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compat-lz4.h File Reference
#include <stddef.h>
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Data Structures

struct  LZ4_stream_t_internal
 
struct  LZ4_streamDecode_t_internal
 
union  LZ4_stream_u
 
union  LZ4_streamDecode_u
 

Macros

#define LZ4_H_2983827168210
 
#define LZ4LIB_VISIBILITY
 Introduction. More...
 
#define LZ4LIB_API   LZ4LIB_VISIBILITY
 
#define LZ4_VERSION_MAJOR   1 /* for breaking interface changes */
 
#define LZ4_VERSION_MINOR   9 /* for new (non-breaking) interface capabilities */
 
#define LZ4_VERSION_RELEASE   2 /* for tweaks, bug-fixes, or development */
 
#define LZ4_VERSION_NUMBER   (LZ4_VERSION_MAJOR *100*100 + LZ4_VERSION_MINOR *100 + LZ4_VERSION_RELEASE)
 
#define LZ4_LIB_VERSION   LZ4_VERSION_MAJOR.LZ4_VERSION_MINOR.LZ4_VERSION_RELEASE
 
#define LZ4_QUOTE(str)   #str
 
#define LZ4_EXPAND_AND_QUOTE(str)   LZ4_QUOTE(str)
 
#define LZ4_VERSION_STRING   LZ4_EXPAND_AND_QUOTE(LZ4_LIB_VERSION)
 
#define LZ4_MEMORY_USAGE   14
 
#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)
 
#define LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize)   (65536 + 14 + (maxBlockSize)) /* for static allocation; maxBlockSize presumed valid */
 
#define LZ4_H_98237428734687
 
#define LZ4_HASHLOG   (LZ4_MEMORY_USAGE-2)
 
#define LZ4_HASHTABLESIZE   (1 << LZ4_MEMORY_USAGE)
 
#define LZ4_HASH_SIZE_U32   (1 << LZ4_HASHLOG) /* required as macro for static allocation */
 
#define LZ4_STREAMSIZE_U64   ((1 << (LZ4_MEMORY_USAGE-3)) + 4 + ((sizeof(void*)==16) ? 4 : 0) /*AS-400*/ )
 
#define LZ4_STREAMSIZE   (LZ4_STREAMSIZE_U64 * sizeof(unsigned long long))
 
#define LZ4_STREAMDECODESIZE_U64   (4 + ((sizeof(void*)==16) ? 2 : 0) /*AS-400*/ )
 
#define LZ4_STREAMDECODESIZE   (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long))
 
#define LZ4_GCC_VERSION   (__GNUC__ * 100 + __GNUC_MINOR__)
 
#define LZ4_DEPRECATED(message)
 

Typedefs

typedef union LZ4_stream_u LZ4_stream_t
 
typedef union LZ4_streamDecode_u LZ4_streamDecode_t
 
typedef struct LZ4_stream_t_internal LZ4_stream_t_internal
 

Functions

LZ4LIB_API int LZ4_versionNumber (void)
 library version number; useful to check dll version More...
 
LZ4LIB_API const char * LZ4_versionString (void)
 library version string; useful to check dll version More...
 
LZ4LIB_API int LZ4_compress_default (const char *src, char *dst, int srcSize, int dstCapacity)
 
LZ4LIB_API int LZ4_decompress_safe (const char *src, char *dst, int compressedSize, int dstCapacity)
 
LZ4LIB_API int LZ4_compressBound (int inputSize)
 
LZ4LIB_API int LZ4_compress_fast (const char *src, char *dst, int srcSize, int dstCapacity, int acceleration)
 
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)
 
LZ4LIB_API int LZ4_compress_destSize (const char *src, char *dst, int *srcSizePtr, int targetDstSize)
 
LZ4LIB_API int LZ4_decompress_safe_partial (const char *src, char *dst, int srcSize, int targetOutputSize, int dstCapacity)
 
LZ4LIB_API LZ4_stream_tLZ4_createStream (void)
 
LZ4LIB_API int LZ4_freeStream (LZ4_stream_t *streamPtr)
 
LZ4LIB_API void LZ4_resetStream_fast (LZ4_stream_t *streamPtr)
 
LZ4LIB_API int LZ4_loadDict (LZ4_stream_t *streamPtr, const char *dictionary, int dictSize)
 
