lz4frame.h File Reference

#include <stddef.h>

Go to the source code of this file.

Data Structures
struct	LZ4F_frameInfo_t
struct	LZ4F_preferences_t
struct	LZ4F_compressOptions_t
struct	LZ4F_decompressOptions_t

Macros
#define	LZ4FLIB_VISIBILITY
#define	LZ4FLIB_API   LZ4FLIB_VISIBILITY
#define	LZ4F_DEPRECATE(x)
#define	LZ4F_OBSOLETE_ENUM(x)
#define	LZ4F_INIT_FRAMEINFO   { LZ4F_max64KB, LZ4F_blockLinked, LZ4F_noContentChecksum, LZ4F_frame, 0ULL, 0U, LZ4F_noBlockChecksum } /* v1.8.3+ */
#define	LZ4F_INIT_PREFERENCES   { LZ4F_INIT_FRAMEINFO, 0, 0u, 0u, { 0u, 0u, 0u } } /* v1.8.3+ */
#define	LZ4F_VERSION   100 /* This number can be used to check for an incompatible API breaking change */
#define	LZ4F_HEADER_SIZE_MIN   7 /* LZ4 Frame header size can vary, depending on selected parameters */
#define	LZ4F_HEADER_SIZE_MAX   19
#define	LZ4F_BLOCK_HEADER_SIZE   4
#define	LZ4F_BLOCK_CHECKSUM_SIZE   4
#define	LZ4F_CONTENT_CHECKSUM_SIZE   4
#define	LZ4F_ENDMARK_SIZE   4
#define	LZ4F_MAGICNUMBER   0x184D2204U
#define	LZ4F_MAGIC_SKIPPABLE_START   0x184D2A50U
#define	LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH   5

Typedefs
typedef LZ4F_cctx *	LZ4F_compressionContext_t
typedef LZ4F_dctx *	LZ4F_decompressionContext_t

Enumerations
enum	LZ4F_blockSizeID_t {   LZ4F_default =0 , LZ4F_max64KB =4 , LZ4F_max256KB =5 , LZ4F_max1MB =6 ,   LZ4F_max4MB =7 }
enum	LZ4F_blockMode_t { LZ4F_blockLinked =0 , LZ4F_blockIndependent }
enum	LZ4F_contentChecksum_t { LZ4F_noContentChecksum =0 , LZ4F_contentChecksumEnabled }
enum	LZ4F_blockChecksum_t { LZ4F_noBlockChecksum =0 , LZ4F_blockChecksumEnabled }
enum	LZ4F_frameType_t { LZ4F_frame =0 , LZ4F_skippableFrame }

