Refactor buildSequencesStatistics() to avoid pointer increment for superblocks

2021-03-24 08:21:29 -07:00
parent e2bb215117
commit eb1ee8686d
3 changed files with 49 additions and 42 deletions
@@ -500,9 +500,9 @@ static size_t ZSTD_compressSubBlock_sequences(const ZSTD_fseCTables_t* fseTables
         * block, since it isn't worth optimizing.
         */
 #ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-        if (writeEntropy && fseMetadata->lastCountSize && fseMetadata->lastCountSize + bitstreamSize < 4) {
+        if (writeEntropy && fseMetadata->lastNCount && (op - fseMetadata->lastNCount) < 4) {
            /* NCountSize >= 2 && bitstreamSize > 0 ==> lastCountSize == 3 */
-            assert(fseMetadata->lastCountSize + bitstreamSize == 3);
+            assert(op - fseMetadata->lastNCount == 3);
            DEBUGLOG(5, "Avoiding bug in zstd decoder in versions <= 1.3.4 by "
                        "emitting an uncompressed block.");
            return 0;