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diff --git a/src/zstd/doc/zstd_manual.html b/src/zstd/doc/zstd_manual.html new file mode 100644 index 000000000..fe58f78cb --- /dev/null +++ b/src/zstd/doc/zstd_manual.html @@ -0,0 +1,1680 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>zstd 1.4.5 Manual</title> +</head> +<body> +<h1>zstd 1.4.5 Manual</h1> +<hr> +<a name="Contents"></a><h2>Contents</h2> +<ol> +<li><a href="#Chapter1">Introduction</a></li> +<li><a href="#Chapter2">Version</a></li> +<li><a href="#Chapter3">Simple API</a></li> +<li><a href="#Chapter4">Explicit context</a></li> +<li><a href="#Chapter5">Advanced compression API</a></li> +<li><a href="#Chapter6">Advanced decompression API</a></li> +<li><a href="#Chapter7">Streaming</a></li> +<li><a href="#Chapter8">Streaming compression - HowTo</a></li> +<li><a href="#Chapter9">Streaming decompression - HowTo</a></li> +<li><a href="#Chapter10">Simple dictionary API</a></li> +<li><a href="#Chapter11">Bulk processing dictionary API</a></li> +<li><a href="#Chapter12">Dictionary helper functions</a></li> +<li><a href="#Chapter13">Advanced dictionary and prefix API</a></li> +<li><a href="#Chapter14">experimental API (static linking only)</a></li> +<li><a href="#Chapter15">Frame size functions</a></li> +<li><a href="#Chapter16">Memory management</a></li> +<li><a href="#Chapter17">Advanced compression functions</a></li> +<li><a href="#Chapter18">Advanced decompression functions</a></li> +<li><a href="#Chapter19">Advanced streaming functions</a></li> +<li><a href="#Chapter20">! ZSTD_initCStream_usingDict() :</a></li> +<li><a href="#Chapter21">! ZSTD_initCStream_advanced() :</a></li> +<li><a href="#Chapter22">! ZSTD_initCStream_usingCDict() :</a></li> +<li><a href="#Chapter23">! ZSTD_initCStream_usingCDict_advanced() :</a></li> +<li><a href="#Chapter24">This function is deprecated, and is equivalent to:</a></li> +<li><a href="#Chapter25">This function is deprecated, and is equivalent to:</a></li> +<li><a href="#Chapter26">Buffer-less and synchronous inner streaming functions</a></li> +<li><a href="#Chapter27">Buffer-less streaming compression (synchronous mode)</a></li> +<li><a href="#Chapter28">Buffer-less streaming decompression (synchronous mode)</a></li> +<li><a href="#Chapter29">Block level API</a></li> +</ol> +<hr> +<a name="Chapter1"></a><h2>Introduction</h2><pre> + 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 regular compression levels from 1 up to ZSTD_maxCLevel(), + which is currently 22. Levels >= 20, labeled `--ultra`, should be used with + caution, as they require more memory. The library also offers negative + compression levels, which extend the range of speed vs. ratio preferences. + The lower the level, the faster the speed (at the cost of compression). + + Compression can be done in: + - a single step (described as Simple API) + - a single step, reusing a context (described as Explicit context) + - unbounded multiple steps (described as Streaming compression) + + The compression ratio achievable on small data can be highly improved using + a dictionary. Dictionary compression can be performed in: + - a single step (described as Simple dictionary API) + - a single step, reusing a dictionary (described as Bulk-processing + dictionary API) + + Advanced experimental functions can be accessed using + `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. + + Advanced experimental APIs should never be used with a dynamically-linked + library. They are not "stable"; their definitions or signatures may change in + the future. Only static linking is allowed. +<BR></pre> + +<a name="Chapter2"></a><h2>Version</h2><pre></pre> + +<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< to check runtime library version */<b> +</b></pre><BR> +<a name="Chapter3"></a><h2>Simple API</h2><pre></pre> + +<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + int compressionLevel); +</b><p> 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()). +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, + const void* src, size_t compressedSize); +</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. + `dstCapacity` is an upper bound of originalSize to regenerate. + 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()). +</p></pre><BR> + +<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) +#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) +unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); +</b><p> `src` should point to the start of a ZSTD encoded frame. + `srcSize` must be at least as large as the frame header. + hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. + @return : - decompressed size of `src` frame content, if known + - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined + - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) + note 1 : a 0 return value means the frame is valid but "empty". + note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode. + When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + Optionally, application can rely on some implicit limit, + as ZSTD_decompress() only needs an upper bound of decompressed size. + (For example, data could be necessarily cut into blocks <= 16 KB). + note 3 : decompressed size is always present when compression is completed using single-pass functions, + such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict(). + note 4 : 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 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. + Always ensure return value fits within application's authorized limits. + Each application can set its own limits. + note 6 : This function replaces ZSTD_getDecompressedSize() +</p></pre><BR> + +<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); +</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). + Both functions work the same way, but ZSTD_getDecompressedSize() blends + "empty", "unknown" and "error" results to the same return value (0), + while ZSTD_getFrameContentSize() gives them separate return values. + @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. +</p></pre><BR> + +<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); +</b><p> `src` should point to the start of a ZSTD frame or skippable frame. + `srcSize` must be >= first frame size + @return : the compressed size of the first frame starting at `src`, + suitable to pass as `srcSize` to `ZSTD_decompress` or similar, + or an error code if input is invalid +</p></pre><BR> + +<h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> +size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b> +unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> +const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> +int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed */<b> +int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> +</pre></b><BR> +<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre> + +<h3>Compression context</h3><pre> When compressing many times, + it is recommended to allocate a context just once, + and re-use it for each successive compression operation. + This will make workload friendlier for system's memory. + Note : re-using context is just a speed / resource optimization. + It doesn't change the compression ratio, which remains identical. + Note 2 : In multi-threaded environments, + use one different context per thread for parallel execution. + +</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; +ZSTD_CCtx* ZSTD_createCCtx(void); +size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); +</pre></b><BR> +<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + int compressionLevel); +</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx. + Important : in order to behave similarly to `ZSTD_compress()`, + this function compresses at requested compression level, + __ignoring any other parameter__ . + If any advanced parameter was set using the advanced API, + they will all be reset. Only `compressionLevel` remains. + +</p></pre><BR> + +<h3>Decompression context</h3><pre> When decompressing many times, + it is recommended to allocate a context only once, + and re-use it for each successive compression operation. + This will make workload friendlier for system's memory. + Use one context per thread for parallel execution. +</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; +ZSTD_DCtx* ZSTD_createDCtx(void); +size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); +</pre></b><BR> +<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize); +</b><p> Same as ZSTD_decompress(), + requires an allocated ZSTD_DCtx. + Compatible with sticky parameters. + +</p></pre><BR> + +<a name="Chapter5"></a><h2>Advanced compression API</h2><pre></pre> + +<pre><b>typedef enum { ZSTD_fast=1, + ZSTD_dfast=2, + ZSTD_greedy=3, + ZSTD_lazy=4, + ZSTD_lazy2=5, + ZSTD_btlazy2=6, + ZSTD_btopt=7, + ZSTD_btultra=8, + ZSTD_btultra2=9 + </b>/* note : new strategies _might_ be added in the future.