diff options
Diffstat (limited to 'lib/lz4.h')
| -rw-r--r-- | lib/lz4.h | 56 |
1 files changed, 37 insertions, 19 deletions
@@ -293,45 +293,62 @@ LZ4LIB_API int LZ4_saveDict (LZ4_stream_t* streamPtr, char* safeBuffer, int maxD * Streaming Decompression Functions * Bufferless synchronous API ************************************************/ -typedef union LZ4_streamDecode_u LZ4_streamDecode_t; /* incomplete type (defined later) */ +typedef union LZ4_streamDecode_u LZ4_streamDecode_t; /* tracking context */ /*! LZ4_createStreamDecode() and LZ4_freeStreamDecode() : - * creation / destruction of streaming decompression tracking structure. - * A tracking structure can be re-used multiple times sequentially. */ + * creation / destruction of streaming decompression tracking context. + * A tracking context can be re-used multiple times. + */ LZ4LIB_API LZ4_streamDecode_t* LZ4_createStreamDecode(void); LZ4LIB_API int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream); /*! LZ4_setStreamDecode() : - * An LZ4_streamDecode_t structure can be allocated once and re-used multiple times. + * An LZ4_streamDecode_t context can be allocated once and re-used multiple times. * Use this function to start decompression of a new stream of blocks. * A dictionary can optionnally be set. Use NULL or size 0 for a reset order. + * Dictionary is presumed stable : it must remain accessible and unmodified during next decompression. * @return : 1 if OK, 0 if error */ LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize); +/*! 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), + * at which stage it resumes from beginning of ring buffer. + * When setting such a ring buffer for streaming decompression, + * provides the minimum size of this ring buffer + * to be compatible with any source respecting maxBlockSize condition. + * @return : minimum ring buffer size, + * 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 */ + /*! LZ4_decompress_*_continue() : * These decoding functions allow decompression of consecutive blocks in "streaming" mode. * A block is an unsplittable entity, it must be presented entirely to a decompression function. - * Decompression functions only accept one block at a time. + * Decompression functions only accepts one block at a time. * The last 64KB of previously decoded data *must* remain available and unmodified at the memory position where they were decoded. - * If less than 64KB of data has been decoded all the data must be present. + * If less than 64KB of data has been decoded, all the data must be present. * - * Special : if application sets a ring buffer for decompression, it must respect one of the following conditions : + * Special : if decompression side sets a ring buffer, it must respect one of the following conditions : + * - Decompression buffer size is _at least_ LZ4_decoderRingBufferSize(maxBlockSize). + * maxBlockSize is the maximum size of any single block. It can have any value > 16 bytes. + * In which case, encoding and decoding buffers do not need to be synchronized. + * Actually, data can be produced by any source compliant with LZ4 format specification, and respecting maxBlockSize. + * - Synchronized mode : + * Decompression buffer size is _exactly_ the same as compression buffer size, + * and follows exactly same update rule (block boundaries at same positions), + * and decoding function is provided with exact decompressed size of each block (exception for last block of the stream), + * _then_ decoding & encoding ring buffer can have any size, including small ones ( < 64 KB). * - Decompression buffer is larger than encoding buffer, by a minimum of maxBlockSize more bytes. - * maxBlockSize is the maximum size of any single block. It is implementation dependent, and can have any value (presumed > 16 bytes). * In which case, encoding and decoding buffers do not need to be synchronized, * and encoding ring buffer can have any size, including small ones ( < 64 KB). - * - Decompression buffer size is _at least_ 64 KB + 8 bytes + maxBlockSize. - * In which case, encoding and decoding buffers do not need to be synchronized, - * and encoding ring buffer can have any size, including larger than decoding buffer. - * - Decompression buffer size is exactly the same as compression buffer size, - * and follows exactly same update rule (block boundaries at same positions). - * If the decoding function is provided with the exact decompressed size of each block, - * then decoding & encoding ring buffer can have any size, including very small ones ( < 64 KB). - * If the decoding function only knows the compressed size, - * then buffer size must be a minimum of 64 KB + 8 bytes + maxBlockSize. - * Whenever these conditions are not possible, save the last 64KB of decoded data into a safe buffer, - * and indicate where it is saved using LZ4_setStreamDecode() before decompressing next block. + * + * Whenever these conditions are not possible, + * save the last 64KB of decoded data into a safe buffer where it can't be modified during decompression, + * then indicate where this data is saved using LZ4_setStreamDecode(), before decompressing next block. */ LZ4LIB_API int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int srcSize, int dstCapacity); LZ4LIB_API int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize); @@ -341,6 +358,7 @@ 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. */ 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); |