lz4.c : corrected compression efficiency issue 97 in 64-bits chained mode (-BD) for streams > 4 GB (thanks Roman Strashkin for reporting)

git-svn-id: https://lz4.googlecode.com/svn/trunk@108 650e7d94-2a16-8b24-b05c-7c0b3f6821cd

1 files changed, 14 insertions, 8 deletions

diff --git a/lz4.c b/lz4.c
index 2d014ca..5668521 100644
--- a/lz4.c
+++ b/lz4.c
@@ -631,21 +631,27 @@ char* LZ4_slideInputBuffer (void* LZ4_Data)
     LZ4_Data_Structure* lz4ds = (LZ4_Data_Structure*)LZ4_Data;

     size_t delta = lz4ds->nextBlock - (lz4ds->bufferStart + 64 KB);

 

-    if(lz4ds->base - delta > lz4ds->base)   // underflow control

+    if ( (lz4ds->base - delta > lz4ds->base)                          // underflow control

+       || ((size_t)(lz4ds->nextBlock - lz4ds->base) > 0xE0000000) )   // close to 32-bits limit

     {

-        size_t newBaseDelta = (lz4ds->nextBlock - 64 KB) - lz4ds->base;

+        size_t deltaLimit = (lz4ds->nextBlock - 64 KB) - lz4ds->base;

         int nH;

 

         for (nH=0; nH < HASHNBCELLS4; nH++)

         {

-            if (lz4ds->hashTable[nH] < (U32)newBaseDelta) lz4ds->hashTable[nH] = 0;

-            else lz4ds->hashTable[nH] -= (U32)newBaseDelta;

+            if ((size_t)(lz4ds->hashTable[nH]) < deltaLimit) lz4ds->hashTable[nH] = 0;

+            else lz4ds->hashTable[nH] -= (U32)deltaLimit;

         }

-        lz4ds->base += newBaseDelta;

+        memcpy((void*)(lz4ds->bufferStart), (const void*)(lz4ds->nextBlock - 64 KB), 64 KB);

+        lz4ds->base = lz4ds->bufferStart;

+        lz4ds->nextBlock = lz4ds->base + 64 KB;

     }

-    memcpy((void*)(lz4ds->bufferStart), (const void*)(lz4ds->nextBlock - 64 KB), 64 KB);

-    lz4ds->nextBlock -= delta;

-    lz4ds->base -= delta;

+    else

+    {

+		memcpy((void*)(lz4ds->bufferStart), (const void*)(lz4ds->nextBlock - 64 KB), 64 KB);

+		lz4ds->nextBlock -= delta;

+		lz4ds->base -= delta;

+	}

 

     return (char*)(lz4ds->nextBlock);

 }