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/*
zstd - standard compression library
Header File
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Copyright ( C ) 2014 - 2016 , Yann Collet .
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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
*/
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# ifndef ZSTD_H_235446
# define ZSTD_H_235446
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# if defined (__cplusplus)
extern " C " {
# endif
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/*====== Dependency ======*/
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# include <stddef.h> /* size_t */
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/*====== Export for Windows ======*/
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/*!
* ZSTD_DLL_EXPORT :
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* Enable exporting of functions when building a Windows DLL
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*/
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# if defined(_WIN32) && defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
# define ZSTDLIB_API __declspec(dllexport)
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# else
# define ZSTDLIB_API
# endif
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/*====== Version ======*/
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# define ZSTD_VERSION_MAJOR 0
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# define ZSTD_VERSION_MINOR 8
# define ZSTD_VERSION_RELEASE 0
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# 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)
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# define ZSTD_VERSION_NUMBER (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
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ZSTDLIB_API unsigned ZSTD_versionNumber ( void ) ;
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/* *************************************
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* Simple API
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*! ZSTD_compress() :
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Compresses ` src ` buffer into already allocated ` dst ` .
Hint : compression runs faster if ` dstCapacity ` > = ` ZSTD_compressBound ( srcSize ) ` .
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@ return : the number of bytes written into ` dst ` ( < = ` dstCapacity ) ,
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or an error code if it fails ( which can be tested using ZSTD_isError ( ) ) */
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ZSTDLIB_API size_t ZSTD_compress ( void * dst , size_t dstCapacity ,
const void * src , size_t srcSize ,
int compressionLevel ) ;
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/*! ZSTD_getDecompressedSize() :
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* @ return : decompressed size if known , 0 otherwise .
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note 1 : if ` 0 ` , follow up with ZSTD_getFrameParams ( ) to know precise failure cause .
note 2 : decompressed size could be wrong or intentionally modified !
always ensure results fit within application ' s authorized limits */
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unsigned long long ZSTD_getDecompressedSize ( const void * src , size_t srcSize ) ;
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/*! ZSTD_decompress() :
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` compressedSize ` : must be _exact_ size of compressed input , otherwise decompression will fail .
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` dstCapacity ` must be equal or larger than originalSize .
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@ return : the number of bytes decompressed into ` dst ` ( < = ` dstCapacity ` ) ,
or an errorCode if it fails ( which can be tested using ZSTD_isError ( ) ) */
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ZSTDLIB_API size_t ZSTD_decompress ( void * dst , size_t dstCapacity ,
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const void * src , size_t compressedSize ) ;
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/*====== Helper functions ======*/
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ZSTDLIB_API size_t ZSTD_compressBound ( size_t srcSize ) ; /*!< maximum compressed size (worst case scenario) */
ZSTDLIB_API unsigned ZSTD_isError ( size_t code ) ; /*!< tells if a `size_t` function result is an error code */
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ZSTDLIB_API const char * ZSTD_getErrorName ( size_t code ) ; /*!< provides readable string from an error code */
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/*-*************************************
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* Explicit memory management
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/** Compression context */
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typedef struct ZSTD_CCtx_s ZSTD_CCtx ; /*< incomplete type */
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ZSTDLIB_API ZSTD_CCtx * ZSTD_createCCtx ( void ) ;
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ZSTDLIB_API size_t ZSTD_freeCCtx ( ZSTD_CCtx * cctx ) ; /*!< @return : errorCode */
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/** ZSTD_compressCCtx() :
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Same as ZSTD_compress ( ) , requires an allocated ZSTD_CCtx ( see ZSTD_createCCtx ( ) ) */
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ZSTDLIB_API size_t ZSTD_compressCCtx ( ZSTD_CCtx * ctx , void * dst , size_t dstCapacity , const void * src , size_t srcSize , int compressionLevel ) ;
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/** Decompression context */
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typedef struct ZSTD_DCtx_s ZSTD_DCtx ;
ZSTDLIB_API ZSTD_DCtx * ZSTD_createDCtx ( void ) ;
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ZSTDLIB_API size_t ZSTD_freeDCtx ( ZSTD_DCtx * dctx ) ; /*!< @return : errorCode */
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/** ZSTD_decompressDCtx() :
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* Same as ZSTD_decompress ( ) , requires an allocated ZSTD_DCtx ( see ZSTD_createDCtx ( ) ) */
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ZSTDLIB_API size_t ZSTD_decompressDCtx ( ZSTD_DCtx * ctx , void * dst , size_t dstCapacity , const void * src , size_t srcSize ) ;
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/*-************************
* Simple dictionary API
* * * * * * * * * * * * * * * * * * * * * * * * * * */
/*! ZSTD_compress_usingDict() :
* Compression using a pre - defined Dictionary content ( see dictBuilder ) .
