diff options
Diffstat (limited to 'lib/lz4.h')
| -rw-r--r-- | lib/lz4.h | 155 |
1 files changed, 81 insertions, 74 deletions
@@ -103,7 +103,7 @@ extern "C" { #define LZ4_VERSION_STRING LZ4_EXPAND_AND_QUOTE(LZ4_LIB_VERSION) LZ4LIB_API int LZ4_versionNumber (void); /**< library version number; useful to check dll version */ -LZ4LIB_API const char* LZ4_versionString (void); /**< library version string; unseful to check dll version */ +LZ4LIB_API const char* LZ4_versionString (void); /**< library version string; useful to check dll version */ /*-************************************ @@ -112,14 +112,15 @@ LZ4LIB_API const char* LZ4_versionString (void); /**< library version string; /*! * LZ4_MEMORY_USAGE : * Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.) - * Increasing memory usage improves compression ratio - * Reduced memory usage may improve speed, thanks to cache effect + * Increasing memory usage improves compression ratio. + * Reduced memory usage may improve speed, thanks to better cache locality. * Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */ #ifndef LZ4_MEMORY_USAGE # define LZ4_MEMORY_USAGE 14 #endif + /*-************************************ * Simple Functions **************************************/ @@ -130,21 +131,22 @@ LZ4LIB_API const char* LZ4_versionString (void); /**< library version string; It also runs faster, so it's a recommended setting. If the function cannot compress 'src' into a more limited 'dst' budget, compression stops *immediately*, and the function result is zero. - Note : as a consequence, 'dst' content is not valid. - Note 2 : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer). + In which case, 'dst' content is undefined (invalid). srcSize : max supported value is LZ4_MAX_INPUT_SIZE. dstCapacity : size of buffer 'dst' (which must be already allocated) - return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity) - or 0 if compression fails */ + @return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity) + or 0 if compression fails + Note : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer). +*/ LZ4LIB_API int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity); /*! LZ4_decompress_safe() : compressedSize : is the exact complete size of the compressed block. dstCapacity : is the size of destination buffer, which must be already allocated. - return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity) + @return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity) If destination buffer is not large enough, decoding will stop and output an error code (negative value). If the source stream is detected malformed, the function will stop decoding and return a negative result. - This function is protected against malicious data packets. + Note : This function is protected against malicious data packets (never writes outside 'dst' buffer, nor read outside 'source' buffer). */ LZ4LIB_API int LZ4_decompress_safe (const char* src, char* dst, int compressedSize, int dstCapacity); @@ -155,8 +157,7 @@ LZ4LIB_API int LZ4_decompress_safe (const char* src, char* dst, int compressedSi #define LZ4_MAX_INPUT_SIZE 0x7E000000 /* 2 113 929 216 bytes */ #define LZ4_COMPRESSBOUND(isize) ((unsigned)(isize) > (unsigned)LZ4_MAX_INPUT_SIZE ? 0 : (isize) + ((isize)/255) + 16) -/*! -LZ4_compressBound() : +/*! LZ4_compressBound() : Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible) This function is primarily useful for memory allocation purposes (destination buffer size). Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example). @@ -167,8 +168,7 @@ LZ4_compressBound() : */ LZ4LIB_API int LZ4_compressBound(int inputSize); -/*! -LZ4_compress_fast() : +/*! LZ4_compress_fast() : Same as LZ4_compress_default(), but allows selection of "acceleration" factor. The larger the acceleration value, the faster the algorithm, but also the lesser the compression. It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed. @@ -178,13 +178,12 @@ LZ4_compress_fast() : LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); -/*! -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 this buffer as 'void* state' to compression function. -*/ +/*! LZ4_compress_fast_extState() : + * Same as LZ4_compress_fast(), using an externally allocated memory space for its state. + * Use LZ4_sizeofState() to know how much memory must be allocated, + * and allocate it on 8-bytes boundaries (using `malloc()` typically). + * Then, provide this buffer as `void* state` to compression function. + */ LZ4LIB_API int LZ4_sizeofState(void); LZ4LIB_API int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); @@ -210,7 +209,7 @@ LZ4LIB_API int LZ4_compress_destSize (const char* src, char* dst, int* srcSizePt * and now `LZ4_decompress_safe()` can be as fast and sometimes faster than `LZ4_decompress_fast()`. * Moreover, LZ4_decompress_fast() is not protected vs malformed input, as it doesn't perform full validation of compressed data. * As a consequence, this function is no longer recommended, and may be deprecated in future versions. - * It's only remaining specificity is that it can decompress data without knowing its compressed size. + * It's last remaining specificity is that it can decompress data without knowing its compressed size. * * originalSize : is the uncompressed size to regenerate. * `dst` must be already allocated, its size must be >= 'originalSize' bytes. @@ -257,10 +256,6 @@ LZ4LIB_API int LZ4_decompress_safe_partial (const char* src, char* dst, int srcS ***********************************************/ typedef union LZ4_stream_u LZ4_stream_t; /* incomplete type (defined later) */ -/*! LZ4_createStream() and