decompress.h File Reference

Lowest-level decompression routines. More...

#include <LDT/APD.h>
#include <stdlib.h>
#include <stdio.h>

Typedefs
typedef struct QSEC_decompression_	QSEC_decompression
	Declaration of the opaque decompression structure.
Functions
void	QSEC_clearDecompression (QSEC_decompression *dcm)
	Clear the decompression structrure of any data from a previous cycle.
QSEC_decompression *	QSEC_constructDecompression (void *buffer, unsigned int nbits, const char *name)
	Initialise the buffer as a decompression structure.
unsigned int	QSEC_decompress (QSEC_decompression *dcm, APD_dtx *dtx)
	Decode the next APE-encoded symbol.
int	QSEC_decompressH (QSEC_decompression *dcm, const unsigned int *buff, unsigned int *posn)
	Decode the next Huffman-encoded symbol.
void	QSEC_deleteDecompression (QSEC_decompression *dcm)
	Free the memory associated with the decompression structure.
unsigned int	QSEC_getCount (QSEC_decompression *dcm)
	Return the 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.
void	QSEC_reportDecompression (QSEC_decompression *dcm, FILE *fp)
	Describe the contents of the decompression structure in formatted ASCII sent to the file fp.
size_t	QSEC_sizeofDecompression (unsigned int nbits)
	Calculate the total size required to accomodate a decompression structure.
const unsigned int *	QSEC_unpack (QSEC_decompression *dcm, const unsigned int *buf)
	Unpack a histogram used for APE encoding.
const unsigned int *	QSEC_unpackH (QSEC_decompression *dcm, const unsigned int *buf)
	Unpack a table used for Huffman encoding.

---

Detailed Description

Lowest-level decompression routines.

Author:

James Swain & Owen Saxton

Id

decompress.h,v 1.5 2011/03/28 19:32:29 saxton Exp

---

Function Documentation

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

References QSEC_decompression_::desc, QSEC_decompression_::freq, QSEC_decompression_::nbits, QSEC_decompression_::rvlu, and QSEC_decompression_::table.

Referenced by QSEC_clearExpansion().

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

References QSEC_decompression_::desc, QSEC_decompression_::freq, QSEC_decompression_::hdd, QSEC_decompression_::name, QSEC_decompression_::nbits, QSEC_decompression_::rvlu, and QSEC_decompression_::table.

Referenced by addDcm(), and QSEC_newDecompression().

unsigned int QSEC_decompress	(	QSEC_decompression *	dcm,
		APD_dtx *	dtx
	)

Decode the next APE-encoded symbol.

Parameters:

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

Returns:

The next symbol

References QSEC_decompression_::rvlu, and QSEC_decompression_::table.

Referenced by decodeCalMeans(), and decodeShorts().

int QSEC_decompressH	(	QSEC_decompression *	dcm,
		const unsigned int *	buff,
		unsigned int *	posn
	)

Decode the next Huffman-encoded symbol.

Parameters:

	dcm	Pointer to an initialsed, populated and processed decompression structure.
	buff	Pointer to the buffer being decoded.
	posn	Pointer to the current bit position in the buffer. Is updated by this routine.

Returns:

The next symbol, which may be negative.

References QSEC_decompression_::hdd.

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

References QSEC_decompression_::desc.

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

References QSEC_constructDecompression(), and QSEC_sizeofDecompression().

void QSEC_reportDecompression	(	QSEC_decompression *	dcm,
		FILE *	fp
	)

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

Parameters:

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

References calc_nbits(), QSEC_decompression_::desc, QSEC_decompression_::freq, QSEC_decompression_::name, QSEC_decompression_::nbits, QSEC_decompression_::rvlu, and QSEC_decompression_::table.

Referenced by QSEC_reportExpansion().

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

Referenced by addDcm(), QSEC_newDecompression(), and QSEC_sizeofExpansion().

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

Unpack a histogram used for APE encoding.

This routine build the necessary lookup and freqency tables by 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

References QSEC_decompression_::desc, QSEC_decompression_::freq, getwrd(), QSEC_decompression_::nbits, QSEC_decompression_::rvlu, and QSEC_decompression_::table.

Referenced by recoverUserAcd(), recoverUserCal(), recoverUserGem(), and recoverUserTkr().

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

Unpack a table used for Huffman encoding.

This routine build the necessary tables by 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

References QSEC_decompression_::hdd.

Referenced by recoverUserCal().