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* Note : This function load the dictionary , resulting in a significant startup time . */
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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 pre - defined Dictionary content ( see dictBuilder ) .
* Dictionary must be identical to the one used during compression .
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* Note : This function load the dictionary , resulting in a significant startup time */
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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 ) ;
/*-**************************
* Advanced Dictionary API
* * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*! ZSTD_createCDict() :
* Create a digested dictionary , ready to start compression operation without startup delay .
* ` dict ` can be released after 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() :
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* Compression using a pre - digested Dictionary .
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* Faster startup than ZSTD_compress_usingDict ( ) , recommended when same dictionary is used multiple times .
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* Note that compression level is decided during dictionary creation */
ZSTDLIB_API size_t ZSTD_compress_usingCDict ( ZSTD_CCtx * cctx ,
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void * dst , size_t dstCapacity ,
const void * src , size_t srcSize ,
const ZSTD_CDict * cdict ) ;
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/*! 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 pre - digested Dictionary
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* Faster startup than ZSTD_decompress_usingDict ( ) , recommended when same dictionary is used multiple times . */
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ZSTDLIB_API size_t ZSTD_decompress_usingDDict ( ZSTD_DCtx * dctx ,
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void * dst , size_t dstCapacity ,
const void * src , size_t srcSize ,
const ZSTD_DDict * ddict ) ;
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# ifdef ZSTD_STATIC_LINKING_ONLY
/* ====================================================================================
* The definitions in this section are considered experimental .
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* They should never be used with a dynamic library , as they may change in the future .
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* They are provided for advanced usages .
* Use them only in association with static linking .
* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */
/*--- Constants ---*/
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# define ZSTD_MAGICNUMBER 0xFD2FB528 /* v0.8 */
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# define ZSTD_MAGIC_SKIPPABLE_START 0x184D2A50U
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# 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))
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# 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
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# 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 */
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/*--- Types ---*/
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typedef enum { ZSTD_fast , ZSTD_dfast , ZSTD_greedy , ZSTD_lazy , ZSTD_lazy2 , ZSTD_btlazy2 , ZSTD_btopt } ZSTD_strategy ; /*< from faster to stronger */
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typedef struct {
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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 */
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ZSTD_strategy strategy ;
} ZSTD_compressionParameters ;
typedef struct {
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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) */
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} 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 ;
/*-*************************************
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* Advanced compression functions
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*! 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 */
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ZSTDLIB_API size_t ZSTD_estimateCCtxSize ( ZSTD_compressionParameters cParams ) ;
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/*! ZSTD_createCCtx_advanced() :
* Create a ZSTD compression context using external alloc and free functions */
ZSTDLIB_API ZSTD_CCtx * ZSTD_createCCtx_advanced ( ZSTD_customMem customMem ) ;
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/*! 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 ) ;
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/*! ZSTD_sizeofCCtx() :
* Gives the amount of memory used by a given ZSTD_CCtx */
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ZSTDLIB_API size_t ZSTD_sizeofCCtx ( const ZSTD_CCtx * cctx ) ;
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ZSTDLIB_API unsigned ZSTD_maxCLevel ( void ) ;
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/*! 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 ) */
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ZSTD_parameters ZSTD_getParams ( int compressionLevel , unsigned long long srcSize , size_t dictSize ) ;
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/*! ZSTD_getCParams() :
* @ return ZSTD_compressionParameters structure for a selected compression level and srcSize .
* ` srcSize ` value is optional , select 0 if not known */
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ZSTDLIB_API ZSTD_compressionParameters ZSTD_getCParams ( int compressionLevel , unsigned long long srcSize , size_t dictSize ) ;
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/*! ZSTD_checkCParams() :
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* Ensure param values remain within authorized range */
ZSTDLIB_API size_t ZSTD_checkCParams ( ZSTD_compressionParameters params ) ;
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/*! ZSTD_adjustCParams() :
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* optimize params for a given ` srcSize ` and ` dictSize ` .
