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zstd/lib/zstd.h

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/*
zstd - standard compression library
Header File
Copyright (C) 2014-2016, Yann Collet.
BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
You can contact the author at :
- zstd source repository : https://github.com/Cyan4973/zstd
*/
#ifndef ZSTD_H_235446
#define ZSTD_H_235446
#if defined (__cplusplus)
extern "C" {
#endif
/*====== Dependency ======*/
#include <stddef.h> /* size_t */
/*====== Export for Windows ======*/
/*!
* ZSTD_DLL_EXPORT :
* Enable exporting of functions when building a Windows DLL
*/
#if defined(_WIN32) && defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
# define ZSTDLIB_API __declspec(dllexport)
#else
# define ZSTDLIB_API
#endif
/*======= Version =======*/
#define ZSTD_VERSION_MAJOR 0
#define ZSTD_VERSION_MINOR 8
#define ZSTD_VERSION_RELEASE 1
#define ZSTD_LIB_VERSION ZSTD_VERSION_MAJOR.ZSTD_VERSION_MINOR.ZSTD_VERSION_RELEASE
#define ZSTD_QUOTE(str) #str
#define ZSTD_EXPAND_AND_QUOTE(str) ZSTD_QUOTE(str)
#define ZSTD_VERSION_STRING ZSTD_EXPAND_AND_QUOTE(ZSTD_LIB_VERSION)
#define ZSTD_VERSION_NUMBER (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
ZSTDLIB_API unsigned ZSTD_versionNumber (void);
/* *************************************
* Simple API
***************************************/
/*! ZSTD_compress() :
Compresses `src` buffer into already allocated `dst`.
Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
@return : the number of bytes written into `dst` (<= `dstCapacity),
or an error code if it fails (which can be tested using ZSTD_isError()) */
ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
int compressionLevel);
/*! ZSTD_getDecompressedSize() :
* @return : decompressed size as a 64-bits value _if known_, 0 otherwise.
* note 1 : decompressed size can be very large (64-bits value),
* potentially larger than what local system can handle as a single memory segment.
* In which case, it's necessary to use streaming mode to decompress data.
* note 2 : decompressed size is an optional field, that may not be present.
* When `return==0`, data to decompress can have any size.
* In which case, it's necessary to use streaming mode to decompress data.
* Optionally, application may rely on its own implied limits.
* (For example, application own data could be necessarily cut into blocks <= 16 KB).
* note 3 : decompressed size could be wrong or intentionally modified !
* Always ensure result fits within application's authorized limits !
* Each application can set its own limits.
* note 4 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more. */
ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
/*! ZSTD_decompress() :
`compressedSize` : must be the _exact_ size of compressed input, otherwise decompression will fail.
`dstCapacity` must be equal or larger than originalSize (see ZSTD_getDecompressedSize() ).
If originalSize is unknown, and if there is no implied application-specific limitations,
it's preferable to use streaming mode to decompress data.
@return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
or an errorCode if it fails (which can be tested using ZSTD_isError()) */
ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
const void* src, size_t compressedSize);
/*====== Helper functions ======*/
ZSTDLIB_API int ZSTD_maxCLevel(void); /*!< maximum compression level available */
ZSTDLIB_API size_t ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case scenario */
ZSTDLIB_API unsigned ZSTD_isError(size_t code); /*!< tells if a `size_t` function result is an error code */
ZSTDLIB_API const char* ZSTD_getErrorName(size_t code); /*!< provides readable string from an error code */
/*-*************************************
* Explicit memory management
***************************************/
/** Compression context */
typedef struct ZSTD_CCtx_s ZSTD_CCtx; /*< incomplete type */
ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx(void);
ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
/** ZSTD_compressCCtx() :
Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()) */
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, int compressionLevel);
/** Decompression context */
typedef struct ZSTD_DCtx_s ZSTD_DCtx; /*< incomplete type */
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
ZSTDLIB_API size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
/** ZSTD_decompressDCtx() :
* Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) */
ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
/*-************************
* Simple dictionary API
***************************/
/*! ZSTD_compress_usingDict() :
* Compression using a predefined Dictionary (see dictBuilder/zdict.h).
* Note : This function load the dictionary, resulting in significant startup delay. */
ZSTDLIB_API size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const void* dict,size_t dictSize,
int compressionLevel);
/*! ZSTD_decompress_usingDict() :
* Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
* Dictionary must be identical to the one used during compression.
* Note : This function load the dictionary, resulting in significant startup delay */
ZSTDLIB_API size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const void* dict,size_t dictSize);
/*-**************************
* Fast Dictionary API
****************************/
/*! ZSTD_createCDict() :
* Create a digested dictionary, ready to start compression operation without startup delay.
