small compression speed improvement

git-svn-id: https://lz4.googlecode.com/svn/trunk@22 650e7d94-2a16-8b24-b05c-7c0b3f6821cd

1 files changed, 33 insertions, 16 deletions

diff --git a/lz4.c b/lz4.c
index 9a96617..a8d1629 100644
--- a/lz4.c
+++ b/lz4.c
@@ -111,7 +111,6 @@ int LZ4_compressCtx(void** ctx,
 

 	const BYTE* ip = (BYTE*) source;       

 	const BYTE* anchor = ip;

-	const BYTE* ref;

 	const BYTE* const iend = ip + isize;

 	const BYTE* const ilimit = iend - MINMATCH;

 

@@ -121,7 +120,7 @@ int LZ4_compressCtx(void** ctx,
 	

 	int len, length;

 	const int skipStrength = SKIPSTRENGTH;

-	U32 skipped = 1U << skipStrength;

+	U32 forwardH;

 

 

 	// Init 

@@ -131,17 +130,34 @@ int LZ4_compressCtx(void** ctx,
 		*ctx = (void*) srt;

 	}

 	HashTable = srt->hashTable;

-	memset(HashTable, 0, sizeof(srt->hashTable));

+	memset((void*)HashTable, 0, sizeof(srt->hashTable));

 

-	// Main Loop

-	while (ip < ilimit+1)

-	{

-		ref = HashTable[HASH_VALUE(ip)];

-		HashTable[HASH_VALUE(ip)] = ip;

 

-		// Min Match

-		if ((ref < ip - MAX_DISTANCE) || (*(U32*)ref != *(U32*)ip)) { ip += (skipped++) >> skipStrength ; continue; }

-		skipped = (1U << skipStrength) + 3;

+	// First Byte

+	HashTable[HASH_VALUE(ip)] = ip++;

+	forwardH = HASH_VALUE(ip);

+	

+	// Main Loop

+    for ( ; ; ) 
+	{
+		int segmentSize = (1U << skipStrength) + 3;
+		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; }
+

+			forwardH = HASH_VALUE(forwardIp);

+			ref = HashTable[h];

+			HashTable[h] = ip;

+
+		} while ((ref < ip - MAX_DISTANCE) || (*(U32*)ref != *(U32*)ip));
 

 		// Catch up

 		while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; }  

@@ -190,15 +206,16 @@ _endCount:
 

 		// Prepare next loop

 		anchor = ip++; 

+		forwardH = HASH_VALUE(ip);

 	}

 

+_last_literals:

 	// Encode Last Literals

-	len = iend - anchor;

-	if (len)

+	if (anchor < iend)

 	{

-		orun=op++;

-		if (len>=(int)RUN_MASK) { *orun=(RUN_MASK<<ML_BITS); len-=RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE) len; } 

-		else *orun = (len<<ML_BITS);

+		int lastLitRun = iend - anchor;

+		if (lastLitRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastLitRun-=RUN_MASK; for(; lastLitRun > 254 ; lastLitRun-=255) *op++ = 255; *op++ = (BYTE) lastLitRun; } 

+		else *op++ = (lastLitRun<<ML_BITS);

 		while (anchor < iend - 3) { *(U32*)op = *(U32*)anchor; op+=4; anchor+=4; }

 		while (anchor < iend ) *op++ = *anchor++;

 	}