Functions
LZ4FLIB_API unsigned	LZ4F_isError (LZ4F_errorCode_t code)
LZ4FLIB_API const char *	LZ4F_getErrorName (LZ4F_errorCode_t code)
LZ4FLIB_API size_t	LZ4F_compressFrame (void *dstBuffer, size_t dstCapacity, const void *srcBuffer, size_t srcSize, const LZ4F_preferences_t *preferencesPtr)
LZ4FLIB_API size_t	LZ4F_compressFrameBound (size_t srcSize, const LZ4F_preferences_t *preferencesPtr)
LZ4FLIB_API int	LZ4F_compressionLevel_max (void)
LZ4FLIB_API unsigned	LZ4F_getVersion (void)
LZ4FLIB_API LZ4F_errorCode_t	LZ4F_createCompressionContext (LZ4F_cctx **cctxPtr, unsigned version)
LZ4FLIB_API LZ4F_errorCode_t	LZ4F_freeCompressionContext (LZ4F_cctx *cctx)
LZ4FLIB_API size_t	LZ4F_compressBegin (LZ4F_cctx *cctx, void *dstBuffer, size_t dstCapacity, const LZ4F_preferences_t *prefsPtr)
LZ4FLIB_API size_t	LZ4F_compressBound (size_t srcSize, const LZ4F_preferences_t *prefsPtr)
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)
LZ4FLIB_API size_t	LZ4F_flush (LZ4F_cctx *cctx, void *dstBuffer, size_t dstCapacity, const LZ4F_compressOptions_t *cOptPtr)
LZ4FLIB_API size_t	LZ4F_compressEnd (LZ4F_cctx *cctx, void *dstBuffer, size_t dstCapacity, const LZ4F_compressOptions_t *cOptPtr)
LZ4FLIB_API LZ4F_errorCode_t	LZ4F_createDecompressionContext (LZ4F_dctx **dctxPtr, unsigned version)
LZ4FLIB_API LZ4F_errorCode_t	LZ4F_freeDecompressionContext (LZ4F_dctx *dctx)
LZ4FLIB_API size_t	LZ4F_headerSize (const void *src, size_t srcSize)
LZ4FLIB_API size_t	LZ4F_getFrameInfo (LZ4F_dctx *dctx, LZ4F_frameInfo_t *frameInfoPtr, const void *srcBuffer, size_t *srcSizePtr)
LZ4FLIB_API size_t	LZ4F_decompress (LZ4F_dctx *dctx, void *dstBuffer, size_t *dstSizePtr, const void *srcBuffer, size_t *srcSizePtr, const LZ4F_decompressOptions_t *dOptPtr)
LZ4FLIB_API void	LZ4F_resetDecompressionContext (LZ4F_dctx *dctx)
LZ4FLIB_API size_t	LZ4F_compressBegin_usingDict (LZ4F_cctx *cctx, void *dstBuffer, size_t dstCapacity, const void *dictBuffer, size_t dictSize, const LZ4F_preferences_t *prefsPtr)
LZ4FLIB_API size_t	LZ4F_decompress_usingDict (LZ4F_dctx *dctxPtr, void *dstBuffer, size_t *dstSizePtr, const void *srcBuffer, size_t *srcSizePtr, const void *dict, size_t dictSize, const LZ4F_decompressOptions_t *decompressOptionsPtr)
LZ4FLIB_API LZ4F_CDict *	LZ4F_createCDict (const void *dictBuffer, size_t dictSize)
LZ4FLIB_API void	LZ4F_freeCDict (LZ4F_CDict *CDict)
LZ4FLIB_API size_t	LZ4F_compressFrame_usingCDict (LZ4F_cctx *cctx, void *dst, size_t dstCapacity, const void *src, size_t srcSize, const LZ4F_CDict *cdict, const LZ4F_preferences_t *preferencesPtr)
LZ4FLIB_API size_t	LZ4F_compressBegin_usingCDict (LZ4F_cctx *cctx, void *dstBuffer, size_t dstCapacity, const LZ4F_CDict *cdict, const LZ4F_preferences_t *prefsPtr)

Macro Definition Documentation

LZ4F_BLOCK_CHECKSUM_SIZE

#define LZ4F_BLOCK_CHECKSUM_SIZE   4

LZ4F_BLOCK_HEADER_SIZE

#define LZ4F_BLOCK_HEADER_SIZE   4

LZ4F_CONTENT_CHECKSUM_SIZE

#define LZ4F_CONTENT_CHECKSUM_SIZE   4

LZ4F_DEPRECATE

#define LZ4F_DEPRECATE

(

x

)

Value:

x   /* no deprecation warning for this compiler */

LZ4F_ENDMARK_SIZE

#define LZ4F_ENDMARK_SIZE   4

LZ4F_HEADER_SIZE_MAX

#define LZ4F_HEADER_SIZE_MAX   19

LZ4F_HEADER_SIZE_MIN

#define LZ4F_HEADER_SIZE_MIN   7 /* LZ4 Frame header size can vary, depending on selected parameters */

