From 2a02455fdfb7250ef629a3ffde5258e95df06e7b Mon Sep 17 00:00:00 2001
From: Yann Collet <yann.collet.73@gmail.com>
Date: Mon, 16 Mar 2015 19:19:39 +0100
Subject: minor refactoring

---
 lib/lz4frame.c       | 24 ++++++++++++++----------
 programs/frametest.c | 23 +++++++++++++++++++++--
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/lib/lz4frame.c b/lib/lz4frame.c
index 99953c1..d08cf94 100644
--- a/lib/lz4frame.c
+++ b/lib/lz4frame.c
@@ -707,7 +707,7 @@ size_t LZ4F_compressEnd(LZ4F_compressionContext_t compressionContext, void* dstB
 * If the result LZ4F_errorCode_t is not zero, there was an error during context creation.
 * Object can release its memory using LZ4F_freeDecompressionContext();
 */
-LZ4F_errorCode_t LZ4F_createDecompressionContext(LZ4F_compressionContext_t* LZ4F_decompressionContextPtr, unsigned versionNumber)
+LZ4F_errorCode_t LZ4F_createDecompressionContext(LZ4F_decompressionContext_t* LZ4F_decompressionContextPtr, unsigned versionNumber)
 {
     LZ4F_dctx_internal_t* dctxPtr;
 
@@ -719,7 +719,7 @@ LZ4F_errorCode_t LZ4F_createDecompressionContext(LZ4F_compressionContext_t* LZ4F
     return OK_NoError;
 }
 
-LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_compressionContext_t LZ4F_decompressionContext)
+LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_decompressionContext_t LZ4F_decompressionContext)
 {
     LZ4F_dctx_internal_t* dctxPtr = (LZ4F_dctx_internal_t*)LZ4F_decompressionContext;
     FREEMEM(dctxPtr->tmpIn);
@@ -766,8 +766,18 @@ static size_t LZ4F_decodeHeader(LZ4F_dctx_internal_t* dctxPtr, const void* srcVo
     {
         memset(&(dctxPtr->frameInfo), 0, sizeof(dctxPtr->frameInfo));
         dctxPtr->frameInfo.frameType = skippableFrame;
-        dctxPtr->dStage = dstage_getSBlockSize;
-        return 4;
+        if (srcVoidPtr == (void*)(dctxPtr->header))
+        {
+            memcpy(dctxPtr->header,  dctxPtr->header + 4, srcSize-4);
+            dctxPtr->tmpInSize = srcSize-4;
+            dctxPtr->dStage = dstage_storeSBlockSize;
+            return srcSize;
+        }
+        else
+        {
+            dctxPtr->dStage = dstage_getSBlockSize;
+            return 4;
+        }
     }
 
     /* control magic number */
@@ -1023,12 +1033,6 @@ size_t LZ4F_decompress(LZ4F_decompressionContext_t decompressionContext,
                 }
                 LZ4F_errorCode_t errorCode = LZ4F_decodeHeader(dctxPtr, dctxPtr->header, 7);
                 if (LZ4F_isError(errorCode)) return errorCode;
-                if (errorCode==4)
-                {
-                    memcpy(dctxPtr->header,  dctxPtr->header + 4, 3);
-                    dctxPtr->tmpInSize = 3;
-                    dctxPtr->dStage = dstage_storeSBlockSize;
-                }
                 break;
             }
 
diff --git a/programs/frametest.c b/programs/frametest.c
index be2be76..62b6fa4 100644
--- a/programs/frametest.c
+++ b/programs/frametest.c
@@ -388,7 +388,7 @@ int basicTests(U32 seed, double compressibility)
         BYTE* op = (BYTE*)decodedBuffer;
         BYTE* const oend = (BYTE*)decodedBuffer + COMPRESSIBLE_NOISE_LENGTH;
         BYTE* ip = (BYTE*)compressedBuffer;
-        BYTE* const iend = (BYTE*)compressedBuffer + cSize + 8;
+        BYTE* iend = (BYTE*)compressedBuffer + cSize + 8;
 
         LZ4F_errorCode_t errorCode = LZ4F_createDecompressionContext(&dCtx, LZ4F_VERSION);
         if (LZ4F_isError(errorCode)) goto _output_error;
@@ -411,6 +411,25 @@ int basicTests(U32 seed, double compressibility)
         }
         DISPLAYLEVEL(3, "Skipped %i bytes \n", (int)decodedBufferSize);
 
+        /* generate zero-size skippable frame */
+        FUZ_writeLE32(ip, LZ4F_MAGIC_SKIPPABLE_START+1);
+        FUZ_writeLE32(ip+4, 0);
+        iend = ip+8;
+
+        DISPLAYLEVEL(3, "random segment sizes : \n");
+        while (ip < iend)
+        {
+            unsigned nbBits = FUZ_rand(&randState) % maxBits;
+            size_t iSize = (FUZ_rand(&randState) & ((1<<nbBits)-1)) + 1;
+            size_t oSize = oend-op;
+            if (iSize > (size_t)(iend-ip)) iSize = iend-ip;
+            errorCode = LZ4F_decompress(dCtx, op, &oSize, ip, &iSize, NULL);
+            if (LZ4F_isError(errorCode)) goto _output_error;
+            op += oSize;
+            ip += iSize;
+        }
+        DISPLAYLEVEL(3, "Skipped %i bytes \n", (int)decodedBufferSize);
+
         errorCode = LZ4F_freeDecompressionContext(dCtx);
         if (LZ4F_isError(errorCode)) goto _output_error;
     }
@@ -509,7 +528,7 @@ int fuzzerTests(U32 seed, unsigned nbTests, unsigned startTest, double compressi
         DISPLAYUPDATE(2, "\r%5u   ", testNb);
         crcOrig = XXH64((BYTE*)srcBuffer+srcStart, srcSize, 1);
 
-        if ((FUZ_rand(&randState) & 0xFFF) == 3)
+        if ((FUZ_rand(&randState) & 0xFFF) == 0)
         {
             /* create a skippable frame (rare case) */
             BYTE* op = (BYTE*)compressedBuffer;
-- 
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