Merge pull request #560 from iburinoc/findcompressedsize

Change name to to findFrameCompressedSize and add skippable support

lib/decompress/zstd_decompress.c

@@ -369,7 +369,7 @@ unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize)
                 totalDstSize += ret;
             }
             {
-                size_t const frameSrcSize = ZSTD_getFrameCompressedSize(src, srcSize);
+                size_t const frameSrcSize = ZSTD_findFrameCompressedSize(src, srcSize);
                 if (ZSTD_isError(frameSrcSize)) {
                     return ZSTD_CONTENTSIZE_ERROR;
                 }
@@ -1437,17 +1437,20 @@ size_t ZSTD_generateNxBytes(void* dst, size_t dstCapacity, BYTE byte, size_t len
     return length;
 }
 
-/** ZSTD_getFrameCompressedSize() :
+/** ZSTD_findFrameCompressedSize() :
  *  compatible with legacy mode
- *  `src` must point to the start of a ZSTD or ZSTD legacy frame
+ *  `src` must point to the start of a ZSTD frame, ZSTD legacy frame, or skippable frame
  *  `srcSize` must be at least as large as the frame contained
  *  @return : the compressed size of the frame starting at `src` */
-size_t ZSTD_getFrameCompressedSize(const void *src, size_t srcSize)
+size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize)
 {
 #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT==1)
-    if (ZSTD_isLegacy(src, srcSize)) return ZSTD_getFrameCompressedSizeLegacy(src, srcSize);
+    if (ZSTD_isLegacy(src, srcSize)) return ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
 #endif
-    {
+    if (srcSize >= ZSTD_skippableHeaderSize &&
+            (MEM_readLE32(src) & 0xFFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
+        return ZSTD_skippableHeaderSize + MEM_readLE32((const BYTE*)src + 4);
+    } else {
         const BYTE* ip = (const BYTE*)src;
         const BYTE* const ipstart = ip;
         size_t remainingSize = srcSize;
@@ -1576,7 +1579,7 @@ static size_t ZSTD_decompressMultiFrame(ZSTD_DCtx* dctx,
 
 #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
         if (ZSTD_isLegacy(src, srcSize)) {
-            size_t const frameSize = ZSTD_getFrameCompressedSizeLegacy(src, srcSize);
+            size_t const frameSize = ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
             size_t decodedSize;
             if (ZSTD_isError(frameSize)) return frameSize;
 

lib/legacy/zstd_legacy.h

@@ -123,26 +123,26 @@ MEM_STATIC size_t ZSTD_decompressLegacy(
     }
 }
 
-MEM_STATIC size_t ZSTD_getFrameCompressedSizeLegacy(const void *src,
+MEM_STATIC size_t ZSTD_findFrameCompressedSizeLegacy(const void *src,
                                              size_t compressedSize)
 {
     U32 const version = ZSTD_isLegacy(src, compressedSize);
     switch(version)
     {
         case 1 :
-            return ZSTDv01_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv01_findFrameCompressedSize(src, compressedSize);
         case 2 :
-            return ZSTDv02_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv02_findFrameCompressedSize(src, compressedSize);
         case 3 :
-            return ZSTDv03_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv03_findFrameCompressedSize(src, compressedSize);
         case 4 :
-            return ZSTDv04_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv04_findFrameCompressedSize(src, compressedSize);
         case 5 :
-            return ZSTDv05_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv05_findFrameCompressedSize(src, compressedSize);
         case 6 :
-            return ZSTDv06_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv06_findFrameCompressedSize(src, compressedSize);
         case 7 :
-            return ZSTDv07_getFrameCompressedSize(src, compressedSize);
+            return ZSTDv07_findFrameCompressedSize(src, compressedSize);
         default :
             return ERROR(prefix_unknown);
     }

lib/legacy/zstd_v01.c

@@ -1992,7 +1992,7 @@ size_t ZSTDv01_decompress(void* dst, size_t maxDstSize, const void* src, size_t
     return ZSTDv01_decompressDCtx(&ctx, dst, maxDstSize, src, srcSize);
 }
 