LZ4F_INIT_FRAMEINFO

#define LZ4F_INIT_FRAMEINFO   { LZ4F_max64KB, LZ4F_blockLinked, LZ4F_noContentChecksum, LZ4F_frame, 0ULL, 0U, LZ4F_noBlockChecksum } /* v1.8.3+ */

LZ4F_INIT_PREFERENCES

#define LZ4F_INIT_PREFERENCES   { LZ4F_INIT_FRAMEINFO, 0, 0u, 0u, { 0u, 0u, 0u } } /* v1.8.3+ */

LZ4F_MAGIC_SKIPPABLE_START

#define LZ4F_MAGIC_SKIPPABLE_START   0x184D2A50U

LZ4F_MAGICNUMBER

#define LZ4F_MAGICNUMBER   0x184D2204U

LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH

#define LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH   5

LZ4F_OBSOLETE_ENUM

#define LZ4F_OBSOLETE_ENUM

(

x

)

LZ4F_VERSION

#define LZ4F_VERSION   100 /* This number can be used to check for an incompatible API breaking change */

LZ4FLIB_API

#define LZ4FLIB_API   LZ4FLIB_VISIBILITY

LZ4FLIB_VISIBILITY

#define LZ4FLIB_VISIBILITY

Introduction

lz4frame.h implements LZ4 frame specification: see doc/lz4_Frame_format.md . LZ4 Frames are compatible with lz4 CLI, and designed to be interoperable with any system.

Typedef Documentation

LZ4F_compressionContext_t

typedef LZ4F_cctx* LZ4F_compressionContext_t

LZ4F_decompressionContext_t

typedef LZ4F_dctx* LZ4F_decompressionContext_t

Enumeration Type Documentation

LZ4F_blockChecksum_t

enum LZ4F_blockChecksum_t

Enumerator
LZ4F_noBlockChecksum
LZ4F_blockChecksumEnabled

LZ4F_blockMode_t

enum LZ4F_blockMode_t

Enumerator
LZ4F_blockLinked
LZ4F_blockIndependent

LZ4F_blockSizeID_t

enum LZ4F_blockSizeID_t

Enumerator
LZ4F_default
LZ4F_max64KB
LZ4F_max256KB
LZ4F_max1MB
LZ4F_max4MB

LZ4F_contentChecksum_t

enum LZ4F_contentChecksum_t

Enumerator
LZ4F_noContentChecksum
LZ4F_contentChecksumEnabled

LZ4F_frameType_t

enum LZ4F_frameType_t

Enumerator
LZ4F_frame
LZ4F_skippableFrame

Function Documentation

LZ4F_compressBegin()

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. dstCapacity must be >= LZ4F_HEADER_SIZE_MAX bytes. prefsPtr is optional : NULL can be provided to set all preferences to default.

Returns

: number of bytes written into dstBuffer for the header or an error code (which can be tested using LZ4F_isError())

LZ4F_compressBegin_usingCDict()

LZ4FLIB_API size_t LZ4F_compressBegin_usingCDict	(	LZ4F_cctx *	cctx,
		void *	dstBuffer,
		size_t	dstCapacity,
		const LZ4F_CDict *	cdict,
		const LZ4F_preferences_t *	prefsPtr )

LZ4F_compressBegin_usingCDict() : stable since v1.10 Inits streaming dictionary compression, and writes the frame header into dstBuffer. @dstCapacity must be >= LZ4F_HEADER_SIZE_MAX bytes. @prefsPtr is optional : one may provide NULL as argument, note however that it's the only way to insert a @dictID in the frame header. @cdict must outlive the compression session.

Returns

: number of bytes written into dstBuffer for the header, or an error code, which can be tested using LZ4F_isError().