LZ4LIB_API int LZ4_compress_fast_continue (LZ4_stream_t *streamPtr, const char *src, char *dst, int srcSize, int dstCapacity, int acceleration)
 
LZ4LIB_API int LZ4_saveDict (LZ4_stream_t *streamPtr, char *safeBuffer, int maxDictSize)
 
LZ4LIB_API LZ4_streamDecode_tLZ4_createStreamDecode (void)
 
LZ4LIB_API int LZ4_freeStreamDecode (LZ4_streamDecode_t *LZ4_stream)
 
LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t *LZ4_streamDecode, const char *dictionary, int dictSize)
 
LZ4LIB_API int LZ4_decoderRingBufferSize (int maxBlockSize)
 
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_safe_usingDict (const char *src, char *dst, int srcSize, int dstCapcity, const char *dictStart, int dictSize)
 
LZ4LIB_API LZ4_stream_tLZ4_initStream (void *buffer, size_t size)
 
 LZ4_DEPRECATED ("use LZ4_compress_default() instead") LZ4LIB_API int LZ4_compress(const char *src
 
 LZ4_DEPRECATED ("use LZ4_compress_fast_extState() instead") LZ4LIB_API int LZ4_compress_withState(void *state
 
 LZ4_DEPRECATED ("use LZ4_compress_fast_continue() instead") LZ4LIB_API int LZ4_compress_continue(LZ4_stream_t *LZ4_streamPtr
 
 LZ4_DEPRECATED ("use LZ4_decompress_fast() instead") LZ4LIB_API int LZ4_uncompress(const char *source
 
 LZ4_DEPRECATED ("use LZ4_decompress_safe() instead") LZ4LIB_API int LZ4_uncompress_unknownOutputSize(const char *source
 
 LZ4_DEPRECATED ("Use LZ4_createStream() instead") LZ4LIB_API void *LZ4_create(char *inputBuffer)
 
 LZ4_DEPRECATED ("Use LZ4_resetStream() instead") LZ4LIB_API int LZ4_resetStreamState(void *state
 
 LZ4_DEPRECATED ("Use LZ4_saveDict() instead") LZ4LIB_API char *LZ4_slideInputBuffer(void *state)
 
 LZ4_DEPRECATED ("use LZ4_decompress_safe_usingDict() instead") LZ4LIB_API int LZ4_decompress_safe_withPrefix64k(const char *src
 
 LZ4_DEPRECATED ("use LZ4_decompress_fast_usingDict() instead") LZ4LIB_API int LZ4_decompress_fast_withPrefix64k(const char *src
 
LZ4LIB_API int LZ4_decompress_fast (const char *src, char *dst, int originalSize)
 
LZ4LIB_API int LZ4_decompress_fast_continue (LZ4_streamDecode_t *LZ4_streamDecode, const char *src, char *dst, int originalSize)
 
LZ4LIB_API int LZ4_decompress_fast_usingDict (const char *src, char *dst, int originalSize, const char *dictStart, int dictSize)
 
LZ4LIB_API void LZ4_resetStream (LZ4_stream_t *streamPtr)
 

Variables

char * dest
 
char int srcSize
 
char int int maxOutputSize
 
const char * source
 
const char char int inputSize
 
char int outputSize
 
char int isize
 
char * inputBuffer
 
char * dst
 
char int compressedSize
 
char int int maxDstSize
 
char int originalSize
 

Macro Definition Documentation

◆ LZ4_COMPRESSBOUND

#define LZ4_COMPRESSBOUND (   isize)    ((unsigned)(isize) > (unsigned)LZ4_MAX_INPUT_SIZE ? 0 : (isize) + ((isize)/255) + 16)

Definition at line 171 of file compat-lz4.h.

◆ LZ4_DECODER_RING_BUFFER_SIZE

#define LZ4_DECODER_RING_BUFFER_SIZE (   maxBlockSize)    (65536 + 14 + (maxBlockSize)) /* for static allocation; maxBlockSize presumed valid */

Definition at line 360 of file compat-lz4.h.

◆ LZ4_DEPRECATED

#define LZ4_DEPRECATED (   message)

Definition at line 681 of file compat-lz4.h.

◆ LZ4_EXPAND_AND_QUOTE

#define LZ4_EXPAND_AND_QUOTE (   str)    LZ4_QUOTE(str)

Definition at line 109 of file compat-lz4.h.

