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created ZSTD_writeFrameHeader()

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This commit is contained in:
Yann Collet 2016-04-12 14:14:10 +02:00
parent abb5c653f1
commit 0085cd3138
1 changed files with 26 additions and 16 deletions
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42
lib/zstd_compress.c
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@ -2249,6 +2249,30 @@ static size_t ZSTD_compress_insertDictionary(ZSTD_CCtx* zc, const void* dict, si
}
}
static size_t ZSTD_writeFrameHeader(void* dst, size_t dstCapacity,
ZSTD_parameters params, U64 pledgedSrcSize)
{ BYTE* const op = (BYTE*)dst;
U32 const fcsId = (pledgedSrcSize>0) + (pledgedSrcSize>=256) + (pledgedSrcSize>=65536+256); /* 0-3 */
BYTE const fdescriptor = (BYTE)((params.cParams.windowLog - ZSTD_WINDOWLOG_ABSOLUTEMIN) /* windowLog : 4 KB - 128 MB */
| (fcsId << 6) );
size_t const hSize = ZSTD_frameHeaderSize_min + ZSTD_fcs_fieldSize[fcsId];
if (hSize > dstCapacity) return ERROR(dstSize_tooSmall);
MEM_writeLE32(dst, ZSTD_MAGICNUMBER);
op[4] = fdescriptor;
switch(fcsId)
{
default: /* impossible */
case 0 : break;
case 1 : op[5] = (BYTE)(pledgedSrcSize); break;
case 2 : MEM_writeLE16(op+5, (U16)(pledgedSrcSize-256)); break;
case 3 : MEM_writeLE64(op+5, (U64)(pledgedSrcSize)); break;
}
return hSize;
}
/*! ZSTD_compressBegin_internal() :
* @return : 0, or an error code */
static size_t ZSTD_compressBegin_internal(ZSTD_CCtx* zc,
@ -2263,22 +2287,8 @@ static size_t ZSTD_compressBegin_internal(ZSTD_CCtx* zc,
if (ZSTD_isError(resetError)) return resetError; }
/* Write Frame Header into ctx headerBuffer */
MEM_writeLE32(zc->headerBuffer, ZSTD_MAGICNUMBER);
{ BYTE* const op = (BYTE*)zc->headerBuffer;
U32 const fcsId = (pledgedSrcSize>0) + (pledgedSrcSize>=256) + (pledgedSrcSize>=65536+256); /* 0-3 */
BYTE fdescriptor = (BYTE)(params.cParams.windowLog - ZSTD_WINDOWLOG_ABSOLUTEMIN); /* windowLog : 4 KB - 128 MB */
fdescriptor |= (BYTE)(fcsId << 6);
op[4] = fdescriptor;
switch(fcsId)
{
default: /* impossible */
case 0 : break;
case 1 : op[5] = (BYTE)(pledgedSrcSize); break;
case 2 : MEM_writeLE16(op+5, (U16)(pledgedSrcSize-256)); break;
case 3 : MEM_writeLE64(op+5, (U64)(pledgedSrcSize)); break;
}
zc->hbSize = ZSTD_frameHeaderSize_min + ZSTD_fcs_fieldSize[fcsId];
}
zc->hbSize = ZSTD_writeFrameHeader(zc->headerBuffer, ZSTD_FRAMEHEADERSIZE_MAX,
params, pledgedSrcSize);
return ZSTD_compress_insertDictionary(zc, dict, dictSize);
}