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-rw-r--r--lib/lz4frame.c90
-rw-r--r--lib/lz4frame.h66
-rw-r--r--tests/frametest.c11
3 files changed, 107 insertions, 60 deletions
diff --git a/lib/lz4frame.c b/lib/lz4frame.c
index efe38da..2b31a0d 100644
--- a/lib/lz4frame.c
+++ b/lib/lz4frame.c
@@ -211,7 +211,7 @@ static void LZ4F_writeLE64 (void* dst, U64 value64)
#define LZ4F_BLOCKUNCOMPRESSED_FLAG 0x80000000U
#define LZ4F_BLOCKSIZEID_DEFAULT LZ4F_max64KB
-static const size_t minFHSize = 7;
+static const size_t minFHSize = LZ4F_HEADER_SIZE_MIN; /* 7 */
static const size_t maxFHSize = LZ4F_HEADER_SIZE_MAX; /* 19 */
static const size_t BHSize = 4; /* block header : size, and compress flag */
static const size_t BFSize = 4; /* block footer : checksum (optional) */
@@ -280,8 +280,9 @@ size_t LZ4F_getBlockSize(unsigned blockSizeID)
static const size_t blockSizes[4] = { 64 KB, 256 KB, 1 MB, 4 MB };
if (blockSizeID == 0) blockSizeID = LZ4F_BLOCKSIZEID_DEFAULT;
- if (blockSizeID < 4 || blockSizeID > 7) return err0r(LZ4F_ERROR_maxBlockSize_invalid);
- blockSizeID -= 4;
+ if (blockSizeID < LZ4F_max64KB || blockSizeID > LZ4F_max4MB)
+ return err0r(LZ4F_ERROR_maxBlockSize_invalid);
+ blockSizeID -= LZ4F_max64KB;
return blockSizes[blockSizeID];
}
@@ -1094,31 +1095,6 @@ void LZ4F_resetDecompressionContext(LZ4F_dctx* dctx)
}
-/*! LZ4F_headerSize() :
- * @return : size of frame header
- * or an error code, which can be tested using LZ4F_isError()
- */
-static size_t LZ4F_headerSize(const void* src, size_t srcSize)
-{
- /* minimal srcSize to determine header size */
- if (srcSize < 5) return err0r(LZ4F_ERROR_frameHeader_incomplete);
-
- /* special case : skippable frames */
- if ((LZ4F_readLE32(src) & 0xFFFFFFF0U) == LZ4F_MAGIC_SKIPPABLE_START) return 8;
-
- /* control magic number */
- if (LZ4F_readLE32(src) != LZ4F_MAGICNUMBER)
- return err0r(LZ4F_ERROR_frameType_unknown);
-
- /* Frame Header Size */
- { BYTE const FLG = ((const BYTE*)src)[4];
- U32 const contentSizeFlag = (FLG>>3) & _1BIT;
- U32 const dictIDFlag = FLG & _1BIT;
- return minFHSize + (contentSizeFlag*8) + (dictIDFlag*4);
- }
-}
-
-
/*! LZ4F_decodeHeader() :
* input : `src` points at the **beginning of the frame**
* output : set internal values of dctx, such as
@@ -1191,6 +1167,7 @@ static size_t LZ4F_decodeHeader(LZ4F_dctx* dctx, const void* src, size_t srcSize
}
/* check header */
+ assert(frameHeaderSize > 5);
{ BYTE const HC = LZ4F_headerChecksum(srcPtr+4, frameHeaderSize-5);
if (HC != srcPtr[frameHeaderSize-1])
return err0r(LZ4F_ERROR_headerChecksum_invalid);
@@ -1214,6 +1191,34 @@ static size_t LZ4F_decodeHeader(LZ4F_dctx* dctx, const void* src, size_t srcSize
}
+/*! LZ4F_headerSize() :
+ * @return : size of frame header
+ * or an error code, which can be tested using LZ4F_isError()
+ */
+size_t LZ4F_headerSize(const void* src, size_t srcSize)
+{
+ if (src == NULL) return err0r(LZ4F_ERROR_srcPtr_wrong);
+
+ /* minimal srcSize to determine header size */
+ if (srcSize < LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH)
+ return err0r(LZ4F_ERROR_frameHeader_incomplete);
+
+ /* special case : skippable frames */
+ if ((LZ4F_readLE32(src) & 0xFFFFFFF0U) == LZ4F_MAGIC_SKIPPABLE_START)
+ return 8;
+
+ /* control magic number */
+ if (LZ4F_readLE32(src) != LZ4F_MAGICNUMBER)
+ return err0r(LZ4F_ERROR_frameType_unknown);
+
+ /* Frame Header Size */
+ { BYTE const FLG = ((const BYTE*)src)[4];
+ U32 const contentSizeFlag = (FLG>>3) & _1BIT;
+ U32 const dictIDFlag = FLG & _1BIT;
+ return minFHSize + (contentSizeFlag*8) + (dictIDFlag*4);
+ }
+}
+
/*! LZ4F_getFrameInfo() :
* This function extracts frame parameters (max blockSize, frame checksum, etc.).