◆ LZ4_GCC_VERSION

#define LZ4_GCC_VERSION   (__GNUC__ * 100 + __GNUC_MINOR__)

Deprecation warnings

Deprecated functions make the compiler generate a warning when invoked. This is meant to invite users to update their source code. Should deprecation warnings be a problem, it is generally possible to disable them, typically with -Wno-deprecated-declarations for gcc or _CRT_SECURE_NO_WARNINGS in Visual.

Another method is to define LZ4_DISABLE_DEPRECATE_WARNINGS before including the header file.

Definition at line 670 of file compat-lz4.h.

◆ LZ4_H_2983827168210

#define LZ4_H_2983827168210

Definition at line 40 of file compat-lz4.h.

◆ LZ4_H_98237428734687

#define LZ4_H_98237428734687

Definition at line 547 of file compat-lz4.h.

◆ LZ4_HASH_SIZE_U32

#define LZ4_HASH_SIZE_U32   (1 << LZ4_HASHLOG) /* required as macro for static allocation */

Definition at line 558 of file compat-lz4.h.

◆ LZ4_HASHLOG

#define LZ4_HASHLOG   (LZ4_MEMORY_USAGE-2)

Definition at line 556 of file compat-lz4.h.

◆ LZ4_HASHTABLESIZE

#define LZ4_HASHTABLESIZE   (1 << LZ4_MEMORY_USAGE)

Definition at line 557 of file compat-lz4.h.

◆ LZ4_LIB_VERSION

Definition at line 107 of file compat-lz4.h.

◆ LZ4_MAX_INPUT_SIZE

#define LZ4_MAX_INPUT_SIZE   0x7E000000 /* 2 113 929 216 bytes */

Definition at line 170 of file compat-lz4.h.

◆ LZ4_MEMORY_USAGE

#define LZ4_MEMORY_USAGE   14

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 better cache locality. Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache

Definition at line 127 of file compat-lz4.h.

◆ LZ4_QUOTE

#define LZ4_QUOTE (   str)    #str

Definition at line 108 of file compat-lz4.h.

◆ LZ4_STREAMDECODESIZE

#define LZ4_STREAMDECODESIZE   (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long))

Definition at line 644 of file compat-lz4.h.

◆ LZ4_STREAMDECODESIZE_U64

#define LZ4_STREAMDECODESIZE_U64   (4 + ((sizeof(void*)==16) ? 2 : 0) /*AS-400*/ )

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 !

Definition at line 643 of file compat-lz4.h.

◆ LZ4_STREAMSIZE

#define LZ4_STREAMSIZE   (LZ4_STREAMSIZE_U64 * sizeof(unsigned long long))

Definition at line 613 of file compat-lz4.h.

◆ LZ4_STREAMSIZE_U64

#define LZ4_STREAMSIZE_U64   ((1 << (LZ4_MEMORY_USAGE-3)) + 4 + ((sizeof(void*)==16) ? 4 : 0) /*AS-400*/ )

LZ4_stream_t : information structure to track an LZ4 stream. LZ4_stream_t can also be created using LZ4_createStream(), which is recommended. The structure definition can be convenient for static allocation (on stack, or as part of larger structure). Init this structure with LZ4_initStream() before first use. note : only use this definition in association with static linking ! this definition is not API/ABI safe, and may change in a future version.

Definition at line 612 of file compat-lz4.h.

◆ LZ4_VERSION_MAJOR

#define LZ4_VERSION_MAJOR   1 /* for breaking interface changes */

Definition at line 101 of file compat-lz4.h.

◆ LZ4_VERSION_MINOR

#define LZ4_VERSION_MINOR   9 /* for new (non-breaking) interface capabilities */

Definition at line 102 of file compat-lz4.h.

◆ LZ4_VERSION_NUMBER

#define LZ4_VERSION_NUMBER   (LZ4_VERSION_MAJOR *100*100 + LZ4_VERSION_MINOR *100 + LZ4_VERSION_RELEASE)

Definition at line 105 of file compat-lz4.h.

◆ LZ4_VERSION_RELEASE

#define LZ4_VERSION_RELEASE   2 /* for tweaks, bug-fixes, or development */

Definition at line 103 of file compat-lz4.h.

◆ LZ4_VERSION_STRING

#define LZ4_VERSION_STRING   LZ4_EXPAND_AND_QUOTE(LZ4_LIB_VERSION)

Definition at line 110 of file compat-lz4.h.

