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4<title>zstd 1.5.0 Manual</title>
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6<body>
7<h1>zstd 1.5.0 Manual</h1>
8<hr>
9<a name="Contents"></a><h2>Contents</h2>
10<ol>
11<li><a href="#Chapter1">Introduction</a></li>
12<li><a href="#Chapter2">Version</a></li>
13<li><a href="#Chapter3">Simple API</a></li>
14<li><a href="#Chapter4">Explicit context</a></li>
15<li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li>
16<li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li>
17<li><a href="#Chapter7">Streaming</a></li>
18<li><a href="#Chapter8">Streaming compression - HowTo</a></li>
19<li><a href="#Chapter9">Streaming decompression - HowTo</a></li>
20<li><a href="#Chapter10">Simple dictionary API</a></li>
21<li><a href="#Chapter11">Bulk processing dictionary API</a></li>
22<li><a href="#Chapter12">Dictionary helper functions</a></li>
23<li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li>
24<li><a href="#Chapter14">experimental API (static linking only)</a></li>
25<li><a href="#Chapter15">Frame size functions</a></li>
26<li><a href="#Chapter16">Memory management</a></li>
27<li><a href="#Chapter17">Advanced compression functions</a></li>
28<li><a href="#Chapter18">Advanced decompression functions</a></li>
29<li><a href="#Chapter19">Advanced streaming functions</a></li>
30<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions</a></li>
31<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
32<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
33<li><a href="#Chapter23">Block level API</a></li>
34</ol>
35<hr>
36<a name="Chapter1"></a><h2>Introduction</h2><pre>
37 zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
38 real-time compression scenarios at zlib-level and better compression ratios.
39 The zstd compression library provides in-memory compression and decompression
40 functions.
41
42 The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
43 which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
44 caution, as they require more memory. The library also offers negative
45 compression levels, which extend the range of speed vs. ratio preferences.
46 The lower the level, the faster the speed (at the cost of compression).
47
48 Compression can be done in:
49 - a single step (described as Simple API)
50 - a single step, reusing a context (described as Explicit context)
51 - unbounded multiple steps (described as Streaming compression)
52
53 The compression ratio achievable on small data can be highly improved using
54 a dictionary. Dictionary compression can be performed in:
55 - a single step (described as Simple dictionary API)
56 - a single step, reusing a dictionary (described as Bulk-processing
57 dictionary API)
58
59 Advanced experimental functions can be accessed using
60 `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
61
62 Advanced experimental APIs should never be used with a dynamically-linked
63 library. They are not "stable"; their definitions or signatures may change in
64 the future. Only static linking is allowed.
65<BR></pre>
66
67<a name="Chapter2"></a><h2>Version</h2><pre></pre>
68
69<pre><b>unsigned ZSTD_versionNumber(void);
70</b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
71</p></pre><BR>
72
73<pre><b>const char* ZSTD_versionString(void);
74</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+.
75</p></pre><BR>
76
77<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
78
79<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
80 const void* src, size_t srcSize,
81 int compressionLevel);
82</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
83 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
84 @return : compressed size written into `dst` (<= `dstCapacity),
85 or an error code if it fails (which can be tested using ZSTD_isError()).
86</p></pre><BR>
87
88<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
89 const void* src, size_t compressedSize);
90</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
91 `dstCapacity` is an upper bound of originalSize to regenerate.
92 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
93 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
94 or an errorCode if it fails (which can be tested using ZSTD_isError()).
95</p></pre><BR>
96
97<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
98#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
99unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
100</b><p> `src` should point to the start of a ZSTD encoded frame.
101 `srcSize` must be at least as large as the frame header.
102 hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
103 @return : - decompressed size of `src` frame content, if known
104 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
105 - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
106 note 1 : a 0 return value means the frame is valid but "empty".
107 note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
108 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
109 In which case, it's necessary to use streaming mode to decompress data.
110 Optionally, application can rely on some implicit limit,
111 as ZSTD_decompress() only needs an upper bound of decompressed size.
112 (For example, data could be necessarily cut into blocks <= 16 KB).
113 note 3 : decompressed size is always present when compression is completed using single-pass functions,
114 such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
115 note 4 : decompressed size can be very large (64-bits value),
116 potentially larger than what local system can handle as a single memory segment.
117 In which case, it's necessary to use streaming mode to decompress data.
118 note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
119 Always ensure return value fits within application's authorized limits.
120 Each application can set its own limits.
121 note 6 : This function replaces ZSTD_getDecompressedSize()
122</p></pre><BR>
123
124<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
125</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
126 Both functions work the same way, but ZSTD_getDecompressedSize() blends
127 "empty", "unknown" and "error" results to the same return value (0),
128 while ZSTD_getFrameContentSize() gives them separate return values.
129 @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise.
130</p></pre><BR>
131
132<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
133</b><p> `src` should point to the start of a ZSTD frame or skippable frame.
134 `srcSize` must be >= first frame size
135 @return : the compressed size of the first frame starting at `src`,
136 suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
137 or an error code if input is invalid
138</p></pre><BR>
139
140<h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
141size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
142unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
143const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
144int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b>
145int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
146int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b>
147</pre></b><BR>
148<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
149
150<h3>Compression context</h3><pre> When compressing many times,
151 it is recommended to allocate a context just once,
152 and re-use it for each successive compression operation.
153 This will make workload friendlier for system's memory.
154 Note : re-using context is just a speed / resource optimization.
155 It doesn't change the compression ratio, which remains identical.
156 Note 2 : In multi-threaded environments,
157 use one different context per thread for parallel execution.
158
159</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
160ZSTD_CCtx* ZSTD_createCCtx(void);
161size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b>
162</pre></b><BR>
163<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
164 void* dst, size_t dstCapacity,
165 const void* src, size_t srcSize,
166 int compressionLevel);
167</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
168 Important : in order to behave similarly to `ZSTD_compress()`,
169 this function compresses at requested compression level,
170 __ignoring any other parameter__ .
171 If any advanced parameter was set using the advanced API,
172 they will all be reset. Only `compressionLevel` remains.
173
174</p></pre><BR>
175
176<h3>Decompression context</h3><pre> When decompressing many times,
177 it is recommended to allocate a context only once,
178 and re-use it for each successive compression operation.
179 This will make workload friendlier for system's memory.
180 Use one context per thread for parallel execution.
181</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
182ZSTD_DCtx* ZSTD_createDCtx(void);
183size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b>
184</pre></b><BR>
185<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
186 void* dst, size_t dstCapacity,
187 const void* src, size_t srcSize);
188</b><p> Same as ZSTD_decompress(),
189 requires an allocated ZSTD_DCtx.
190 Compatible with sticky parameters.
191
192</p></pre><BR>
193
194<a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre>
195
196<pre><b>typedef enum { ZSTD_fast=1,
197 ZSTD_dfast=2,
198 ZSTD_greedy=3,
199 ZSTD_lazy=4,
200 ZSTD_lazy2=5,
201 ZSTD_btlazy2=6,
202 ZSTD_btopt=7,
203 ZSTD_btultra=8,
204 ZSTD_btultra2=9
205 </b>/* note : new strategies _might_ be added in the future.<b>
206 Only the order (from fast to strong) is guaranteed */
207} ZSTD_strategy;
208</b></pre><BR>
209<pre><b>typedef enum {
210
211 </b>/* compression parameters<b>
212 * Note: When compressing with a ZSTD_CDict these parameters are superseded
213 * by the parameters used to construct the ZSTD_CDict.
214 * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
215 ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
216 * Note that exact compression parameters are dynamically determined,
217 * depending on both compression level and srcSize (when known).
218 * Default level is ZSTD_CLEVEL_DEFAULT==3.
