decodecorpus

lib/decompress/zstd_decompress_block.c

@@ -505,7 +505,7 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
     *nbSeqPtr = nbSeq;
 
     /* FSE table descriptors */
-    RETURN_ERROR_IF(ip+4 > iend, srcSize_wrong); /* minimum possible size */
+    RETURN_ERROR_IF(ip+1 > iend, srcSize_wrong); /* minimum possible size: 1 byte for symbol encoding types */
     {   symbolEncodingType_e const LLtype = (symbolEncodingType_e)(*ip >> 6);
         symbolEncodingType_e const OFtype = (symbolEncodingType_e)((*ip >> 4) & 3);
         symbolEncodingType_e const MLtype = (symbolEncodingType_e)((*ip >> 2) & 3);

tests/decodecorpus.c

@@ -840,16 +840,16 @@ static size_t writeSequences(U32* seed, frame_t* frame, seqStore_t* seqStorePtr,
     {   unsigned max = MaxLL;
         size_t const mostFrequent = HIST_countFast_wksp(count, &max, llCodeTable, nbSeq, WKSP, sizeof(WKSP));   /* cannot fail */
         assert(!HIST_isError(mostFrequent));
-        if (mostFrequent == nbSeq) {
-            /* do RLE if we have the chance */
-            *op++ = llCodeTable[0];
-            FSE_buildCTable_rle(CTable_LitLength, (BYTE)max);
-            LLtype = set_rle;
-        } else if (frame->stats.fseInit && !(RAND(seed) & 3) &&
+        if (frame->stats.fseInit && !(RAND(seed) & 3) &&
                    isSymbolSubset(llCodeTable, nbSeq,
                                   frame->stats.litlengthSymbolSet, 35)) {
             /* maybe do repeat mode if we're allowed to */
             LLtype = set_repeat;
+        } else if (mostFrequent == nbSeq) {
+            /* do RLE if we have the chance */
+            *op++ = llCodeTable[0];
+            FSE_buildCTable_rle(CTable_LitLength, (BYTE)max);
+            LLtype = set_rle;
         } else if (!(RAND(seed) & 3)) {
             /* maybe use the default distribution */
             FSE_buildCTable_wksp(CTable_LitLength, LL_defaultNorm, MaxLL, LL_defaultNormLog, scratchBuffer, sizeof(scratchBuffer));
@@ -872,14 +872,14 @@ static size_t writeSequences(U32* seed, frame_t* frame, seqStore_t* seqStorePtr,
     {   unsigned max = MaxOff;
         size_t const mostFrequent = HIST_countFast_wksp(count, &max, ofCodeTable, nbSeq, WKSP, sizeof(WKSP));   /* cannot fail */
         assert(!HIST_isError(mostFrequent));
-        if (mostFrequent == nbSeq) {
-            *op++ = ofCodeTable[0];
-            FSE_buildCTable_rle(CTable_OffsetBits, (BYTE)max);
-            Offtype = set_rle;
-        } else if (frame->stats.fseInit && !(RAND(seed) & 3) &&
+        if (frame->stats.fseInit && !(RAND(seed) & 3) &&
                    isSymbolSubset(ofCodeTable, nbSeq,
                                   frame->stats.offsetSymbolSet, 28)) {
             Offtype = set_repeat;
+        } else if (mostFrequent == nbSeq) {
+            *op++ = ofCodeTable[0];
+            FSE_buildCTable_rle(CTable_OffsetBits, (BYTE)max);
+            Offtype = set_rle;
         } else if (!(RAND(seed) & 3)) {
             FSE_buildCTable_wksp(CTable_OffsetBits, OF_defaultNorm, DefaultMaxOff, OF_defaultNormLog, scratchBuffer, sizeof(scratchBuffer));
             Offtype = set_basic;
@@ -900,14 +900,14 @@ static size_t writeSequences(U32* seed, frame_t* frame, seqStore_t* seqStorePtr,
     {   unsigned max = MaxML;
         size_t const mostFrequent = HIST_countFast_wksp(count, &max, mlCodeTable, nbSeq, WKSP, sizeof(WKSP));   /* cannot fail */
         assert(!HIST_isError(mostFrequent));
-        if (mostFrequent == nbSeq) {
-            *op++ = *mlCodeTable;
-            FSE_buildCTable_rle(CTable_MatchLength, (BYTE)max);
-            MLtype = set_rle;
-        } else if (frame->stats.fseInit && !(RAND(seed) & 3) &&
+        if (frame->stats.fseInit && !(RAND(seed) & 3) &&
                    isSymbolSubset(mlCodeTable, nbSeq,
                                   frame->stats.matchlengthSymbolSet, 52)) {
             MLtype = set_repeat;
+        } else if (mostFrequent == nbSeq) {
+            *op++ = *mlCodeTable;
+            FSE_buildCTable_rle(CTable_MatchLength, (BYTE)max);
+            MLtype = set_rle;
         } else if (!(RAND(seed) & 3)) {
             /* sometimes do default distribution */
             FSE_buildCTable_wksp(CTable_MatchLength, ML_defaultNorm, MaxML, ML_defaultNormLog, scratchBuffer, sizeof(scratchBuffer));

tests/zstreamtest.c

@@ -1184,6 +1184,68 @@ static int basicUnitTests(U32 seed, double compressibility)
     }
     DISPLAYLEVEL(3, "OK \n");
 