<b> + Only the order (from fast to strong) is guaranteed */ +} ZSTD_strategy; +</b></pre><BR> +<pre><b>typedef enum { + + </b>/* compression parameters<b> + * Note: When compressing with a ZSTD_CDict these parameters are superseded + * by the parameters used to construct the ZSTD_CDict. + * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */ + ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b> + * Note that exact compression parameters are dynamically determined, + * depending on both compression level and srcSize (when known). + * Default level is ZSTD_CLEVEL_DEFAULT==3. + * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. + * Note 1 : it's possible to pass a negative compression level. + * Note 2 : setting a level does not automatically set all other compression parameters + * to default. Setting this will however eventually dynamically impact the compression + * parameters which have not been manually set. The manually set + * ones will 'stick'. */ + </b>/* Advanced compression parameters :<b> + * It's possible to pin down compression parameters to some specific values. + * In which case, these values are no longer dynamically selected by the compressor */ + ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> + * This will set a memory budget for streaming decompression, + * with larger values requiring more memory + * and typically compressing more. + * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. + * Special: value 0 means "use default windowLog". + * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT + * requires explicitly allowing such size at streaming decompression stage. */ + ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> + * Resulting memory usage is (1 << (hashLog+2)). + * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. + * Larger tables improve compression ratio of strategies <= dFast, + * and improve speed of strategies > dFast. + * Special: value 0 means "use default hashLog". */ + ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> + * Resulting memory usage is (1 << (chainLog+2)). + * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. + * Larger tables result in better and slower compression. + * This parameter is useless for "fast" strategy. + * It's still useful when using "dfast" strategy, + * in which case it defines a secondary probe table. + * Special: value 0 means "use default chainLog". */ + ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> + * More attempts result in better and slower compression. + * This parameter is useless for "fast" and "dFast" strategies. + * Special: value 0 means "use default searchLog". */ + ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> + * Note that Zstandard can still find matches of smaller size, + * it just tweaks its search algorithm to look for this size and larger. + * Larger values increase compression and decompression speed, but decrease ratio. + * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. + * Note that currently, for all strategies < btopt, effective minimum is 4. + * , for all strategies > fast, effective maximum is 6. + * Special: value 0 means "use default minMatchLength". */ + ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> + * For strategies btopt, btultra & btultra2: + * Length of Match considered "good enough" to stop search. + * Larger values make compression stronger, and slower. + * For strategy fast: + * Distance between match sampling. + * Larger values make compression faster, and weaker. + * Special: value 0 means "use default targetLength". */ + ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> + * The higher the value of selected strategy, the more complex it is, + * resulting in stronger and slower compression. + * Special: value 0 means "use default strategy". */ + + </b>/* LDM mode parameters */<b> + ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> + * This parameter is designed to improve compression ratio + * for large inputs, by finding large matches at long distance. + * It increases memory usage and window size. + * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB + * except when expressly set to a different value. */ + ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> + * Larger values increase memory usage and compression ratio, + * but decrease compression speed. + * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX + * default: windowlog - 7. + * Special: value 0 means "automatically determine hashlog". */ + ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> + * Larger/too small values usually decrease compression ratio. + * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. + * Special: value 0 means "use default value" (default: 64). */ + ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> + * Larger values improve collision resolution but decrease compression speed. + * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. + * Special: value 0 means "use default value" (default: 3). */ + ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> + * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). + * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. + * Larger values improve compression speed. + * Deviating far from default value will likely result in a compression ratio decrease. + * Special: value 0 means "automatically determine hashRateLog". */ + + </b>/* frame parameters */<b> + ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> + * Content size must be known at the beginning of compression. + * This is automatically the case when using ZSTD_compress2(), + * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ + ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> + ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> + + </b>/* multi-threading parameters */<b> + </b>/* These parameters are only useful if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> + * They return an error otherwise. */ + ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> + * When nbWorkers >= 1, triggers asynchronous mode when used with ZSTD_compressStream*() : + * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, + * while compression work is performed in parallel, within worker threads. + * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : + * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). + * More workers improve speed, but also increase memory usage. + * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */ + ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> + * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. + * 0 means default, which is dynamically determined based on compression parameters. + * Job size must be a minimum of overlap size, or 1 MB, whichever is largest. + * The minimum size is automatically and transparently enforced. */ + ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> + * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. + * It helps preserve compression ratio, while each job is compressed in parallel. + * This value is enforced only when nbWorkers >= 1. + * Larger values increase compression ratio, but decrease speed. + * Possible values range from 0 to 9 : + * - 0 means "default" : value will be determined by the library, depending on strategy + * - 1 means "no overlap" + * - 9 means "full overlap", using a full window size. + * Each intermediate rank increases/decreases load size by a factor 2 : + * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default + * default value varies between 6 and 9, depending on strategy */ + + </b>/* note : additional experimental parameters are also available<b> + * within the experimental section of the API. + * At the time of this writing, they include : + * ZSTD_c_rsyncable + * ZSTD_c_format + * ZSTD_c_forceMaxWindow + * ZSTD_c_forceAttachDict + * ZSTD_c_literalCompressionMode + * ZSTD_c_targetCBlockSize + * ZSTD_c_srcSizeHint + * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. + * note : never ever use experimentalParam? names directly; + * also, the enums values themselves are unstable and can still change. + */ + ZSTD_c_experimentalParam1=500, + ZSTD_c_experimentalParam2=10, + ZSTD_c_experimentalParam3=1000, + ZSTD_c_experimentalParam4=1001, + ZSTD_c_experimentalParam5=1002, + ZSTD_c_experimentalParam6=1003, + ZSTD_c_experimentalParam7=1004 +} ZSTD_cParameter; +</b></pre><BR> +<pre><b>typedef struct { + size_t error; + int lowerBound; + int upperBound; +} ZSTD_bounds; +</b></pre><BR> +<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); +</b><p> All parameters must belong to an interval with lower and upper bounds, + otherwise they will either trigger an error or be automatically clamped. + @return : a structure, ZSTD_bounds, which contains + - an error status field, which must be tested using ZSTD_isError() + - lower and upper bounds, both inclusive + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); +</b><p> Set one compression parameter, selected by enum ZSTD_cParameter. + All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). + Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). + Setting a parameter is generally only possible during frame initialization (before starting compression). + Exception : when using multi-threading mode (nbWorkers >= 1), + the following parameters can be updated _during_ compression (within same frame): + => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. + new parameters will be active for next job only (after a flush()). + @return : an error code (which can be tested using ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); +</b><p> Total input data size to be compressed as a single frame. + Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. + This value will also be controlled at end of frame, and trigger an error if not respected. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. + In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. + ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. + Note 2 : pledgedSrcSize is only valid once, for the next frame. + It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. + Note 3 : Whenever all input data is provided and consumed in a single round, + for example with ZSTD_compress2(), + or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), + this value is automatically overridden by srcSize instead. + +</p></pre><BR> + +<pre><b>typedef enum { + ZSTD_reset_session_only = 1, + ZSTD_reset_parameters = 2, + ZSTD_reset_session_and_parameters = 3 +} ZSTD_ResetDirective; +</b></pre><BR> +<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); +</b><p> There are 2 different things that can be reset, independently or jointly : + - The session : will stop compressing current frame, and make CCtx ready to start a new one. + Useful after an error, or to interrupt any ongoing compression. + Any internal data not yet flushed is cancelled. + Compression parameters and dictionary remain unchanged. + They will be used to compress next frame. + Resetting session never fails. + - The parameters : changes all parameters back to "default". + This removes any reference to any dictionary too. + Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) + otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) + - Both : similar to resetting the session, followed by resetting parameters. + +</p></pre><BR> + +<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize); +</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. + ZSTD_compress2() always starts a new frame. + Should cctx hold data from a previously unfinished frame, everything about it is forgotten. + - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() + - The function is always blocking, returns when compression is completed. + 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()). + +</p></pre><BR> + +<a name="Chapter6"></a><h2>Advanced decompression API</h2><pre></pre> + +<pre><b>typedef enum { + + ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> + * the streaming API will refuse to allocate memory buffer + * in order to protect the host from unreasonable memory requirements. + * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. + * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). + * Special: value 0 means "use default maximum windowLog". */ + + </b>/* note : additional experimental parameters are also available<b> + * within the experimental section of the API. + * At the time of this writing, they include : + * ZSTD_d_format + * ZSTD_d_stableOutBuffer + * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. + * note : never ever use experimentalParam? names directly + */ + ZSTD_d_experimentalParam1=1000, + ZSTD_d_experimentalParam2=1001 + +} ZSTD_dParameter; +</b></pre><BR> +<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); +</b><p> All parameters must belong to an interval with lower and upper bounds, + otherwise they will either trigger an error or be automatically clamped. + @return : a structure, ZSTD_bounds, which contains + - an error status field, which must be tested using ZSTD_isError() + - both lower and upper bounds, inclusive + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); +</b><p> Set one compression parameter, selected by enum ZSTD_dParameter. + All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). + Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). + Setting a parameter is only possible during frame initialization (before starting decompression). + @return : 0, or an error code (which can be tested using ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); +</b><p> Return a DCtx to clean state. + Session and parameters can be reset jointly or separately. + Parameters can only be reset when no active frame is being decompressed. + @return : 0, or an error code, which can be tested with ZSTD_isError() + +</p></pre><BR> + +<a name="Chapter7"></a><h2>Streaming</h2><pre></pre> + +<pre><b>typedef struct ZSTD_inBuffer_s { + const void* src; </b>/**< start of input buffer */<b> + size_t size; </b>/**< size of input buffer */<b> + size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> +} ZSTD_inBuffer; +</b></pre><BR> +<pre><b>typedef struct ZSTD_outBuffer_s { + void* dst; </b>/**< start of output buffer */<b> + size_t size; </b>/**< size of output buffer */<b> + size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> +} ZSTD_outBuffer; +</b></pre><BR> +<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> + 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. + It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. + + For parallel execution, use one separate ZSTD_CStream per thread. + + note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. + + Parameters are sticky : when starting a new compression on the same context, + it will re-use the same sticky parameters as previous compression session. + When in doubt, it's recommended to fully initialize the context before usage. + Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), + ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to + set more specific parameters, the pledged source size, or load a dictionary. + + Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to + consume input stream. The function will automatically update both `pos` + fields within `input` and `output`. + Note that the function may not consume the entire input, for example, because + the output buffer is already full, in which case `input.pos < input.size`. + The caller must check if input has been entirely consumed. + If not, the caller must make some room to receive more compressed data, + and then present again remaining input data. + note: ZSTD_e_continue is guaranteed to make some forward progress when called, + but doesn't guarantee maximal forward progress. This is especially relevant + when compressing with multiple threads. The call won't block if it can + consume some input, but if it can't it will wait for some, but not all, + output to be flushed. + @return : provides a minimum amount of data remaining to be flushed from internal buffers + or an error code, which can be tested using ZSTD_isError(). + + At any moment, it's possible to flush whatever data might remain stuck within internal buffer, + using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. + Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). + In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. + You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the + operation. + note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will + block until the flush is complete or the output buffer is full. + @return : 0 if internal buffers are entirely flushed, + >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), + or an error code, which can be tested using ZSTD_isError(). + + Calling ZSTD_compressStream2() with ZSTD_e_end 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. + flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. + You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to + start a new frame. + note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will + block until the flush is complete or the output buffer is full. + @return : 0 if frame fully completed and fully flushed, + >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), + or an error code, which can be tested using ZSTD_isError(). + + +<BR></pre> + +<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> +</b></pre><BR> +<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); +size_t ZSTD_freeCStream(ZSTD_CStream* zcs); +</pre></b><BR> +<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { + ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> + ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> + * it creates (at least) one new block, that can be decoded immediately on reception; + * frame will continue: any future data can still reference previously compressed data, improving compression. + * note : multithreaded compression will block to flush as much output as possible. */ + ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> + * note that frame is only closed after compressed data is fully flushed (return value == 0). + * After that point, any additional data starts a new frame. + * note : each frame is independent (does not reference any content from previous frame). + : note : multithreaded compression will block to flush as much output as possible. */ +} ZSTD_EndDirective; +</pre></b><BR> +<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, + ZSTD_outBuffer* output, + ZSTD_inBuffer* input, + ZSTD_EndDirective endOp); +</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. + - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() + - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) + - output->pos must be <= dstCapacity, input->pos must be <= srcSize + - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. + - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. + - When nbWorkers>=1, function is non-blocking : it just acquires a copy of input, and distributes jobs to internal worker threads, flush whatever is available, + and then immediately returns, just indicating that there is some data remaining to be flushed. + The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. + - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking. + - @return provides a minimum amount of data remaining to be flushed from internal buffers + or an error code, which can be tested using ZSTD_isError(). + if @return != 0, flush is not fully completed, there is still some data left within internal buffers. + This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. + For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. + - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), + only ZSTD_e_end or ZSTD_e_flush operations are allowed. + Before starting a new compression job, or changing compression parameters, + it is required to fully flush internal buffers. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> +</b></pre><BR> +<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b> +</b></pre><BR> +<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); +</b>/*!<b> + * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue). + * NOTE: The return value is different. ZSTD_compressStream() returns a hint for + * the next read size (if non-zero and not an error). ZSTD_compressStream2() + * returns the minimum nb of bytes left to flush (if non-zero and not an error). + */ +size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b> +size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b> +size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +</b><p> + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) + ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); + +</p></pre><BR> + +<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> + 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. + @return : recommended first input size + Alternatively, use advanced API to set specific properties. + + 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. + The function tries to flush all data decoded immediately, respecting output buffer size. + If `output.pos < output.size`, decoder has flushed everything it could. + But if `output.pos == output.size`, there might be some data left within internal buffers., + In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. + Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. + @return : 0 when a frame is completely decoded and fully flushed, + or an error code, which can be tested using ZSTD_isError(), + or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : + the return value is a suggested next input size (just a hint for better latency) + that will never request more than the remaining frame size. + +<BR></pre> + +<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> +</b></pre><BR> +<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); +size_t ZSTD_freeDStream(ZSTD_DStream* zds); +</pre></b><BR> +<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> +<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> +</b></pre><BR> +<pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> +</b></pre><BR> +<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre> + +<pre><b>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); +</b><p> Compression at an explicit compression level using a Dictionary. + A dictionary can be any arbitrary data segment (also called a prefix), + or a buffer with specified information (see dictBuilder/zdict.h). + Note : This function loads the dictionary, resulting in significant startup delay. + It's intended for a dictionary used only once. + Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. +</p></pre><BR> + +<pre><b>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); +</b><p> Decompression using a known Dictionary. + Dictionary must be identical to the one used during compression. + Note : This function loads the dictionary, resulting in significant startup delay. + It's intended for a dictionary used only once. + Note : When `dict == NULL || dictSize < 8` no dictionary is used. +</p></pre><BR> + +<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> + +<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, + int compressionLevel); +</b><p> When compressing multiple messages or blocks using the same dictionary, + it's recommended to digest the dictionary only once, since it's a costly operation. + ZSTD_createCDict() will create a state from digesting a dictionary. + The resulting state can be used for future compression operations with very limited startup cost. + ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. + @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict. + Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content. + Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer, + in which case the only thing that it transports is the @compressionLevel. + This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively, + expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. +</p></pre><BR> + +<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); +</b><p> Function frees memory allocated by ZSTD_createCDict(). +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_CDict* cdict); +</b><p> Compression using a digested Dictionary. + Recommended when same dictionary is used multiple times. + Note : compression level is _decided at dictionary creation time_, + and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); +</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. + dictBuffer can be released after DDict creation, as its content is copied inside DDict. +</p></pre><BR> + +<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); +</b><p> Function frees memory allocated with ZSTD_createDDict() +</p></pre><BR> + +<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_DDict* ddict); +</b><p> Decompression using a digested Dictionary. + Recommended when same dictionary is used multiple times. +</p></pre><BR> + +<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre> + +<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); +</b><p> Provides the dictID stored within dictionary. + if @return == 0, the dictionary is not conformant with Zstandard specification. + It can still be loaded, but as a content-only dictionary. +</p></pre><BR> + +<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); +</b><p> Provides the dictID of the dictionary loaded into `ddict`. + If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. + Non-conformant dictionaries can still be loaded, but as content-only dictionaries. +</p></pre><BR> + +<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); +</b><p> Provides the dictID required to decompressed the frame stored within `src`. + If @return == 0, the dictID could not be decoded. + This could for one of the following reasons : + - The frame does not require a dictionary to be decoded (most common case). + - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information. + Note : this use case also happens when using a non-conformant dictionary. + - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). + - This is not a Zstandard frame. + When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. +</p></pre><BR> + +<a name="Chapter13"></a><h2>Advanced dictionary and prefix API</h2><pre> + This API allows dictionaries to be used with ZSTD_compress2(), + ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and + only reset with the context is reset with ZSTD_reset_parameters or + ZSTD_reset_session_and_parameters. Prefixes are single-use. +<BR></pre> + +<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); +</b><p> Create an internal CDict from `dict` buffer. + Decompression will have to use same dictionary. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, + meaning "return to no-dictionary mode". + Note 1 : Dictionary is sticky, it will be used for all future compressed frames. + To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters). + Note 2 : Loading a dictionary involves building tables. + It's also a CPU consuming operation, with non-negligible impact on latency. + Tables are dependent on compression parameters, and for this reason, + compression parameters can no longer be changed after loading a dictionary. + Note 3 :`dict` content will be copied internally. + Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. + In such a case, dictionary buffer must outlive its users. + Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() + to precisely select how dictionary content must be interpreted. +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); +</b><p> Reference a prepared dictionary, to be used for all next compressed frames. + Note that compression parameters are enforced from within CDict, + and supersede any compression parameter previously set within CCtx. + The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. + The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. + The dictionary will remain valid for future compressed frames using same CCtx. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Referencing a NULL CDict means "return to no-dictionary mode". + Note 1 : Currently, only one dictionary can be managed. + Referencing a new dictionary effectively "discards" any previous one. + Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, + const void* prefix, size_t prefixSize); +</b><p> Reference a prefix (single-usage dictionary) for next compressed frame. + A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). + Decompression will need same prefix to properly regenerate data. + Compressing with a prefix is similar in outcome as performing a diff and compressing it, + but performs much faster, especially during decompression (compression speed is tunable with compression level). + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary + Note 1 : Prefix buffer is referenced. It **must** outlive compression. + Its content must remain unmodified during compression. + Note 2 : If the intention is to diff some large src data blob with some prior version of itself, + ensure that the window size is large enough to contain the entire source. + See ZSTD_c_windowLog. + Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. + It's a CPU consuming operation, with non-negligible impact on latency. + If there is a need to use the same prefix multiple times, consider loadDictionary instead. + Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent). + Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); +</b><p> Create an internal DDict from dict buffer, + to be used to decompress next frames. + The dictionary remains valid for all future frames, until explicitly invalidated. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, + meaning "return to no-dictionary mode". + Note 1 : Loading a dictionary involves building tables, + which has a non-negligible impact on CPU usage and latency. + It's recommended to "load once, use many times", to amortize the cost + Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. + Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. + Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of + how dictionary content is loaded and interpreted. + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); +</b><p> Reference a prepared dictionary, to be used to decompress next frames. + The dictionary remains active for decompression of future frames using same DCtx. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : Currently, only one dictionary can be managed. + Referencing a new dictionary effectively "discards" any previous one. + Special: referencing a NULL DDict means "return to no-dictionary mode". + Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, + const void* prefix, size_t prefixSize); +</b><p> Reference a prefix (single-usage dictionary) to decompress next frame. + This is the reverse operation of ZSTD_CCtx_refPrefix(), + and must use the same prefix as the one used during compression. + Prefix is **only used once**. Reference is discarded at end of frame. + End of frame is reached when ZSTD_decompressStream() returns 0. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary + Note 2 : Prefix buffer is referenced. It **must** outlive decompression. + Prefix buffer must remain unmodified up to the end of frame, + reached when ZSTD_decompressStream() returns 0. + Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent). + Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) + Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. + A full dictionary is more costly, as it requires building tables. + +</p></pre><BR> + +<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); +size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); +size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); +size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); +size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); +size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); +</b><p> These functions give the _current_ memory usage of selected object. + Note that object memory usage can evolve (increase or decrease) over time. +</p></pre><BR> + +<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre> + The following symbols and constants + are not planned to join "stable API" status in the near future. + They can still change in future versions. + Some of them are planned to remain in the static_only section indefinitely. + Some of them might be removed in the future (especially when redundant with existing stable functions) + +<BR></pre> + +<pre><b>typedef struct { + unsigned int matchPos; </b>/* Match pos in dst */<b> + </b>/* If seqDef.offset > 3, then this is seqDef.offset - 3<b> + * If seqDef.offset < 3, then this is the corresponding repeat offset + * But if seqDef.offset < 3 and litLength == 0, this is the + * repeat offset before the corresponding repeat offset + * And if seqDef.offset == 3 and litLength == 0, this is the + * most recent repeat offset - 1 + */ + unsigned int offset; + unsigned int litLength; </b>/* Literal length */<b> + unsigned int matchLength; </b>/* Match length */<b> + </b>/* 0 when seq not rep and seqDef.offset otherwise<b> + * when litLength == 0 this will be <= 4, otherwise <= 3 like normal + */ + unsigned int rep; +} ZSTD_Sequence; +</b></pre><BR> +<pre><b>typedef struct { + unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> + unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> + unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> + unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> + unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> + unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> + ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> +} ZSTD_compressionParameters; +</b></pre><BR> +<pre><b>typedef struct { + int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> + int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> + int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> +} ZSTD_frameParameters; +</b></pre><BR> +<pre><b>typedef struct { + ZSTD_compressionParameters cParams; + ZSTD_frameParameters fParams; +} ZSTD_parameters; +</b></pre><BR> +<pre><b>typedef enum { + ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> + ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> + ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> +} ZSTD_dictContentType_e; +</b></pre><BR> +<pre><b>typedef enum { + ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> + ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> +} ZSTD_dictLoadMethod_e; +</b></pre><BR> +<pre><b>typedef enum { + ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> + ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> + * Useful to save 4 bytes per generated frame. + * Decoder cannot recognise automatically this format, requiring this instruction. */ +} ZSTD_format_e; +</b></pre><BR> +<pre><b>typedef enum { + </b>/* Note: this enum and the behavior it controls are effectively internal<b> + * implementation details of the compressor. They are expected to continue + * to evolve and should be considered only in the context of extremely + * advanced performance tuning. + * + * Zstd currently supports the use of a CDict in three ways: + * + * - The contents of the CDict can be copied into the working context. This + * means that the compression can search both the dictionary and input + * while operating on a single set of internal tables. This makes + * the compression faster per-byte of input. However, the initial copy of + * the CDict's tables incurs a fixed cost at the beginning of the + * compression. For small compressions (< 8 KB), that copy can dominate + * the cost of the compression. + * + * - The CDict's tables can be used in-place. In this model, compression is + * slower per input byte, because the compressor has to search two sets of + * tables. However, this model incurs no start-up cost (as long as the + * working context's tables can be reused). For small inputs, this can be + * faster than copying the CDict's tables. + * + * - The CDict's tables are not used at all, and instead we use the working + * context alone to reload the dictionary and use params based on the source + * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict(). + * This method is effective when the dictionary sizes are very small relative + * to the input size, and the input size is fairly large to begin with. + * + * Zstd has a simple internal heuristic that selects which strategy to use + * at the beginning of a compression. However, if experimentation shows that + * Zstd is making poor choices, it is possible to override that choice with + * this enum. + */ + ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> + ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> + ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> + ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b> +} ZSTD_dictAttachPref_e; +</b></pre><BR> +<pre><b>typedef enum { + ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> + * Negative compression levels