Add LZ4_compress_fast_safeExtState Function

2 files changed, 17 insertions, 1 deletions

diff --git a/lib/lz4.c b/lib/lz4.c
index 7b8de77..45cc7c9 100644
--- a/lib/lz4.c
+++ b/lib/lz4.c
@@ -739,9 +739,17 @@ _clean_up:
 
 int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
 {
+  LZ4_resetStream((LZ4_stream_t*)state);
+  return LZ4_compress_fast_safeExtState(state, source, dest, inputSize, maxOutputSize, acceleration);
+}
+
+
+int LZ4_compress_fast_safeExtState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
+{
     LZ4_stream_t_internal* ctx = &((LZ4_stream_t*)state)->internal_donotuse;
-    LZ4_resetStream((LZ4_stream_t*)state);
     if (acceleration < 1) acceleration = ACCELERATION_DEFAULT;
+    ctx->dictionary = NULL;
+    ctx->dictSize = 0;
 
     if (maxOutputSize >= LZ4_compressBound(inputSize)) {
         if (inputSize < LZ4_64Klimit)
diff --git a/lib/lz4.h b/lib/lz4.h
index d2e2103..0013ffe 100644
--- a/lib/lz4.h
+++ b/lib/lz4.h
@@ -179,13 +179,21 @@ LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int d
 
 
 /*!
+LZ4_compress_fast_safeExtState() :
 LZ4_compress_fast_extState() :
     Same compression function, just using an externally allocated memory space to store compression state.
     Use LZ4_sizeofState() to know how much memory must be allocated,
     and allocate it on 8-bytes boundaries (using malloc() typically).
     Then, provide it as 'void* state' to compression function.
+
+    Use _safeExtState variant if LZ4_resetStream() was called on the state
+    buffer before being used for the first time (calls to this function leave
+    the state in a safe state, so zeroing is not required between calls).
+    Otherwise, using legacy _extState requires LZ4 to reinitialize the state
+    internally for every call.
 */
 LZ4LIB_API int LZ4_sizeofState(void);
+LZ4LIB_API int LZ4_compress_fast_safeExtState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 LZ4LIB_API int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);