LZ4F_compressBegin_usingDict()

LZ4FLIB_API size_t LZ4F_compressBegin_usingDict	(	LZ4F_cctx *	cctx,
		void *	dstBuffer,
		size_t	dstCapacity,
		const void *	dictBuffer,
		size_t	dictSize,
		const LZ4F_preferences_t *	prefsPtr )

LZ4F_compressBegin_usingDict() : stable since v1.10 Inits dictionary compression streaming, and writes the frame header into dstBuffer. @dstCapacity must be >= LZ4F_HEADER_SIZE_MAX bytes. @prefsPtr is optional : one may provide NULL as argument, however, it's the only way to provide dictID in the frame header. @dictBuffer must outlive the compression session.

Returns

: number of bytes written into dstBuffer for the header, or an error code (which can be tested using LZ4F_isError()) NOTE: The LZ4Frame spec allows each independent block to be compressed with the dictionary, but this entry supports a more limited scenario, where only the first block uses the dictionary. This is still useful for small data, which only need one block anyway. For larger inputs, one may be more interested in LZ4F_compressFrame_usingCDict() below.

LZ4F_compressBound()

LZ4FLIB_API size_t LZ4F_compressBound	(	size_t	srcSize,
		const LZ4F_preferences_t *	prefsPtr )

LZ4F_compressBound() : Provides minimum dstCapacity required to guarantee success of LZ4F_compressUpdate(), given a srcSize and preferences, for a worst case scenario. When srcSize==0, LZ4F_compressBound() provides an upper bound for LZ4F_flush() and LZ4F_compressEnd() instead. Note that the result is only valid for a single invocation of LZ4F_compressUpdate(). When invoking LZ4F_compressUpdate() multiple times, if the output buffer is gradually filled up instead of emptied and re-used from its start, one must check if there is enough remaining capacity before each invocation, using LZ4F_compressBound().

Returns

is always the same for a srcSize and prefsPtr. prefsPtr is optional : when NULL is provided, preferences will be set to cover worst case scenario. tech details :

if automatic flushing is not enabled, includes the possibility that internal buffer might already be filled by up to (blockSize-1) bytes. It also includes frame footer (ending + checksum), since it might be generated by LZ4F_compressEnd().

doesn't include frame header, as it was already generated by LZ4F_compressBegin().

LZ4F_compressEnd()

LZ4FLIB_API size_t LZ4F_compressEnd	(	LZ4F_cctx *	cctxPtr,
		void *	dstBuffer,
		size_t	dstCapacity,
		const LZ4F_compressOptions_t *	compressOptionsPtr )

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 : NULL can be provided, in which case all options will be set to default.

Returns

: nb of bytes written into dstBuffer, necessarily >= 4 (endMark), or an error code if it fails (which can be tested using LZ4F_isError()) Note : LZ4F_compressEnd() is guaranteed to be successful when dstCapacity >= LZ4F_compressBound(0, prefsPtr). A successful call to LZ4F_compressEnd() makes cctx available again for another compression task.

LZ4F_compressEnd() : When you want to properly finish the compressed frame, just call LZ4F_compressEnd(). It will flush whatever data remained within compressionContext (like LZ4_flush()) but also properly finalize the frame, with an endMark and an (optional) checksum. LZ4F_compressOptions_t structure is optional : you can provide NULL as argument.

Returns

: the number of bytes written into dstBuffer (necessarily >= 4 (endMark size)) or an error code if it fails (can be tested using LZ4F_isError()) The context can then be used again to compress a new frame, starting with LZ4F_compressBegin().

LZ4F_compressFrame()

LZ4FLIB_API size_t LZ4F_compressFrame	(	void *	dstBuffer,
		size_t	dstCapacity,
		const void *	srcBuffer,
		size_t	srcSize,
		const LZ4F_preferences_t *	preferencesPtr )

LZ4F_compressFrame() : Compress srcBuffer content into an LZ4-compressed frame. It's a one shot operation, all input content is consumed, and all output is generated.

Note : it's a stateless operation (no LZ4F_cctx state needed). In order to reduce load on the allocator, LZ4F_compressFrame(), by default, uses the stack to allocate space for the compression state and some table. If this usage of the stack is too much for your application, consider compiling lz4frame.c with compile-time macro LZ4F_HEAPMODE set to 1 instead. All state allocations will use the Heap. It also means each invocation of LZ4F_compressFrame() will trigger several internal alloc/free invocations.