◆ LZ4LIB_API

#define LZ4LIB_API   LZ4LIB_VISIBILITY

Definition at line 97 of file compat-lz4.h.

◆ LZ4LIB_VISIBILITY

#define LZ4LIB_VISIBILITY

Introduction.

LZ4 is lossless compression algorithm, providing compression speed >500 MB/s per core, scalable with multi-cores CPU. It features an extremely fast decoder, with speed in multiple GB/s per core, typically reaching RAM speed limits on multi-core systems.

The LZ4 compression library provides in-memory compression and decompression functions. It gives full buffer control to user. Compression can be done in:

  • a single step (described as Simple Functions)
  • a single step, reusing a context (described in Advanced Functions)
  • unbounded multiple steps (described as Streaming compression)

lz4.h generates and decodes LZ4-compressed blocks (doc/lz4_Block_format.md). Decompressing such a compressed block requires additional metadata. Exact metadata depends on exact decompression function. For the typical case of LZ4_decompress_safe(), metadata includes block's compressed size, and maximum bound of decompressed size. Each application is free to encode and pass such metadata in whichever way it wants.

lz4.h only handle blocks, it can not generate Frames.

Blocks are different from Frames (doc/lz4_Frame_format.md). Frames bundle both blocks and metadata in a specified manner. Embedding metadata is required for compressed data to be self-contained and portable. Frame format is delivered through a companion API, declared in lz4frame.h. The lz4 CLI can only manage frames.

Definition at line 89 of file compat-lz4.h.

Typedef Documentation

◆ LZ4_stream_t

typedef union LZ4_stream_u LZ4_stream_t

Definition at line 249 of file compat-lz4.h.

◆ LZ4_stream_t_internal

Definition at line 583 of file compat-lz4.h.

◆ LZ4_streamDecode_t

Definition at line 330 of file compat-lz4.h.

Function Documentation

◆ LZ4_compress_default()

LZ4LIB_API int LZ4_compress_default ( const char *  src,
char *  dst,
int  srcSize,
int  dstCapacity 
)

LZ4_compress_default() : Compresses 'srcSize' bytes from buffer 'src' into already allocated 'dst' buffer of size 'dstCapacity'. Compression is guaranteed to succeed if 'dstCapacity' >= LZ4_compressBound(srcSize). 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. 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)

Returns
: 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).

◆ LZ4_compress_destSize()

LZ4LIB_API int LZ4_compress_destSize ( const char *  src,
char *  dst,
int *  srcSizePtr,
int  targetDstSize 
)

LZ4_compress_destSize() : Reverse the logic : compresses as much data as possible from 'src' buffer into already allocated buffer 'dst', of size >= 'targetDestSize'. This function either compresses the entire 'src' content into 'dst' if it's large enough, or fill 'dst' buffer completely with as much data as possible from 'src'. note: acceleration parameter is fixed to "default".

*srcSizePtr : will be modified to indicate how many bytes where read from 'src' to fill 'dst'. New value is necessarily <= input value.

Returns
: Nb bytes written into 'dst' (necessarily <= targetDestSize) or 0 if compression fails.

◆ LZ4_compress_fast()

LZ4LIB_API int LZ4_compress_fast ( const char *  src,
char *  dst,
int  srcSize,
int  dstCapacity,
int  acceleration 
)

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. An acceleration value of "1" is the same as regular LZ4_compress_default() Values <= 0 will be replaced by ACCELERATION_DEFAULT (currently == 1, see lz4.c).

◆ LZ4_compress_fast_continue()

LZ4LIB_API int LZ4_compress_fast_continue ( LZ4_stream_t streamPtr,
const char *  src,
char *  dst,
int  srcSize,
int  dstCapacity,
int  acceleration 
)

LZ4_compress_fast_continue() : Compress 'src' content using data from previously compressed blocks, for better compression ratio. 'dst' buffer must be already allocated. If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster.

Returns
: size of compressed block or 0 if there is an error (typically, cannot fit into 'dst').

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.

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. This construction ensures that each block only depends on previous block.

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 undefined (invalid), it can only be reset or freed.