219 * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
220 * Note 1 : it's possible to pass a negative compression level.
221 * Note 2 : setting a level does not automatically set all other compression parameters
222 * to default. Setting this will however eventually dynamically impact the compression
223 * parameters which have not been manually set. The manually set
224 * ones will 'stick'. */
225 </b>/* Advanced compression parameters :<b>
226 * It's possible to pin down compression parameters to some specific values.
227 * In which case, these values are no longer dynamically selected by the compressor */
228 ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
229 * This will set a memory budget for streaming decompression,
230 * with larger values requiring more memory
231 * and typically compressing more.
232 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
233 * Special: value 0 means "use default windowLog".
234 * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
235 * requires explicitly allowing such size at streaming decompression stage. */
236 ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
237 * Resulting memory usage is (1 << (hashLog+2)).
238 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
239 * Larger tables improve compression ratio of strategies <= dFast,
240 * and improve speed of strategies > dFast.
241 * Special: value 0 means "use default hashLog". */
242 ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b>
243 * Resulting memory usage is (1 << (chainLog+2)).
244 * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
245 * Larger tables result in better and slower compression.
246 * This parameter is useless for "fast" strategy.
247 * It's still useful when using "dfast" strategy,
248 * in which case it defines a secondary probe table.
249 * Special: value 0 means "use default chainLog". */
250 ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
251 * More attempts result in better and slower compression.
252 * This parameter is useless for "fast" and "dFast" strategies.
253 * Special: value 0 means "use default searchLog". */
254 ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b>
255 * Note that Zstandard can still find matches of smaller size,
256 * it just tweaks its search algorithm to look for this size and larger.
257 * Larger values increase compression and decompression speed, but decrease ratio.
258 * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
259 * Note that currently, for all strategies < btopt, effective minimum is 4.
260 * , for all strategies > fast, effective maximum is 6.
261 * Special: value 0 means "use default minMatchLength". */
262 ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
263 * For strategies btopt, btultra & btultra2:
264 * Length of Match considered "good enough" to stop search.
265 * Larger values make compression stronger, and slower.
266 * For strategy fast:
267 * Distance between match sampling.
268 * Larger values make compression faster, and weaker.
269 * Special: value 0 means "use default targetLength". */
270 ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b>
271 * The higher the value of selected strategy, the more complex it is,
272 * resulting in stronger and slower compression.
273 * Special: value 0 means "use default strategy". */
274 </b>/* LDM mode parameters */<b>
275 ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
276 * This parameter is designed to improve compression ratio
277 * for large inputs, by finding large matches at long distance.
278 * It increases memory usage and window size.
279 * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
280 * except when expressly set to a different value.
281 * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
282 * compression strategy >= ZSTD_btopt (== compression level 16+) */
283 ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
284 * Larger values increase memory usage and compression ratio,
285 * but decrease compression speed.
286 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
287 * default: windowlog - 7.
288 * Special: value 0 means "automatically determine hashlog". */
289 ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
290 * Larger/too small values usually decrease compression ratio.
291 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
292 * Special: value 0 means "use default value" (default: 64). */
293 ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
294 * Larger values improve collision resolution but decrease compression speed.
295 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
296 * Special: value 0 means "use default value" (default: 3). */
297 ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
298 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
299 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
300 * Larger values improve compression speed.
301 * Deviating far from default value will likely result in a compression ratio decrease.
302 * Special: value 0 means "automatically determine hashRateLog". */
303
304 </b>/* frame parameters */<b>
305 ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
306 * Content size must be known at the beginning of compression.
307 * This is automatically the case when using ZSTD_compress2(),
308 * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
309 ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
310 ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
311
312 </b>/* multi-threading parameters */<b>
313 </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
314 * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
315 * In a situation where it's unknown if the linked library supports multi-threading or not,
316 * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
317 */
318 ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
319 * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
320 * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
321 * while compression is performed in parallel, within worker thread(s).
322 * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
323 * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
324 * More workers improve speed, but also increase memory usage.
325 * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
326 * compression is performed inside Caller's thread, and all invocations are blocking */
327 ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
328 * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
329 * 0 means default, which is dynamically determined based on compression parameters.
330 * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
331 * The minimum size is automatically and transparently enforced. */
332 ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
333 * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
334 * It helps preserve compression ratio, while each job is compressed in parallel.
335 * This value is enforced only when nbWorkers >= 1.
336 * Larger values increase compression ratio, but decrease speed.
337 * Possible values range from 0 to 9 :
338 * - 0 means "default" : value will be determined by the library, depending on strategy
339 * - 1 means "no overlap"
340 * - 9 means "full overlap", using a full window size.
341 * Each intermediate rank increases/decreases load size by a factor 2 :
342 * 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
343 * default value varies between 6 and 9, depending on strategy */
344
345 </b>/* note : additional experimental parameters are also available<b>
346 * within the experimental section of the API.
347 * At the time of this writing, they include :
348 * ZSTD_c_rsyncable
349 * ZSTD_c_format
350 * ZSTD_c_forceMaxWindow
351 * ZSTD_c_forceAttachDict
352 * ZSTD_c_literalCompressionMode
353 * ZSTD_c_targetCBlockSize
354 * ZSTD_c_srcSizeHint
355 * ZSTD_c_enableDedicatedDictSearch
356 * ZSTD_c_stableInBuffer
357 * ZSTD_c_stableOutBuffer
358 * ZSTD_c_blockDelimiters
359 * ZSTD_c_validateSequences
360 * ZSTD_c_splitBlocks
361 * ZSTD_c_useRowMatchFinder
362 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
363 * note : never ever use experimentalParam? names directly;
364 * also, the enums values themselves are unstable and can still change.
365 */
366 ZSTD_c_experimentalParam1=500,
367 ZSTD_c_experimentalParam2=10,
368 ZSTD_c_experimentalParam3=1000,
369 ZSTD_c_experimentalParam4=1001,
370 ZSTD_c_experimentalParam5=1002,
371 ZSTD_c_experimentalParam6=1003,
372 ZSTD_c_experimentalParam7=1004,
373 ZSTD_c_experimentalParam8=1005,
374 ZSTD_c_experimentalParam9=1006,
375 ZSTD_c_experimentalParam10=1007,
376 ZSTD_c_experimentalParam11=1008,
377 ZSTD_c_experimentalParam12=1009,
378 ZSTD_c_experimentalParam13=1010,
379 ZSTD_c_experimentalParam14=1011,
380 ZSTD_c_experimentalParam15=1012
381} ZSTD_cParameter;
382</b></pre><BR>
383<pre><b>typedef struct {
384 size_t error;
385 int lowerBound;
386 int upperBound;
387} ZSTD_bounds;
388</b></pre><BR>
389<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
390</b><p> All parameters must belong to an interval with lower and upper bounds,
391 otherwise they will either trigger an error or be automatically clamped.
392 @return : a structure, ZSTD_bounds, which contains
393 - an error status field, which must be tested using ZSTD_isError()
394 - lower and upper bounds, both inclusive
395
396</p></pre><BR>
397
398<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
399</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
400 All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
401 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
402 Setting a parameter is generally only possible during frame initialization (before starting compression).
403 Exception : when using multi-threading mode (nbWorkers >= 1),
404 the following parameters can be updated _during_ compression (within same frame):
405 => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
406 new parameters will be active for next job only (after a flush()).
407 @return : an error code (which can be tested using ZSTD_isError()).
408
409</p></pre><BR>
410
411<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
412</b><p> Total input data size to be compressed as a single frame.
413 Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
414 This value will also be controlled at end of frame, and trigger an error if not respected.
415 @result : 0, or an error code (which can be tested with ZSTD_isError()).