@dstCapacity MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). @preferencesPtr is optional : one can provide NULL, in which case all preferences are set to default.

Returns

: number of bytes written into dstBuffer. or an error code if it fails (can be tested using LZ4F_isError())

LZ4F_compressFrame() : Compress an entire srcBuffer into a valid LZ4 frame, in a single step. dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). The LZ4F_preferences_t structure is optional : you can provide NULL as argument. All preferences will be set to default.

Returns

: number of bytes written into dstBuffer. or an error code if it fails (can be tested using LZ4F_isError())

LZ4F_compressFrame_usingCDict()

LZ4FLIB_API size_t LZ4F_compressFrame_usingCDict	(	LZ4F_cctx *	cctx,
		void *	dstBuffer,
		size_t	dstCapacity,
		const void *	srcBuffer,
		size_t	srcSize,
		const LZ4F_CDict *	cdict,
		const LZ4F_preferences_t *	preferencesPtr )

LZ4_compressFrame_usingCDict() : stable since v1.10 Compress an entire srcBuffer into a valid LZ4 frame using a digested Dictionary. @cctx must point to a context created by LZ4F_createCompressionContext(). If @cdict==NULL, compress without a dictionary. @dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). If this condition is not respected, function will fail (

Returns

an errorCode). The LZ4F_preferences_t structure is optional : one may provide NULL as argument, but it's not recommended, as it's the only way to provide @dictID in the frame header.

: number of bytes written into dstBuffer. or an error code if it fails (can be tested using LZ4F_isError()) Note: for larger inputs generating multiple independent blocks, this entry point uses the dictionary for each block.

LZ4F_compressFrame_usingCDict() : Compress srcBuffer using a dictionary, in a single step. cdict can be NULL, in which case, no dictionary is used. dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr). The LZ4F_preferences_t structure is optional : you may provide NULL as argument, however, it's the only way to provide a dictID, so it's not recommended.

Returns

: number of bytes written into dstBuffer, or an error code if it fails (can be tested using LZ4F_isError())

LZ4F_compressFrameBound()

LZ4FLIB_API size_t LZ4F_compressFrameBound	(	size_t	srcSize,
		const LZ4F_preferences_t *	preferencesPtr )

LZ4F_compressFrameBound() : Returns the maximum possible compressed size with LZ4F_compressFrame() given srcSize and preferences. preferencesPtr is optional. It can be replaced by NULL, in which case, the function will assume default preferences. Note : this result is only usable with LZ4F_compressFrame(). It may also be relevant to LZ4F_compressUpdate() only if no flush() operation is ever performed.

LZ4F_compressionLevel_max()

LZ4FLIB_API int LZ4F_compressionLevel_max

(

void

)

LZ4F_compressionLevel_max() :

Returns

maximum allowed compression level (currently: 12)

LZ4F_compressUpdate()

LZ4FLIB_API size_t LZ4F_compressUpdate	(	LZ4F_cctx *	cctxPtr,
		void *	dstBuffer,
		size_t	dstCapacity,
		const void *	srcBuffer,
		size_t	srcSize,
		const LZ4F_compressOptions_t *	compressOptionsPtr )

LZ4F_compressUpdate() : LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary. Important rule: 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). After an error, the state is left in a UB state, and must be re-initialized or freed. If previously an uncompressed block was written, buffered data is flushed before appending compressed data is continued. cOptPtr is optional : NULL can be provided, in which case all options are set to default.

Returns

: 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())

LZ4F_compressUpdate() : LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary. When successful, the function always entirely consumes @srcBuffer. src data is either buffered or compressed into @dstBuffer. If previously an uncompressed block was written, buffered data is flushed before appending compressed data is continued. @dstCapacity MUST be >= LZ4F_compressBound(srcSize, preferencesPtr). @compressOptionsPtr is optional : provide NULL to mean "default".

