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+<title>zstd 1.5.5 Manual</title>
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+<body>
+<h1>zstd 1.5.5 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 (Requires v1.4.0+)</a></li>
+<li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</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 (Requires v1.4.0+)</a></li>
+<li><a href="#Chapter14">experimental API (static linking only)</a></li>
+<li><a href="#Chapter15">Frame header and 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">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li>
+<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
+<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
+<li><a href="#Chapter23">Block level API (DEPRECATED)</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><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
+</p></pre><BR>
+
+<pre><b>const char* ZSTD_versionString(void);
+</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+.
+</p></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`.
+ NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
+ enough space to successfully compress the data.
+ @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>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize")
+ZSTDLIB_API
+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></b>/* ZSTD_compressBound() :<b>
+ * maximum compressed size in worst case single-pass scenario.
+ * When invoking `ZSTD_compress()` or any other one-pass compression function,
+ * it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize)
+ * as it eliminates one potential failure scenario,
+ * aka not enough room in dst buffer to write the compressed frame.
+ * Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE .
+ * In which case, ZSTD_compressBound() will return an error code
+ * which can be tested using ZSTD_isError().
+ *
+ * ZSTD_COMPRESSBOUND() :
+ * same as ZSTD_compressBound(), but as a macro.
+ * It can be used to produce constants, which can be useful for static allocation,
+ * for example to size a static array on stack.
+ * Will produce constant value 0 if srcSize too large.
+ */
+#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00LLU : 0xFF00FF00U)
+#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (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>
+</b>/* ZSTD_isError() :<b>
+ * Most ZSTD_* functions returning a size_t value can be tested for error,
+ * using ZSTD_isError().
+ * @return 1 if error, 0 otherwise
+ */
+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, requires v1.4.0+ */<b>
+int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
+int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<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); </b>/* accept NULL pointer */<b>
+</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); </b>/* accept NULL pointer */<b>
+</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 (Requires v1.4.0+)</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.
+ * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
+ * compression strategy >= ZSTD_btopt (== compression level 16+) */
+ 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 active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
+ * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
+ * In a situation where it's unknown if the linked library supports multi-threading or not,
+ * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
+ */
+ ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
+ * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
+ * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
+ * while compression is performed in parallel, within worker thread(s).
+ * (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, and 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 ZSTDMT_JOBSIZE_MIN (= 512 KB), 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
+ * ZSTD_c_enableDedicatedDictSearch
+ * ZSTD_c_stableInBuffer
+ * ZSTD_c_stableOutBuffer
+ * ZSTD_c_blockDelimiters
+ * ZSTD_c_validateSequences
+ * ZSTD_c_useBlockSplitter
+ * ZSTD_c_useRowMatchFinder
+ * ZSTD_c_prefetchCDictTables
+ * ZSTD_c_enableSeqProducerFallback
+ * ZSTD_c_maxBlockSize
+ * 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_c_experimentalParam8=1005,
+ ZSTD_c_experimentalParam9=1006,
+ ZSTD_c_experimentalParam10=1007,
+ ZSTD_c_experimentalParam11=1008,
+ ZSTD_c_experimentalParam12=1009,
+ ZSTD_c_experimentalParam13=1010,
+ ZSTD_c_experimentalParam14=1011,
+ ZSTD_c_experimentalParam15=1012,
+ ZSTD_c_experimentalParam16=1013,
+ ZSTD_c_experimentalParam17=1014,
+ ZSTD_c_experimentalParam18=1015,
+ ZSTD_c_experimentalParam19=1016
+} 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 also removes any reference to any dictionary or external sequence producer.
+ 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.
+ NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
+ enough space to successfully compress the data, though it is possible it fails for other reasons.
+ @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 (Requires v1.4.0+)</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
+ * ZSTD_d_forceIgnoreChecksum
+ * ZSTD_d_refMultipleDDicts
+ * ZSTD_d_disableHuffmanAssembly
+ * 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_d_experimentalParam3=1002,
+ ZSTD_d_experimentalParam4=1003,
+ ZSTD_d_experimentalParam5=1004
+
+} 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); </b>/* accept NULL pointer */<b>
+</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.
