Further Test that ExtDictCtx Mode Produces the Exact Same Output

1 files changed, 21 insertions, 2 deletions

diff --git a/tests/fuzzer.c b/tests/fuzzer.c
index 98b3d9f..db05738 100644
--- a/tests/fuzzer.c
+++ b/tests/fuzzer.c
@@ -303,9 +303,9 @@ static int FUZ_test(U32 seed, U32 nbCycles, const U32 startCycle, const double c
         U32 testNb = 0;
         U32 randState = FUZ_rand(&coreRandState) ^ PRIME3;
         int const blockSize  = (FUZ_rand(&randState) % (FUZ_MAX_BLOCK_SIZE-1)) + 1;
-        int const blockStart = FUZ_rand(&randState) % (COMPRESSIBLE_NOISE_LENGTH - blockSize);
+        int const blockStart = (FUZ_rand(&randState) % (COMPRESSIBLE_NOISE_LENGTH - blockSize - 1)) + 1;
         int const dictSizeRand = FUZ_rand(&randState) % FUZ_MAX_DICT_SIZE;
-        int const dictSize = MIN(dictSizeRand, blockStart);
+        int const dictSize = MIN(dictSizeRand, blockStart - 1);
         int const compressionLevel = FUZ_rand(&randState) % (LZ4HC_CLEVEL_MAX+1);
         char* const block = ((char*)CNBuffer) + blockStart;
         const char* dict = block - dictSize;
@@ -636,6 +636,13 @@ static int FUZ_test(U32 seed, U32 nbCycles, const U32 startCycle, const double c
         FUZ_DISPLAYTEST;
         {
             LZ4_stream_t LZ4_stream;
+            int expectedSize;
+            U32 expectedCrc;
+
+            LZ4_loadDict(&LZ4dict, dict, dictSize);
+            expectedSize = LZ4_compress_fast_continue(&LZ4dict, block, compressedBuffer, blockSize, (int)compressedBufferSize, 1);
+            FUZ_CHECKTEST(expectedSize<=0, "LZ4_compress_fast_continue reference compression for extDictCtx should have succeeded");
+            expectedCrc = XXH32(compressedBuffer, expectedSize, 0);
 
             LZ4_loadDict(&LZ4dict, dict, dictSize);
 
@@ -644,6 +651,14 @@ static int FUZ_test(U32 seed, U32 nbCycles, const U32 startCycle, const double c
             blockContinueCompressedSize = LZ4_compress_fast_continue(&LZ4_stream, block, compressedBuffer, blockSize, (int)compressedBufferSize, 1);
             FUZ_CHECKTEST(blockContinueCompressedSize==0, "LZ4_compress_fast_continue using extDictCtx failed");
 
+            /* In the future, it might be desirable to let extDictCtx mode's
+             * output diverge from the output generated by regular extDict mode.
+             * Until that time, this comparison serves as a good regression
+             * test.
+             */
+            FUZ_CHECKTEST(blockContinueCompressedSize != expectedSize, "LZ4_compress_fast_continue using extDictCtx produced different-sized output (%d expected vs %d actual)", expectedSize, blockContinueCompressedSize);
+            FUZ_CHECKTEST(XXH32(compressedBuffer, blockContinueCompressedSize, 0) != expectedCrc, "LZ4_compress_fast_continue using extDictCtx produced different output");
+
             FUZ_DISPLAYTEST;
             LZ4_resetStream(&LZ4_stream);
             LZ4_attach_dictionary(&LZ4_stream, &LZ4dict);
@@ -656,6 +671,8 @@ static int FUZ_test(U32 seed, U32 nbCycles, const U32 startCycle, const double c
             ret = LZ4_compress_fast_continue(&LZ4_stream, block, compressedBuffer, blockSize, blockContinueCompressedSize, 1);
             FUZ_CHECKTEST(ret!=blockContinueCompressedSize, "LZ4_compress_limitedOutput_compressed size is different (%i != %i)", ret, blockContinueCompressedSize);
             FUZ_CHECKTEST(ret<=0, "LZ4_compress_fast_continue using extDictCtx should work : enough size available within output buffer");
+            FUZ_CHECKTEST(ret != expectedSize, "LZ4_compress_fast_continue using extDictCtx produced different-sized output");
+            FUZ_CHECKTEST(XXH32(compressedBuffer, ret, 0) != expectedCrc, "LZ4_compress_fast_continue using extDictCtx produced different output");
 
             FUZ_DISPLAYTEST;
             LZ4_resetStream_fast(&LZ4_stream);
@@ -663,6 +680,8 @@ static int FUZ_test(U32 seed, U32 nbCycles, const U32 startCycle, const double c
             ret = LZ4_compress_fast_continue(&LZ4_stream, block, compressedBuffer, blockSize, blockContinueCompressedSize, 1);
             FUZ_CHECKTEST(ret!=blockContinueCompressedSize, "LZ4_compress_limitedOutput_compressed size is different (%i != %i)", ret, blockContinueCompressedSize);
             FUZ_CHECKTEST(ret<=0, "LZ4_compress_fast_continue using extDictCtx with re-used context should work : enough size available within output buffer");
+            FUZ_CHECKTEST(ret != expectedSize, "LZ4_compress_fast_continue using extDictCtx produced different-sized output");
+            FUZ_CHECKTEST(XXH32(compressedBuffer, ret, 0) != expectedCrc, "LZ4_compress_fast_continue using extDictCtx produced different output");
         }
 
         /* Decompress with dictionary as external */