Returns

: the 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()) After an error, the state is left in a UB state, and must be re-initialized.

LZ4F_createCDict()

LZ4FLIB_API LZ4F_CDict * LZ4F_createCDict	(	const void *	dictBuffer,
		size_t	dictSize )

LZ4_createCDict() : stable since v1.10 When compressing multiple messages / blocks using the same dictionary, it's recommended to initialize it just once. LZ4_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay. LZ4_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. @dictBuffer can be released after LZ4_CDict creation, since its content is copied within CDict.

LZ4F_createCDict() : When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once. LZ4F_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay. LZ4F_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. @dictBuffer can be released after LZ4F_CDict creation, since its content is copied within CDict

Returns

: digested dictionary for compression, or NULL if failed

LZ4F_createCompressionContext()

LZ4FLIB_API LZ4F_errorCode_t LZ4F_createCompressionContext	(	LZ4F_cctx **	LZ4F_compressionContextPtr,
		unsigned	version )

LZ4F_createCompressionContext() : The first thing to do is to create a compressionContext object, which will keep track of operation state during streaming compression. This is achieved using LZ4F_createCompressionContext(), which takes as argument a version, and a pointer to LZ4F_cctx*, to write the resulting pointer into.

Version

provided MUST be LZ4F_VERSION. It is intended to track potential version mismatch, notably when using DLL. The function provides a pointer to a fully allocated LZ4F_cctx object. @cctxPtr MUST be != NULL. If

Returns

!= zero, context creation failed. A created compression context can be employed multiple times for consecutive streaming operations. Once all streaming compression jobs are completed, the state object can be released using LZ4F_freeCompressionContext(). Note1 : LZ4F_freeCompressionContext() is always successful. Its return value can be ignored. Note2 : LZ4F_freeCompressionContext() works fine with NULL input pointers (do nothing).

LZ4F_createCompressionContext() : The first thing to do is to create a compressionContext object, which will be used in all compression operations. This is achieved using LZ4F_createCompressionContext(), which takes as argument a version and an LZ4F_preferences_t structure. The version provided MUST be LZ4F_VERSION. It is intended to track potential incompatible differences between different binaries. The function will provide a pointer to an allocated LZ4F_compressionContext_t object. If the result LZ4F_errorCode_t is not OK_NoError, there was an error during context creation. Object can release its memory using LZ4F_freeCompressionContext();

LZ4F_createDecompressionContext()

LZ4FLIB_API LZ4F_errorCode_t LZ4F_createDecompressionContext	(	LZ4F_dctx **	LZ4F_decompressionContextPtr,
		unsigned	versionNumber )

LZ4F_createDecompressionContext() : Create an LZ4F_dctx object, to track all decompression operations.

Version

provided MUST be LZ4F_VERSION. @dctxPtr MUST be valid. The function fills @dctxPtr with the value of a pointer to an allocated and initialized LZ4F_dctx object. The

Returns

is an errorCode, which can be tested using LZ4F_isError(). dctx memory can be released using LZ4F_freeDecompressionContext(); Result of LZ4F_freeDecompressionContext() indicates current state of decompressionContext when being released. That is, it should be == 0 if decompression has been completed fully and correctly.

LZ4F_createDecompressionContext() : Create a decompressionContext object, which will track all decompression operations. Provides a pointer to a fully allocated and initialized LZ4F_decompressionContext object. Object can later be released using LZ4F_freeDecompressionContext().

Returns

: if != 0, there was an error during context creation.

LZ4F_decompress()

LZ4FLIB_API size_t LZ4F_decompress	(	LZ4F_dctx *	dctx,
		void *	dstBuffer,
		size_t *	dstSizePtr,
		const void *	srcBuffer,
		size_t *	srcSizePtr,
		const LZ4F_decompressOptions_t *	decompressOptionsPtr )

LZ4F_decompress() : Call this function repetitively to regenerate data compressed in srcBuffer.