416 Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
417 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
418 ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
419 Note 2 : pledgedSrcSize is only valid once, for the next frame.
420 It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
421 Note 3 : Whenever all input data is provided and consumed in a single round,
422 for example with ZSTD_compress2(),
423 or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
424 this value is automatically overridden by srcSize instead.
425
426</p></pre><BR>
427
428<pre><b>typedef enum {
429 ZSTD_reset_session_only = 1,
430 ZSTD_reset_parameters = 2,
431 ZSTD_reset_session_and_parameters = 3
432} ZSTD_ResetDirective;
433</b></pre><BR>
434<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
435</b><p> There are 2 different things that can be reset, independently or jointly :
436 - The session : will stop compressing current frame, and make CCtx ready to start a new one.
437 Useful after an error, or to interrupt any ongoing compression.
438 Any internal data not yet flushed is cancelled.
439 Compression parameters and dictionary remain unchanged.
440 They will be used to compress next frame.
441 Resetting session never fails.
442 - The parameters : changes all parameters back to "default".
443 This removes any reference to any dictionary too.
444 Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
445 otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
446 - Both : similar to resetting the session, followed by resetting parameters.
447
448</p></pre><BR>
449
450<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
451 void* dst, size_t dstCapacity,
452 const void* src, size_t srcSize);
453</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
454 ZSTD_compress2() always starts a new frame.
455 Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
456 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
457 - The function is always blocking, returns when compression is completed.
458 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
459 @return : compressed size written into `dst` (<= `dstCapacity),
460 or an error code if it fails (which can be tested using ZSTD_isError()).
461
462</p></pre><BR>
463
464<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre>
465
466<pre><b>typedef enum {
467
468 ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
469 * the streaming API will refuse to allocate memory buffer
470 * in order to protect the host from unreasonable memory requirements.
471 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
472 * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
473 * Special: value 0 means "use default maximum windowLog". */
474
475 </b>/* note : additional experimental parameters are also available<b>
476 * within the experimental section of the API.
477 * At the time of this writing, they include :
478 * ZSTD_d_format
479 * ZSTD_d_stableOutBuffer
480 * ZSTD_d_forceIgnoreChecksum
481 * ZSTD_d_refMultipleDDicts
482 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
483 * note : never ever use experimentalParam? names directly
484 */
485 ZSTD_d_experimentalParam1=1000,
486 ZSTD_d_experimentalParam2=1001,
487 ZSTD_d_experimentalParam3=1002,
488 ZSTD_d_experimentalParam4=1003
489
490} ZSTD_dParameter;
491</b></pre><BR>
492<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
493</b><p> All parameters must belong to an interval with lower and upper bounds,
494 otherwise they will either trigger an error or be automatically clamped.
495 @return : a structure, ZSTD_bounds, which contains
496 - an error status field, which must be tested using ZSTD_isError()
497 - both lower and upper bounds, inclusive
498
499</p></pre><BR>
500
501<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
502</b><p> Set one compression parameter, selected by enum ZSTD_dParameter.
503 All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
504 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
505 Setting a parameter is only possible during frame initialization (before starting decompression).
506 @return : 0, or an error code (which can be tested using ZSTD_isError()).
507
508</p></pre><BR>
509
510<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
511</b><p> Return a DCtx to clean state.
512 Session and parameters can be reset jointly or separately.
513 Parameters can only be reset when no active frame is being decompressed.
514 @return : 0, or an error code, which can be tested with ZSTD_isError()
515
516</p></pre><BR>
517
518<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
519
520<pre><b>typedef struct ZSTD_inBuffer_s {
521 const void* src; </b>/**< start of input buffer */<b>
522 size_t size; </b>/**< size of input buffer */<b>
523 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
524} ZSTD_inBuffer;
525</b></pre><BR>
526<pre><b>typedef struct ZSTD_outBuffer_s {
527 void* dst; </b>/**< start of output buffer */<b>
528 size_t size; </b>/**< size of output buffer */<b>
529 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
530} ZSTD_outBuffer;
531</b></pre><BR>
532<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
533 A ZSTD_CStream object is required to track streaming operation.
534 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
535 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
536 It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
537
538 For parallel execution, use one separate ZSTD_CStream per thread.
539
540 note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
541
542 Parameters are sticky : when starting a new compression on the same context,
543 it will re-use the same sticky parameters as previous compression session.
544 When in doubt, it's recommended to fully initialize the context before usage.
545 Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
546 ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
547 set more specific parameters, the pledged source size, or load a dictionary.
548
549 Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
550 consume input stream. The function will automatically update both `pos`
551 fields within `input` and `output`.
552 Note that the function may not consume the entire input, for example, because
553 the output buffer is already full, in which case `input.pos < input.size`.
554 The caller must check if input has been entirely consumed.
555 If not, the caller must make some room to receive more compressed data,
556 and then present again remaining input data.
557 note: ZSTD_e_continue is guaranteed to make some forward progress when called,
558 but doesn't guarantee maximal forward progress. This is especially relevant
559 when compressing with multiple threads. The call won't block if it can
560 consume some input, but if it can't it will wait for some, but not all,
561 output to be flushed.
562 @return : provides a minimum amount of data remaining to be flushed from internal buffers
563 or an error code, which can be tested using ZSTD_isError().
564
565 At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
566 using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
567 Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
568 In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
569 You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
570 operation.
571 note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
572 block until the flush is complete or the output buffer is full.
573 @return : 0 if internal buffers are entirely flushed,
574 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
575 or an error code, which can be tested using ZSTD_isError().
576
577 Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
578 It will perform a flush and write frame epilogue.
579 The epilogue is required for decoders to consider a frame completed.
580 flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
581 You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
582 start a new frame.
583 note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
584 block until the flush is complete or the output buffer is full.
585 @return : 0 if frame fully completed and fully flushed,
586 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
587 or an error code, which can be tested using ZSTD_isError().
588
589
590<BR></pre>
591
592<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
593</b></pre><BR>
594<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
595size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b>
596</pre></b><BR>
597<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
598 ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
599 ZSTD_e_flush=1, </b>/* flush any data provided so far,<b>
600 * it creates (at least) one new block, that can be decoded immediately on reception;
601 * frame will continue: any future data can still reference previously compressed data, improving compression.
602 * note : multithreaded compression will block to flush as much output as possible. */
603 ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b>
604 * note that frame is only closed after compressed data is fully flushed (return value == 0).
605 * After that point, any additional data starts a new frame.
606 * note : each frame is independent (does not reference any content from previous frame).
607 : note : multithreaded compression will block to flush as much output as possible. */
608} ZSTD_EndDirective;
609</pre></b><BR>
610<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
611 ZSTD_outBuffer* output,
612 ZSTD_inBuffer* input,
613 ZSTD_EndDirective endOp);
614</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive.
615 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
616 - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
617 - output->pos must be <= dstCapacity, input->pos must be <= srcSize
618 - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
619 - endOp must be a valid directive
620 - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
621 - 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,
622 and then immediately returns, just indicating that there is some data remaining to be flushed.
623 The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
624 - 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.
625 - @return provides a minimum amount of data remaining to be flushed from internal buffers
626 or an error code, which can be tested using ZSTD_isError().
627 if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
628 This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
629 For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
630 - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
631 only ZSTD_e_end or ZSTD_e_flush operations are allowed.
632 Before starting a new compression job, or changing compression parameters,
633 it is required to fully flush internal buffers.
634
635</p></pre><BR>
636
637<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
638</b></pre><BR>
639<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
640</b></pre><BR>
641<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
642</b>/*!<b>
643 * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
644 * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
645 * the next read size (if non-zero and not an error). ZSTD_compressStream2()
646 * returns the minimum nb of bytes left to flush (if non-zero and not an error).
