DcmRLEEncoder Class Reference

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

List of all members.

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
DcmRLEEncoder &	operator= (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_.

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Detailed Description

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

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

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Constructor & Destructor Documentation

DcmRLEEncoder::DcmRLEEncoder

(

int

doPad

)

[inline]

default constructor

Parameters:

doPad

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

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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:

ch	byte to be added

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:

buf	buffer to be added
bufcount	number of bytes in buffer

OFBool DcmRLEEncoder::fail

(

)

const [inline]

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

In this case, no output has been created.

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.

void DcmRLEEncoder::move

(

size_t

numberOfBytes

)

[inline, private]

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

Parameters:

numberOfBytes

number of bytes to copy

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

void DcmRLEEncoder::write

(

void *

target

)

const [inline]

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

Parameters:

target

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

void DcmRLEEncoder::write

(

DcmEncoderOutputStream &

os

)

const [inline]

copies the compressed RLE byte stream into an output stream

Parameters:

os	output stream

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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.

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

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.

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.

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

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

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

• dcmdata/include/dcmtk/dcmdata/dcrleenc.h