of compressed RLE stream in bytes.
 
OFBool fail () const
 returns true if the RLE compressor has run out of memory.
 
void write (void *target) const
 copies the compressed RLE byte stream into a target array of at least size() bytes.
 
void write (DcmEncoderOutputStream &os) const
 copies the compressed RLE byte stream into an output stream
 

Private Member Functions

 DcmRLEEncoder (const DcmRLEEncoder &)
 private undefined copy constructor
 
DcmRLEEncoderoperator= (const DcmRLEEncoder &)
 private undefined copy assignment operator
 
void move (size_t numberOfBytes)
 this method moves the given number of bytes from buff_ to currentBlock_ and "flushes" currentBlock_ to blockList_ if necessary.
 

Private Attributes

int fail_
 this flag indicates a failure of the RLE codec.
 
int pad_
 this flag indicates whether the RLE codec must pad encoded data to an even number of bytes (as required by DICOM).
 
unsigned char * currentBlock_
 this member points to a block of size DcmRLEEncoder_BLOCKSIZE (unless fail_ is true).
 
size_t offset_
 contains the number of bytes already written the the memory block pointed to by currentBlock_.
 
OFList< unsigned char * > blockList_
 this member contains a list of memory blocks of size DcmRLEEncoder_BLOCKSIZE which already have been filled with encoded RLE data.
 
unsigned char * RLE_buff_
 this member points to a buffer of 132 bytes that is used by the RLE encoding algorithm.
 
int RLE_prev_
 value of the last byte fed to the RLE compressor.
 
int RLE_pcount_
 repeat counter, for RLE compressor may temporarily become negative, guaranteed to be >= 0 between method calls.
 
unsigned int RLE_bindex_
 index of next unused byte in RLE_buff_.
 

Detailed Description

this class implements an RLE compressor conforming to the DICOM standard.

The class is loosely based on an implementation by Phil Norman.

Definition at line 64 of file dcrleenc.h.

Constructor & Destructor Documentation

DcmRLEEncoder::DcmRLEEncoder ( int  doPad)
inline

default constructor

Parameters
doPadif true, RLE codec will pad output data to even number of bytes

Definition at line 71 of file dcrleenc.h.

References currentBlock_, fail_, and RLE_buff_.

Member Function Documentation

void DcmRLEEncoder::add ( unsigned char  ch)
inline

this method adds one byte to the byte stream to be compressed with the RLE compressor.

Parameters
chbyte to be added

Definition at line 104 of file dcrleenc.h.

References fail_, move(), RLE_bindex_, RLE_buff_, RLE_pcount_, and RLE_prev_.

Referenced by add().

void DcmRLEEncoder::add ( const unsigned char *  buf,
size_t  bufcount 
)
inline

this method adds a block of bytes to the byte stream to be compressed with the RLE compressor.

Parameters
bufbuffer to be added
bufcountnumber of bytes in buffer

Definition at line 181 of file dcrleenc.h.

References add().

OFBool DcmRLEEncoder::fail ( ) const
inline

returns true if the RLE compressor has run out of memory.

In this case, no output has been created.

Definition at line 266 of file dcrleenc.h.

References fail_.

void DcmRLEEncoder::flush ( )
inline

this method finalizes the compressed RLE stream, i.e.

flushes all pending literal or repeat runs. This method can be called at any time; however, it must be called before size() or write() can be used. Intermediate calls should be avoided since they possibly decrease the compression ratio.

Definition at line 195 of file dcrleenc.h.

References fail_, move(), RLE_bindex_, RLE_buff_, RLE_pcount_, and RLE_prev_.

void DcmRLEEncoder::move ( size_t  numberOfBytes)
inlineprivate

this method moves the given number of bytes from buff_ to currentBlock_ and "flushes" currentBlock_ to blockList_ if necessary.

Parameters
numberOfBytesnumber of bytes to copy

Definition at line 346 of file dcrleenc.h.

References blockList_, currentBlock_, fail_, offset_, OFList< T >::push_back(), and RLE_buff_.

Referenced by add(), and flush().

size_t DcmRLEEncoder::size ( ) const
inline

returns the size of compressed RLE stream in bytes.

The size is guaranteed to be an even number of bytes (padded with a trailing zero byte as required by DICOM if necessary). This method may only be called after flush() has been executed to finalize the compressed stream.

Returns
size of compressed stream, in bytes

Definition at line 256 of file dcrleenc.h.

References blockList_, offset_, pad_, and OFList< T >::size().

void DcmRLEEncoder::write ( void *  target) const
inline

copies the compressed RLE byte stream into a target array of at least size() bytes.

Parameters
targetpointer to array of at least size() bytes, must not be NULL.

Definition at line 275 of file dcrleenc.h.

References OFList< T >::begin(), blockList_, currentBlock_, OFList< T >::end(), fail_, offset_, pad_, and OFList< T >::size().

void DcmRLEEncoder::write ( DcmEncoderOutputStream os) const
inline

copies the compressed RLE byte stream into an output stream

Parameters
osoutput stream

Definition at line 308 of file dcrleenc.h.

References OFList< T >::begin(), blockList_, currentBlock_, OFList< T >::end(), fail_, offset_, pad_, OFList< T >::size(), and DcmEncoderOutputStream::write().

Member Data Documentation

OFList<unsigned char *> DcmRLEEncoder::blockList_
private

this member contains a list of memory blocks of size DcmRLEEncoder_BLOCKSIZE which already have been filled with encoded RLE data.

The current block (pointed to by currentBlock_) is not contained in this list.

Definition at line 397 of file dcrleenc.h.

Referenced by move(), size(), write(), and ~DcmRLEEncoder().

unsigned char* DcmRLEEncoder::currentBlock_
private

this member points to a block of size DcmRLEEncoder_BLOCKSIZE (unless fail_ is true).

This is the current block of data to which the RLE stream is written

Definition at line 385 of file dcrleenc.h.

Referenced by DcmRLEEncoder(), move(), write(), and ~DcmRLEEncoder().

int DcmRLEEncoder::fail_
private

this flag indicates a failure of the RLE codec.

Once a failure is flagged, the codec will consume all input and not produce any more output. A failure status can only be caused by an out-of-memory condition.

Definition at line 373 of file dcrleenc.h.

Referenced by add(), DcmRLEEncoder(), fail(), flush(), move(), and write().

size_t DcmRLEEncoder::offset_
private

contains the number of bytes already written the the memory block pointed to by currentBlock_.

Value is always less than DcmRLEEncoder_BLOCKSIZE.

Definition at line 391 of file dcrleenc.h.

Referenced by move(), size(), and write().

int DcmRLEEncoder::pad_
private

this flag indicates whether the RLE codec must pad encoded data to an even number of bytes (as required by DICOM).

True if padding is required, false otherwise

Definition at line 379 of file dcrleenc.h.

Referenced by size(), and write().

int DcmRLEEncoder::RLE_prev_
private

value of the last byte fed to the RLE compressor.

This byte is not yet stored in the RLE_buff_ buffer. Type is int because this allows an "impossible" -1 as default value

Definition at line 408 of file dcrleenc.h.

Referenced by add(), and flush().


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


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