/** * Copyright (c) 2016-present, Yann Collet, Facebook, Inc. * All rights reserved. * * This source code is licensed under the BSD-style license found in the * LICENSE file in the root directory of this source tree. An additional grant * of patent rights can be found in the PATENTS file in the same directory. */ #ifndef ZSTD_H_235446 #define ZSTD_H_235446 #if defined (__cplusplus) extern "C" { #endif /*====== Dependency ======*/ #include /* 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 1 #define ZSTD_VERSION_MINOR 0 #define ZSTD_VERSION_RELEASE 0 #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 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; 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; 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); /*-************************** * 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; /*====== streaming 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 size hint, preferred nb of bytes to use as input for next function call * (it's just a hint, to help latency a little, any other value will work fine) * (note : the size hint is guaranteed to be <= ZSTD_CStreamInSize() ) * 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; ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void); ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs); ZSTDLIB_API size_t ZSTD_CStreamInSize(void); /**< recommended size for input buffer */ ZSTDLIB_API size_t ZSTD_CStreamOutSize(void); /**< recommended size for output buffer */ ZSTDLIB_API size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); ZSTDLIB_API size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); ZSTDLIB_API size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); ZSTDLIB_API size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); /*====== 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-used 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; ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void); ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds); ZSTDLIB_API size_t ZSTD_DStreamInSize(void); /*!< recommended size for input buffer */ ZSTDLIB_API size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output buffer */ ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds); ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); #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_sizeof_CCtx(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) */ ZSTDLIB_API 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_sizeof_DCtx(const ZSTD_DCtx* dctx); /* ****************************************************************** * Advanced Streaming functions ********************************************************************/ /*====== compression ======*/ ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem); ZSTDLIB_API size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); ZSTDLIB_API size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); /*====== decompression ======*/ typedef enum { ZSTDdsp_maxWindowSize } ZSTD_DStreamParameter_e; ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem); ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); ZSTDLIB_API size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue); ZSTDLIB_API size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); /* ****************************************************************** * 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 */