◆ LZ4_compress_fast_extState()

LZ4LIB_API int LZ4_compress_fast_extState ( void *  state,
const char *  src,
char *  dst,
int  srcSize,
int  dstCapacity,
int  acceleration 
)

◆ LZ4_compressBound()

LZ4LIB_API int LZ4_compressBound ( int  inputSize)

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). Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize) inputSize : max supported value is LZ4_MAX_INPUT_SIZE return : maximum output size in a "worst case" scenario or 0, if input size is incorrect (too large or negative)

◆ LZ4_createStream()

LZ4LIB_API LZ4_stream_t* LZ4_createStream ( void  )

◆ LZ4_createStreamDecode()

LZ4LIB_API LZ4_streamDecode_t* LZ4_createStreamDecode ( void  )

LZ4_createStreamDecode() and LZ4_freeStreamDecode() : creation / destruction of streaming decompression tracking context. A tracking context can be re-used multiple times.

◆ LZ4_decoderRingBufferSize()

LZ4LIB_API int LZ4_decoderRingBufferSize ( int  maxBlockSize)

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.

Returns
: minimum ring buffer size, or 0 if there is an error (invalid maxBlockSize).

◆ LZ4_decompress_fast()

LZ4LIB_API int LZ4_decompress_fast ( const char *  src,
char *  dst,
int  originalSize 
)

LZ4_decompress_fast() : unsafe! These functions used to be faster than LZ4_decompress_safe(), but it has changed, and they are now slower than LZ4_decompress_safe(). This is because LZ4_decompress_fast() doesn't know the input size, and therefore must progress more cautiously in the input buffer to not read beyond the end of block. On top of that LZ4_decompress_fast() is not protected vs malformed or malicious inputs, making it a security liability. As a consequence, LZ4_decompress_fast() is strongly discouraged, and deprecated.

The last remaining LZ4_decompress_fast() specificity is that it can decompress a block without knowing its compressed size. Such functionality could be achieved in a more secure manner, by also providing the maximum size of input buffer, but it would require new prototypes, and adaptation of the implementation to this new use case.

Parameters: originalSize : is the uncompressed size to regenerate. dst must be already allocated, its size must be >= 'originalSize' bytes.

Returns
: number of bytes read from source buffer (== compressed size). The function expects to finish at block's end exactly. If the source stream is detected malformed, the function stops decoding and returns a negative result. note : LZ4_decompress_fast*() requires originalSize. Thanks to this information, it never writes past the output buffer. However, since it doesn't know its 'src' size, it may read an unknown amount of input, past input buffer bounds. Also, since match offsets are not validated, match reads from 'src' may underflow too. These issues never happen if input (compressed) data is correct. But they may happen if input data is invalid (error or intentional tampering). As a consequence, use these functions in trusted environments with trusted data only.

◆ LZ4_decompress_fast_continue()

LZ4LIB_API int LZ4_decompress_fast_continue ( LZ4_streamDecode_t LZ4_streamDecode,
const char *  src,
char *  dst,
int  originalSize 
)

◆ LZ4_decompress_fast_usingDict()

LZ4LIB_API int LZ4_decompress_fast_usingDict ( const char *  src,
char *  dst,
int  originalSize,
const char *  dictStart,
int  dictSize 
)

◆ LZ4_decompress_safe()

LZ4LIB_API int LZ4_decompress_safe ( const char *  src,
char *  dst,
int  compressedSize,
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), presumed an upper bound of decompressed size.

Returns
: 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. Note 1 : This function is protected against malicious data packets : it will never writes outside 'dst' buffer, nor read outside 'source' buffer, even if the compressed block is maliciously modified to order the decoder to do these actions. In such case, the decoder stops immediately, and considers the compressed block malformed. Note 2 : compressedSize and dstCapacity must be provided to the function, the compressed block does not contain them. The implementation is free to send / store / derive this information in whichever way is most beneficial. If there is a need for a different format which bundles together both compressed data and its metadata, consider looking at lz4frame.h instead.

◆ LZ4_decompress_safe_continue()

LZ4LIB_API int LZ4_decompress_safe_continue ( LZ4_streamDecode_t LZ4_streamDecode,
const char *  src,
char *  dst,
int  srcSize,
int  dstCapacity 
)

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 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.

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. 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).

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.