647 */
648size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
649</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
650size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
651</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
652size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
653</b><p>
654 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
655 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
656 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
657
658</p></pre><BR>
659
660<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
661 A ZSTD_DStream object is required to track streaming operations.
662 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
663 ZSTD_DStream objects can be re-used multiple times.
664
665 Use ZSTD_initDStream() to start a new decompression operation.
666 @return : recommended first input size
667 Alternatively, use advanced API to set specific properties.
668
669 Use ZSTD_decompressStream() repetitively to consume your input.
670 The function will update both `pos` fields.
671 If `input.pos < input.size`, some input has not been consumed.
672 It's up to the caller to present again remaining data.
673 The function tries to flush all data decoded immediately, respecting output buffer size.
674 If `output.pos < output.size`, decoder has flushed everything it could.
675 But if `output.pos == output.size`, there might be some data left within internal buffers.,
676 In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
677 Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
678 @return : 0 when a frame is completely decoded and fully flushed,
679 or an error code, which can be tested using ZSTD_isError(),
680 or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
681 the return value is a suggested next input size (just a hint for better latency)
682 that will never request more than the remaining frame size.
683
684<BR></pre>
685
686<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
687</b></pre><BR>
688<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
689size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b>
690</pre></b><BR>
691<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
692<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
693</b></pre><BR>
694<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>
695</b></pre><BR>
696<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
697
698<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
699 void* dst, size_t dstCapacity,
700 const void* src, size_t srcSize,
701 const void* dict,size_t dictSize,
702 int compressionLevel);
703</b><p> Compression at an explicit compression level using a Dictionary.
704 A dictionary can be any arbitrary data segment (also called a prefix),
705 or a buffer with specified information (see zdict.h).
706 Note : This function loads the dictionary, resulting in significant startup delay.
707 It's intended for a dictionary used only once.
708 Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
709</p></pre><BR>
710
711<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
712 void* dst, size_t dstCapacity,
713 const void* src, size_t srcSize,
714 const void* dict,size_t dictSize);
715</b><p> Decompression using a known Dictionary.
716 Dictionary must be identical to the one used during compression.
717 Note : This function loads the dictionary, resulting in significant startup delay.
718 It's intended for a dictionary used only once.
719 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
720</p></pre><BR>
721
722<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
723
724<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
725 int compressionLevel);
726</b><p> When compressing multiple messages or blocks using the same dictionary,
727 it's recommended to digest the dictionary only once, since it's a costly operation.
728 ZSTD_createCDict() will create a state from digesting a dictionary.
729 The resulting state can be used for future compression operations with very limited startup cost.
730 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
731 @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
732 Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
733 Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
734 in which case the only thing that it transports is the @compressionLevel.
735 This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
736 expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
737</p></pre><BR>
738
739<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
740</b><p> Function frees memory allocated by ZSTD_createCDict().
741 If a NULL pointer is passed, no operation is performed.
742</p></pre><BR>
743
744<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
745 void* dst, size_t dstCapacity,
746 const void* src, size_t srcSize,
747 const ZSTD_CDict* cdict);
748</b><p> Compression using a digested Dictionary.
749 Recommended when same dictionary is used multiple times.
750 Note : compression level is _decided at dictionary creation time_,
751 and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
752</p></pre><BR>
753
754<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
755</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
756 dictBuffer can be released after DDict creation, as its content is copied inside DDict.
757</p></pre><BR>
758
759<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
760</b><p> Function frees memory allocated with ZSTD_createDDict()
761 If a NULL pointer is passed, no operation is performed.
762</p></pre><BR>
763
764<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
765 void* dst, size_t dstCapacity,
766 const void* src, size_t srcSize,
767 const ZSTD_DDict* ddict);
768</b><p> Decompression using a digested Dictionary.
769 Recommended when same dictionary is used multiple times.
770</p></pre><BR>
771
772<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
773
774<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
775</b><p> Provides the dictID stored within dictionary.
776 if @return == 0, the dictionary is not conformant with Zstandard specification.
777 It can still be loaded, but as a content-only dictionary.
778</p></pre><BR>
779
780<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
781</b><p> Provides the dictID of the dictionary loaded into `cdict`.
782 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
783 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
784</p></pre><BR>
785
786<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
787</b><p> Provides the dictID of the dictionary loaded into `ddict`.
788 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
789 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
790</p></pre><BR>
791
792<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
793</b><p> Provides the dictID required to decompressed the frame stored within `src`.
794 If @return == 0, the dictID could not be decoded.
795 This could for one of the following reasons :
796 - The frame does not require a dictionary to be decoded (most common case).
797 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
798 Note : this use case also happens when using a non-conformant dictionary.
799 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
800 - This is not a Zstandard frame.
801 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
802</p></pre><BR>
803
804<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre>
805 This API allows dictionaries to be used with ZSTD_compress2(),
806 ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and
807 only reset with the context is reset with ZSTD_reset_parameters or
808 ZSTD_reset_session_and_parameters. Prefixes are single-use.
809<BR></pre>
810
811<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
812</b><p> Create an internal CDict from `dict` buffer.
813 Decompression will have to use same dictionary.
814 @result : 0, or an error code (which can be tested with ZSTD_isError()).
815 Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
816 meaning "return to no-dictionary mode".
817 Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
818 To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
819 Note 2 : Loading a dictionary involves building tables.
820 It's also a CPU consuming operation, with non-negligible impact on latency.
821 Tables are dependent on compression parameters, and for this reason,
822 compression parameters can no longer be changed after loading a dictionary.
823 Note 3 :`dict` content will be copied internally.
824 Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
825 In such a case, dictionary buffer must outlive its users.
826 Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
827 to precisely select how dictionary content must be interpreted.
828</p></pre><BR>
829
830<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
831</b><p> Reference a prepared dictionary, to be used for all next compressed frames.
832 Note that compression parameters are enforced from within CDict,
833 and supersede any compression parameter previously set within CCtx.
834 The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
835 The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
836 The dictionary will remain valid for future compressed frames using same CCtx.
837 @result : 0, or an error code (which can be tested with ZSTD_isError()).
838 Special : Referencing a NULL CDict means "return to no-dictionary mode".
839 Note 1 : Currently, only one dictionary can be managed.
840 Referencing a new dictionary effectively "discards" any previous one.
841 Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
842</p></pre><BR>
843
844<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
845 const void* prefix, size_t prefixSize);
846</b><p> Reference a prefix (single-usage dictionary) for next compressed frame.
847 A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
848 Decompression will need same prefix to properly regenerate data.
849 Compressing with a prefix is similar in outcome as performing a diff and compressing it,
850 but performs much faster, especially during decompression (compression speed is tunable with compression level).
851 @result : 0, or an error code (which can be tested with ZSTD_isError()).
852 Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
853 Note 1 : Prefix buffer is referenced. It **must** outlive compression.
854 Its content must remain unmodified during compression.
855 Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
856 ensure that the window size is large enough to contain the entire source.
857 See ZSTD_c_windowLog.
858 Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
859 It's a CPU consuming operation, with non-negligible impact on latency.
860 If there is a need to use the same prefix multiple times, consider loadDictionary instead.
861 Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
862 Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
863</p></pre><BR>
864
865<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
866</b><p> Create an internal DDict from dict buffer,
867 to be used to decompress next frames.
868 The dictionary remains valid for all future frames, until explicitly invalidated.
869 @result : 0, or an error code (which can be tested with ZSTD_isError()).
870 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
871 meaning "return to no-dictionary mode".
872 Note 1 : Loading a dictionary involves building tables,
873 which has a non-negligible impact on CPU usage and latency.
874 It's recommended to "load once, use many times", to amortize the cost
875 Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
876 Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
877 Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
878 how dictionary content is loaded and interpreted.