+ - endOp must be a valid directive
+ - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
+ - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output 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);
+
+ Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API
+ to compress with a dictionary.
+
+</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); </b>/* accept NULL pointer */<b>
+</pre></b><BR>
+<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
+<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds);
+</b><p> Initialize/reset DStream state for new decompression operation.
+ Call before new decompression operation using same DStream.
+
+ Note : This function is redundant with the advanced API and equivalent to:
+ ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
+ ZSTD_DCtx_refDDict(zds, NULL);
+
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
+</b><p> Streaming decompression function.
+ Call repetitively to consume full input updating it as necessary.
+ Function will update both input and output `pos` fields exposing current state via these fields:
+ - `input.pos < input.size`, some input remaining and caller should provide remaining input
+ on the next call.
+ - `output.pos < output.size`, decoder finished and flushed all remaining buffers.
+ - `output.pos == output.size`, potentially uncflushed data present in the internal buffers,
+ call ZSTD_decompressStream() again to flush remaining data to output.
+ Note : with no additional input, amount of data flushed <= 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 some decoding or flushing to do to complete current frame.
+
+</p></pre><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 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().
+ If a NULL pointer is passed, no operation is performed.
+</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()
+ If a NULL pointer is passed, no operation is performed.
+</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_fromCDict(const ZSTD_CDict* cdict);
+</b><p> Provides the dictID of the dictionary loaded into `cdict`.
+ 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_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 piece of 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 (Requires v1.4.0+)</h2><pre>
+ This API allows dictionaries to be used with ZSTD_compress2(),
+ ZSTD_compressStream2(), and ZSTD_decompressDCtx().
+ Dictionaries are sticky, they remain valid when same context is re-used,
+ they only reset when the context is reset
+ with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters.
+ In contrast, 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,
+ until parameters are reset, a new dictionary is loaded, or the dictionary
+ is explicitly invalidated by loading a NULL dictionary.
+ 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.
+ Note 5 : This method does not benefit from LDM (long distance mode).
+ If you want to employ LDM on some large dictionary content,
+ prefer employing ZSTD_CCtx_refPrefix() described below.
+
+</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 future compressed frames.
+ Note that compression parameters are enforced from within CDict,
+ and supersede any compression parameter previously set within CCtx.
+ The parameters ignored are labelled 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).
+ This method is compatible with LDM (long distance mode).
+ @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 all future frames.
+ The dictionary remains valid for all future frames, until explicitly invalidated, or
+ a new dictionary is loaded.
+ @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.
+
+ If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
+ will store the DDict references in a table, and the DDict used for decompression
+ will be determined at decompression time, as per the dict ID in the frame.
+ The memory for the table is allocated on the first call to refDDict, and can be
+ freed with ZSTD_freeDCtx().
+
+ If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary
+ will be managed, and referencing a dictionary effectively "discards" any previous one.
+
+ @result : 0, or an error code (which can be tested with ZSTD_isError()).
+ 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 offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
+ * If offset == 0 and matchLength == 0, this sequence represents the last
+ * literals in the block of litLength size.
+ */
+
+ unsigned int litLength; </b>/* Literal length of the sequence. */<b>
+ unsigned int matchLength; </b>/* Match length of the sequence. */<b>
+
+ </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
+ * In this case, we will treat the sequence as a marker for a block boundary.
+ */
+
+ unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
+ * Ranges from [0, 3].
+ *
+ * Repeat offsets are essentially previous offsets from previous sequences sorted in
+ * recency order. For more detail, see doc/zstd_compression_format.md
+ *
+ * If rep == 0, then 'offset' does not contain a repeat offset.
+ * If rep > 0:
+ * If litLength != 0:
+ * rep == 1 --> offset == repeat_offset_1
+ * rep == 2 --> offset == repeat_offset_2
+ * rep == 3 --> offset == repeat_offset_3
+ * If litLength == 0:
+ * rep == 1 --> offset == repeat_offset_2
+ * rep == 2 --> offset == repeat_offset_3
+ * rep == 3 --> offset == repeat_offset_1 - 1
+ *
+ * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
+ * 'rep', but repeat offsets do not necessarily need to be calculated from an external
+ * sequence provider's perspective. For example, ZSTD_compressSequences() does not
+ * use this 'rep' field at all (as of now).