* `dict` can be released after ZSTD_CDict creation */
typedef struct ZSTD_CDict_s ZSTD_CDict;
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dict, size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
/*! ZSTD_compress_usingCDict() :
* Compression using a digested Dictionary.
* Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
* Note that compression level is decided during dictionary creation */
ZSTDLIB_API size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const ZSTD_CDict* cdict);
/*! ZSTD_createDDict() :
* Create a digested dictionary, ready to start decompression operation without startup delay.
* `dict` can be released after creation */
typedef struct ZSTD_DDict_s ZSTD_DDict;
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dict, size_t dictSize);
ZSTDLIB_API size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
/*! ZSTD_decompress_usingDDict() :
* Decompression using a digested Dictionary
* Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times. */
ZSTDLIB_API size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const ZSTD_DDict* ddict);
#ifdef ZSTD_STATIC_LINKING_ONLY
/* ====================================================================================
* The definitions in this section are considered experimental.
* They should never be used with a dynamic library, as they may change in the future.
* They are provided for advanced usages.
* Use them only in association with static linking.
* ==================================================================================== */
/*--- Constants ---*/
#define ZSTD_MAGICNUMBER 0xFD2FB528 /* v0.8 */
#define ZSTD_MAGIC_SKIPPABLE_START 0x184D2A50U
#define ZSTD_WINDOWLOG_MAX_32 25
#define ZSTD_WINDOWLOG_MAX_64 27
#define ZSTD_WINDOWLOG_MAX ((U32)(MEM_32bits() ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
#define ZSTD_WINDOWLOG_MIN 18
#define ZSTD_CHAINLOG_MAX (ZSTD_WINDOWLOG_MAX+1)
#define ZSTD_CHAINLOG_MIN 4
#define ZSTD_HASHLOG_MAX ZSTD_WINDOWLOG_MAX
#define ZSTD_HASHLOG_MIN 12
#define ZSTD_HASHLOG3_MAX 17
#define ZSTD_SEARCHLOG_MAX (ZSTD_WINDOWLOG_MAX-1)
#define ZSTD_SEARCHLOG_MIN 1
#define ZSTD_SEARCHLENGTH_MAX 7
#define ZSTD_SEARCHLENGTH_MIN 3
#define ZSTD_TARGETLENGTH_MIN 4
#define ZSTD_TARGETLENGTH_MAX 999
#define ZSTD_FRAMEHEADERSIZE_MAX 18 /* for static allocation */
static const size_t ZSTD_frameHeaderSize_min = 5;
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_skippableHeaderSize = 8; /* magic number + skippable frame length */
/*--- Types ---*/
typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt } ZSTD_strategy; /*< from faster to stronger */
typedef struct {
unsigned windowLog; /**< largest match distance : larger == more compression, more memory needed during decompression */
unsigned chainLog; /**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */
unsigned hashLog; /**< dispatch table : larger == faster, more memory */
unsigned searchLog; /**< nb of searches : larger == more compression, slower */
unsigned searchLength; /**< match length searched : larger == faster decompression, sometimes less compression */
unsigned targetLength; /**< acceptable match size for optimal parser (only) : larger == more compression, slower */
ZSTD_strategy strategy;
} ZSTD_compressionParameters;
typedef struct {
unsigned contentSizeFlag; /**< 1: content size will be in frame header (if known). */
unsigned checksumFlag; /**< 1: will generate a 22-bits checksum at end of frame, to be used for error detection by decompressor */
unsigned noDictIDFlag; /**< 1: no dict ID will be saved into frame header (if dictionary compression) */
} ZSTD_frameParameters;
typedef struct {
ZSTD_compressionParameters cParams;
ZSTD_frameParameters fParams;
} ZSTD_parameters;
/* custom memory allocation functions */
typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
/*-*************************************
* Advanced compression functions
***************************************/
/*! ZSTD_estimateCCtxSize() :
* Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters.
* `frameContentSize` is an optional parameter, provide `0` if unknown */
ZSTDLIB_API size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
/*! ZSTD_createCCtx_advanced() :
* Create a ZSTD compression context using external alloc and free functions */
ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
/*! ZSTD_createCDict_advanced() :
* Create a ZSTD_CDict using external alloc and free, and customized compression parameters */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
ZSTD_parameters params, ZSTD_customMem customMem);
/*! ZSTD_sizeofCCtx() :
* Gives the amount of memory used by a given ZSTD_CCtx */
ZSTDLIB_API size_t ZSTD_sizeofCCtx(const ZSTD_CCtx* cctx);
/*! ZSTD_getParams() :
* same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of a `ZSTD_compressionParameters`.
* All fields of `ZSTD_frameParameters` are set to default (0) */
ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long srcSize, size_t dictSize);
/*! ZSTD_getCParams() :
* @return ZSTD_compressionParameters structure for a selected compression level and srcSize.
