+ Zstd, short for Zstandard, is a fast lossless compression algorithm, targeting real-time compression scenarios + at zlib-level and better compression ratios. The zstd compression library provides in-memory compression and + decompression functions. The library supports compression levels from 1 up to ZSTD_maxCLevel() which is 22. + Levels from 20 to 22 should be used with caution as they require about 300-1300 MB for compression. + Compression can be done in: + - a single step (described as Simple API) + - a single step, reusing a context (described as Explicit memory management) + - repeated calls of the compression function (described as Streaming compression) + The compression ratio achievable on small data can be highly improved using compression with a dictionary in: + - a single step (described as Simple dictionary API) + - a single step, reusing a dictionary (described as Fast dictionary API) + + Advanced and experimantal functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h. + These APIs shall never be used with a dynamic library. + They are not "stable", their definition may change in the future. Only static linking is allowed. ++ +
unsigned ZSTD_versionNumber (void); /**< returns version number of ZSTD */ +
size_t ZSTD_compress( void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + int compressionLevel); +Compresses `src` content as a single zstd compressed frame into already allocated `dst`. + Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`. + @return : compressed size written into `dst` (<= `dstCapacity), + or an error code if it fails (which can be tested using ZSTD_isError()) +
size_t ZSTD_decompress( void* dst, size_t dstCapacity, + const void* src, size_t compressedSize); +`compressedSize` : must be the _exact_ size of a single compressed frame. + `dstCapacity` is an upper bound of originalSize. + If user cannot imply a maximum upper bound, it's better 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()) +
unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); +'src' is the start of a zstd compressed frame. + @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise. + note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. + When `return==0`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + Optionally, application can still use ZSTD_decompress() while relying on implied limits. + (For example, data may be necessarily cut into blocks <= 16 KB). + note 2 : decompressed size is always present when compression is done with ZSTD_compress() + note 3 : 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 4 : If source is untrusted, 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 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more. +
int ZSTD_maxCLevel(void); /*!< maximum compression level available */ +size_t ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case scenario */ +unsigned ZSTD_isError(size_t code); /*!< tells if a `size_t` function result is an error code */ +const char* ZSTD_getErrorName(size_t code); /*!< provides readable string from an error code */ +
typedef struct ZSTD_CCtx_s ZSTD_CCtx; +ZSTD_CCtx* ZSTD_createCCtx(void); +size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); +
size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, int compressionLevel); +Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()) +
typedef struct ZSTD_DCtx_s ZSTD_DCtx; +ZSTD_DCtx* ZSTD_createDCtx(void); +size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); +
size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) +
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); +Compression using a predefined Dictionary (see dictBuilder/zdict.h). + Note : This function load the dictionary, resulting in significant startup delay. +
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); +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 +
ZSTD_CDict* ZSTD_createCDict(const void* dict, size_t dictSize, int compressionLevel); +Create a digested dictionary, ready to start compression operation without startup delay. + `dict` can be released after ZSTD_CDict creation +
size_t ZSTD_freeCDict(ZSTD_CDict* CDict); +Function frees memory allocated with ZSTD_createCDict() +
size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_CDict* cdict); +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 +
ZSTD_DDict* ZSTD_createDDict(const void* dict, size_t dictSize); +Create a digested dictionary, ready to start decompression operation without startup delay. + `dict` can be released after creation +
size_t ZSTD_freeDDict(ZSTD_DDict* ddict); +Function frees memory allocated with ZSTD_createDDict() +
size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_DDict* ddict); +Decompression using a digested Dictionary + Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times. +
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;
++ 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` fields. + 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; +ZSTD_CStream* ZSTD_createCStream(void); +size_t ZSTD_freeCStream(ZSTD_CStream* zcs); +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); +
size_t ZSTD_CStreamInSize(void); /**< recommended size for input buffer */ +
size_t ZSTD_CStreamOutSize(void); /**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */ +
+ 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. + @return : recommended first input size + + Use ZSTD_decompressStream() repetitively to consume your input. + The function will update both `pos` fields. + If `input.pos < input.size`, some input has not been consumed. + It's up to the caller to present again remaining data. + If `output.pos < output.size`, decoder has flushed everything it could. + @return : 0 when a frame is completely decoded and fully flushed, + an error code, which can be tested using ZSTD_isError(), + any other value > 0, which means there is still some work to do to complete the frame. + The return value is a suggested next input size (just an hint, to help latency). + ++ +
typedef struct ZSTD_DStream_s ZSTD_DStream; +ZSTD_DStream* ZSTD_createDStream(void); +size_t ZSTD_freeDStream(ZSTD_DStream* zds); +size_t ZSTD_initDStream(ZSTD_DStream* zds); +size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +
size_t ZSTD_DStreamInSize(void); /*!< recommended size for input buffer */ +
size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */ +
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. + ++ +
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;
+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;
+size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams); +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 +
ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem); +Create a ZSTD compression context using external alloc and free functions +
size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); +Gives the amount of memory used by a given ZSTD_CCtx +
ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, + ZSTD_parameters params, ZSTD_customMem customMem); +Create a ZSTD_CDict using external alloc and free, and customized compression parameters +
size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); +Gives the amount of memory used by a given ZSTD_sizeof_CDict +
ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long srcSize, size_t dictSize); +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_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long srcSize, size_t dictSize); +@return ZSTD_compressionParameters structure for a selected compression level and srcSize. + `srcSize` value is optional, select 0 if not known +
size_t ZSTD_checkCParams(ZSTD_compressionParameters params); +Ensure param values remain within authorized range +
ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); +optimize params for a given `srcSize` and `dictSize`. + both values are optional, select `0` if unknown. +
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); +Same as ZSTD_compress_usingDict(), with fine-tune control of each compression parameter +
size_t ZSTD_estimateDCtxSize(void); +Gives the potential amount of memory allocated to create a ZSTD_DCtx +
ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem); +Create a ZSTD decompression context using external alloc and free functions +
size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); +Gives the amount of memory used by a given ZSTD_DCtx +
size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); +Gives the amount of memory used by a given ZSTD_DDict +
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); /**< pledgedSrcSize is optional and can be zero == unknown */ +size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); /**< re-use compression parameters from previous init; saves dictionary loading */ +size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); +
typedef enum { ZSTDdsp_maxWindowSize } ZSTD_DStreamParameter_e;
+ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
+size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
+size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
+size_t ZSTD_resetDStream(ZSTD_DStream* zds); /**< re-use decompression parameters from previous init; saves dictionary loading */
+size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
++ 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 + ++ +
+ 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. ++ +
size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); +size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); +size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); +size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); +size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +
+ 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. ++ +
typedef struct {
+ unsigned long long frameContentSize;
+ unsigned windowSize;
+ unsigned dictID;
+ unsigned checksumFlag;
+} ZSTD_frameParams;
+size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize); /**< doesn't consume input, see details below */
+size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
+size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
+void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
+size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
+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;
+ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
++ 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. ++ +
size_t ZSTD_getBlockSizeMax(ZSTD_CCtx* cctx); +size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); +size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); /**< insert block into `dctx` history. Useful for uncompressed blocks */ +