+ */
+} 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 controls ZSTD_d_forceIgnoreChecksum */<b>
+ ZSTD_d_validateChecksum = 0,
+ ZSTD_d_ignoreChecksum = 1
+} ZSTD_forceIgnoreChecksum_e;
+</b></pre><BR>
+<pre><b>typedef enum {
+ </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
+ ZSTD_rmd_refSingleDDict = 0,
+ ZSTD_rmd_refMultipleDDicts = 1
+} ZSTD_refMultipleDDicts_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>
+<pre><b>typedef enum {
+ </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b>
+ * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable
+ * or ZSTD_ps_disable allow for a force enable/disable the feature.
+ */
+ ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b>
+ ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b>
+ ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b>
+} ZSTD_paramSwitch_e;
+</b></pre><BR>
+<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre>
+
+<pre><b>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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 occurred: 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>ZSTDLIB_STATIC_API 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>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
+</b></pre><BR>
+<pre><b>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;
+ unsigned _reserved1;
+ unsigned _reserved2;
+} ZSTD_frameHeader;
+</b></pre><BR>
+<pre><b>ZSTDLIB_STATIC_API 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) */
+ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
+</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>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize);
+</b><p> Zstd supports in-place decompression, where the input and output buffers overlap.
+ In this case, the output buffer must be at least (Margin + Output_Size) bytes large,
+ and the input buffer must be at the end of the output buffer.
+
+ _______________________ Output Buffer ________________________
+ | |
+ | ____ Input Buffer ____|
+ | | |
+ v v v
+ |---------------------------------------|-----------|----------|
+ ^ ^ ^
+ |___________________ Output_Size ___________________|_ Margin _|
+
+ NOTE: See also ZSTD_DECOMPRESSION_MARGIN().
+ NOTE: This applies only to single-pass decompression through ZSTD_decompress() or
+ ZSTD_decompressDCtx().
+ NOTE: This function supports multi-frame input.
+
+ @param src The compressed frame(s)
+ @param srcSize The size of the compressed frame(s)
+ @returns The decompression margin or an error that can be checked with ZSTD_isError().
+
+</p></pre><BR>
+
+<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \
+ ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b>
+ 4 </b>/* checksum */ + \<b>
+ ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b>
+ (blockSize) </b>/* One block of margin */ \<b>
+ ))
+</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from
+ the compressed frame, compute it from the original size and the blockSizeLog.
+ See ZSTD_decompressionMargin() for details.
+
+ WARNING: This macro does not support multi-frame input, the input must be a single
+ zstd frame. If you need that support use the function, or implement it yourself.
+
+ @param originalSize The original uncompressed size of the data.
+ @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX).
+ Unless you explicitly set the windowLog smaller than
+ ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX.
+
+</p></pre><BR>
+
+<pre><b>typedef enum {
+ ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
+ ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
+} ZSTD_sequenceFormat_e;
+</b></pre><BR>
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize);
+</b><p> `srcSize` : size of the input buffer
+ @return : upper-bound for the number of sequences that can be generated
+ from a buffer of srcSize bytes
+
+ note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence).
+
+</p></pre><BR>
+
+<pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer.
+
+ Each block will end with a dummy sequence
+ with offset == 0, matchLength == 0, and litLength == length of last literals.
+ litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
+ simply acts as a block delimiter.
+
+ @zc can be used to insert custom compression params.
+ This function invokes ZSTD_compress2().
+
+ The output of this function can be fed into ZSTD_compressSequences() with CCtx
+ setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
+ @return : number of sequences generated
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
+</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
+ by merging them into the literals of the next sequence.
+
+ As such, the final generated result has no explicit representation of block boundaries,
+ and the final last literals segment is not represented in the sequences.
