From 824aaa695f811d081fb29ee0fb198e6cb0efdcfd Mon Sep 17 00:00:00 2001
From: Nick Terrell <terrelln@fb.com>
Date: Tue, 9 Apr 2019 17:59:27 -0700
Subject: [PATCH] [libzstd] Fix ZSTD_decompressDCtx() with a dictionary

* `ZSTD_decompressDCtx()` did not use the dictionary loaded by
  `ZSTD_DCtx_loadDictionary()`.
* Add a unit test.
* A stacked diff uses `ZSTD_decompressDCtx()` in the
  `dictionary_round_trip` and `dictionary_decompress` fuzzers.
---
 lib/decompress/zstd_decompress.c |  2 +-
 tests/fuzzer.c                   | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 14cc12a4..d8f14882 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -788,7 +788,7 @@ size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
 
 size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize)
 {
-    return ZSTD_decompress_usingDict(dctx, dst, dstCapacity, src, srcSize, NULL, 0);
+    return ZSTD_decompress_usingDDict(dctx, dst, dstCapacity, src, srcSize, dctx->ddict);
 }
 
 
diff --git a/tests/fuzzer.c b/tests/fuzzer.c
index cfb07eb1..c38aef61 100644
--- a/tests/fuzzer.c
+++ b/tests/fuzzer.c
@@ -1438,6 +1438,32 @@ static int basicUnitTests(U32 seed, double compressibility)
         }
         DISPLAYLEVEL(3, "OK \n");
 
+        ZSTD_CCtx_reset(cctx, ZSTD_reset_session_and_parameters);
+        CHECK_Z( ZSTD_CCtx_loadDictionary(cctx, dictBuffer, dictSize) );
+        cSize = ZSTD_compress2(cctx, compressedBuffer, compressedBufferSize, CNBuffer, MIN(CNBuffSize, 100 KB));
+        CHECK_Z(cSize);
+        DISPLAYLEVEL(3, "test%3i : ZSTD_decompressDCtx() with dictionary : ", testNb++);
+        {
+            ZSTD_DCtx* dctx = ZSTD_createDCtx();
+            size_t ret;
+            /* We should fail to decompress without a dictionary. */
+            ZSTD_DCtx_reset(dctx, ZSTD_reset_session_and_parameters);
+            ret = ZSTD_decompressDCtx(dctx, decodedBuffer, CNBuffSize, compressedBuffer, cSize);
+            if (!ZSTD_isError(ret)) goto _output_error;
+            /* We should succeed to decompress with the dictionary. */
+            ZSTD_DCtx_reset(dctx, ZSTD_reset_session_and_parameters);
+            CHECK_Z( ZSTD_DCtx_loadDictionary(dctx, dictBuffer, dictSize) );
+            CHECK_Z( ZSTD_decompressDCtx(dctx, decodedBuffer, CNBuffSize, compressedBuffer, cSize) );
+            /* The dictionary should presist across calls. */
+            CHECK_Z( ZSTD_decompressDCtx(dctx, decodedBuffer, CNBuffSize, compressedBuffer, cSize) );
+            /* When we reset the context the dictionary is cleared. */
+            ZSTD_DCtx_reset(dctx, ZSTD_reset_session_and_parameters);
+            ret = ZSTD_decompressDCtx(dctx, decodedBuffer, CNBuffSize, compressedBuffer, cSize);
+            if (!ZSTD_isError(ret)) goto _output_error;
+            ZSTD_freeDCtx(dctx);
+        }
+        DISPLAYLEVEL(3, "OK \n");
+
         DISPLAYLEVEL(3, "test%3i : Dictionary with non-default repcodes : ", testNb++);
         { U32 u; for (u=0; u<nbSamples; u++) samplesSizes[u] = sampleUnitSize; }
         dictSize = ZDICT_trainFromBuffer(dictBuffer, dictSize,