diff options
Diffstat (limited to 'lib/lz4.h')
| -rw-r--r-- | lib/lz4.h | 39 |
1 files changed, 24 insertions, 15 deletions
@@ -74,15 +74,14 @@ int LZ4_compress_safe (const char* source, char* dest, int sourceSize, int max int LZ4_decompress_safe (const char* source, char* dest, int compressedSize, int maxDecompressedSize); /* -LZ4_compress_limitedOutput() : +LZ4_compress_safe() : Compresses 'sourceSize' bytes from buffer 'source' - into already allocated 'dest' of size 'maxOutputSize'. - Compression runs faster when 'maxOutputSize' >= LZ4_compressBound(sourceSize). - That's because in such case, it is guaranteed to compress within 'dest' budget, even in worst case scenario. - Compressing into a more limited space budget requires additional checks. - If the function cannot compress 'source' into a limited 'dest' budget, - compression stops *immediately*, and result of the function is zero. - It greatly accelerates behavior on non-compressible input, but as a consequence, 'dest' content is not valid either. + into already allocated 'dest' buffer of size 'maxDestSize'. + Compression is guaranteed to succeed if 'maxDestSize' >= LZ4_compressBound(sourceSize). + It also runs faster, so it's a recommended setting. + If the function cannot compress 'source' into a more limited 'dest' budget, + compression stops *immediately*, and the function result is zero. + As a consequence, 'dest' content is not valid. This function never writes outside 'dest' buffer, nor read outside 'source' buffer. sourceSize : Max supported value is LZ4_MAX_INPUT_VALUE maxDestSize : full or partial size of buffer 'dest' (which must be already allocated) @@ -132,13 +131,13 @@ int LZ4_compress_safe_extState (void* state, const char* source, char* dest, int LZ4_compress_fast() : Same as LZ4_compress_safe(), but allows to select an "acceleration" factor. The larger the acceleration value, the faster the algorithm, but also the lesser the compression. - It's a trade-off, which can be fine tuned, selecting whichever value you want. + It's a trade-off. It can be fine tuned, with each successive value providing an additional +2/3% to speed. An acceleration value of "0" means "use Default value", which is typically 17 (see lz4.c source code). An acceleration value of "1" is the same as regular LZ4_compress_safe() Note : this function is "safe", even if its name does not explicitly contain the word. It's just faster and compress less. */ -int LZ4_compress_fast (const char* source, char* dest, int sourceSize, int maxOutputSize, unsigned acceleration); -int LZ4_compress_fast_extState (void* state, const char* source, char* dest, int inputSize, int maxOutputSize, unsigned acceleration); +int LZ4_compress_fast (const char* source, char* dest, int sourceSize, int maxDestSize, unsigned acceleration); +int LZ4_compress_fast_extState (void* state, const char* source, char* dest, int inputSize, int maxDestSize, unsigned acceleration); /* @@ -260,8 +259,18 @@ int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dicti *_continue() : These decoding functions allow decompression of multiple blocks in "streaming" mode. Previously decoded blocks *must* remain available at the memory position where they were decoded (up to 64 KB) - If this condition is not possible, save the relevant part of decoded data into a safe buffer, - and indicate where is its new address using LZ4_setStreamDecode() + In the case of a ring buffers, decoding buffer must be either : + - Exactly same size as encoding buffer, with same update rule (block boundaries at same positions) + In which case, the decoding & encoding ring buffer can have any size, including very small ones ( < 64 KB). + - Larger than encoding buffer, by a minimum of maxBlockSize more bytes. + maxBlockSize is implementation dependent. It's the maximum size you intend to compress into a single block. + 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). + - _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. + 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() */ int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* source, char* dest, int compressedSize, int maxDecompressedSize); int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* source, char* dest, int originalSize); @@ -271,8 +280,8 @@ int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const ch Advanced decoding functions : *_usingDict() : These decoding functions work the same as - a combination of LZ4_setDictDecode() followed by LZ4_decompress_x_continue() - They are stand-alone and don't use nor update an LZ4_streamDecode_t structure. + a combination of LZ4_setStreamDecode() followed by LZ4_decompress_x_continue() + They are stand-alone. They don't need nor update an LZ4_streamDecode_t structure. */ int LZ4_decompress_safe_usingDict (const char* source, char* dest, int compressedSize, int maxDecompressedSize, const char* dictStart, int dictSize); int LZ4_decompress_fast_usingDict (const char* source, char* dest, int originalSize, const char* dictStart, int dictSize); |