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GLAST / LAT > DAQ and FSW > FSW > Doxygen Index> LDT / V0-5-0 > encdec / linux-gcc

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HDD.c File Reference

Implementation ofthe routines to decode a distribution of symbols previously encoded using HDE_encodeSS. More...

#include "LDT/HDD.h"
#include "LDT/HUFF.h"
#include "LDT/BFU.h"
#include "ffs.h"
#include "PBI/Endianness.h"
#include "dprintf.h"

Classes
struct	_HDD
union	_DeltaInfo_bf
	Union of the delta information word as (signed) bit fields. More...
union	_DeltaInfo
	Union of the delta information word as an interpretted 32-bit integer and its (signed) bit fields. More...
Defines
#define	_CV_TO_CODETREE(_0, _1, _2)   ((_2 << 4) | (_1 << 2) | (_0 << 0))
#define	_CODES(_c0, _c1, _c2)   ((_c2 << 4) | (_c1 << 2) | (_c0 << 0))
Typedefs
typedef struct _HDD	HDD
typedef struct _DeltaInfo_bf	DeltaInfo_bf
	Typedef for union _DeltaInfo_bf.
typedef union _DeltaInfo	DeltaInfo
	Typedef for union _DeltaInfo.
Functions
static __inline BFU	unpack_short (BFU bfu, const unsigned int *src, int *val)
static __inline BFU	unpack_nshort (BFU bfu, const unsigned int *src, int *val)
static __inline BFU	unpack_ushort (BFU bfu, const unsigned int *src, unsigned int *val)
static __inline BFU	unpack_delta_min_max_seed (BFU bfu, const unsigned int *src, int *delta_min, int *delta_max, unsigned int *seed)
static __inline void	fill_code_lens (unsigned char *lens, int nlens, unsigned int seed, int delta)
	Routine to form the code length when all the deltas are the same.
static __inline BFU	unpack_code_lens1 (unsigned char *lens, int nlens, unsigned int seed, int min, const unsigned int *src, unsigned int max, BFU bfu)
	Optimized routine to unpack the deltas and form the code length array when the deltas are all 0s or 1s.
static __inline BFU	unpack_code_lens2 (unsigned char *lens, int nlens, unsigned int seed, int min, const unsigned int *src, unsigned int max, BFU bfu)
	Optimized routine to unpack the deltas and form the code length array when the deltas ranges is 2 (0,1,2).
static __inline BFU	unpack_code_lensN (unsigned char *lens, int nlens, unsigned int seed, int delta_min, int delta_max, const unsigned int *src, unsigned int max, BFU bfu, HUFF_dtable *dtable)
	Generic routine to unpack the deltas and form the code length array when the deltas are themselves encoded as a Huffman table The routines unpack_deltas1 and deltas2 are used when the range of the huffman encoding table is only 1 (2 symbols) or 2 (3 symbols) In these cases, a more optimal scheme, tailored to these small tables is used.
static __inline BFU	unpack_code_lens (unsigned char *lens, int nlens, const unsigned int *src, unsigned int max, BFU bfu, HUFF_dtable *dtable)
	Dispatch routine to unpack the deltas and form the code length array when the deltas are themselves encoded as a Huffman table.
static __inline BFU	unpack_syms (signed short int *syms, int nsyms, const HUFF_dtable *dtable, int nlens, int min, unsigned int nunderflow, unsigned int noverflow, const unsigned int *src, unsigned int max_pos, BFU bfu)
	Restores the differences between the original PHA value and its pedestal.
unsigned int	HDD_sizeof (unsigned int nhuff)
	Returns the size, in bytes, for a handle to hold a Huffman distribution of huffman_bins.
void *	HDD_construct (HDD *hdd, unsigned int nhuff)
	Constructs (initializes) the specified HDD structure.
unsigned int	HDD_tableDecode (HDD *hdd, const unsigned int *src, unsigned int pos, unsigned int max_pos)
	Unpacks the table encoded with HDE_tableEncode.
unsigned int	HDD_symbolsDecodeS (HDD *hdd, const unsigned int *src, unsigned int pos, unsigned int max_pos, short *syms, unsigned int nsyms)
	Unpacks the distribution encoded with HDD_symbolsEncodeS.
unsigned int	HDD_decodeS (HDD *hdd, const unsigned int *src, unsigned int pos, unsigned int max_pos, short *syms, unsigned int nsyms)
	Unpacks the distribution encoded with HDD_encodeSS.