will be uncompressed, and positive compression + * levels will be compressed. */ + ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> + * emitted if Huffman compression is not profitable. */ + ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b> +} ZSTD_literalCompressionMode_e; +</b></pre><BR> +<a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre> + +<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); +</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames + `srcSize` must be the _exact_ size of this series + (i.e. there should be a frame boundary at `src + srcSize`) + @return : - decompressed size of all data in all successive frames + - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN + - if an error occurred: ZSTD_CONTENTSIZE_ERROR + + note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. + When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. + In which case, it's necessary to use streaming mode to decompress data. + 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 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to + read each contained frame header. This is fast as most of the data is skipped, + however it does mean that all frame data must be present and valid. +</p></pre><BR> + +<pre><b>unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize); +</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames + `srcSize` must be the _exact_ size of this series + (i.e. there should be a frame boundary at `src + srcSize`) + @return : - upper-bound for the decompressed size of all data in all successive frames + - if an error occured: ZSTD_CONTENTSIZE_ERROR + + note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. + note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. + in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. + note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: + upper-bound = # blocks * min(128 KB, Window_Size) + +</p></pre><BR> + +<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); +</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. + @return : size of the Frame Header, + or an error code (if srcSize is too small) +</p></pre><BR> + +<pre><b>size_t ZSTD_getSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs, + size_t outSeqsSize, const void* src, size_t srcSize); +</b><p> Extract sequences from the sequence store + zc can be used to insert custom compression params. + This function invokes ZSTD_compress2 + @return : number of sequences extracted + +</p></pre><BR> + +<a name="Chapter16"></a><h2>Memory management</h2><pre></pre> + +<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel); +size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); +size_t ZSTD_estimateDCtxSize(void); +</b><p> These functions make it possible to estimate memory usage + of a future {D,C}Ctx, before its creation. + + ZSTD_estimateCCtxSize() will provide a memory budget large enough + for any compression level up to selected one. + Note : Unlike ZSTD_estimateCStreamSize*(), this estimate + does not include space for a window buffer. + Therefore, the estimation is only guaranteed for single-shot compressions, not streaming. + The estimate will assume the input may be arbitrarily large, + which is the worst case. + + When srcSize can be bound by a known and rather "small" value, + this fact can be used to provide a tighter estimation + because the CCtx compression context will need less memory. + This tighter estimation can be provided by more advanced functions + ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(), + and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter(). + Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits. + + Note 2 : only single-threaded compression is supported. + ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. + +</p></pre><BR> + +<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel); +size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); +size_t ZSTD_estimateDStreamSize(size_t windowSize); +size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); +</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one. + It will also consider src size to be arbitrarily "large", which is worst case. + If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. + ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. + ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1. + Note : CStream size estimation is only correct for single-threaded compression. + ZSTD_DStream memory budget depends on window Size. + This information can be passed manually, using ZSTD_estimateDStreamSize, + or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); + Note : if streaming is init with function ZSTD_init?Stream_usingDict(), + an internal ?Dict will be created, which additional size is not estimated here. + In this case, get total size by adding ZSTD_estimate?DictSize +</p></pre><BR> + +<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); +size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); +size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); +</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). + ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). + Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. + +</p></pre><BR> + +<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); +ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> +</b><p> Initialize an object using a pre-allocated fixed-size buffer. + workspace: The memory area to emplace the object into. + Provided pointer *must be 8-bytes aligned*. + Buffer must outlive object. + workspaceSize: Use ZSTD_estimate*Size() to determine + how large workspace must be to support target scenario. + @return : pointer to object (same address as workspace, just different type), + or NULL if error (size too small, incorrect alignment, etc.) + Note : zstd will never resize nor malloc() when using a static buffer. + If the object requires more memory than available, + zstd will just error out (typically ZSTD_error_memory_allocation). + Note 2 : there is no corresponding "free" function. + Since workspace is allocated externally, it must be freed externally too. + Note 3 : cParams : use ZSTD_getCParams() to convert a compression level + into its associated cParams. + Limitation 1 : currently not compatible with internal dictionary creation, triggered by + ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). + Limitation 2 : static cctx currently not compatible with multi-threading. + Limitation 3 : static dctx is incompatible with legacy support. + +</p></pre><BR> + +<pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> +</b></pre><BR> +<pre><b>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; +static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> +</b><p> These prototypes make it possible to pass your own allocation/free functions. + ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. + All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. + +</p></pre><BR> + +<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre> + +<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); +</b><p> Create a digested dictionary for compression + Dictionary content is just referenced, not duplicated. + As a consequence, `dictBuffer` **must** outlive CDict, + and its content must remain unmodified throughout the lifetime of CDict. + note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef +</p></pre><BR> + +<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); +</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. + `estimatedSrcSize` value is optional, select 0 if not known +</p></pre><BR> + +<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); +</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. + All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 +</p></pre><BR> + +<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params); +</b><p> Ensure param values remain within authorized range. + @return 0 on success, or an error code (can be checked with ZSTD_isError()) +</p></pre><BR> + +<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); +</b><p> optimize params for a given `srcSize` and `dictSize`. + `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. + `dictSize` must be `0` when there is no dictionary. + cPar can be invalid : all parameters will be clamped within valid range in the @return struct. + This function never fails (wide contract) +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const void* dict,size_t dictSize, + ZSTD_parameters params); +</b><p> Note : this function is now DEPRECATED. + It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters. + This prototype will be marked as deprecated and generate compilation warning on reaching v1.5.x +</p></pre><BR> + +<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, + const void* src, size_t srcSize, + const ZSTD_CDict* cdict, + ZSTD_frameParameters fParams); +</b><p> Note : this function is now REDUNDANT. + It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters. + This prototype will be marked as deprecated and generate compilation warning in some future version +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); +</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. + It