LZ4_freeStream() : - * LZ4_createStream() will allocate and initialize an `LZ4_stream_t` structure. - * LZ4_freeStream() releases its memory. - */ LZ4LIB_API LZ4_stream_t* LZ4_createStream(void); LZ4LIB_API int LZ4_freeStream (LZ4_stream_t* streamPtr); @@ -280,7 +275,7 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in /*! LZ4_compress_fast_continue() : * Compress 'src' content using data from previously compressed blocks, for better compression ratio. - * 'dst' buffer must be already allocated. + * 'dst' buffer must be already allocated. * If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster. * * @return : size of compressed block @@ -288,10 +283,10 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in * * Note 1 : Each invocation to LZ4_compress_fast_continue() generates a new block. * Each block has precise boundaries. + * Each block must be decompressed separately, calling LZ4_decompress_*() with relevant metadata. * It's not possible to append blocks together and expect a single invocation of LZ4_decompress_*() to decompress them together. - * Each block must be decompressed separately, calling LZ4_decompress_*() with associated metadata. * - * Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory! + * Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory ! * * Note 3 : When input is structured as a double-buffer, each buffer can have any size, including < 64 KB. * Make sure that buffers are separated, by at least one byte. @@ -299,7 +294,7 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in * * Note 4 : If input buffer is a ring-buffer, it can have any size, including < 64 KB. * - * Note 5 : After an error, the stream status is invalid, it can only be reset or freed. + * Note 5 : After an error, the stream status is undefined (invalid), it can only be reset or freed. */ LZ4LIB_API int LZ4_compress_fast_continue (LZ4_stream_t* streamPtr, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); @@ -335,7 +330,7 @@ LZ4LIB_API int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_str */ LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize); -/*! LZ4_decoderRingBufferSize() : v1.8.2 +/*! LZ4_decoderRingBufferSize() : v1.8.2+ * Note : in a ring buffer scenario (optional), * blocks are presumed decompressed next to each other * up to the moment there is not enough remaining space for next block (remainingSize < maxBlockSize), @@ -347,7 +342,7 @@ LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const * or 0 if there is an error (invalid maxBlockSize). */ LZ4LIB_API int LZ4_decoderRingBufferSize(int maxBlockSize); -#define LZ4_DECODER_RING_BUFFER_SIZE(mbs) (65536 + 14 + (mbs)) /* for static allocation; mbs presumed valid */ +#define LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize) (65536 + 14 + (maxBlockSize)) /* for static allocation; maxBlockSize presumed valid */ /*! LZ4_decompress_*_continue() : * These decoding functions allow decompression of consecutive blocks in "streaming" mode. @@ -382,7 +377,9 @@ LZ4LIB_API int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecod * These decoding functions work the same as * a combination of LZ4_setStreamDecode() followed by LZ4_decompress_*_continue() * They are stand-alone, and don't need an LZ4_streamDecode_t structure. - * Dictionary is presumed stable : it must remain accessible and unmodified during next decompression. + * Dictionary is presumed stable : it must remain accessible and unmodified during decompression. + * Performance tip : Decompression speed can be substantially increased + * when dst == dictStart + dictSize. */ LZ4LIB_API int LZ4_decompress_safe_usingDict (const char* src, char* dst, int srcSize, int dstCapcity, const char* dictStart, int dictSize); LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize); @@ -395,29 +392,41 @@ LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int or /*-************************************ * Unstable declarations ************************************** - * Declarations in this section should be considered unstable. - * Use at your own peril, etc., etc. - * They may be removed in the future. - * Their signatures may change. + * Declarations in this section must be considered unstable. + * Their signatures may change, or may be removed in the future. + * They are therefore only safe to depend on + * when the caller is statically linked against the library. + * To access their declarations, define LZ4_STATIC_LINKING_ONLY. **************************************/ #ifdef LZ4_STATIC_LINKING_ONLY +/* By default, symbols in this section aren't published into shared/dynamic libraries. + * You can override this behavior and force them to be published + * by defining LZ4_PUBLISH_STATIC_FUNCTIONS. + * Use at your own risk. + */ + +#ifdef LZ4_PUBLISH_STATIC_FUNCTIONS +#define LZ4LIB_STATIC_API LZ4LIB_API +#else +#define LZ4LIB_STATIC_API +#endif + /*! LZ4_resetStream_fast() : * Use this, like LZ4_resetStream(), to prepare a context for a new chain of * calls to a streaming API (e.g., LZ4_compress_fast_continue()). * * Note: - * Using this in advance of a non- streaming-compression function is redundant, - * and potentially bad for performance, since they all perform their own custom - * reset internally. + * Using this in advance of a non-streaming-compression function is redundant, + * since they all perform their own custom reset internally. * * Differences from LZ4_resetStream(): * When an LZ4_stream_t is known to be in a internally coherent state, - * it can often be prepared for a new compression with almost no work, only - * sometimes falling back to the full, expensive