* Usage is optional. Objective is to provide relevant information for allocation purposes.
@@ -1229,10 +1234,12 @@ static size_t LZ4F_decodeHeader(LZ4F_dctx* dctx, const void* src, size_t srcSize
* note 1 : in case of error, dctx is not modified. Decoding operations can resume from where they stopped.
* note 2 : frame parameters are *copied into* an already allocated LZ4F_frameInfo_t structure.
*/
-LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctx, LZ4F_frameInfo_t* frameInfoPtr,
- const void* srcBuffer, size_t* srcSizePtr)
+LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctx,
+ LZ4F_frameInfo_t* frameInfoPtr,
+ const void* srcBuffer, size_t* srcSizePtr)
{
- if (dctx->dStage > dstage_storeFrameHeader) { /* assumption : dstage_* header enum at beginning of range */
+ LZ4F_STATIC_ASSERT(dstage_getFrameHeader < dstage_storeFrameHeader);
+ if (dctx->dStage > dstage_storeFrameHeader) {
/* frameInfo already decoded */
size_t o=0, i=0;
*srcSizePtr = 0;
@@ -1245,7 +1252,6 @@ LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctx, LZ4F_frameInfo_t* frameInfoP
*srcSizePtr = 0;
return err0r(LZ4F_ERROR_frameDecoding_alreadyStarted);
} else {
- size_t decodeResult;
size_t const hSize = LZ4F_headerSize(srcBuffer, *srcSizePtr);
if (LZ4F_isError(hSize)) { *srcSizePtr=0; return hSize; }
if (*srcSizePtr < hSize) {
@@ -1253,16 +1259,16 @@ LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctx, LZ4F_frameInfo_t* frameInfoP
return err0r(LZ4F_ERROR_frameHeader_incomplete);
}
- decodeResult = LZ4F_decodeHeader(dctx, srcBuffer, hSize);
- if (LZ4F_isError(decodeResult)) {
- *srcSizePtr = 0;
- } else {
- *srcSizePtr = decodeResult;
- decodeResult = BHSize; /* block header size */
- }
- *frameInfoPtr = dctx->frameInfo;
- return decodeResult;
- } }
+ { size_t decodeResult = LZ4F_decodeHeader(dctx, srcBuffer, hSize);
+ if (LZ4F_isError(decodeResult)) {
+ *srcSizePtr = 0;
+ } else {
+ *srcSizePtr = decodeResult;
+ decodeResult = BHSize; /* block header size */
+ }
+ *frameInfoPtr = dctx->frameInfo;
+ return decodeResult;
+ } } }
}
diff --git a/lib/lz4frame.h b/lib/lz4frame.h
index 68f4118..2ada8b8 100644
--- a/lib/lz4frame.h
+++ b/lib/lz4frame.h
@@ -247,7 +247,8 @@ LZ4FLIB_API LZ4F_errorCode_t LZ4F_freeCompressionContext(LZ4F_cctx* cctx);
/*---- Compression ----*/
-#define LZ4F_HEADER_SIZE_MAX 19 /* LZ4 Frame header size can vary from 7 to 19 bytes */
+#define LZ4F_HEADER_SIZE_MIN 7 /* LZ4 Frame header size can vary, depending on selected paramaters */
+#define LZ4F_HEADER_SIZE_MAX 19
/*! LZ4F_compressBegin() :
* will write the frame header into dstBuffer.
@@ -352,23 +353,58 @@ LZ4FLIB_API LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_dctx* dctx);
* Streaming decompression functions
*************************************/
+#define LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH 5
+
+/*! LZ4F_headerSize() : v1.9.0+
+ * Provide the header size of a frame starting at `src`.
+ * `srcSize` must be >= LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH,
+ * which is enough to decode the header length.
+ * @return : size of frame header
+ * or an error code, which can be tested using LZ4F_isError()
+ * note : Frame header size is variable, but is guaranteed to be
+ * >= LZ4F_HEADER_SIZE_MIN bytes, and <= LZ4F_HEADER_SIZE_MAX bytes.
+ */
+size_t LZ4F_headerSize(const void* src, size_t srcSize);
+
/*! LZ4F_getFrameInfo() :
* This function extracts frame parameters (max blockSize, dictID, etc.).