The function requires a valid dctx state. It will read up to *srcSizePtr bytes from srcBuffer, and decompress data into dstBuffer, of capacity *dstSizePtr.

The nb of bytes consumed from srcBuffer will be written into *srcSizePtr (necessarily <= original value). The nb of bytes decompressed into dstBuffer will be written into *dstSizePtr (necessarily <= original value).

The function does not necessarily read all input bytes, so always check value in *srcSizePtr. Unconsumed source data must be presented again in subsequent invocations.

dstBuffer can freely change between each consecutive function invocation. dstBuffer content will be overwritten.

Note: if LZ4F_getFrameInfo() is called before LZ4F_decompress(), srcBuffer must be updated to reflect the number of bytes consumed after reading the frame header. Failure to update srcBuffer before calling LZ4F_decompress() will cause decompression failure or, even worse, successful but incorrect decompression. See the LZ4F_getFrameInfo() docs for details.

Returns

: an hint of how many srcSize bytes LZ4F_decompress() expects for next call. Schematically, it's the size of the current (or remaining) compressed block + header of next block. Respecting the hint provides some small speed benefit, because it skips intermediate buffers. This is just a hint though, it's always possible to provide any srcSize.

When a frame is fully decoded,

Returns

will be 0 (no more data expected). When provided with more bytes than necessary to decode a frame, LZ4F_decompress() will stop reading exactly at end of current frame, and

0.

If decompression failed,

Returns

is an error code, which can be tested using LZ4F_isError(). After a decompression error, the dctx context is not resumable. Use LZ4F_resetDecompressionContext() to return to clean state.

After a frame is fully decoded, dctx can be used again to decompress another frame.

LZ4F_decompress() : Call this function repetitively to regenerate compressed data in srcBuffer. The function will attempt to decode up to *srcSizePtr bytes from srcBuffer into dstBuffer of capacity *dstSizePtr.

The number of bytes regenerated into dstBuffer will be provided within *dstSizePtr (necessarily <= original value).

The number of bytes effectively read from srcBuffer will be provided within *srcSizePtr (necessarily <= original value). If number of bytes read is < number of bytes provided, then decompression operation is not complete. Remaining data will have to be presented again in a subsequent invocation.

The function result is an hint of the better srcSize to use for next call to LZ4F_decompress. Schematically, it's the size of the current (or remaining) compressed block + header of next block. Respecting the hint provides a small boost to performance, since it allows less buffer shuffling. Note that this is just a hint, and it's always possible to any srcSize value. When a frame is fully decoded,

Returns

will be 0. If decompression failed,

is an error code which can be tested using LZ4F_isError().

LZ4F_decompress_usingDict()

LZ4FLIB_API size_t LZ4F_decompress_usingDict	(	LZ4F_dctx *	dctx,
		void *	dstBuffer,
		size_t *	dstSizePtr,
		const void *	srcBuffer,
		size_t *	srcSizePtr,
		const void *	dict,
		size_t	dictSize,
		const LZ4F_decompressOptions_t *	decompressOptionsPtr )

LZ4F_decompress_usingDict() : stable since v1.10 Same as LZ4F_decompress(), using a predefined dictionary. Dictionary is used "in place", without any preprocessing. It must remain accessible throughout the entire frame decoding.

LZ4F_decompress_usingDict() : Same as LZ4F_decompress(), using a predefined dictionary. Dictionary is used "in place", without any preprocessing. It must remain accessible throughout the entire frame decoding.

