LZ4F_compressBound(0) provides upper bound for LZ4F_flush() and LZ4F_compressEnd() [#290, suggested by @vtermanis]

1 files changed, 12 insertions, 11 deletions

diff --git a/lib/lz4frame.h b/lib/lz4frame.h
index 3104d2e..a4a4ce6 100644
--- a/lib/lz4frame.h
+++ b/lib/lz4frame.h
@@ -206,10 +206,11 @@ LZ4FLIB_API LZ4F_errorCode_t LZ4F_freeCompressionContext(LZ4F_cctx* cctx);
 
 /* Compression */
 
+#define LZ4F_HEADER_SIZE_MAX 15
 LZ4FLIB_API size_t LZ4F_compressBegin(LZ4F_cctx* cctx, void* dstBuffer, size_t dstCapacity, const LZ4F_preferences_t* prefsPtr);
 /* LZ4F_compressBegin() :
  * will write the frame header into dstBuffer.
- * dstBuffer must be large enough to accommodate a header. Maximum header size is 15 bytes.
+ * dstCapacity must be large enough to store the header. Maximum header size is LZ4F_HEADER_SIZE_MAX bytes.
  * `prefsPtr` is optional : you can provide NULL as argument, all preferences will then be set to default.
  * @return : number of bytes written into dstBuffer for the header
  *           or an error code (which can be tested using LZ4F_isError())
@@ -217,20 +218,20 @@ LZ4FLIB_API size_t LZ4F_compressBegin(LZ4F_cctx* cctx, void* dstBuffer, size_t d
 
 LZ4FLIB_API size_t LZ4F_compressBound(size_t srcSize, const LZ4F_preferences_t* prefsPtr);
 /* LZ4F_compressBound() :
- * Provides the minimum size of Dst buffer given srcSize to handle worst case situations.
- * Different preferences can produce different results.
- * prefsPtr is optional : you can provide NULL as argument, all preferences will then be set to cover worst case.
- * This function includes frame termination cost (4 bytes, or 8 if frame checksum is enabled)
+ * Provides dstCapacity given a srcSize to guarantee operation success in worst case situations.
+ * prefsPtr is optional : you can provide NULL as argument, preferences will be set to cover worst case scenario.
+ * Result is always the same for a srcSize and prefsPtr, so it can be trusted to size reusable buffers.
+ * When srcSize==0, LZ4F_compressBound() provides an upper bound for LZ4F_flush() and LZ4F_compressEnd() operations.
  */
 
 LZ4FLIB_API size_t LZ4F_compressUpdate(LZ4F_cctx* cctx, void* dstBuffer, size_t dstCapacity, const void* srcBuffer, size_t srcSize, const LZ4F_compressOptions_t* cOptPtr);
 /* LZ4F_compressUpdate() :
  * LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary.
- * An important rule is that dstBuffer MUST be large enough (dstCapacity) to ensure compression completion even in worst case.
- * This value is provided by using LZ4F_compressBound().
+ * An important rule is that dstCapacity MUST be large enough to ensure operation success even in worst case situations.
+ * This value is provided by LZ4F_compressBound().
  * If this condition is not respected, LZ4F_compress() will fail (result is an errorCode).
  * LZ4F_compressUpdate() doesn't guarantee error recovery. When an error occurs, compression context must be freed or resized.
- * `cOptPtr` is optional : it's possible to provide NULL, all options will be set to default.
+ * `cOptPtr` is optional : NULL can be provided, in which case all options are set to default.
  * @return : number of bytes written into `dstBuffer` (it can be zero, meaning input data was just buffered).
  *           or an error code if it fails (which can be tested using LZ4F_isError())
  */
@@ -245,12 +246,12 @@ LZ4FLIB_API size_t LZ4F_flush(LZ4F_cctx* cctx, void* dstBuffer, size_t dstCapaci
  *           or an error code if it fails (which can be tested using LZ4F_isError())
  */
 
-LZ4FLIB_API size_t LZ4F_compressEnd(LZ4F_cctx* cctx, void* dstBuffer, size_t dstMaxSize, const LZ4F_compressOptions_t* cOptPtr);
+LZ4FLIB_API size_t LZ4F_compressEnd(LZ4F_cctx* cctx, void* dstBuffer, size_t dstCapacity, const LZ4F_compressOptions_t* cOptPtr);
 /* LZ4F_compressEnd() :
- * To properly finish the compressed frame, invoke LZ4F_compressEnd().
+ * To properly finish an LZ4 frame, invoke LZ4F_compressEnd().
  * It will flush whatever data remained within `cctx` (like LZ4_flush())
  * and properly finalize the frame, with an endMark and a checksum.
- * `cOptPtr` is optional : it's possible to provide NULL, all options will be set to default.
+ * `cOptPtr` is optional : NULL can be provided, in which case all options will be set to default.
  * @return : number of bytes written into dstBuffer (necessarily >= 4 (endMark), or 8 if optional frame checksum is enabled)
  *           or an error code if it fails (which can be tested using LZ4F_isError())
  * A successful call to LZ4F_compressEnd() makes `cctx` available again for another compression task.