-size_t ZSTDv01_getFrameCompressedSize(const void* src, size_t srcSize)
+size_t ZSTDv01_findFrameCompressedSize(const void* src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;

lib/legacy/zstd_v01.h

@@ -40,7 +40,7 @@ ZSTDv01_getFrameSrcSize() : get the source length of a ZSTD frame compliant with
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv01_isError())
 */
-size_t ZSTDv01_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv01_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /**
 ZSTDv01_isError() : tells if the result of ZSTDv01_decompress() is an error

lib/legacy/zstd_v02.c

@@ -3378,7 +3378,7 @@ static size_t ZSTD_decompress(void* dst, size_t maxDstSize, const void* src, siz
     return ZSTD_decompressDCtx(&ctx, dst, maxDstSize, src, srcSize);
 }
 
-static size_t ZSTD_getFrameCompressedSize(const void *src, size_t srcSize)
+static size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize)
 {
 
     const BYTE* ip = (const BYTE*)src;
@@ -3524,9 +3524,9 @@ size_t ZSTDv02_decompress( void* dst, size_t maxOriginalSize,
 	return ZSTD_decompress(dst, maxOriginalSize, src, compressedSize);
 }
 
-size_t ZSTDv02_getFrameCompressedSize(const void *src, size_t compressedSize)
+size_t ZSTDv02_findFrameCompressedSize(const void *src, size_t compressedSize)
 {
-    return ZSTD_getFrameCompressedSize(src, compressedSize);
+    return ZSTD_findFrameCompressedSize(src, compressedSize);
 }
 
 ZSTDv02_Dctx* ZSTDv02_createDCtx(void)

lib/legacy/zstd_v02.h

@@ -40,7 +40,7 @@ ZSTDv02_getFrameSrcSize() : get the source length of a ZSTD frame compliant with
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv02_isError())
 */
-size_t ZSTDv02_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv02_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /**
 ZSTDv02_isError() : tells if the result of ZSTDv02_decompress() is an error

lib/legacy/zstd_v03.c

@@ -3019,7 +3019,7 @@ static size_t ZSTD_decompress(void* dst, size_t maxDstSize, const void* src, siz
     return ZSTD_decompressDCtx(&ctx, dst, maxDstSize, src, srcSize);
 }
 
-static size_t ZSTD_getFrameCompressedSize(const void* src, size_t srcSize)
+static size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;
@@ -3165,9 +3165,9 @@ size_t ZSTDv03_decompress( void* dst, size_t maxOriginalSize,
 	return ZSTD_decompress(dst, maxOriginalSize, src, compressedSize);
 }
 
-size_t ZSTDv03_getFrameCompressedSize(const void* src, size_t srcSize)
+size_t ZSTDv03_findFrameCompressedSize(const void* src, size_t srcSize)
 {
-    return ZSTD_getFrameCompressedSize(src, srcSize);
+    return ZSTD_findFrameCompressedSize(src, srcSize);
 }
 
 ZSTDv03_Dctx* ZSTDv03_createDCtx(void)

lib/legacy/zstd_v03.h

@@ -40,7 +40,7 @@ ZSTDv03_getFrameSrcSize() : get the source length of a ZSTD frame compliant with
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv03_isError())
 */
-size_t ZSTDv03_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv03_findFrameCompressedSize(const void* src, size_t compressedSize);
 
     /**
 ZSTDv03_isError() : tells if the result of ZSTDv03_decompress() is an error

lib/legacy/zstd_v04.c

@@ -3326,7 +3326,7 @@ static size_t ZSTD_decompress_usingDict(ZSTD_DCtx* ctx,
     return op-ostart;
 }
 
-static size_t ZSTD_getFrameCompressedSize(const void* src, size_t srcSize)
+static size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;
@@ -3782,9 +3782,9 @@ size_t ZSTDv04_decompress(void* dst, size_t maxDstSize, const void* src, size_t
 #endif
 }
 
