LZ4F_getFrameInfo() : provides srcSize hint like LZ4F_decompress()

2 files changed, 9 insertions, 4 deletions

diff --git a/lz4frame.c b/lz4frame.c
index 1be6cff..4996d28 100644
--- a/lz4frame.c
+++ b/lz4frame.c
@@ -733,7 +733,9 @@ typedef enum { dstage_getHeader=0, dstage_storeHeader, dstage_decodeHeader,
  * The objective is to extract header information without starting decompression, typically for allocation purposes.
  * LZ4F_getFrameInfo() can also be used *after* starting decompression, on a valid LZ4F_decompressionContext_t.
  * The number of bytes read from srcBuffer will be provided within *srcSizePtr (necessarily <= original value).
- * The function result is an error code which can be tested using LZ4F_isError().
+ * You are expected to resume decompression from where it stopped (srcBuffer + *srcSizePtr)
+ * The function result is an hint of the better srcSize to use for next call to LZ4F_decompress.
+ * or an error code which can be tested using LZ4F_isError().
  */
 LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_decompressionContext_t decompressionContext, LZ4F_frameInfo_t* frameInfoPtr, const void* srcBuffer, size_t* srcSizePtr)
 {
@@ -745,14 +747,15 @@ LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_decompressionContext_t decompressionCont
         if (LZ4F_isError(errorCode)) return errorCode;
         *srcSizePtr = errorCode;
         *frameInfoPtr = dctxPtr->frameInfo;
+        dctxPtr->srcExpect = (BYTE*)srcBuffer + errorCode;
         dctxPtr->dStage = dstage_getCBlockSize;
-        return OK_NoError;
+        return 4;
     }
 
     /* frameInfo already decoded */
     *srcSizePtr = 0;
     *frameInfoPtr = dctxPtr->frameInfo;
-    return OK_NoError;
+    return 0;
 }
 
 
diff --git a/lz4frame.h b/lz4frame.h
index 4c8dd86..40f5e3f 100644
--- a/lz4frame.h
+++ b/lz4frame.h
@@ -223,7 +223,9 @@ size_t LZ4F_getFrameInfo(LZ4F_decompressionContext_t decompressionContext, LZ4F_
  * The objective is to extract header information without starting decompression, typically for allocation purposes.
  * LZ4F_getFrameInfo() can also be used *after* starting decompression, on a valid LZ4F_decompressionContext_t.
  * The number of bytes read from srcBuffer will be provided within *srcSizePtr (necessarily <= original value).
- * The function result is an error code which can be tested using LZ4F_isError().
+ * You are expected to resume decompression from where it stopped (srcBuffer + *srcSizePtr)
+ * The function result is an hint of the better srcSize to use for next call to LZ4F_decompress.
+ * or an error code which can be tested using LZ4F_isError().
  */
 
 size_t LZ4F_decompress(LZ4F_decompressionContext_t decompressionContext, void* dstBuffer, size_t* dstSizePtr, const void* srcBuffer, size_t* srcSizePtr, const LZ4F_decompressOptions_t* decompressOptionsPtr);