879
880</p></pre><BR>
881
882<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
883</b><p> Reference a prepared dictionary, to be used to decompress next frames.
884 The dictionary remains active for decompression of future frames using same DCtx.
885
886 If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
887 will store the DDict references in a table, and the DDict used for decompression
888 will be determined at decompression time, as per the dict ID in the frame.
889 The memory for the table is allocated on the first call to refDDict, and can be
890 freed with ZSTD_freeDCtx().
891
892 @result : 0, or an error code (which can be tested with ZSTD_isError()).
893 Note 1 : Currently, only one dictionary can be managed.
894 Referencing a new dictionary effectively "discards" any previous one.
895 Special: referencing a NULL DDict means "return to no-dictionary mode".
896 Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
897
898</p></pre><BR>
899
900<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
901 const void* prefix, size_t prefixSize);
902</b><p> Reference a prefix (single-usage dictionary) to decompress next frame.
903 This is the reverse operation of ZSTD_CCtx_refPrefix(),
904 and must use the same prefix as the one used during compression.
905 Prefix is **only used once**. Reference is discarded at end of frame.
906 End of frame is reached when ZSTD_decompressStream() returns 0.
907 @result : 0, or an error code (which can be tested with ZSTD_isError()).
908 Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
909 Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
910 Prefix buffer must remain unmodified up to the end of frame,
911 reached when ZSTD_decompressStream() returns 0.
912 Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
913 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
914 Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
915 A full dictionary is more costly, as it requires building tables.
916
917</p></pre><BR>
918
919<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
920size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
921size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
922size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
923size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
924size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
925</b><p> These functions give the _current_ memory usage of selected object.
926 Note that object memory usage can evolve (increase or decrease) over time.
927</p></pre><BR>
928
929<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
930 The following symbols and constants
931 are not planned to join "stable API" status in the near future.
932 They can still change in future versions.
933 Some of them are planned to remain in the static_only section indefinitely.
934 Some of them might be removed in the future (especially when redundant with existing stable functions)
935
936<BR></pre>
937
938<pre><b>typedef struct {
939 unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
940 * If offset == 0 and matchLength == 0, this sequence represents the last
941 * literals in the block of litLength size.
942 */
943
944 unsigned int litLength; </b>/* Literal length of the sequence. */<b>
945 unsigned int matchLength; </b>/* Match length of the sequence. */<b>
946
947 </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
948 * In this case, we will treat the sequence as a marker for a block boundary.
949 */
950
951 unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
952 * Ranges from [0, 3].
953 *
954 * Repeat offsets are essentially previous offsets from previous sequences sorted in
955 * recency order. For more detail, see doc/zstd_compression_format.md
956 *
957 * If rep == 0, then 'offset' does not contain a repeat offset.
958 * If rep > 0:
959 * If litLength != 0:
960 * rep == 1 --> offset == repeat_offset_1
961 * rep == 2 --> offset == repeat_offset_2
962 * rep == 3 --> offset == repeat_offset_3
963 * If litLength == 0:
964 * rep == 1 --> offset == repeat_offset_2
965 * rep == 2 --> offset == repeat_offset_3
966 * rep == 3 --> offset == repeat_offset_1 - 1
967 *
968 * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
969 * 'rep', but repeat offsets do not necessarily need to be calculated from an external
970 * sequence provider's perspective. For example, ZSTD_compressSequences() does not
971 * use this 'rep' field at all (as of now).
972 */
973} ZSTD_Sequence;
974</b></pre><BR>
975<pre><b>typedef struct {
976 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
977 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
978 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
979 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
980 unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
981 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
982 ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
983} ZSTD_compressionParameters;
984</b></pre><BR>
985<pre><b>typedef struct {
986 int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
987 int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
988 int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
989} ZSTD_frameParameters;
990</b></pre><BR>
991<pre><b>typedef struct {
992 ZSTD_compressionParameters cParams;
993 ZSTD_frameParameters fParams;
994} ZSTD_parameters;
995</b></pre><BR>
996<pre><b>typedef enum {
997 ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
998 ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
999 ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
1000} ZSTD_dictContentType_e;
1001</b></pre><BR>
1002<pre><b>typedef enum {
1003 ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
1004 ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
1005} ZSTD_dictLoadMethod_e;
1006</b></pre><BR>
1007<pre><b>typedef enum {
1008 ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
1009 ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
1010 * Useful to save 4 bytes per generated frame.
1011 * Decoder cannot recognise automatically this format, requiring this instruction. */
1012} ZSTD_format_e;
1013</b></pre><BR>
1014<pre><b>typedef enum {
1015 </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
1016 ZSTD_d_validateChecksum = 0,
1017 ZSTD_d_ignoreChecksum = 1
1018} ZSTD_forceIgnoreChecksum_e;
1019</b></pre><BR>
1020<pre><b>typedef enum {
1021 </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
1022 ZSTD_rmd_refSingleDDict = 0,
1023 ZSTD_rmd_refMultipleDDicts = 1
1024} ZSTD_refMultipleDDicts_e;
1025</b></pre><BR>
1026<pre><b>typedef enum {
1027 </b>/* Note: this enum and the behavior it controls are effectively internal<b>
1028 * implementation details of the compressor. They are expected to continue
1029 * to evolve and should be considered only in the context of extremely
1030 * advanced performance tuning.
1031 *
1032 * Zstd currently supports the use of a CDict in three ways:
1033 *
1034 * - The contents of the CDict can be copied into the working context. This
1035 * means that the compression can search both the dictionary and input
1036 * while operating on a single set of internal tables. This makes
1037 * the compression faster per-byte of input. However, the initial copy of
1038 * the CDict's tables incurs a fixed cost at the beginning of the
1039 * compression. For small compressions (< 8 KB), that copy can dominate
1040 * the cost of the compression.
1041 *
1042 * - The CDict's tables can be used in-place. In this model, compression is
1043 * slower per input byte, because the compressor has to search two sets of
1044 * tables. However, this model incurs no start-up cost (as long as the
1045 * working context's tables can be reused). For small inputs, this can be
1046 * faster than copying the CDict's tables.
1047 *
1048 * - The CDict's tables are not used at all, and instead we use the working
1049 * context alone to reload the dictionary and use params based on the source
1050 * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1051 * This method is effective when the dictionary sizes are very small relative
1052 * to the input size, and the input size is fairly large to begin with.
1053 *
1054 * Zstd has a simple internal heuristic that selects which strategy to use
1055 * at the beginning of a compression. However, if experimentation shows that
1056 * Zstd is making poor choices, it is possible to override that choice with
1057 * this enum.
1058 */
1059 ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
1060 ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
1061 ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
1062 ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b>
1063} ZSTD_dictAttachPref_e;
1064</b></pre><BR>
1065<pre><b>typedef enum {
1066 ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b>
1067 * Negative compression levels will be uncompressed, and positive compression
1068 * levels will be compressed. */
1069 ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
1070 * emitted if Huffman compression is not profitable. */
1071 ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
1072} ZSTD_literalCompressionMode_e;
1073</b></pre><BR>
1074<pre><b>typedef enum {
1075 ZSTD_urm_auto = 0, </b>/* Automatically determine whether or not we use row matchfinder */<b>
1076 ZSTD_urm_disableRowMatchFinder = 1, </b>/* Never use row matchfinder */<b>
1077 ZSTD_urm_enableRowMatchFinder = 2 </b>/* Always use row matchfinder when applicable */<b>
1078} ZSTD_useRowMatchFinderMode_e;
1079</b></pre><BR>
1080<a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre>
1081
1082<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1083</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1084 `srcSize` must be the _exact_ size of this series
1085 (i.e. there should be a frame boundary at `src + srcSize`)
1086 @return : - decompressed size of all data in all successive frames
1087 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1088 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1089
1090 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1091 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1092 In which case, it's necessary to use streaming mode to decompress data.
