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small compression speed improvement

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git-svn-id: https://lz4.googlecode.com/svn/trunk@22 650e7d94-2a16-8b24-b05c-7c0b3f6821cd
This commit is contained in:
yann.collet.73@gmail.com 2011-09-15 21:37:09 +00:00
parent e154e125fc
commit e8d1e99112
1 changed files with 32 additions and 15 deletions
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47
lz4.c
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@ -111,7 +111,6 @@ int LZ4_compressCtx(void** ctx,
const BYTE* ip = (BYTE*) source; const BYTE* ip = (BYTE*) source;
const BYTE* anchor = ip; const BYTE* anchor = ip;
const BYTE* ref;
const BYTE* const iend = ip + isize; const BYTE* const iend = ip + isize;
const BYTE* const ilimit = iend - MINMATCH; const BYTE* const ilimit = iend - MINMATCH;
@ -121,7 +120,7 @@ int LZ4_compressCtx(void** ctx,
int len, length; int len, length;
const int skipStrength = SKIPSTRENGTH; const int skipStrength = SKIPSTRENGTH;
U32 skipped = 1U << skipStrength; U32 forwardH;
// Init // Init
@ -131,17 +130,34 @@ int LZ4_compressCtx(void** ctx,
*ctx = (void*) srt; *ctx = (void*) srt;
} }
HashTable = srt->hashTable; HashTable = srt->hashTable;
memset(HashTable, 0, sizeof(srt->hashTable)); memset((void*)HashTable, 0, sizeof(srt->hashTable));
// First Byte
HashTable[HASH_VALUE(ip)] = ip++;
forwardH = HASH_VALUE(ip);
// Main Loop // Main Loop
while (ip < ilimit+1) for ( ; ; )
{ {
ref = HashTable[HASH_VALUE(ip)]; int segmentSize = (1U << skipStrength) + 3;
HashTable[HASH_VALUE(ip)] = ip; const BYTE* forwardIp = ip;
const BYTE* ref;
// Find a match
do {
U32 h = forwardH;
int skipped = segmentSize++ >> skipStrength;
ip = forwardIp;
forwardIp = ip + skipped;
if (forwardIp > ilimit) { goto _last_literals; }
// Min Match forwardH = HASH_VALUE(forwardIp);
if ((ref < ip - MAX_DISTANCE) || (*(U32*)ref != *(U32*)ip)) { ip += (skipped++) >> skipStrength ; continue; } ref = HashTable[h];
skipped = (1U << skipStrength) + 3; HashTable[h] = ip;
} while ((ref < ip - MAX_DISTANCE) || (*(U32*)ref != *(U32*)ip));
// Catch up // Catch up
while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; } while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; }
@ -190,15 +206,16 @@ _endCount:
// Prepare next loop // Prepare next loop
anchor = ip++; anchor = ip++;
forwardH = HASH_VALUE(ip);
} }
_last_literals:
// Encode Last Literals // Encode Last Literals
len = iend - anchor; if (anchor < iend)
if (len)
{ {
orun=op++; int lastLitRun = iend - anchor;
if (len>=(int)RUN_MASK) { *orun=(RUN_MASK<<ML_BITS); len-=RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE) len; } if (lastLitRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastLitRun-=RUN_MASK; for(; lastLitRun > 254 ; lastLitRun-=255) *op++ = 255; *op++ = (BYTE) lastLitRun; }
else *orun = (len<<ML_BITS); else *op++ = (lastLitRun<<ML_BITS);
while (anchor < iend - 3) { *(U32*)op = *(U32*)anchor; op+=4; anchor+=4; } while (anchor < iend - 3) { *(U32*)op = *(U32*)anchor; op+=4; anchor+=4; }
while (anchor < iend ) *op++ = *anchor++; while (anchor < iend ) *op++ = *anchor++;
} }