-size_t ZSTDv04_getFrameCompressedSize(const void* src, size_t srcSize)
+size_t ZSTDv04_findFrameCompressedSize(const void* src, size_t srcSize)
 {
-    return ZSTD_getFrameCompressedSize(src, srcSize);
+    return ZSTD_findFrameCompressedSize(src, srcSize);
 }
 
 size_t ZSTDv04_resetDCtx(ZSTDv04_Dctx* dctx) { return ZSTD_resetDCtx(dctx); }

lib/legacy/zstd_v04.h

@@ -40,7 +40,7 @@ ZSTDv04_getFrameSrcSize() : get the source length of a ZSTD frame compliant with
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv04_isError())
 */
-size_t ZSTDv04_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv04_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /**
 ZSTDv04_isError() : tells if the result of ZSTDv04_decompress() is an error

lib/legacy/zstd_v05.c

@@ -3583,7 +3583,7 @@ size_t ZSTDv05_decompress(void* dst, size_t maxDstSize, const void* src, size_t
 #endif
 }
 
-size_t ZSTDv05_getFrameCompressedSize(const void *src, size_t srcSize)
+size_t ZSTDv05_findFrameCompressedSize(const void *src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;

lib/legacy/zstd_v05.h

@@ -38,7 +38,7 @@ ZSTDv05_getFrameSrcSize() : get the source length of a ZSTD frame
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv05_isError())
 */
-size_t ZSTDv05_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv05_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /* *************************************
 *  Helper functions

lib/legacy/zstd_v06.c

@@ -3729,7 +3729,7 @@ size_t ZSTDv06_decompress(void* dst, size_t dstCapacity, const void* src, size_t
 #endif
 }
 
-size_t ZSTDv06_getFrameCompressedSize(const void* src, size_t srcSize)
+size_t ZSTDv06_findFrameCompressedSize(const void* src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;

lib/legacy/zstd_v06.h

@@ -47,7 +47,7 @@ ZSTDv06_getFrameSrcSize() : get the source length of a ZSTD frame
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv06_isError())
 */
-size_t ZSTDv06_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv06_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /* *************************************
 *  Helper functions

lib/legacy/zstd_v07.c

@@ -3968,7 +3968,7 @@ size_t ZSTDv07_decompress(void* dst, size_t dstCapacity, const void* src, size_t
 #endif
 }
 
-size_t ZSTDv07_getFrameCompressedSize(const void* src, size_t srcSize)
+size_t ZSTDv07_findFrameCompressedSize(const void* src, size_t srcSize)
 {
     const BYTE* ip = (const BYTE*)src;
     size_t remainingSize = srcSize;

lib/legacy/zstd_v07.h

@@ -54,7 +54,7 @@ ZSTDv07_getFrameSrcSize() : get the source length of a ZSTD frame
     return : the number of bytes that would be read to decompress this frame
              or an errorCode if it fails (which can be tested using ZSTDv07_isError())
 */
-size_t ZSTDv07_getFrameCompressedSize(const void* src, size_t compressedSize);
+size_t ZSTDv07_findFrameCompressedSize(const void* src, size_t compressedSize);
 
 /*======  Helper functions  ======*/
 ZSTDLIBv07_API unsigned    ZSTDv07_isError(size_t code);          /*!< tells if a `size_t` function result is an error code */

lib/zstd.h

@@ -400,12 +400,12 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; v
 *  Compressed size functions
 ***************************************/
 
-/*! ZSTD_getFrameCompressedSize() :
- *  `src` should point to the start of a ZSTD encoded frame
+/*! ZSTD_findFrameCompressedSize() :
+ *  `src` should point to the start of a ZSTD encoded frame or skippable frame
  *  `srcSize` must be at least as large as the frame
  *  @return : the compressed size of the frame pointed to by `src`, suitable to pass to
  *      `ZSTD_decompress` or similar, or an error code if given invalid input. */
-ZSTDLIB_API size_t ZSTD_getFrameCompressedSize(const void* src, size_t srcSize);
+ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
 
 /***************************************
 *  Decompressed size functions
@@ -700,6 +700,9 @@ ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapaci
   c) Frame Content - any content (User Data) of length equal to Frame Size
   For skippable frames ZSTD_decompressContinue() always returns 0.
   For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
+    Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
+           For purposes of decompression, it is valid in both cases to skip the frame using
+           ZSTD_findFrameCompressedSize to find its size in bytes.
   It also returns Frame Size as fparamsPtr->frameContentSize.
 */