◆ LZ4_decompress_safe_partial()

LZ4LIB_API int LZ4_decompress_safe_partial ( const char *  src,
char *  dst,
int  srcSize,
int  targetOutputSize,
int  dstCapacity 
)

LZ4_decompress_safe_partial() : Decompress an LZ4 compressed block, of size 'srcSize' at position 'src', into destination buffer 'dst' of size 'dstCapacity'. Up to 'targetOutputSize' bytes will be decoded. The function stops decoding on reaching this objective, which can boost performance when only the beginning of a block is required.

Returns
: the number of bytes decoded in dst (necessarily <= dstCapacity) If source stream is detected malformed, function returns a negative result.

Note :

Returns
can be < targetOutputSize, if compressed block contains less data.

Note 2 : this function features 2 parameters, targetOutputSize and dstCapacity, and expects targetOutputSize <= dstCapacity. It effectively stops decoding on reaching targetOutputSize, so dstCapacity is kind of redundant. This is because in a previous version of this function, decoding operation would not "break" a sequence in the middle. As a consequence, there was no guarantee that decoding would stop at exactly targetOutputSize, it could write more bytes, though only up to dstCapacity. Some "margin" used to be required for this operation to work properly. This is no longer necessary. The function nonetheless keeps its signature, in an effort to not break API.

◆ LZ4_decompress_safe_usingDict()

LZ4LIB_API int LZ4_decompress_safe_usingDict ( const char *  src,
char *  dst,
int  srcSize,
int  dstCapcity,
const char *  dictStart,
int  dictSize 
)

LZ4_decompress_*_usingDict() : 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 decompression. Performance tip : Decompression speed can be substantially increased when dst == dictStart + dictSize.

◆ LZ4_DEPRECATED() [1/10]

LZ4_DEPRECATED ( "use LZ4_compress_default() instead"  ) const

◆ LZ4_DEPRECATED() [2/10]

LZ4_DEPRECATED ( "use LZ4_compress_fast_extState() instead"  )

◆ LZ4_DEPRECATED() [3/10]

LZ4_DEPRECATED ( "use LZ4_compress_fast_continue() instead"  )

◆ LZ4_DEPRECATED() [4/10]

LZ4_DEPRECATED ( "use LZ4_decompress_fast() instead"  ) const

◆ LZ4_DEPRECATED() [5/10]

LZ4_DEPRECATED ( "use LZ4_decompress_safe() instead"  ) const

◆ LZ4_DEPRECATED() [6/10]

LZ4_DEPRECATED ( "Use LZ4_createStream() instead"  )

◆ LZ4_DEPRECATED() [7/10]

LZ4_DEPRECATED ( "Use LZ4_resetStream() instead"  )

◆ LZ4_DEPRECATED() [8/10]

LZ4_DEPRECATED ( "Use LZ4_saveDict() instead"  )

◆ LZ4_DEPRECATED() [9/10]

LZ4_DEPRECATED ( "use LZ4_decompress_safe_usingDict() instead"  ) const

◆ LZ4_DEPRECATED() [10/10]

LZ4_DEPRECATED ( "use LZ4_decompress_fast_usingDict() instead"  ) const

◆ LZ4_freeStream()

LZ4LIB_API int LZ4_freeStream ( LZ4_stream_t streamPtr)

◆ LZ4_freeStreamDecode()

LZ4LIB_API int LZ4_freeStreamDecode ( LZ4_streamDecode_t LZ4_stream)

◆ LZ4_initStream()

LZ4LIB_API LZ4_stream_t* LZ4_initStream ( void *  buffer,
size_t  size 
)

LZ4_initStream() : v1.9.0+ An LZ4_stream_t structure must be initialized at least once. This is automatically done when invoking LZ4_createStream(), but it's not when the structure is simply declared on stack (for example).

Use LZ4_initStream() to properly initialize a newly declared LZ4_stream_t. It can also initialize any arbitrary buffer of sufficient size, and will

Returns
a pointer of proper type upon initialization.

Note : initialization fails if size and alignment conditions are not respected. In which case, the function will

Returns
NULL. Note2: An LZ4_stream_t structure guarantees correct alignment and size. Note3: Before v1.9.0, use LZ4_resetStream() instead

◆ LZ4_loadDict()

LZ4LIB_API int LZ4_loadDict ( LZ4_stream_t streamPtr,
const char *  dictionary,
int  dictSize 
)

LZ4_loadDict() : Use this function to reference a static dictionary into LZ4_stream_t. The dictionary must remain available during compression. LZ4_loadDict() triggers a reset, so any previous data will be forgotten. The same dictionary will have to be loaded on decompression side for successful decoding. Dictionary are useful for better compression of small data (KB range). While LZ4 accept any input as dictionary, results are generally better when using Zstandard's Dictionary Builder. Loading a size of 0 is allowed, and is the same as reset.