+
+ The output of this function can be fed into ZSTD_compressSequences() with CCtx
+ setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
+ @return : number of sequences left after merging
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t
+ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize,
+ const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
+ const void* src, size_t srcSize);
+</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst.
+ @src contains the entire input (not just the literals).
+ If @srcSize > sum(sequence.length), the remaining bytes are considered all literals
+ If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
+ The entire source is compressed into a single frame.
+
+ The compression behavior changes based on cctx params. In particular:
+ If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
+ no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
+ the block size derived from the cctx, and sequences may be split. This is the default setting.
+
+ If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
+ block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
+
+ If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
+ behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
+ specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
+
+ In addition to the two adjustable experimental params, there are other important cctx params.
+ - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN.
+ - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
+ - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
+ is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
+
+ Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
+ Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
+ and cannot emit an RLE block that disagrees with the repcode history
+ @return : final compressed size, or a ZSTD error code.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
+ const void* src, size_t srcSize, unsigned magicVariant);
+</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
+
+ Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number,
+ ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
+ As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
+ the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
+
+ Returns an error if destination buffer is not large enough, if the source size is not representable
+ with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
+
+ @return : number of bytes written or a ZSTD error.
+
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
+ const void* src, size_t srcSize);
+</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
+
+ The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
+ i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested
+ in the magicVariant.
+
+ Returns an error if destination buffer is not large enough, or if the frame is not skippable.
+
+ @return : number of bytes written or a ZSTD error.
+
+</p></pre><BR>
+
+<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
+</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
+
+</p></pre><BR>
+
+<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+ZSTDLIB_STATIC_API 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 : only single-threaded compression is supported.
+ ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
+
+ Note 2 : ZSTD_estimateCCtxSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
+ Size estimates assume that no external sequence producer is registered.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
+ZSTDLIB_STATIC_API 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
+ Note 2 : only single-threaded compression is supported.
+ ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
+ Note 3 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
+ Size estimates assume that no external sequence producer is registered.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
+ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
+ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
+ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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
+#ifdef __GNUC__
+__attribute__((__unused__))
+#endif
+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>
+
+<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool;
+ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads);
+ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b>
+ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool);
+</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts.
+ This can limit resources for applications with multiple threads where each one uses
+ a threaded compression mode (via ZSTD_c_nbWorkers parameter).
+ ZSTD_createThreadPool creates a new thread pool with a given number of threads.
+ Note that the lifetime of such pool must exist while being used.
+ ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value
+ to use an internal thread pool).
+ ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer.
+
+</p></pre><BR>
+
+<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
+
+<pre><b>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams);
+</b><p> Set all parameters provided within @p cparams into the working @p cctx.
+ Note : if modifying parameters during compression (MT mode only),
+ note that changes to the .windowLog parameter will be ignored.
+ @return 0 on success, or an error code (can be checked with ZSTD_isError()).
+ On failure, no parameters are updated.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams);
+</b><p> Set all parameters provided within @p fparams into the working @p cctx.
+ @return 0 on success, or an error code (can be checked with ZSTD_isError()).
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params);
+</b><p> Set all parameters provided within @p params into the working @p cctx.
+ @return 0 on success, or an error code (can be checked with ZSTD_isError()).
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
+ZSTDLIB_STATIC_API
+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 generate compilation warnings.
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
+ZSTDLIB_STATIC_API
+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 DEPRECATED.
+ It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
+ This prototype will generate compilation warnings.
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const 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>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
+ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
+</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, accept NULL pointer.
+
+ This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
+ for static allocation of CCtx for single-threaded compression.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
+</b><p> Reset params to default values.
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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 : a code representing success or failure (which can be tested with
+ ZSTD_isError()).
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API 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>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
+</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
+ 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_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
+ZSTDLIB_STATIC_API
+size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
+</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
+ 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>ZSTDLIB_STATIC_API 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></pre></b><BR>
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
+ int compressionLevel,
+ unsigned long long pledgedSrcSize);
+</b><p> 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.
