added : ZSTD_getDecompressedSize()

lib/legacy/zstd_legacy.h

@@ -69,6 +69,30 @@ MEM_STATIC unsigned ZSTD_isLegacy (U32 magicNumberLE)
 }
 
 
+MEM_STATIC unsigned long long ZSTD_getDecompressedSize_legacy(const void* src, size_t srcSize)
+{
+    if (srcSize < 4) return 0;
+
+    {   U32 const magic = MEM_readLE32(src);
+        U32 const version = ZSTD_isLegacy(magic);
+        if (!version) return 0;   /* not a supported legacy format */
+        if (version < 5) return 0;  /* no decompressed size in frame header */
+        if (version==5) {
+            ZSTDv05_parameters fParams;
+            size_t const frResult = ZSTDv05_getFrameParams(&fParams, src, srcSize);
+            if (frResult != 0) return 0;
+            return fParams.srcSize;
+        }
+        if (version==6) {
+            ZSTDv06_frameParams fParams;
+            size_t const frResult = ZSTDv06_getFrameParams(&fParams, src, srcSize);
+            if (frResult != 0) return 0;
+            return fParams.frameContentSize;
+        }
+        return 0;   /* should not be possible */
+    }
+}
+
 MEM_STATIC size_t ZSTD_decompressLegacy(
                      void* dst, size_t dstCapacity,
                const void* src, size_t compressedSize,

lib/legacy/zstd_v06.c

@@ -36,7 +36,7 @@
 #include "zstd_v06.h"
 #include <stddef.h>    /* size_t, ptrdiff_t */
 #include <string.h>    /* memcpy */
-#include <stdlib.h>    /* malloc, free, qsort */ 
+#include <stdlib.h>    /* malloc, free, qsort */
 
 
 
@@ -535,8 +535,6 @@ ZSTDLIB_API size_t ZSTDv06_decompress_usingPreparedDCtx(
 
 
 
-struct ZSTDv06_frameParams_s { U64 frameContentSize; U32 windowLog; };
-
 #define ZSTDv06_FRAMEHEADERSIZE_MAX 13    /* for static allocation */
 static const size_t ZSTDv06_frameHeaderSize_min = 5;
 static const size_t ZSTDv06_frameHeaderSize_max = ZSTDv06_FRAMEHEADERSIZE_MAX;

lib/legacy/zstd_v06.h

@@ -107,7 +107,7 @@ ZSTDLIB_API size_t ZSTDv06_decompress_usingDict(ZSTDv06_DCtx* dctx,
 /*-************************
 *  Advanced Streaming API
 ***************************/
-
+struct ZSTDv06_frameParams_s { unsigned long long frameContentSize; unsigned windowLog; };
 typedef struct ZSTDv06_frameParams_s ZSTDv06_frameParams;
 
 ZSTDLIB_API size_t ZSTDv06_getFrameParams(ZSTDv06_frameParams* fparamsPtr, const void* src, size_t srcSize);   /**< doesn't consume input */