1093 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1094 note 3 : decompressed size can be very large (64-bits value),
1095 potentially larger than what local system can handle as a single memory segment.
1096 In which case, it's necessary to use streaming mode to decompress data.
1097 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1098 Always ensure result fits within application's authorized limits.
1099 Each application can set its own limits.
1100 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1101 read each contained frame header. This is fast as most of the data is skipped,
1102 however it does mean that all frame data must be present and valid.
1103</p></pre><BR>
1104
1105<pre><b>unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1106</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1107 `srcSize` must be the _exact_ size of this series
1108 (i.e. there should be a frame boundary at `src + srcSize`)
1109 @return : - upper-bound for the decompressed size of all data in all successive frames
1110 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1111
1112 note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1113 note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1114 in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1115 note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1116 upper-bound = # blocks * min(128 KB, Window_Size)
1117
1118</p></pre><BR>
1119
1120<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1121</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1122 @return : size of the Frame Header,
1123 or an error code (if srcSize is too small)
1124</p></pre><BR>
1125
1126<pre><b>typedef enum {
1127 ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
1128 ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
1129} ZSTD_sequenceFormat_e;
1130</b></pre><BR>
1131<pre><b></b><p> Generate sequences using ZSTD_compress2, given a source buffer.
1132
1133 Each block will end with a dummy sequence
1134 with offset == 0, matchLength == 0, and litLength == length of last literals.
1135 litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
1136 simply acts as a block delimiter.
1137
1138 zc can be used to insert custom compression params.
1139 This function invokes ZSTD_compress2
1140
1141 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1142 setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
1143 @return : number of sequences generated
1144
1145</p></pre><BR>
1146
1147<pre><b>size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
1148</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
1149 by merging them into into the literals of the next sequence.
1150
1151 As such, the final generated result has no explicit representation of block boundaries,
1152 and the final last literals segment is not represented in the sequences.
1153
1154 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1155 setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
1156 @return : number of sequences left after merging
1157
1158</p></pre><BR>
1159
1160<pre><b>size_t ZSTD_compressSequences(ZSTD_CCtx* const cctx, void* dst, size_t dstSize,
1161 const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
1162 const void* src, size_t srcSize);
1163</b><p> Compress an array of ZSTD_Sequence, generated from the original source buffer, into dst.
1164 If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
1165 The entire source is compressed into a single frame.
1166
1167 The compression behavior changes based on cctx params. In particular:
1168 If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1169 no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
1170 the block size derived from the cctx, and sequences may be split. This is the default setting.
1171
1172 If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1173 block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
1174
1175 If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
1176 behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
1177 specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
1178
1179 In addition to the two adjustable experimental params, there are other important cctx params.
1180 - 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.
1181 - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
1182 - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
1183 is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
1184
1185 Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
1186 Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
1187 and cannot emit an RLE block that disagrees with the repcode history
1188 @return : final compressed size or a ZSTD error.
1189
1190</p></pre><BR>
1191
1192<pre><b>size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
1193 const void* src, size_t srcSize, unsigned magicVariant);
1194</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
1195
1196 Skippable frames begin with a a 4-byte magic number. There are 16 possible choices of magic number,
1197 ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
1198 As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
1199 the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
1200
1201 Returns an error if destination buffer is not large enough, if the source size is not representable
1202 with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
1203
1204 @return : number of bytes written or a ZSTD error.
1205
1206</p></pre><BR>
1207
1208<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
1209
1210<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
1211size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1212size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1213size_t ZSTD_estimateDCtxSize(void);
1214</b><p> These functions make it possible to estimate memory usage
1215 of a future {D,C}Ctx, before its creation.
1216
1217 ZSTD_estimateCCtxSize() will provide a memory budget large enough
1218 for any compression level up to selected one.
1219 Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
1220 does not include space for a window buffer.
1221 Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
1222 The estimate will assume the input may be arbitrarily large,
1223 which is the worst case.
1224
1225 When srcSize can be bound by a known and rather "small" value,
1226 this fact can be used to provide a tighter estimation
1227 because the CCtx compression context will need less memory.
1228 This tighter estimation can be provided by more advanced functions
1229 ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1230 and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1231 Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1232
1233 Note 2 : only single-threaded compression is supported.
1234 ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1235
1236</p></pre><BR>
1237
1238<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
1239size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1240size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1241size_t ZSTD_estimateDStreamSize(size_t windowSize);
1242size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1243</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1244 It will also consider src size to be arbitrarily "large", which is worst case.
1245 If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1246 ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1247 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.
1248 Note : CStream size estimation is only correct for single-threaded compression.
1249 ZSTD_DStream memory budget depends on window Size.
1250 This information can be passed manually, using ZSTD_estimateDStreamSize,
1251 or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1252 Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1253 an internal ?Dict will be created, which additional size is not estimated here.
1254 In this case, get total size by adding ZSTD_estimate?DictSize
1255</p></pre><BR>
1256
1257<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1258size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1259size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1260</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1261 ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1262 Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1263
1264</p></pre><BR>
1265
1266<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1267ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
1268</b><p> Initialize an object using a pre-allocated fixed-size buffer.
1269 workspace: The memory area to emplace the object into.
1270 Provided pointer *must be 8-bytes aligned*.
1271 Buffer must outlive object.
1272 workspaceSize: Use ZSTD_estimate*Size() to determine
1273 how large workspace must be to support target scenario.
1274 @return : pointer to object (same address as workspace, just different type),
1275 or NULL if error (size too small, incorrect alignment, etc.)
1276 Note : zstd will never resize nor malloc() when using a static buffer.
1277 If the object requires more memory than available,
1278 zstd will just error out (typically ZSTD_error_memory_allocation).
1279 Note 2 : there is no corresponding "free" function.
1280 Since workspace is allocated externally, it must be freed externally too.
1281 Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1282 into its associated cParams.
1283 Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1284 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1285 Limitation 2 : static cctx currently not compatible with multi-threading.
1286 Limitation 3 : static dctx is incompatible with legacy support.
1287
1288</p></pre><BR>
1289
1290<pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
1291</b></pre><BR>
1292<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1293typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
1294typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1295static
1296#ifdef __GNUC__
1297__attribute__((__unused__))
1298#endif
1299ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
1300</b><p> These prototypes make it possible to pass your own allocation/free functions.
1301 ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1302 All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1303
1304</p></pre><BR>
1305
1306<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
1307
1308<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1309</b><p> Create a digested dictionary for compression
1310 Dictionary content is just referenced, not duplicated.
1311 As a consequence, `dictBuffer` **must** outlive CDict,
1312 and its content must remain unmodified throughout the lifetime of CDict.
1313 note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
1314</p></pre><BR>
1315
1316<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1317</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1318 `estimatedSrcSize` value is optional, select 0 if not known
1319</p></pre><BR>
1320
1321<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1322</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1323 All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
1324</p></pre><BR>
1325
1326<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1327</b><p> Ensure param values remain within authorized range.
1328 @return 0 on success, or an error code (can be checked with ZSTD_isError())
1329</p></pre><BR>
1330
1331<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1332</b><p> optimize params for a given `srcSize` and `dictSize`.
1333 `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1334 `dictSize` must be `0` when there is no dictionary.
1335 cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1336 This function never fails (wide contract)
1337</p></pre><BR>
1338
1339<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
1340size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1341 void* dst, size_t dstCapacity,
1342 const void* src, size_t srcSize,
1343 const void* dict,size_t dictSize,
1344 ZSTD_parameters params);
1345</b><p> Note : this function is now DEPRECATED.
