Doxygen Page for QSEC / V3-1-1 / qsec / linux-gcc

#include "decompress_p.h"
#include "LDT/APM.h"
#include <string.h>
#include <math.h>


Functions
static const unsigned *	getwrd (const unsigned buffer, unsigned bcnt, unsigned *word, unsigned nbits)
	Get bits from a buffer.
double	calc_nbits (const int *f, int cnt, int tot)
	Calculate the number of bits need to encode a sample with the specified frequency distribution.
size_t	QSEC_sizeofDecompression (unsigned int nbits)
	Calculate the total size required to accomodate a decompression structure.
QSEC_decompression *	QSEC_constructDecompression (void buffer, unsigned int nbits, const char name)
	Initialise the buffer as a decompression structure.
QSEC_decompression *	QSEC_newDecompression (unsigned int nbits, const char *name)
	Allocate and initialise a new decompression structure.
void	QSEC_deleteDecompression (QSEC_decompression *dcm)
	Free the memory associated with the decompression structure.
void	QSEC_clearDecompression (QSEC_decompression *dcm)
	Clear the decompression structrure of any data from a previous cycle.
unsigned int	QSEC_getCount (QSEC_decompression *dcm)
	Return the number of non-zero bins in the histogram.
const unsigned int *	QSEC_unpack (QSEC_decompression dcm, const unsigned int buffer)
	Build the lookup and freqency tables by retrieving and unpacking data from the consignment.
unsigned	QSEC_decompress (QSEC_decompression dcm, APD_dtx dtx)
	Decode the next symbol.
void	QSEC_reportDecompression (QSEC_decompression dcm, FILE fp)
	Describe the contents of the decompression structure in formatted ASCII send to the file fp.

Detailed Description

Function Documentation

double calc_nbits	(	const int *	f,
		int	cnt,
		int	tot
	)

Calculate the number of bits need to encode a sample with the specified frequency distribution.

This is based on the following formula

nbits = - TOT * SUM [ f[i] / TOT * ln (f[i] / TOT) ] = - TOT/TOT * SUM [ f[i] * (ln (f[i]) - ln (TOT)) ] = - SUM [ f[i] * ln (f[i] ] + SUM [ f[i] * ln (TOT) ] = - SUM [ f[i] * ln (f[i] ] + TOT * ln (TOT) ]

Parameters:

	f	The frequency distribution
	cnt	The count of entries in the frequency distribution
	tot	The total number of entries in the frequency distribution

const unsigned * getwrd	(	const unsigned *	buffer,
		unsigned *	bcnt,
		unsigned *	word,
		unsigned	nbits
	)			`[inline, static]`

Get bits from a buffer.

Parameters:

	buffer	Pointer to the current word in the buffer
	bcnt	Number of bits already used in the current word
	word	Word to add to the buffer
	nbits	Number of bits from the word to add to the buffer

Returns:: Pointer to the next word to use in the buffer

void QSEC_clearDecompression ( QSEC_decompression * dcm )

Clear the decompression structrure of any data from a previous cycle.

Parameters:

dcm

Pointer to an allocated, initialised, decompression structure

QSEC_decompression* QSEC_constructDecompression	(	void *	buffer,
		unsigned int	nbits,
		const char *	name
	)

Initialise the buffer as a decompression structure.

Parameters:

	buffer	Pointer to the uninitialised memory to use for this decompression structure
	nbits	Number of bits in the symbols to be handled by this decompression strcuture
	name	String identifying this structure

Returns:: Pointer to an initialised decompression structure

unsigned QSEC_decompress	(	QSEC_decompression *	dcm,
		APD_dtx *	dtx
	)

Decode the next symbol.

Parameters:

	dcm	Pointer to an initialsed, populated and processed decompression structure
	dtx	Pointer to the arithmetic encoder context

Returns:: The next symbol

void QSEC_deleteDecompression ( QSEC_decompression * dcm )

Free the memory associated with the decompression structure.

Parameters:

dcm

Pointer to an allocated decompression structure

unsigned int QSEC_getCount ( QSEC_decompression * dcm )

Return the number of non-zero bins in the histogram.

Parameters:

dcm

Pointer to a decompression structure

Returns:: Number of non-zero bins in the histogram

QSEC_decompression* QSEC_newDecompression	(	unsigned int	nbits,
		const char *	name
	)

Allocate and initialise a new decompression structure.

Parameters:

	name	String used in the reporting of error to identify a decompression structure
	nbits	Number of symbols in the complete range of possible symbols (including excluded internal sub-ranges), hence the number of bins in the histogram and frequency tables

Returns:: Pointer to an allocated and initialised QSEC_decompression structure

void QSEC_reportDecompression	(	QSEC_decompression *	dcm,
		FILE *	fp
	)

Describe the contents of the decompression structure in formatted ASCII send to the file fp.

Parameters:

	dcm	Pointer to the decompression structure
	fp	Pointer to the file used as the destination

size_t QSEC_sizeofDecompression ( unsigned int nbits )

Calculate the total size required to accomodate a decompression structure.

Parameters:

nbits

Number of symbols in the complete range of possible symbols (including excluded internal sub-ranges), hence the number of bins in the histogram and frequency tables

Returns:: Size of memory block required to accomodate a decompression structure

const unsigned int* QSEC_unpack	(	QSEC_decompression *	dcm,
		const unsigned int *	buffer
	)

Build the lookup and freqency tables by retrieving and unpacking data from the consignment.

Parameters:

	dcm	Pointer to an initialsed decompression structure
	buffer	Pointer to the start of the buffer holding the packed structure

Returns:: Pointer to the next input location or NULL if there is an error in the unpacking

decompress.c File Reference

Functions

Detailed Description

Function Documentation