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removed special case all-1 huffman distribution

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This commit is contained in:
Yann Collet
2016-07-24 15:35:59 +02:00
parent 7ed5e33b89
commit 38b75ddeb2
3 changed files with 50 additions and 104 deletions
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lib/compress/huf_compress.c
+19 -48
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@@ -105,68 +105,39 @@ size_t HUF_writeCTable (void* dst, size_t maxDstSize,
const HUF_CElt* CTable, U32 maxSymbolValue, U32 huffLog)
{
BYTE bitsToWeight[HUF_TABLELOG_MAX + 1];
BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1];
U32 n;
BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
BYTE* op = (BYTE*)dst;
size_t size;
U32 n;
/* check conditions */
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX + 1)
return ERROR(GENERIC);
if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(GENERIC);
/* convert to weight */
bitsToWeight[0] = 0;
for (n=1; n<=huffLog; n++)
for (n=1; n<huffLog+1; n++)
bitsToWeight[n] = (BYTE)(huffLog + 1 - n);
for (n=0; n<maxSymbolValue; n++)
huffWeight[n] = bitsToWeight[CTable[n].nbBits];
size = FSE_compress(op+1, maxDstSize-1, huffWeight, maxSymbolValue); /* don't need last symbol stat : implied */
if (HUF_isError(size)) return size;
if (size >= 128) return ERROR(GENERIC); /* should never happen, since maxSymbolValue <= 255 */
if ((size <= 1) || (size >= maxSymbolValue/2)) {
if (size==1) { /* RLE */
/* only possible case : series of 1 (because there are at least 2) */
/* can only be 2^n or (2^n-1), otherwise not an huffman tree */
BYTE code;
switch(maxSymbolValue)
{
case 1: code = 0; break;
case 2: code = 1; break;
case 3: code = 2; break;
case 4: code = 3; break;
case 7: code = 4; break;
case 8: code = 5; break;
case 15: code = 6; break;
case 16: code = 7; break;
case 31: code = 8; break;
case 32: code = 9; break;
case 63: code = 10; break;
case 64: code = 11; break;
case 127: code = 12; break;
case 128: code = 13; break;
default : return ERROR(corruption_detected);
}
op[0] = (BYTE)(255-13 + code);
return 1;
}
/* Not compressible */
if (maxSymbolValue > (241-128)) return ERROR(GENERIC); /* not implemented (not possible with current format) */
if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall); /* not enough space within dst buffer */
op[0] = (BYTE)(128 /*special case*/ + 0 /* Not Compressible */ + (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;
}
{ size_t const size = FSE_compress(op+1, maxDstSize-1, huffWeight, maxSymbolValue);
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+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;
/* normal header case */
op[0] = (BYTE)size;
return size+1;
}
size_t HUF_readCTable (HUF_CElt* CTable, U32 maxSymbolValue, const void* src, size_t srcSize)
{
BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1];