LZ4F_flush()

LZ4FLIB_API size_t LZ4F_flush	(	LZ4F_cctx *	cctxPtr,
		void *	dstBuffer,
		size_t	dstCapacity,
		const LZ4F_compressOptions_t *	compressOptionsPtr )

LZ4F_flush() : When data must be generated and sent immediately, without waiting for a block to be completely filled, it's possible to call LZ4_flush(). It will immediately compress any data buffered within cctx. dstCapacity must be large enough to ensure the operation will be successful. cOptPtr is optional : it's possible to provide NULL, all options will be set to default.

Returns

: nb of bytes written into dstBuffer (can be zero, when there is no data stored within cctx) or an error code if it fails (which can be tested using LZ4F_isError()) Note : LZ4F_flush() is guaranteed to be successful when dstCapacity >= LZ4F_compressBound(0, prefsPtr).

LZ4F_flush() : When compressed data must be sent immediately, without waiting for a block to be filled, invoke LZ4_flush(), which will immediately compress any remaining data stored within LZ4F_cctx. The result of the function is the number of bytes written into dstBuffer. It can be zero, this means there was no data left within LZ4F_cctx. The function outputs an error code if it fails (can be tested using LZ4F_isError()) LZ4F_compressOptions_t* is optional. NULL is a valid argument.

LZ4F_freeCDict()

LZ4FLIB_API void LZ4F_freeCDict

(

LZ4F_CDict *

CDict

)

LZ4F_freeCompressionContext()

LZ4FLIB_API LZ4F_errorCode_t LZ4F_freeCompressionContext

(

LZ4F_cctx *

cctx

)

LZ4F_freeDecompressionContext()

LZ4FLIB_API LZ4F_errorCode_t LZ4F_freeDecompressionContext

(

LZ4F_dctx *

dctx

)

LZ4F_getErrorName()

LZ4FLIB_API const char * LZ4F_getErrorName

(

LZ4F_errorCode_t

code

)

return error code string; for debugging

LZ4F_getFrameInfo()

LZ4FLIB_API size_t LZ4F_getFrameInfo	(	LZ4F_dctx *	dctx,
		LZ4F_frameInfo_t *	frameInfoPtr,
		const void *	srcBuffer,
		size_t *	srcSizePtr )

LZ4F_getFrameInfo() : This function extracts frame parameters (max blockSize, dictID, etc.). Its usage is optional: user can also invoke 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 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).

Returns

: 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.

LZ4F_getFrameInfo() : This function extracts frame parameters (max blockSize, frame checksum, etc.). Usage is optional. Objective is to provide relevant information for allocation purposes. This function works in 2 situations :

• At the beginning of a new frame, in which case it will decode this information from srcBuffer, and start the decoding process. Amount of input data provided must be large enough to successfully decode the frame header. A header size is variable, but is guaranteed to be <= LZ4F_HEADER_SIZE_MAX bytes. It's possible 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. The number of bytes consumed from srcBuffer will be updated within *srcSizePtr (necessarily <= original value). Decompression must resume from (srcBuffer + *srcSizePtr).

  Returns

  : an 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 operations can resume from where they stopped. note 2 : frame parameters are copied into an already allocated LZ4F_frameInfo_t structure.

LZ4F_getVersion()

LZ4FLIB_API unsigned LZ4F_getVersion

(

void

)

LZ4F_headerSize()

LZ4FLIB_API size_t LZ4F_headerSize	(	const void *	src,
		size_t	srcSize )

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.

Returns

: 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.

LZ4F_headerSize() :

Returns

: size of frame header or an error code, which can be tested using LZ4F_isError()

LZ4F_isError()

LZ4FLIB_API unsigned LZ4F_isError

(

LZ4F_errorCode_t

code

)

tells when a function result is an error code

LZ4F_resetDecompressionContext()

LZ4FLIB_API void LZ4F_resetDecompressionContext

(

LZ4F_dctx *

dctx

)

LZ4F_resetDecompressionContext() : added in v1.8.0 In case of an error, the context is left in "undefined" state. In which case, it's necessary to reset it, before re-using it. This method can also be used to abruptly stop any unfinished decompression, and start a new one using same context resources.