* `srcSize` value is optional, select 0 if not known */
ZSTDLIB_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long srcSize, size_t dictSize);
/*! ZSTD_checkCParams() :
* Ensure param values remain within authorized range */
ZSTDLIB_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
/*! ZSTD_adjustCParams() :
* optimize params for a given `srcSize` and `dictSize`.
* both values are optional, select `0` if unknown. */
ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
/*! ZSTD_compress_advanced() :
* Same as ZSTD_compress_usingDict(), with fine-tune control of each compression parameter */
ZSTDLIB_API size_t ZSTD_compress_advanced (ZSTD_CCtx* ctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const void* dict,size_t dictSize,
ZSTD_parameters params);
/*--- Advanced Decompression functions ---*/
/*! ZSTD_estimateDCtxSize() :
* Gives the potential amount of memory allocated to create a ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_estimateDCtxSize(void);
/*! ZSTD_createDCtx_advanced() :
* Create a ZSTD decompression context using external alloc and free functions */
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
/*! ZSTD_sizeofDCtx() :
* Gives the amount of memory used by a given ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_sizeofDCtx(const ZSTD_DCtx* dctx);
/* ******************************************************************
* Streaming
********************************************************************/
typedef struct ZSTD_inBuffer_s {
const void* src; /**< start of input buffer */
size_t size; /**< size of input buffer */
size_t pos; /**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */
} ZSTD_inBuffer;
typedef struct ZSTD_outBuffer_s {
void* dst; /**< start of output buffer */
size_t size; /**< size of output buffer */
size_t pos; /**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */
} ZSTD_outBuffer;
/*====== compression ======*/
/*-***********************************************************************
* Streaming compression - howto
*
* A ZSTD_CStream object is required to track streaming operation.
* Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
* ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
*
* Start by initializing ZSTD_CStream.
* Use ZSTD_initCStream() to start a new compression operation.
* Use ZSTD_initCStream_usingDict() for a compression which requires a dictionary.
*
* Use ZSTD_compressStream() repetitively to consume input stream.
* The function will automatically update both `pos`.
* Note that it may not consume the entire input, in which case `pos < size`,
* and it's up to the caller to present again remaining data.
* @return : a hint to preferred nb of bytes to use as input for next function call (it's just a hint, to improve latency)
* or an error code, which can be tested using ZSTD_isError().
*
* At any moment, it's possible to flush whatever data remains within buffer, using ZSTD_flushStream().
* `output->pos` will be updated.
* Note some content might still be left within internal buffer if `output->size` is too small.
* @return : nb of bytes still present within internal buffer (0 if it's empty)
* or an error code, which can be tested using ZSTD_isError().
*
* ZSTD_endStream() instructs to finish a frame.
* It will perform a flush and write frame epilogue.
* The epilogue is required for decoders to consider a frame completed.
* Similar to ZSTD_flushStream(), it may not be able to flush the full content if `output->size` is too small.
* In which case, call again ZSTD_endStream() to complete the flush.
* @return : nb of bytes still present within internal buffer (0 if it's empty)
* or an error code, which can be tested using ZSTD_isError().
*
* *******************************************************************/
typedef struct ZSTD_CStream_s ZSTD_CStream;
ZSTD_CStream* ZSTD_createCStream(void);
size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
size_t ZSTD_CStreamInSize(void); /**< recommended size for input buffer */
size_t ZSTD_CStreamOutSize(void); /**< recommended size for output buffer */
size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
/* advanced */
ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel);
size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
ZSTD_parameters params, unsigned long long pledgedSrcSize);
/*====== decompression ======*/
/*-***************************************************************************
* Streaming decompression howto
*
* A ZSTD_DStream object is required to track streaming operations.
* Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
* ZSTD_DStream objects can be re-init multiple times.
*
* Use ZSTD_initDStream() to start a new decompression operation,
* or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
*
* Use ZSTD_decompressStream() repetitively to consume your input.
* The function will update both `pos`.
* Note that it may not consume the entire input (pos < size),
* in which case it's up to the caller to present remaining input again.
* @return : 0 when a frame is completely decoded and fully flushed,
* 1 when there is still some data left within internal buffer to flush,
* >1 when more data is expected, with value being a suggested next input size (it's just a hint, which helps latency, any size is accepted),
* or an error code, which can be tested using ZSTD_isError().
*
* *******************************************************************************/
typedef struct ZSTD_DStream_s ZSTD_DStream;
ZSTD_DStream* ZSTD_createDStream(void);
size_t ZSTD_freeDStream(ZSTD_DStream* zds);
size_t ZSTD_DStreamInSize(void); /*!< recommended size for input buffer */
size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output buffer */
size_t ZSTD_initDStream(ZSTD_DStream* zds);
size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
/* advanced */
ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
/* ******************************************************************
* Buffer-less and synchronous inner streaming functions
********************************************************************/
/* This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
* But it's also a complex one, with many restrictions (documented below).