+ This prototype will generate compilation warnings.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
+ const void* dict, size_t dictSize,
+ int compressionLevel);
+</b><p> 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.
+ This prototype will generate compilation warnings.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
+ const void* dict, size_t dictSize,
+ ZSTD_parameters params,
+ unsigned long long pledgedSrcSize);
+</b><p> This function is DEPRECATED, and is equivalent to:
+ ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
+ ZSTD_CCtx_setParams(zcs, params);
+ 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.
+ This prototype will generate compilation warnings.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
+</b><p> 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
+ This prototype will generate compilation warnings.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
+ const ZSTD_CDict* cdict,
+ ZSTD_frameParameters fParams,
+ unsigned long long pledgedSrcSize);
+</b><p> This function is DEPRECATED, and is equivalent to:
+ ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
+ ZSTD_CCtx_setFParams(zcs, fParams);
+ 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.
+ This prototype will generate compilation warnings.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API
+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);
+ Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
+ ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
+ explicitly specified.
+
+ 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())
+ This prototype will generate compilation warnings.
+
+</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>ZSTDLIB_STATIC_API 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></pre></b><BR>
+<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
+</b><p>
+ 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
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
+</b><p>
+ ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
+ ZSTD_DCtx_refDDict(zds, ddict);
+
+ note : ddict is referenced, it must outlive decompression session
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions")
+ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
+</b><p>
+ ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
+
+ re-use decompression parameters from previous init; saves dictionary loading
+
+</p></pre><BR>
+
+<pre><b>ZSTDLIB_STATIC_API void
+ZSTD_registerSequenceProducer(
+ ZSTD_CCtx* cctx,
+ void* sequenceProducerState,
+ ZSTD_sequenceProducer_F* sequenceProducer
+);
+</b><p> Instruct zstd to use a block-level external sequence producer function.
+
+ The sequenceProducerState must be initialized by the caller, and the caller is
+ responsible for managing its lifetime. This parameter is sticky across
+ compressions. It will remain set until the user explicitly resets compression
+ parameters.
+
+ Sequence producer registration is considered to be an "advanced parameter",
+ part of the "advanced API". This means it will only have an effect on compression
+ APIs which respect advanced parameters, such as compress2() and compressStream2().
+ Older compression APIs such as compressCCtx(), which predate the introduction of
+ "advanced parameters", will ignore any external sequence producer setting.
+
+ The sequence producer can be "cleared" by registering a NULL function pointer. This
+ removes all limitations described above in the "LIMITATIONS" section of the API docs.
+
+ The user is strongly encouraged to read the full API documentation (above) before
+ calling this function.
+</p></pre><BR>
+
+<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre>
+ This API is deprecated, and will be removed in a future version.
+ It allows streaming (de)compression with user allocated buffers.
+ However, it is hard to use, and not as well tested as the rest of
+ our API.
+
+ Please use the normal streaming API instead: ZSTD_compressStream2,
+ and ZSTD_decompressStream.
+ If there is functionality that you need, but it doesn't provide,
+ please open an issue on our GitHub.
+
+<BR></pre>
+
+<a name="Chapter21"></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.
+
+ 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>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
+ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
+ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
+</pre></b><BR>
+<pre><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>
+</b></pre><BR>
+<pre><b>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>
+</b></pre><BR>
+<a name="Chapter22"></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></pre></b><BR>
+<pre><b>ZSTDLIB_STATIC_API 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></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="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre>
+
+<pre><b></b><p> You can get the frame header down to 2 bytes by setting:
+ - ZSTD_c_format = ZSTD_f_zstd1_magicless
+ - ZSTD_c_contentSizeFlag = 0
+ - ZSTD_c_checksumFlag = 0
+ - ZSTD_c_dictIDFlag = 0
+
+ This API is not as well tested as our normal API, so we recommend not using it.
+ We will be removing it in a future version. If the normal API doesn't provide
+ the functionality you need, please open a GitHub issue.
+
+ Block functions produce and decode raw zstd blocks, without frame metadata.
+ 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
+ - 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>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
+ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
+ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
+ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
+ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
+ZSTDLIB_STATIC_API 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>
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