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GLAST/LAT > DAQ and FSW > FSW > Doxygen Index > QSEC / V2-0-0

Constituent: qsec     Tag: linux-gcc

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decompress.c File Reference

Routines used to manipulate the tables used to decode the compressed events. More...

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

Include dependency graph for decompress.c:

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.

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Detailed Description

Routines used to manipulate the tables used to decode the compressed events.

Author:

James Swain & Owen Saxton

Id

decompress.c,v 1.8 2007/04/05 23:05:17 saxton Exp

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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

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