saves some memory, but also requires that `dict` outlives its usage within `cctx` +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); +</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over + how to load the dictionary (by copy ? by reference ?) + and how to interpret it (automatic ? force raw mode ? full mode only ?) +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); +</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over + how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_getParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); +</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, + and store it into int* value. + @return : 0, or an error code (which can be tested with ZSTD_isError()). + +</p></pre><BR> + +<pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void); +size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); +</b><p> Quick howto : + - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure + - ZSTD_CCtxParams_setParameter() : Push parameters one by one into + an existing ZSTD_CCtx_params structure. + This is similar to + ZSTD_CCtx_setParameter(). + - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to + an existing CCtx. + These parameters will be applied to + all subsequent frames. + - ZSTD_compressStream2() : Do compression using the CCtx. + - ZSTD_freeCCtxParams() : Free the memory. + + This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() + for static allocation of CCtx for single-threaded compression. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); +</b><p> Reset params to default values. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); +</b><p> Initializes the compression parameters of cctxParams according to + compression level. All other parameters are reset to their default values. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); +</b><p> Initializes the compression and frame parameters of cctxParams according to + params. All other parameters are reset to their default values. + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); +</b><p> Similar to ZSTD_CCtx_setParameter. + Set one compression parameter, selected by enum ZSTD_cParameter. + Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams(). + @result : 0, or an error code (which can be tested with ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtxParams_getParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); +</b><p> Similar to ZSTD_CCtx_getParameter. + Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams( + ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); +</b><p> Apply a set of ZSTD_CCtx_params to the compression context. + This can be done even after compression is started, + if nbWorkers==0, this will have no impact until a new compression is started. + if nbWorkers>=1, new parameters will be picked up at next job, + with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). + +</p></pre><BR> + +<pre><b>size_t ZSTD_compressStream2_simpleArgs ( + ZSTD_CCtx* cctx, + void* dst, size_t dstCapacity, size_t* dstPos, + const void* src, size_t srcSize, size_t* srcPos, + ZSTD_EndDirective endOp); +</b><p> Same as ZSTD_compressStream2(), + but using only integral types as arguments. + This variant might be helpful for binders from dynamic languages + which have troubles handling structures containing memory pointers. + +</p></pre><BR> + +<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre> + +<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size); +</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. + Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. + Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. + Note 3 : Skippable Frame Identifiers are considered valid. +</p></pre><BR> + +<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); +</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. + Dictionary content is referenced, and therefore stays in dictBuffer. + It is important that dictBuffer outlives DDict, + it must remain read accessible throughout the lifetime of DDict +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); +</b><p> Same as ZSTD_DCtx_loadDictionary(), + but references `dict` content instead of copying it into `dctx`. + This saves memory if `dict` remains around., + However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); +</b><p> Same as ZSTD_DCtx_loadDictionary(), + but gives direct control over + how to load the dictionary (by copy ? by reference ?) + and how to interpret it (automatic ? force raw mode ? full mode only ?). +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); +</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over + how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); +</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. + This protects a decoder context from reserving too much memory for itself (potential attack scenario). + This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. + By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) + @return : 0, or an error code (which can be tested using ZSTD_isError()). + +</p></pre><BR> + +<pre><b>size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); +</b><p> Instruct the decoder context about what kind of data to decode next. + This instruction is mandatory to decode data without a fully-formed header, + such ZSTD_f_zstd1_magicless for example. + @return : 0, or an error code (which can be tested using ZSTD_isError()). +</p></pre><BR> + +<pre><b>size_t ZSTD_decompressStream_simpleArgs ( + ZSTD_DCtx* dctx, + void* dst, size_t dstCapacity, size_t* dstPos, + const void* src, size_t srcSize, size_t* srcPos); +</b><p> Same as ZSTD_decompressStream(), + but using only integral types as arguments. + This can be helpful for binders from dynamic languages + which have troubles handling structures containing memory pointers. + +</p></pre><BR> + +<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. + Once Advanced API reaches "stable" status, + redundant functions will be deprecated, and then at some point removed. +<BR></pre> + +<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></b>/**! ZSTD_initCStream_srcSize() :<b> + * This function is deprecated, and equivalent to: + * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + * ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) + * ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); + * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); + * + * pledgedSrcSize must be correct. If it is not known at init time, use + * ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, + * "0" also disables frame content size field. It may be enabled in the future. + * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + */ +size_t +ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, + int compressionLevel, + unsigned long long pledgedSrcSize); +</pre></b><BR> +<a name="Chapter20"></a><h2>! ZSTD_initCStream_usingDict() :</h2><pre> This function is deprecated, and is equivalent to: + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); + ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); + + Creates of an internal CDict (incompatible with static CCtx), except if + dict == NULL or dictSize < 8, in which case no dict is used. + Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if + it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<a name="Chapter21"></a><h2>! ZSTD_initCStream_advanced() :</h2><pre> This function is deprecated, and is approximately equivalent to: + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + // Pseudocode: Set each zstd parameter and leave the rest as-is. + for ((param, value) : params) { + ZSTD_CCtx_setParameter(zcs, param, value); + } + ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); + ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); + + dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy. + pledgedSrcSize must be correct. + If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<a name="Chapter22"></a><h2>! ZSTD_initCStream_usingCDict() :</h2><pre> This function is deprecated, and equivalent to: + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + ZSTD_CCtx_refCDict(zcs, cdict); + + note : cdict will just be referenced, and must outlive compression session + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<a name="Chapter23"></a><h2>! ZSTD_initCStream_usingCDict_advanced() :</h2><pre> This function is DEPRECATED, and is approximately equivalent to: + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + // Pseudocode: Set each zstd frame parameter and leave the rest as-is. + for ((fParam, value) : fParams) { + ZSTD_CCtx_setParameter(zcs, fParam, value); + } + ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); + ZSTD_CCtx_refCDict(zcs, cdict); + + same as ZSTD_initCStream_usingCDict(), with control over frame parameters. + pledgedSrcSize must be correct. If srcSize is not known at init time, use + value ZSTD_CONTENTSIZE_UNKNOWN. + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); +</b><p> This function is deprecated, and is equivalent to: + ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); + ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); + + start