* both values are optional , select ` 0 ` if unknown . */
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ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams ( ZSTD_compressionParameters cPar , unsigned long long srcSize , size_t dictSize ) ;
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/*! 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 ) ;
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/*--- Advanced Decompression functions ---*/
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/*! ZSTD_estimateDCtxSize() :
* Gives the potential amount of memory allocated to create a ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_estimateDCtxSize ( void ) ;
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/*! ZSTD_createDCtx_advanced() :
* Create a ZSTD decompression context using external alloc and free functions */
ZSTDLIB_API ZSTD_DCtx * ZSTD_createDCtx_advanced ( ZSTD_customMem customMem ) ;
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/*! ZSTD_sizeofDCtx() :
* Gives the amount of memory used by a given ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_sizeofDCtx ( const ZSTD_DCtx * dctx ) ;
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/* ******************************************************************
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* Buffer - less streaming functions ( synchronous mode )
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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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 ) ;
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ZSTDLIB_API size_t ZSTD_compressBegin_advanced ( ZSTD_CCtx * cctx , const void * dict , size_t dictSize , ZSTD_parameters params , unsigned long long pledgedSrcSize ) ;
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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 ) ;
/*
A ZSTD_CCtx object is required to track streaming operations .
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Use ZSTD_createCCtx ( ) / ZSTD_freeCCtx ( ) to manage resource .
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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 ( ) .
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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 .
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- Interface is synchronous : input is consumed entirely and produce 1 ( or more ) compressed blocks .
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- 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 .
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Finish a frame with ZSTD_compressEnd ( ) , which will write the epilogue .
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Without epilogue , frames will be considered unfinished ( broken ) by decoders .
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You can then reuse ` ZSTD_CCtx ` ( ZSTD_compressBegin ( ) ) to compress some new frame .
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*/
typedef struct {
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unsigned long long frameContentSize ;
unsigned windowSize ;
unsigned dictID ;
unsigned checksumFlag ;
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} ZSTD_frameParams ;
ZSTDLIB_API size_t ZSTD_getFrameParams ( ZSTD_frameParams * fparamsPtr , const void * src , size_t srcSize ) ; /**< doesn't consume input */
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 ) ;
/*
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Buffer - less streaming decompression ( synchronous mode )
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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 optional operation is to retrieve frame parameters , using ZSTD_getFrameParams ( ) , which doesn ' t consume the input .
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It can provide the minimum size of rolling buffer required to properly decompress data ( ` windowSize ` ) ,
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and optionally the final size of uncompressed content .
( Note : content size is an optional info that may not be present . 0 means : content size unknown )
Frame parameters are extracted from the beginning of compressed frame .
The amount of data to read is variable , from ZSTD_frameHeaderSize_min to ZSTD_frameHeaderSize_max ( so if ` srcSize ` > = ZSTD_frameHeaderSize_max , it will always work )
If ` srcSize ` is too small for operation to succeed , function will return the minimum size it requires to produce a result .
Result : 0 when successful , it means the ZSTD_frameParams structure has been filled .
> 0 : means there is not enough data into ` src ` . Provides the expected size to successfully decode header .
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 much bytes to provide as ' srcSize ' to ZSTD_decompressContinue ( ) .
ZSTD_decompressContinue ( ) requires this exact amount of bytes , or it will fail .
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@ result of ZSTD_decompressContinue ( ) is the number of bytes regenerated within ' dst ' ( necessarily < = dstCapacity ) .
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It can be zero , which is not an error ; it just means ZSTD_decompressContinue ( ) has decoded some header .
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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 .
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A frame is fully decoded when ZSTD_nextSrcSizeToDecompress ( ) returns zero .
Context can then be reset to start a new decompression .
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= = Special case : skippable frames = =
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Skippable frames allow the integration of user - defined data into a flow of concatenated frames .
Skippable frames will be ignored ( skipped ) by a decompressor . The format of skippable frame is following :
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.
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Frame metadata cost is typically ~ 18 bytes , which can be non - negligible for very small blocks ( < 100 bytes ) .
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User will have to take in charge required information to regenerate data , such as compressed and content sizes .
A few rules to respect :
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- Compressing and decompressing require a context structure
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+ 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
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- 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 .
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- 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
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+ 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 .
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*/
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# define ZSTD_BLOCKSIZE_ABSOLUTEMAX (128 * 1024) /* define, for static allocation */
ZSTDLIB_API size_t ZSTD_getBlockSizeMax ( ZSTD_CCtx * cctx ) ;
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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 ) ;
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ZSTDLIB_API size_t ZSTD_insertBlock ( ZSTD_DCtx * dctx , const void * blockStart , size_t blockSize ) ; /**< insert block into `dctx` history. Useful for uncompressed blocks */
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# endif /* ZSTD_STATIC_LINKING_ONLY */
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# if defined (__cplusplus)
}
# endif
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# endif /* ZSTD_H_235446 */