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Introduced FSE_compress_wksp() and FSE_buildCTable_wksp() to reduce stack memory usage

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This commit is contained in:
Yann Collet
2016-11-30 15:52:20 -08:00
parent 4ab3a4228f
commit d79a9a00d9
4 changed files with 90 additions and 55 deletions
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lib/compress/huf_compress.c
+8 -7
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@@ -88,13 +88,15 @@ typedef struct nodeElt_s {
size_t HUF_writeCTable (void* dst, size_t maxDstSize,
const HUF_CElt* CTable, U32 maxSymbolValue, U32 huffLog)
{
BYTE bitsToWeight[HUF_TABLELOG_MAX + 1];
BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */
BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
BYTE* op = (BYTE*)dst;
#define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6
BYTE scratchBuffer[1<<MAX_FSE_TABLELOG_FOR_HUFF_HEADER];
U32 n;
/* check conditions */
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(GENERIC);
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);
/* convert to weight */
bitsToWeight[0] = 0;
@@ -103,23 +105,22 @@ size_t HUF_writeCTable (void* dst, size_t maxDstSize,
for (n=0; n<maxSymbolValue; n++)
huffWeight[n] = bitsToWeight[CTable[n].nbBits];
{ size_t const size = FSE_compress(op+1, maxDstSize-1, huffWeight, maxSymbolValue);
/* attempt weights compression by FSE */
{ size_t const size = FSE_compress_wksp(op+1, maxDstSize-1, huffWeight, maxSymbolValue, HUF_TABLELOG_MAX, MAX_FSE_TABLELOG_FOR_HUFF_HEADER, scratchBuffer);
if (FSE_isError(size)) return size;
if ((size>1) & (size < maxSymbolValue/2)) { /* FSE compressed */
op[0] = (BYTE)size;
return size+1;
}
}
} }
/* raw values */
if (maxSymbolValue > (256-128)) return ERROR(GENERIC); /* should not happen */
if (maxSymbolValue > (256-128)) return ERROR(GENERIC); /* should not happen : likely means source cannot be compressed */
if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall); /* not enough space within dst buffer */
op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1));
huffWeight[maxSymbolValue] = 0; /* to be sure it doesn't cause issue in final combination */
for (n=0; n<maxSymbolValue; n+=2)
op[(n/2)+1] = (BYTE)((huffWeight[n] << 4) + huffWeight[n+1]);
return ((maxSymbolValue+1)/2) + 1;
}