* Prefer using normal streaming API for an easier experience */
ZSTDLIB_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
ZSTDLIB_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize);
ZSTDLIB_API size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx);
ZSTDLIB_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
/*
A ZSTD_CCtx object is required to track streaming operations.
Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
ZSTD_CCtx object can be re-used multiple times within successive compression operations.
Start by initializing a context.
Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
or ZSTD_compressBegin_advanced(), for finer parameter control.
It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
Then, consume your input using ZSTD_compressContinue().
There are some important considerations to keep in mind when using this advanced function :
- ZSTD_compressContinue() has no internal buffer. It uses externally provided buffer only.
- Interface is synchronous : input is consumed entirely and produce 1+ (or more) compressed blocks.
- Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
Worst case evaluation is provided by ZSTD_compressBound().
ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
- ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
- ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
In which case, it will "discard" the relevant memory section from its history.
Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
It's possible to use a NULL,0 src content, in which case, it will write a final empty block to end the frame,
Without last block mark, frames will be considered unfinished (broken) by decoders.
You can then reuse `ZSTD_CCtx` (ZSTD_compressBegin()) to compress some new frame.
*/
typedef struct {
unsigned long long frameContentSize;
unsigned windowSize;
unsigned dictID;
unsigned checksumFlag;
} ZSTD_frameParams;
ZSTDLIB_API size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize); /**< doesn't consume input, see details below */
ZSTDLIB_API size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
ZSTDLIB_API size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
ZSTDLIB_API void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
ZSTDLIB_API size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
ZSTDLIB_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
ZSTDLIB_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
/*
Buffer-less streaming decompression (synchronous mode)
A ZSTD_DCtx object is required to track streaming operations.
Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
A ZSTD_DCtx object can be re-used multiple times.
First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams().
It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame,
such as the minimum rolling buffer size to allocate to decompress data (`windowSize`),
and the dictionary ID used.
(Note : content size is optional, it may not be present. 0 means : content size unknown).
Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB.
Frame parameters are extracted from the beginning of the compressed frame.
Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes.
@result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled.
>0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
errorCode, which can be tested using ZSTD_isError().
Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict().
Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().
Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
@result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
It can be zero, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
It can also be an error code, which can be tested with ZSTD_isError().
ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
They should preferably be located contiguously, prior to current block.
Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
ZSTD_decompressContinue() is very sensitive to contiguity,
if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
or that previous contiguous segment is large enough to properly handle maximum back-reference.
A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
Context can then be reset to start a new decompression.
Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
This information is not required to properly decode a frame.
== Special case : skippable frames ==
Skippable frames allow integration of user-defined data into a flow of concatenated frames.
Skippable frames will be ignored (skipped) by a decompressor. The format of skippable frames is as follows :
a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
c) Frame Content - any content (User Data) of length equal to Frame Size
For skippable frames ZSTD_decompressContinue() always returns 0.
For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
It also returns Frame Size as fparamsPtr->frameContentSize.
*/
/* **************************************
* Block functions
****************************************/
/*! Block functions produce and decode raw zstd blocks, without frame metadata.
Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
User will have to take in charge required information to regenerate data, such as compressed and content sizes.
A few rules to respect :
- Compressing and decompressing require a context structure
+ Use ZSTD_createCCtx() and ZSTD_createDCtx()
- It is necessary to init context before starting
+ compression : ZSTD_compressBegin()
+ decompression : ZSTD_decompressBegin()
+ variants _usingDict() are also allowed
+ copyCCtx() and copyDCtx() work too
- Block size is limited, it must be <= ZSTD_getBlockSizeMax()
+ If you need to compress more, cut data into multiple blocks
+ Consider using the regular ZSTD_compress() instead, as frame metadata costs become negligible when source size is large.
- When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
In which case, nothing is produced into `dst`.
+ User must test for such outcome and deal directly with uncompressed data
+ ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
+ In case of multiple successive blocks, decoder must be informed of uncompressed block existence to follow proper history.
Use ZSTD_insertBlock() in such a case.
*/
#define ZSTD_BLOCKSIZE_ABSOLUTEMAX (128 * 1024) /* define, for static allocation */
ZSTDLIB_API size_t ZSTD_getBlockSizeMax(ZSTD_CCtx* cctx);
ZSTDLIB_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); /**< insert block into `dctx` history. Useful for uncompressed blocks */
#endif /* ZSTD_STATIC_LINKING_ONLY */
#if defined (__cplusplus)
}
#endif
#endif /* ZSTD_H_235446 */
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