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Detailed Description

Implementation ofthe routines to decode a distribution of symbols previously encoded using HDE_encodeSS.

Author:

JJRussell - russell@slac.stanford.edu

   CVS $Id: HDD.c,v 1.10 2010/08/23 16:32:41 saxton Exp $

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Typedef Documentation

DeltaInfo_bf

Typedef for union _DeltaInfo_bf.

The advantage of defining these structures is that it allows the compiler to sign-extend the bit fields where needed.

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Function Documentation

static __inline BFU fill_code_lens	(	unsigned char *	lens,
		int	nlens,
		unsigned int	seed,
		int	delta
	)			[static]

Routine to form the code length when all the deltas are the same.

Parameters:

	lens	The array of code lengths to fill in
	nlens	The number of lengths to fill in
	seed	The starting value to integrate the deltas from
	delta	The delta length

void* HDD_construct	(	HDD *	hdd,
		unsigned int	nhuff
	)

Constructs (initializes) the specified HDD structure.

Returns:

The next address after this structure.

Parameters:

	hdd	The HDD control structure to construct
	nhuff	The maximum number of Huffman encoding bins that this control structure is meant to support.

The size of this structure should be acquired by a call to HDD_sizeof. The parameter huffman_nbins must be the same in the call to HDD_sizeof and HDD_construct.

unsigned int HDD_decodeS	(	HDD *	hdd,
		const unsigned int *	src,
		unsigned int	pos,
		unsigned int	max_pos,
		short *	syms,
		unsigned int	nsyms
	)

Unpacks the distribution encoded with HDD_encodeSS.

Returns:

The next bit position to read.

Parameters:

	hdd	The decode handle
	src	The source stream
	pos	The current bit read position
	max_pos	The maximum bit position, i.e. do not read past this point
	syms	The array to receive the decoded symbols
	nsyms	The number of symbols to decode

unsigned int HDD_sizeof

(

unsigned int

nhuff

)

Returns the size, in bytes, for a handle to hold a Huffman distribution of huffman_bins.

Parameters:

nhuff

The maximum number of Huffman codes

For the most part, this only provides a working area. On host-based workstations with expandable stacks, this memory would go on the stack, except for the fact that it is variable length.

unsigned int HDD_symbolsDecodeS	(	HDD *	hdd,
		const unsigned int *	src,
		unsigned int	pos,
		unsigned int	max_pos,
		short *	syms,
		unsigned int	nsyms
	)

Unpacks the distribution encoded with HDD_symbolsEncodeS.

Returns:

The next bit position to read.

Parameters:

	hdd	The decode handle
	src	The source stream
	pos	The current bit read position
	max_pos	The maximum bit position, i.e. do not read past this point
	syms	The array to receive the decoded symbols
	nsyms	The number of symbols to decode

unsigned int HDD_tableDecode	(	HDD *	hdd,
		const unsigned int *	src,
		unsigned int	pos,
		unsigned int	max_pos
	)

Unpacks the table encoded with HDE_tableEncode.

Returns:

The next bit position to read.

Parameters:

	hdd	The decode handle
	src	The source stream
	pos	The current bit read position
	max_pos	The maximum bit position, i.e. do not read past this point

static __inline BFU unpack_code_lens	(	unsigned char *	lens,
		int	nlens,
		const unsigned int *	src,
		unsigned int	max,
		BFU	bfu,
		HUFF_dtable *	dtable
	)			[static]

Dispatch routine to unpack the deltas and form the code length array when the deltas are themselves encoded as a Huffman table.

