fixed potential ptrdiff_t overflow (32-bits mode)

Also removed pointer comparison, which should solve #485

diff --git a/lib/lz4.c b/lib/lz4.c
index f55e4e1..c48aca4 100644 (file)
--- a/lib/lz4.c
+++ b/lib/lz4.c
@@ -1315,15 +1315,14 @@ void LZ4_attach_dictionary(LZ4_stream_t *working_stream, const LZ4_stream_t *dic
 }
 
 
-static void LZ4_renormDictT(LZ4_stream_t_internal* LZ4_dict, const BYTE* src)
+static void LZ4_renormDictT(LZ4_stream_t_internal* LZ4_dict, int nextSize)
 {
-    if ((LZ4_dict->currentOffset > 0x80000000) ||
-        ((uptrval)LZ4_dict->currentOffset > (uptrval)src)) {   /* address space overflow */
+    if (LZ4_dict->currentOffset + nextSize > 0x80000000) {   /* potential ptrdiff_t overflow (32-bits mode) */
         /* rescale hash table */
         U32 const delta = LZ4_dict->currentOffset - 64 KB;
         const BYTE* dictEnd = LZ4_dict->dictionary + LZ4_dict->dictSize;
         int i;
-        DEBUGLOG(4, "LZ4_renormDictT %p", LZ4_dict);
+        DEBUGLOG(4, "LZ4_renormDictT");
         for (i=0; i<LZ4_HASH_SIZE_U32; i++) {
             if (LZ4_dict->hashTable[i] < delta) LZ4_dict->hashTable[i]=0;
             else LZ4_dict->hashTable[i] -= delta;
@@ -1341,10 +1340,8 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream, const char* source, ch
     LZ4_stream_t_internal* streamPtr = &LZ4_stream->internal_donotuse;
     const BYTE* const dictEnd = streamPtr->dictionary + streamPtr->dictSize;
 
-    const BYTE* smallest = (const BYTE*) source;
     if (streamPtr->initCheck) return 0;   /* Uninitialized structure detected */
-    if ((streamPtr->dictSize>0) && (smallest>dictEnd)) smallest = dictEnd;
-    LZ4_renormDictT(streamPtr, smallest);
+    LZ4_renormDictT(streamPtr, inputSize);   /* avoid index overflow */
     if (acceleration < 1) acceleration = ACCELERATION_DEFAULT;
 
     /* Check overlapping input/dictionary space */
@@ -1377,7 +1374,7 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream, const char* source, ch
             if (inputSize > 4 KB) {
                 /* For compressing large blobs, it is faster to pay the setup
                  * cost to copy the dictionary's tables into the active context,
-                 * so that the compression loop is only looking in one table.
+                 * so that the compression loop is only looking into one table.
                  */
                 memcpy(streamPtr, streamPtr->dictCtx, sizeof(LZ4_stream_t));
                 result = LZ4_compress_generic(streamPtr, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
@@ -1398,8 +1395,8 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream, const char* source, ch
 }
 
 
-/* Hidden debug function, to force external dictionary mode */
-int LZ4_compress_forceExtDict (LZ4_stream_t* LZ4_dict, const char* source, char* dest, int inputSize)
+/* Hidden debug function, to force-test external dictionary mode */
+int LZ4_compress_forceExtDict (LZ4_stream_t* LZ4_dict, const char* source, char* dest, int srcSize)
 {
     LZ4_stream_t_internal* streamPtr = &LZ4_dict->internal_donotuse;
     int result;
@@ -1407,16 +1404,16 @@ int LZ4_compress_forceExtDict (LZ4_stream_t* LZ4_dict, const char* source, char*
 
     const BYTE* smallest = dictEnd;
     if (smallest > (const BYTE*) source) smallest = (const BYTE*) source;
-    LZ4_renormDictT(streamPtr, smallest);
+    LZ4_renormDictT(streamPtr, srcSize);
 
     if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset)) {
-        result = LZ4_compress_generic(streamPtr, source, dest, inputSize, 0, notLimited, byU32, usingExtDict, dictSmall, 1);
+        result = LZ4_compress_generic(streamPtr, source, dest, srcSize, 0, notLimited, byU32, usingExtDict, dictSmall, 1);
     } else {
-        result = LZ4_compress_generic(streamPtr, source, dest, inputSize, 0, notLimited, byU32, usingExtDict, noDictIssue, 1);
+        result = LZ4_compress_generic(streamPtr, source, dest, srcSize, 0, notLimited, byU32, usingExtDict, noDictIssue, 1);
     }
 
     streamPtr->dictionary = (const BYTE*)source;
-    streamPtr->dictSize = (U32)inputSize;
+    streamPtr->dictSize = (U32)srcSize;
 
     return result;
 }