Returns
: loaded dictionary size, in bytes (necessarily <= 64 KB)

◆ LZ4_resetStream()

LZ4LIB_API void LZ4_resetStream ( LZ4_stream_t streamPtr)

LZ4_resetStream() : An LZ4_stream_t structure must be initialized at least once. This is done with LZ4_initStream(), or LZ4_resetStream(). Consider switching to LZ4_initStream(), invoking LZ4_resetStream() will trigger deprecation warnings in the future.

◆ LZ4_resetStream_fast()

LZ4LIB_API void LZ4_resetStream_fast ( LZ4_stream_t streamPtr)

LZ4_resetStream_fast() : v1.9.0+ Use this to prepare an LZ4_stream_t for a new chain of dependent blocks (e.g., LZ4_compress_fast_continue()).

An LZ4_stream_t must be initialized once before usage. This is automatically done when created by LZ4_createStream(). However, should the LZ4_stream_t be simply declared on stack (for example), it's necessary to initialize it first, using LZ4_initStream().

After init, start any new stream with LZ4_resetStream_fast(). A same LZ4_stream_t can be re-used multiple times consecutively and compress multiple streams, provided that it starts each new stream with LZ4_resetStream_fast().

LZ4_resetStream_fast() is much faster than LZ4_initStream(), but is not compatible with memory regions containing garbage data.

Note: it's only useful to call LZ4_resetStream_fast() in the context of streaming compression. The extState functions perform their own resets. Invoking LZ4_resetStream_fast() before is redundant, and even counterproductive.

◆ LZ4_saveDict()

LZ4LIB_API int LZ4_saveDict ( LZ4_stream_t streamPtr,
char *  safeBuffer,
int  maxDictSize 
)

LZ4_saveDict() : If last 64KB data cannot be guaranteed to remain available at its current memory location, save it into a safer place (char* safeBuffer). This is schematically equivalent to a memcpy() followed by LZ4_loadDict(), but is much faster, because LZ4_saveDict() doesn't need to rebuild tables.

Returns
: saved dictionary size in bytes (necessarily <= maxDictSize), or 0 if error.

◆ LZ4_setStreamDecode()

LZ4LIB_API int LZ4_setStreamDecode ( LZ4_streamDecode_t LZ4_streamDecode,
const char *  dictionary,
int  dictSize 
)

LZ4_setStreamDecode() : 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 optionally be set. Use NULL or size 0 for a reset order. Dictionary is presumed stable : it must remain accessible and unmodified during next decompression.

Returns
: 1 if OK, 0 if error

◆ LZ4_sizeofState()

LZ4LIB_API int LZ4_sizeofState ( void  )

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.

◆ LZ4_versionNumber()

LZ4LIB_API int LZ4_versionNumber ( void  )

library version number; useful to check dll version

◆ LZ4_versionString()

LZ4LIB_API const char* LZ4_versionString ( void  )

library version string; useful to check dll version

Variable Documentation

◆ compressedSize

char int compressedSize

Definition at line 712 of file compat-lz4.h.

◆ dest

char * dest

◆ dst

char * dst

Definition at line 712 of file compat-lz4.h.

Referenced by net__route_v4_add(), net__route_v4_add_gw(), and net_ctx_free().

◆ inputBuffer

char* inputBuffer

Definition at line 708 of file compat-lz4.h.

◆ inputSize

const char char int inputSize

Definition at line 688 of file compat-lz4.h.

◆ isize

char int isize

Definition at line 695 of file compat-lz4.h.

◆ maxDstSize

char int int maxDstSize

Definition at line 712 of file compat-lz4.h.

◆ maxOutputSize

char int int maxOutputSize

Definition at line 687 of file compat-lz4.h.

◆ originalSize

char int originalSize

Definition at line 713 of file compat-lz4.h.

◆ outputSize

char int outputSize

Definition at line 694 of file compat-lz4.h.

◆ source

const char * source

Definition at line 688 of file compat-lz4.h.

Referenced by tls_ctx_load_ecdh_params().

◆ srcSize

char int srcSize

Definition at line 686 of file compat-lz4.h.