- * Its usage is optional.
- * Extracted information is typically useful for allocation and dictionary.
- * This function works in 2 situations :
- * - At the beginning of a new frame, in which case
- * it will decode information from `srcBuffer`, starting the decoding process.
- * Input size must be large enough to successfully decode the entire frame header.
- * Frame header size is variable, but is guaranteed to be <= LZ4F_HEADER_SIZE_MAX bytes.
- * It's allowed to provide more input data than this minimum.
- * - After decoding has been started.
- * In which case, no input is read, frame parameters are extracted from dctx.
- * - If decoding has barely started, but not yet extracted information from header,
+ * Its usage is optional: user can call LZ4F_decompress() directly.
+ *
+ * Extracted information will fill an existing LZ4F_frameInfo_t structure.
+ * This can be useful for allocation and dictionary identification purposes.
+ *
+ * LZ4F_getFrameInfo() can work in the following situations :
+ *
+ * 1) At the beginning of a new frame, before any invocation of LZ4F_decompress().
+ * It will decode header from `srcBuffer`,
+ * consuming the header and starting the decoding process.
+ *
+ * Input size must be large enough to contain the full frame header.
+ * Frame header size can be known beforehand by LZ4F_headerSize().
+ * Frame header size is variable, but is guaranteed to be >= LZ4F_HEADER_SIZE_MIN bytes,
+ * and not more than <= LZ4F_HEADER_SIZE_MAX bytes.
+ * Hence, blindly providing LZ4F_HEADER_SIZE_MAX bytes or more will always work.
+ * It's allowed to provide more input data than the header size,
+ * LZ4F_getFrameInfo() will only consume the header.
+ *
+ * If input size is not large enough,
+ * aka if it's smaller than header size,
+ * function will fail and return an error code.
+ *
+ * 2) After decoding has been started,
+ * it's possible to invoke LZ4F_getFrameInfo() anytime
+ * to extract already decoded frame parameters stored within dctx.
+ *
+ * Note that, if decoding has barely started,
+ * and not yet read enough information to decode the header,
* LZ4F_getFrameInfo() will fail.
- * The number of bytes consumed from srcBuffer will be updated within *srcSizePtr (necessarily <= original value).
- * Decompression must resume from (srcBuffer + *srcSizePtr).
- * @return : an hint about how many srcSize bytes LZ4F_decompress() expects for next call,
+ *
+ * The number of bytes consumed from srcBuffer will be updated in *srcSizePtr (necessarily <= original value).
+ * LZ4F_getFrameInfo() only consumes bytes when decoding has not yet started,
+ * and when decoding the header has been successful.
+ * Decompression must then resume from (srcBuffer + *srcSizePtr).
+ *
+ * @return : a hint about how many srcSize bytes LZ4F_decompress() expects for next call,
* or an error code which can be tested using LZ4F_isError().
* note 1 : in case of error, dctx is not modified. Decoding operation can resume from beginning safely.
* note 2 : frame parameters are *copied into* an already allocated LZ4F_frameInfo_t structure.
diff --git a/tests/frametest.c b/tests/frametest.c
index fa005db..59e866c 100644
--- a/tests/frametest.c
+++ b/tests/frametest.c
@@ -211,9 +211,13 @@ int basicTests(U32 seed, double compressibility)
CHECK ( LZ4F_createDecompressionContext(&dCtx, LZ4F_VERSION) );
DISPLAYLEVEL(3, "LZ4F_getFrameInfo on null-content frame (#157) \n");
- { size_t avail_in = cSize;
- LZ4F_frameInfo_t frame_info;
+ assert(cSize >= LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH);
+ { LZ4F_frameInfo_t frame_info;
+ size_t const fhs = LZ4F_headerSize(compressedBuffer, LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH);
+ size_t avail_in = fhs;
+ CHECK( fhs );
CHECK( LZ4F_getFrameInfo(dCtx, &frame_info, compressedBuffer, &avail_in) );
+ if (avail_in != fhs) goto _output_error; /* must consume all, since header size is supposed to be exact */
}
DISPLAYLEVEL(3, "LZ4F_freeDecompressionContext \n");
@@ -306,7 +310,8 @@ int basicTests(U32 seed, double compressibility)
}
DISPLAYLEVEL(3, "LZ4F_getFrameInfo on enough input : ");
- iSize = 15 - iSize;
+ iSize = LZ4F_headerSize(ip, LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH);
+ CHECK( iSize );
CHECK( LZ4F_getFrameInfo(dCtx, &fi, ip, &iSize) );
DISPLAYLEVEL(3, " correctly decoded \n");
}
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