a new frame, using same parameters from previous frame. + This is typically useful to skip dictionary loading stage, since it will re-use it in-place. + Note that zcs must be init at least once before using ZSTD_resetCStream(). + If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. + If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. + For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, + but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. + @return : 0, or an error code (which can be tested using ZSTD_isError()) + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +</p></pre><BR> + +<pre><b>typedef struct { + unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> + unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> + unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> + unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> + unsigned currentJobID; </b>/* MT only : latest started job nb */<b> + unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> +} ZSTD_frameProgression; +</b></pre><BR> +<pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); +</b><p> Tell how many bytes are ready to be flushed immediately. + Useful for multithreading scenarios (nbWorkers >= 1). + Probe the oldest active job, defined as oldest job not yet entirely flushed, + and check its output buffer. + @return : amount of data stored in oldest job and ready to be flushed immediately. + if @return == 0, it means either : + + there is no active job (could be checked with ZSTD_frameProgression()), or + + oldest job is still actively compressing data, + but everything it has produced has also been flushed so far, + therefore flush speed is limited by production speed of oldest job + irrespective of the speed of concurrent (and newer) jobs. + +</p></pre><BR> + +<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></b>/**<b> + * This function is deprecated, and is equivalent to: + * + * ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); + * ZSTD_DCtx_loadDictionary(zds, dict, dictSize); + * + * note: no dictionary will be used if dict == NULL or dictSize < 8 + * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + */ +size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); +</pre></b><BR> +<a name="Chapter24"></a><h2>This function is deprecated, and is equivalent to:</h2><pre> + ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); + ZSTD_DCtx_refDDict(zds, ddict); + + note : ddict is referenced, it must outlive decompression session + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<a name="Chapter25"></a><h2>This function is deprecated, and is equivalent to:</h2><pre> + ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); + + re-use decompression parameters from previous init; saves dictionary loading + Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x + +<BR></pre> + +<a name="Chapter26"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre> + 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 several restrictions, documented below. + Prefer normal streaming API for an easier experience. + +<BR></pre> + +<a name="Chapter27"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> + 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 buffers only. + - Interface is synchronous : input is consumed entirely and produces 1+ 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 srcSize==0, in which case, it will write a final empty block to end the frame. + Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. + + `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again. +<BR></pre> + +<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>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); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b> +size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> +size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b> +size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b> +</pre></b><BR> +<a name="Chapter28"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> + 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_getFrameHeader(). + Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. + Data fragment must be large enough to ensure successful decoding. + `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. + @result : 0 : successful decoding, the `ZSTD_frameHeader` 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(). + + It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, + such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). + Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. + As a consequence, check that values remain within valid application range. + For example, do not allocate memory blindly, check that `windowSize` is within expectation. + Each application can set its own limits, depending on local restrictions. + For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. + + ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. + 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 distance. + There are multiple ways to guarantee this condition. + + The most memory efficient way is to use a round buffer of sufficient size. + Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), + which can @return an error code if required value is too large for current system (in 32-bits mode). + In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, + up to the moment there is not enough room left in the buffer to guarantee decoding another full block, + which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. + At which point, decoding can resume from the beginning of the buffer. + Note that already decoded data stored in the buffer should be flushed before being overwritten. + + There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. + + Finally, if you control the compression process, you can also ignore all buffer size rules, + as long as the encoder and decoder progress in "lock-step", + aka use exactly the same buffer sizes, break contiguity at the same place, etc. + + Once buffers are setup, start decompression, with ZSTD_decompressBegin(). + If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). + + 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 : it just means ZSTD_decompressContinue() has decoded some metadata item. + It can also be an error code, which can be tested with ZSTD_isError(). + + 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 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_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. + For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. +<BR></pre> + +<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; +typedef struct { + unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> + unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> + unsigned blockSizeMax; + ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> + unsigned headerSize; + unsigned dictID; + unsigned checksumFlag; +} ZSTD_frameHeader; +</pre></b><BR> +<pre><b>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> +</b>/*! ZSTD_getFrameHeader_advanced() :<b> + * same as ZSTD_getFrameHeader(), + * with added capability to select a format (like ZSTD_f_zstd1_magicless) */ +size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); +size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> +</b><p> decode Frame Header, or requires larger `srcSize`. + @return : 0, `zfhPtr` is correctly filled, + >0, `srcSize` is too small, value is wanted `srcSize` amount, + or an error code, which can be tested using ZSTD_isError() +</p></pre><BR> + +<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; +</b></pre><BR> +<a name="Chapter29"></a><h2>Block level API</h2><pre></pre> + +<pre><b></b><p> Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes). + But users will have to take in charge needed metadata 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 : any ZSTD_compressBegin*() variant, including with dictionary + + decompression : any ZSTD_decompressBegin*() variant, including with dictionary + + copyCCtx() and copyDCtx() can be used too + - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB + + If input is larger than a block size, it's necessary to split input data into multiple blocks + + For inputs larger than a single block, consider using regular ZSTD_compress() instead. + Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block. + - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) ! + ===> In which case, nothing is produced into `dst` ! + + User __must__ test for such outcome and deal directly with uncompressed data + + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0. + Doing so would mess up with statistics history, leading to potential data corruption. + + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !! + + In case of multiple successive blocks, should some of them be uncompressed, + decoder must be informed of their existence in order to follow proper history. + Use ZSTD_insertBlock() for such a case. +</p></pre><BR> + +<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const 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); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b> +</pre></b><BR> +</html> +</body> |