@ -8,8 +8,8 @@
*
* Entry routines :
*
* bool
* pglz_compress ( const char * source , int32 slen , PGLZ_Heade r* dest ,
* int32
* pglz_compress ( const char * source , int32 slen , cha r* dest ,
* const PGLZ_Strategy * strategy ) ;
*
* source is the input data to be compressed .
@ -23,44 +23,43 @@
* the compression algorithm . If NULL , the compiled
* in default strategy is used .
*
* The return value is TRUE if compression succeeded ,
* FALSE if not ; in the latter case the contents of dest
* are undefined .
* The return value is the number of bytes written in the
* buffer dest , or - 1 if compression fails ; in the latter
* case the contents of dest are undefined .
*
* void
* pglz_decompress ( const PGLZ_Header * source , char * dest )
* int32
* pglz_decompress ( const char * source , int32 slen , char * dest ,
* int32 rawsize )
*
* source is the compressed input .
*
* slen is the length of the compressed input .
*
* dest is the area where the uncompressed data will be
* written to . It is the callers responsibility to
* provide enough space . The required amount can be
* obtained with the macro PGLZ_RAW_SIZE ( source ) .
* provide enough space .
*
* The data is written to buff exactly as it was handed
* to pglz_compress ( ) . No terminating zero byte is added .
*
* The decompression algorithm and internal data format :
* rawsize is the length of the uncompressed data .
*
* PGLZ_Header is defined as
* The return value is the number of bytes written in the
* buffer dest , or - 1 if decompression fails .
*
* typedef struct PGLZ_Header {
* int32 vl_len_ ;
* int32 rawsize ;
* }
* The decompression algorithm and internal data format :
*
* The header is followed by the compressed data itself .
* It is made with the compressed data itself .
*
* The data representation is easiest explained by describing
* the process of decompression .
*
* If VARSIZE ( x ) = = rawsize + sizeof ( PGLZ_Header ) , then the data
* If compressed_size = = rawsize , then the data
* is stored uncompressed as plain bytes . Thus , the decompressor
* simply copies rawsize bytes from the location after the
* header to the destination .
* simply copies rawsize bytes to the destination .
*
* Otherwise the first byte after the header tells what to do
* the next 8 times . We call this the control byte .
* Otherwise the first byte tells what to do the next 8 times .
* We call this the control byte .
*
* An unset bit in the control byte means , that one uncompressed
* byte follows , which is copied from input to output .
@ -169,14 +168,18 @@
*
* Copyright ( c ) 1999 - 2015 , PostgreSQL Global Development Group
*
* src / backend / utils / adt / pg_lzcompress . c
* src / common / pg_lzcompress . c
* - - - - - - - - - -
*/
# ifndef FRONTEND
# include "postgres.h"
# else
# include "postgres_fe.h"
# endif
# include <limits.h>
# include "utils /pg_lzcompress.h"
# include "common /pg_lzcompress.h"
/* ----------
@ -492,14 +495,15 @@ pglz_find_match(int16 *hstart, const char *input, const char *end,
/* ----------
* pglz_compress -
*
* Compresses source into dest using strategy .
* Compresses source into dest using strategy . Returns the number of
* bytes written in buffer dest , or - 1 if compression fails .
* - - - - - - - - - -
*/
bool
pglz_compress ( const char * source , int32 slen , PGLZ_Heade r* dest ,
int32
pglz_compress ( const char * source , int32 slen , cha r* dest ,
const PGLZ_Strategy * strategy )
{
unsigned char * bp = ( ( unsigned char * ) dest ) + sizeof ( PGLZ_Header ) ;
unsigned char * bp = ( unsigned char * ) dest ;
unsigned char * bstart = bp ;
int hist_next = 1 ;
bool hist_recycle = false ;
@ -533,12 +537,7 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
if ( strategy - > match_size_good < = 0 | |
slen < strategy - > min_input_size | |
slen > strategy - > max_input_size )
return false ;
/*
* Save the original source size in the header .
*/
dest - > rawsize = slen ;
return - 1 ;
/*
* Limit the match parameters to the supported range .
@ -611,7 +610,7 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
* allow 4 slop bytes .
*/
if ( bp - bstart > = result_max )
return false ;
return - 1 ;
/*
* If we ' ve emitted more than first_success_by bytes without finding
@ -620,7 +619,7 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
* pre - compressed data ) .
*/
if ( ! found_match & & bp - bstart > = strategy - > first_success_by )
return false ;
return - 1 ;
/*
* Try to find a match in the history
@ -664,35 +663,34 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
* ctrlp = ctrlb ;
result_size = bp - bstart ;
if ( result_size > = result_max )
return false ;
/*
* Success - need only fill in the actual length of the compressed datum .
*/
SET_VARSIZE_COMPRESSED ( dest , result_size + sizeof ( PGLZ_Header ) ) ;
return - 1 ;
return true ;
/* success */
return result_size ;
}
/* ----------
* pglz_decompress -
*
* Decompresses source into dest .
* Decompresses source into dest . Returns the number of bytes
* decompressed in the destination buffer , or - 1 if decompression
* fails .
* - - - - - - - - - -
*/
void
pglz_decompress ( const PGLZ_Header * source , char * dest )
int32
pglz_decompress ( const char * source , int32 slen , char * dest ,
int32 rawsize )
{
const unsigned char * sp ;
const unsigned char * srcend ;
unsigned char * dp ;
unsigned char * destend ;
sp = ( ( const unsigned char * ) source ) + sizeof ( PGLZ_Header ) ;
srcend = ( ( const unsigned char * ) source ) + VARSIZE ( sourc e) ;
sp = ( const unsigned char * ) source ;
srcend = ( ( const unsigned char * ) source ) + sl en ;
dp = ( unsigned char * ) dest ;
destend = dp + source - > rawsize ;
destend = dp + rawsize ;
while ( sp < srcend & & dp < destend )
{
@ -771,9 +769,10 @@ pglz_decompress(const PGLZ_Header *source, char *dest)
* Check we decompressed the right amount .
*/
if ( dp ! = destend | | sp ! = srcend )
elog ( ERROR , " compressed data is corrupt " ) ;
return - 1 ;
/*
* That ' s it .
*/
return rawsize ;
}
Fujii Masao
11 years ago