Returns:

The updated bit position and current deblocked 32-bit buffer

Parameters:

	lens	The array of code lengths to fill in
	nlens	The number of lengths to fill in
	src	The data source, i.e. the bit stream
	max	The maximum bit position
	bfu	The current bit position and temporary buffer
	dtable	Temporary storage to hold the huffman decode table for the lengths

static __inline BFU unpack_code_lens1	(	unsigned char *	lens,
		int	nlens,
		unsigned int	seed,
		int	min,
		const unsigned int *	src,
		unsigned int	max,
		BFU	bfu
	)			[static]

Optimized routine to unpack the deltas and form the code length array when the deltas are all 0s or 1s.

Returns:

The updated bit position and current deblocked 32-bit buffer

Parameters:

	lens	The array of code lengths to fill in
	nlens	The number of lengths to fill in
	seed	The starting value to integrate the deltas from
	min	The minimum delta, this is almost certainly 0, but..
	src	The data source, i.e. the bit stream
	max	The maximum bit position
	bfu	The current bit position and temporary buffer

This routine starts at the mid point and works its way first down to the code length 0, then restarts and works its way up to the last code length. In each case the deltas are integrated starting with the seed value

static __inline BFU unpack_code_lens2	(	unsigned char *	lens,
		int	nlens,
		unsigned int	seed,
		int	min,
		const unsigned int *	src,
		unsigned int	max,
		BFU	bfu
	)			[static]

Optimized routine to unpack the deltas and form the code length array when the deltas ranges is 2 (0,1,2).

Returns:

The updated bit position and current deblocked 32-bit buffer

Parameters:

	lens	The array of code lengths to fill in
	nlens	The number of lengths to fill in
	seed	The starting value to integrate the deltas from
	min	The minimum delta, this is almost certainly -1 or 0
	src	The data source, i.e. the bit stream
	max	The maximum bit position
	bfu	The current bit position and temporary buffer

This routine starts at the mid point and works its way first down to the code length 0, then restarts and works its way up to the last code length. In each case the deltas are integrated starting with the seed value

static __inline BFU unpack_code_lensN	(	unsigned char *	lens,
		int	nlens,
		unsigned int	seed,
		int	delta_min,
		int	delta_max,
		const unsigned int *	src,
		unsigned int	max,
		BFU	bfu,
		HUFF_dtable *	dtable
	)			[static]

Generic routine to unpack the deltas and form the code length array when the deltas are themselves encoded as a Huffman table The routines unpack_deltas1 and deltas2 are used when the range of the huffman encoding table is only 1 (2 symbols) or 2 (3 symbols) In these cases, a more optimal scheme, tailored to these small tables is used.

Returns:

The updated bit position and current deblocked 32-bit buffer

Parameters:

	lens	The array of code lengths to fill in
	nlens	The number of lengths to fill in
	delta_min	The minimum delta value
	delta_max	The maximum delta value
	seed	The starting value to integrate the deltas from
	src	The data source, i.e. the bit stream
	max	The maximum bit position
	bfu	The current bit position and temporary buffer
	dtable	Temporary storage to hold the huffman decode table for the lengths. While this is returned to the caller, its purpose, to extract the lengths of the codes, has already been served.

static __inline BFU unpack_syms	(	signed short int *	syms,
		int	nsyms,
		const HUFF_dtable *	dtable,
		int	nlens,
		int	min,
		unsigned int	nunderflow,
		unsigned int	noverflow,
		const unsigned int *	src,
		unsigned int	max_pos,
		BFU	bfu
	)			[static]

Restores the differences between the original PHA value and its pedestal.

Returns:

The updated bit position and current deblocked 32-bit buffer

Parameters:

	syms	The array of symbol values, corresponding to the difference between the PHA value and its pedestal to be filled in
	nsyms	The number of symbols to decode
	dtable	The decoding table
	nlens	The number of code lengths
	min	The minimum symbol value. This is the biase that most be added to all symbols when they are decoded. It restores the symbol to its original value.
	nunderflow	The number of bins below the first HUFFman bin to be decoded
	noverflow	The number of bins above the last HUFFman bin to be decoded
	src	The data source, i.e. the bit stream
	max_pos	The maximum bit position
	bfu	The current bit position and temporary buffer

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