ddidderr/zstd-rs
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stream control

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This commit is contained in:
Yann Collet
2016-01-25 04:10:46 +01:00
parent 59d1f79768
commit afe0709964
4 changed files with 99 additions and 16 deletions
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lib/zstd_compress.c
+13 -6
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@@ -55,7 +55,7 @@
#include <string.h> /* memset */
#include "mem.h"
#include "fse_static.h"
#include "huff0.h"
#include "huff0_static.h"
#include "zstd_static.h"
#include "zstd_internal.h"
@@ -259,10 +259,14 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc,
Note : delta map ? => compressed ?
1.1.1) Huff0-compressed literal block : 3-5 bytes
srcSize < 1 KB => 3 bytes (2-2-10-10) => single stream
srcSize < 1 KB => 3 bytes (2-2-10-10)
srcSize < 17KB => 4 bytes (2-2-14-14)
else => 5 bytes (2-2-18-18)
big endian convention
Note : 1 or 4 streams ? => controlled by zstd => requires 1 bit => reserved to < 1 KB
1 stream : orig size ? (note : not required )
if not : get orig size from decoding, & saves 10 bits
1.1.2) Raw (uncompressed) literal block header : 1-3 bytes
size : 5 bits: (IS_RAW<<6) + (0<<4) + size
@@ -281,8 +285,9 @@ static void ZSTD_reduceIndex (ZSTD_CCtx* zc,
size&255
1.1.4) Unused
Use Huff0 w/ precalculated DTable ?
FSE ? => probably not, not efficient on literals
Use Huff0 w/ precalculated CTable ?
Store CTable into workspace : build during dict Loading, use during encoding
Same issue about size and Nstreams
1.2) Literal block content
@@ -382,11 +387,13 @@ static size_t ZSTD_compressLiterals (void* dst, size_t maxDstSize,
const size_t minGain = ZSTD_minGain(srcSize);
BYTE* const ostart = (BYTE*)dst;
size_t lhSize = 3 + (srcSize >= 1 KB) + (srcSize >= 16 KB);
U32 singleStream = srcSize < 256;
size_t clitSize;
if (maxDstSize < 4) return ERROR(dstSize_tooSmall); /* not enough space for compression */
clitSize = HUF_compress(ostart+lhSize, maxDstSize-lhSize, src, srcSize);
clitSize = singleStream ? HUF_compress1X(ostart+lhSize, maxDstSize-lhSize, src, srcSize, 255, 12)
: HUF_compress2 (ostart+lhSize, maxDstSize-lhSize, src, srcSize, 255, 12);
if ((clitSize==0) || (clitSize >= srcSize - minGain)) return ZSTD_noCompressLiterals(dst, maxDstSize, src, srcSize);
if (clitSize==1) return ZSTD_compressRleLiteralsBlock(dst, maxDstSize, src, srcSize);
@@ -395,7 +402,7 @@ static size_t ZSTD_compressLiterals (void* dst, size_t maxDstSize,
switch(lhSize)
{
case 3: /* 2 - 2 - 10 - 10 */
ostart[0] = (BYTE) (srcSize>>6) + (0<< 4);
ostart[0] = (BYTE) (srcSize>>6) + (singleStream << 4);
ostart[1] = (BYTE)((srcSize<<2) + (clitSize>>8));
ostart[2] = (BYTE)(clitSize);
break;
@@ -419,7 +426,7 @@ static size_t ZSTD_compressLiterals (void* dst, size_t maxDstSize,
}
#define LITERAL_NOENTROPY 63 /* cheap heuristic */
#define LITERAL_NOENTROPY 63 /* don't even attempt to compress literals below this threshold (cheap heuristic) */
size_t ZSTD_compressSequences(void* dst, size_t maxDstSize,
const seqStore_t* seqStorePtr,