1346 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1347 This prototype will generate compilation warnings.
1348</p></pre><BR>
1349
1350<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
1351size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1352 void* dst, size_t dstCapacity,
1353 const void* src, size_t srcSize,
1354 const ZSTD_CDict* cdict,
1355 ZSTD_frameParameters fParams);
1356</b><p> Note : this function is now DEPRECATED.
1357 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1358 This prototype will generate compilation warnings.
1359</p></pre><BR>
1360
1361<pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1362</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1363 It saves some memory, but also requires that `dict` outlives its usage within `cctx`
1364</p></pre><BR>
1365
1366<pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1367</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1368 how to load the dictionary (by copy ? by reference ?)
1369 and how to interpret it (automatic ? force raw mode ? full mode only ?)
1370</p></pre><BR>
1371
1372<pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1373</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1374 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1375</p></pre><BR>
1376
1377<pre><b>size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1378</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1379 and store it into int* value.
1380 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1381
1382</p></pre><BR>
1383
1384<pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1385size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
1386</b><p> Quick howto :
1387 - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1388 - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1389 an existing ZSTD_CCtx_params structure.
1390 This is similar to
1391 ZSTD_CCtx_setParameter().
1392 - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1393 an existing CCtx.
1394 These parameters will be applied to
1395 all subsequent frames.
1396 - ZSTD_compressStream2() : Do compression using the CCtx.
1397 - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
1398
1399 This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1400 for static allocation of CCtx for single-threaded compression.
1401
1402</p></pre><BR>
1403
1404<pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1405</b><p> Reset params to default values.
1406
1407</p></pre><BR>
1408
1409<pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1410</b><p> Initializes the compression parameters of cctxParams according to
1411 compression level. All other parameters are reset to their default values.
1412
1413</p></pre><BR>
1414
1415<pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1416</b><p> Initializes the compression and frame parameters of cctxParams according to
1417 params. All other parameters are reset to their default values.
1418
1419</p></pre><BR>
1420
1421<pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1422</b><p> Similar to ZSTD_CCtx_setParameter.
1423 Set one compression parameter, selected by enum ZSTD_cParameter.
1424 Parameters must be applied to a ZSTD_CCtx using
1425 ZSTD_CCtx_setParametersUsingCCtxParams().
1426 @result : a code representing success or failure (which can be tested with
1427 ZSTD_isError()).
1428
1429</p></pre><BR>
1430
1431<pre><b>size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1432</b><p> Similar to ZSTD_CCtx_getParameter.
1433 Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1434 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1435
1436</p></pre><BR>
1437
1438<pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1439 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1440</b><p> Apply a set of ZSTD_CCtx_params to the compression context.
1441 This can be done even after compression is started,
1442 if nbWorkers==0, this will have no impact until a new compression is started.
1443 if nbWorkers>=1, new parameters will be picked up at next job,
1444 with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1445
1446</p></pre><BR>
1447
1448<pre><b>size_t ZSTD_compressStream2_simpleArgs (
1449 ZSTD_CCtx* cctx,
1450 void* dst, size_t dstCapacity, size_t* dstPos,
1451 const void* src, size_t srcSize, size_t* srcPos,
1452 ZSTD_EndDirective endOp);
1453</b><p> Same as ZSTD_compressStream2(),
1454 but using only integral types as arguments.
1455 This variant might be helpful for binders from dynamic languages
1456 which have troubles handling structures containing memory pointers.
1457
1458</p></pre><BR>
1459
1460<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
1461
1462<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
1463</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
1464 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1465 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1466 Note 3 : Skippable Frame Identifiers are considered valid.
1467</p></pre><BR>
1468
1469<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1470</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
1471 Dictionary content is referenced, and therefore stays in dictBuffer.
1472 It is important that dictBuffer outlives DDict,
1473 it must remain read accessible throughout the lifetime of DDict
1474</p></pre><BR>
1475
1476<pre><b>size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1477</b><p> Same as ZSTD_DCtx_loadDictionary(),
1478 but references `dict` content instead of copying it into `dctx`.
1479 This saves memory if `dict` remains around.,
1480 However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
1481</p></pre><BR>
1482
1483<pre><b>size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1484</b><p> Same as ZSTD_DCtx_loadDictionary(),
1485 but gives direct control over
1486 how to load the dictionary (by copy ? by reference ?)
1487 and how to interpret it (automatic ? force raw mode ? full mode only ?).
1488</p></pre><BR>
1489
1490<pre><b>size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1491</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1492 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1493</p></pre><BR>
1494
1495<pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1496</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1497 This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1498 This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1499 By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1500 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1501
1502</p></pre><BR>
1503
1504<pre><b>size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
1505</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
1506 and store it into int* value.
1507 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1508
1509</p></pre><BR>
1510
1511<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
1512size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1513</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
1514 Instruct the decoder context about what kind of data to decode next.
1515 This instruction is mandatory to decode data without a fully-formed header,
1516 such ZSTD_f_zstd1_magicless for example.
1517 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1518</p></pre><BR>
1519
1520<pre><b>size_t ZSTD_decompressStream_simpleArgs (
1521 ZSTD_DCtx* dctx,
1522 void* dst, size_t dstCapacity, size_t* dstPos,
1523 const void* src, size_t srcSize, size_t* srcPos);
1524</b><p> Same as ZSTD_decompressStream(),
1525 but using only integral types as arguments.
1526 This can be helpful for binders from dynamic languages
1527 which have troubles handling structures containing memory pointers.
1528
1529</p></pre><BR>
1530
1531<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
1532 Once Advanced API reaches "stable" status,
1533 redundant functions will be deprecated, and then at some point removed.
1534<BR></pre>
1535
1536<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
1537<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1538size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
1539 int compressionLevel,
1540 unsigned long long pledgedSrcSize);
1541</b><p> This function is DEPRECATED, and equivalent to:
1542 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1543 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
1544 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1545 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1546
1547 pledgedSrcSize must be correct. If it is not known at init time, use
1548 ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
1549 "0" also disables frame content size field. It may be enabled in the future.
1550 This prototype will generate compilation warnings.
1551
1552</p></pre><BR>
1553
1554<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1555size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
1556 const void* dict, size_t dictSize,
1557 int compressionLevel);
1558</b><p> This function is DEPRECATED, and is equivalent to:
1559 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1560 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1561 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1562
1563 Creates of an internal CDict (incompatible with static CCtx), except if
1564 dict == NULL or dictSize < 8, in which case no dict is used.
1565 Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
1566 it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
1567 This prototype will generate compilation warnings.
1568
1569</p></pre><BR>
1570
1571<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1572size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
1573 const void* dict, size_t dictSize,
1574 ZSTD_parameters params,
1575 unsigned long long pledgedSrcSize);
1576</b><p> This function is DEPRECATED, and is approximately equivalent to:
1577 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1578 // Pseudocode: Set each zstd parameter and leave the rest as-is.
1579 for ((param, value) : params) {
1580 ZSTD_CCtx_setParameter(zcs, param, value);
1581 }
1582 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1583 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1584
1585 dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
1586 pledgedSrcSize must be correct.
1587 If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
1588 This prototype will generate compilation warnings.
1589
1590</p></pre><BR>
1591
1592<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1593size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
1594</b><p> This function is DEPRECATED, and equivalent to:
1595 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1596 ZSTD_CCtx_refCDict(zcs, cdict);
1597
1598 note : cdict will just be referenced, and must outlive compression session
1599 This prototype will generate compilation warnings.
1600
1601</p></pre><BR>
1602
1603<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1604size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
1605 const ZSTD_CDict* cdict,
1606 ZSTD_frameParameters fParams,
1607 unsigned long long pledgedSrcSize);
1608</b><p> This function is DEPRECATED, and is approximately equivalent to:
1609 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1610 // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
1611 for ((fParam, value) : fParams) {
1612 ZSTD_CCtx_setParameter(zcs, fParam, value);
1613 }
1614 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1615 ZSTD_CCtx_refCDict(zcs, cdict);
1616
1617 same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
1618 pledgedSrcSize must be correct. If srcSize is not known at init time, use
1619 value ZSTD_CONTENTSIZE_UNKNOWN.