+    /* Small Sequence Section bug */
+    DISPLAYLEVEL(3, "test%3i : decompress blocks with small sequences section : ", testNb++);
+    {   /* This test consists of 3 blocks. Each block has one sequence.
+            The sequence has literal length of 10, match length of 10 and offset of 10.
+            The sequence value and compression mode for the blocks are following:
+            The order of values are ll, ml, of.
+              - First block  : (10, 7, 13) (rle, rle, rle)
+                 - size of sequences section: 6 bytes (1 byte for nbSeq, 1 byte for encoding mode, 3 bytes for rle, 1 byte bitstream)
+              - Second block : (10, 7, 1) (repeat, repeat, rle)
+                 - size of sequences section: 4 bytes (1 byte for nbSeq, 1 byte for encoding mode, 1 bytes for rle, 1 byte bitstream)
+              - Third block  : (10, 7, 1) (repeat, repeat, repeat)
+                 - size of sequences section: 3 bytes (1 byte for nbSeq, 1 byte for encoding mode, 1 byte bitstream) */
+
+        unsigned char compressed[] = {
+            0x28, 0xb5, 0x2f, 0xfd, 0x24, 0x3c, 0x35, 0x01, 0x00, 0xf0, 0x85, 0x08,
+            0xc2, 0xc4, 0x70, 0xcf, 0xd7, 0xc0, 0x96, 0x7e, 0x4c, 0x6b, 0xa9, 0x8b,
+            0xbc, 0xc5, 0xb6, 0xd9, 0x7f, 0x4c, 0xf1, 0x05, 0xa6, 0x54, 0xef, 0xac,
+            0x69, 0x94, 0x89, 0x1c, 0x03, 0x44, 0x0a, 0x07, 0x00, 0xb4, 0x04, 0x80,
+            0x40, 0x0a, 0xa4
+        };
+        unsigned int compressedSize = 51;
+        unsigned char decompressed[] = {
+            0x85, 0x08, 0xc2, 0xc4, 0x70, 0xcf, 0xd7, 0xc0, 0x96, 0x7e, 0x85, 0x08,
+            0xc2, 0xc4, 0x70, 0xcf, 0xd7, 0xc0, 0x96, 0x7e, 0x4c, 0x6b, 0xa9, 0x8b,
+            0xbc, 0xc5, 0xb6, 0xd9, 0x7f, 0x4c, 0x4c, 0x6b, 0xa9, 0x8b, 0xbc, 0xc5,
+            0xb6, 0xd9, 0x7f, 0x4c, 0xf1, 0x05, 0xa6, 0x54, 0xef, 0xac, 0x69, 0x94,
+            0x89, 0x1c, 0xf1, 0x05, 0xa6, 0x54, 0xef, 0xac, 0x69, 0x94, 0x89, 0x1c
+        };
+        unsigned int decompressedSize = 60;
+
+        ZSTD_DStream* const zds = ZSTD_createDStream();
+        if (zds==NULL) goto _output_error;
+
+        CHECK_Z( ZSTD_initDStream(zds) );
+        inBuff.src = compressed;
+        inBuff.size = compressedSize;
+        inBuff.pos = 0;
+        outBuff.dst = decodedBuffer;
+        outBuff.size = CNBufferSize;
+        outBuff.pos = 0;
+
+        while (inBuff.pos < inBuff.size) {
+            CHECK_Z( ZSTD_decompressStream(zds, &outBuff, &inBuff) );
+        }
+
+        {   XXH64_state_t xxhStateIn, xxhStateOut;
+            U32 checkIn, checkOut;
+            XXH64_reset(&xxhStateIn, 0);
+            XXH64_reset(&xxhStateOut, 0);
+
+            XXH64_update(&xxhStateIn, decompressed, decompressedSize);
+            XXH64_update(&xxhStateOut, outBuff.dst, outBuff.pos);
+
+            checkIn = (U32)XXH64_digest(&xxhStateIn);
+            checkOut = (U32)XXH64_digest(&xxhStateOut);
+            CHECK(checkIn != checkOut, "Checksum does not match");
+        }
+
+        ZSTD_freeDStream(zds);
+    }
+    DISPLAYLEVEL(3, "OK \n");
+
     DISPLAYLEVEL(3, "test%3i : dictionary + uncompressible block + reusing tables checks offset table validity: ", testNb++);
     {   ZSTD_CDict* const cdict = ZSTD_createCDict_advanced(
             dictionary.start, dictionary.filled,