reset that is always required - * when the stream is in an indeterminate state (i.e., the reset performed by - * LZ4_resetStream()). + * it can often be prepared for a new compression with almost no work, + * only sometimes falling back to the full, expensive reset + * that is always required when the stream is in an indeterminate state + * (i.e., the reset performed by LZ4_resetStream()). * * LZ4_streams are guaranteed to be in a valid state when: * - returned from LZ4_createStream() @@ -434,24 +443,23 @@ LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int or * any fastReset or streaming function. It must first be cleansed by the full * LZ4_resetStream(). */ -LZ4LIB_API void LZ4_resetStream_fast (LZ4_stream_t* streamPtr); +LZ4LIB_STATIC_API void LZ4_resetStream_fast (LZ4_stream_t* streamPtr); /*! LZ4_compress_fast_extState_fastReset() : * A variant of LZ4_compress_fast_extState(). * - * Using this variant avoids an expensive initialization step. It is only safe - * to call if the state buffer is known to be correctly initialized already - * (see above comment on LZ4_resetStream_fast() for a definition of "correctly - * initialized"). From a high level, the difference is that this function - * initializes the provided state with a call to something like - * LZ4_resetStream_fast() while LZ4_compress_fast_extState() starts with a - * call to LZ4_resetStream(). + * Using this variant avoids an expensive initialization step. + * It is only safe to call if the state buffer is known to be correctly initialized already + * (see above comment on LZ4_resetStream_fast() for a definition of "correctly initialized"). + * From a high level, the difference is that + * this function initializes the provided state with a call to something like LZ4_resetStream_fast() + * while LZ4_compress_fast_extState() starts with a call to LZ4_resetStream(). */ -LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); +LZ4LIB_STATIC_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); /*! LZ4_attach_dictionary() : - * This is an experimental API that allows for the efficient use of a - * static dictionary many times. + * This is an experimental API that allows + * efficient use of a static dictionary many times. * * Rather than re-loading the dictionary buffer into a working context before * each compression, or copying a pre-loaded dictionary's LZ4_stream_t into a @@ -462,8 +470,8 @@ LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* sr * Currently, only streams which have been prepared by LZ4_loadDict() should * be expected to work. * - * Alternatively, the provided dictionary stream pointer may be NULL, in which - * case any existing dictionary stream is unset. + * Alternatively, the provided dictionaryStream may be NULL, + * in which case any existing dictionary stream is unset. * * If a dictionary is provided, it replaces any pre-existing stream history. * The dictionary contents are the only history that can be referenced and @@ -475,16 +483,17 @@ LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* sr * stream (and source buffer) must remain in-place / accessible / unchanged * through the completion of the first compression call on the stream. */ -LZ4LIB_API void LZ4_attach_dictionary(LZ4_stream_t *working_stream, const LZ4_stream_t *dictionary_stream); +LZ4LIB_STATIC_API void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream); #endif + /*-************************************ * Private definitions ************************************** - * Do not use these definitions. - * They are exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`. - * Using these definitions will expose code to API and/or ABI break in future versions of the library. + * Do not use these definitions directly. + * They are only exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`. + * Accessing members will expose code to API and/or ABI break in future versions of the library. **************************************/ #define LZ4_HASHLOG (LZ4_MEMORY_USAGE-2) #define LZ4_HASHTABLESIZE (1 << LZ4_MEMORY_USAGE) @@ -533,13 +542,12 @@ typedef struct { #endif -/*! - * LZ4_stream_t : - * information structure to track an LZ4 stream. - * init this structure before first use. - * note : only use in association with static linking ! - * this definition is not API/ABI safe, - * it may change in a future version ! +/*! LZ4_stream_t : + * information structure to track an LZ4 stream. + * init this structure with LZ4_resetStream() before first use. + * note : only use in association with static linking ! + * this definition is not API/ABI safe, + * it may change in a future version ! */ #define LZ4_STREAMSIZE_U64 ((1 << (LZ4_MEMORY_USAGE-3)) + 4) #define LZ4_STREAMSIZE (LZ4_STREAMSIZE_U64 * sizeof(unsigned long long)) @@ -549,13 +557,12 @@ union LZ4_stream_u { } ; /* previously typedef'd to LZ4_stream_t */ -/*! - * LZ4_streamDecode_t : - * information structure to track an LZ4 stream during decompression. - * init this structure using LZ4_setStreamDecode (or memset()) before first use - * note : only use in association with static linking ! - * this definition is not API/ABI safe, - * and may change in a future version ! +/*! LZ4_streamDecode_t : + * information structure to track an LZ4 stream during decompression. + * init this structure using LZ4_setStreamDecode() before first use. + * note : only use in association with static linking ! + * this definition is not API/ABI safe, + * and may change in a future version ! */ #define LZ4_STREAMDECODESIZE_U64 4 #define LZ4_STREAMDECODESIZE (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long)) |