1620 This prototype will generate compilation warnings.
1621
1622</p></pre><BR>
1623
1624<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1625size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1626</b><p> This function is DEPRECATED, and is equivalent to:
1627 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1628 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1629 Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
1630 ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
1631 explicitly specified.
1632
1633 start a new frame, using same parameters from previous frame.
1634 This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
1635 Note that zcs must be init at least once before using ZSTD_resetCStream().
1636 If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1637 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1638 For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1639 but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1640 @return : 0, or an error code (which can be tested using ZSTD_isError())
1641 This prototype will generate compilation warnings.
1642
1643</p></pre><BR>
1644
1645<pre><b>typedef struct {
1646 unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
1647 unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
1648 unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
1649 unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
1650 unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
1651 unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
1652} ZSTD_frameProgression;
1653</b></pre><BR>
1654<pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1655</b><p> Tell how many bytes are ready to be flushed immediately.
1656 Useful for multithreading scenarios (nbWorkers >= 1).
1657 Probe the oldest active job, defined as oldest job not yet entirely flushed,
1658 and check its output buffer.
1659 @return : amount of data stored in oldest job and ready to be flushed immediately.
1660 if @return == 0, it means either :
1661 + there is no active job (could be checked with ZSTD_frameProgression()), or
1662 + oldest job is still actively compressing data,
1663 but everything it has produced has also been flushed so far,
1664 therefore flush speed is limited by production speed of oldest job
1665 irrespective of the speed of concurrent (and newer) jobs.
1666
1667</p></pre><BR>
1668
1669<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
1670<pre><b>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
1671</b><p>
1672 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1673 ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
1674
1675 note: no dictionary will be used if dict == NULL or dictSize < 8
1676 Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1677
1678</p></pre><BR>
1679
1680<pre><b>size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
1681</b><p>
1682 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1683 ZSTD_DCtx_refDDict(zds, ddict);
1684
1685 note : ddict is referenced, it must outlive decompression session
1686 Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1687
1688</p></pre><BR>
1689
1690<pre><b>size_t ZSTD_resetDStream(ZSTD_DStream* zds);
1691</b><p>
1692 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1693
1694 re-use decompression parameters from previous init; saves dictionary loading
1695 Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1696
1697</p></pre><BR>
1698
1699<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
1700 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
1701 But it's also a complex one, with several restrictions, documented below.
1702 Prefer normal streaming API for an easier experience.
1703
1704<BR></pre>
1705
1706<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
1707 A ZSTD_CCtx object is required to track streaming operations.
1708 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
1709 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
1710
1711 Start by initializing a context.
1712 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
1713 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
1714
1715 Then, consume your input using ZSTD_compressContinue().
1716 There are some important considerations to keep in mind when using this advanced function :
1717 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
1718 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
1719 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
1720 Worst case evaluation is provided by ZSTD_compressBound().
1721 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
1722 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
1723 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
1724 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
1725 In which case, it will "discard" the relevant memory section from its history.
1726
1727 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
1728 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
1729 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
1730
1731 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
1732<BR></pre>
1733
1734<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
1735size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
1736size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
1737size_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>
1738</pre></b><BR>
1739<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>
1740</b></pre><BR>
1741<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
1742 A ZSTD_DCtx object is required to track streaming operations.
1743 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
1744 A ZSTD_DCtx object can be re-used multiple times.
1745
1746 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
1747 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
1748 Data fragment must be large enough to ensure successful decoding.
1749 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
1750 @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
1751 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
1752 errorCode, which can be tested using ZSTD_isError().
1753
1754 It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
1755 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
1756 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
1757 As a consequence, check that values remain within valid application range.
1758 For example, do not allocate memory blindly, check that `windowSize` is within expectation.
1759 Each application can set its own limits, depending on local restrictions.
1760 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
1761
1762 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
1763 ZSTD_decompressContinue() is very sensitive to contiguity,
1764 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
1765 or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
1766 There are multiple ways to guarantee this condition.
1767
1768 The most memory efficient way is to use a round buffer of sufficient size.
1769 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
1770 which can @return an error code if required value is too large for current system (in 32-bits mode).
1771 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
1772 up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
1773 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
1774 At which point, decoding can resume from the beginning of the buffer.
1775 Note that already decoded data stored in the buffer should be flushed before being overwritten.
1776
1777 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
1778
1779 Finally, if you control the compression process, you can also ignore all buffer size rules,
1780 as long as the encoder and decoder progress in "lock-step",
1781 aka use exactly the same buffer sizes, break contiguity at the same place, etc.
1782
1783 Once buffers are setup, start decompression, with ZSTD_decompressBegin().
1784 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
1785
1786 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
1787 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
1788 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
1789
1790 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
1791 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
1792 It can also be an error code, which can be tested with ZSTD_isError().
1793
1794 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
1795 Context can then be reset to start a new decompression.
1796
1797 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
1798 This information is not required to properly decode a frame.
1799
1800 == Special case : skippable frames
1801
1802 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
1803 Skippable frames will be ignored (skipped) by decompressor.
1804 The format of skippable frames is as follows :
1805 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
1806 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
1807 c) Frame Content - any content (User Data) of length equal to Frame Size
1808 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
1809 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
1810<BR></pre>
1811
1812<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
1813typedef struct {
1814 unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
1815 unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
1816 unsigned blockSizeMax;
1817 ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
1818 unsigned headerSize;
1819 unsigned dictID;
1820 unsigned checksumFlag;
1821} ZSTD_frameHeader;
1822</pre></b><BR>
1823<pre><b>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
1824</b>/*! ZSTD_getFrameHeader_advanced() :<b>
1825 * same as ZSTD_getFrameHeader(),
1826 * with added capability to select a format (like ZSTD_f_zstd1_magicless) */
1827size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
1828size_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>
1829</b><p> decode Frame Header, or requires larger `srcSize`.
1830 @return : 0, `zfhPtr` is correctly filled,
1831 >0, `srcSize` is too small, value is wanted `srcSize` amount,
1832 or an error code, which can be tested using ZSTD_isError()
1833</p></pre><BR>
1834
1835<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
1836</b></pre><BR>
1837<a name="Chapter23"></a><h2>Block level API</h2><pre></pre>
1838
1839<pre><b></b><p> Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
1840 But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
1841
1842 A few rules to respect :
1843 - Compressing and decompressing require a context structure
1844 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
1845 - It is necessary to init context before starting
1846 + compression : any ZSTD_compressBegin*() variant, including with dictionary
1847 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
1848 + copyCCtx() and copyDCtx() can be used too
1849 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
1850 + If input is larger than a block size, it's necessary to split input data into multiple blocks
1851 + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
1852 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
1853 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
1854 ===> In which case, nothing is produced into `dst` !
1855 + User __must__ test for such outcome and deal directly with uncompressed data
1856 + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
1857 Doing so would mess up with statistics history, leading to potential data corruption.
1858 + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
1859 + In case of multiple successive blocks, should some of them be uncompressed,
1860 decoder must be informed of their existence in order to follow proper history.
1861 Use ZSTD_insertBlock() for such a case.
1862</p></pre><BR>
1863
1864<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
1865size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1866size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1867size_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>
1868</pre></b><BR>
1869</html>
1870</body>
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