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4<title>zstd 1.5.5 Manual</title>
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6<body>
7<h1>zstd 1.5.5 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 header and 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 (DEPRECATED)</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 (DEPRECATED)</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 NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
84 enough space to successfully compress the data.
85 @return : compressed size written into `dst` (<= `dstCapacity),
86 or an error code if it fails (which can be tested using ZSTD_isError()).
87</p></pre><BR>
88
89<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
90 const void* src, size_t compressedSize);
91</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
92 `dstCapacity` is an upper bound of originalSize to regenerate.
93 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
94 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
95 or an errorCode if it fails (which can be tested using ZSTD_isError()).
96</p></pre><BR>
97
98<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
99#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
100unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
101</b><p> `src` should point to the start of a ZSTD encoded frame.
102 `srcSize` must be at least as large as the frame header.
103 hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
104 @return : - decompressed size of `src` frame content, if known
105 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
106 - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
107 note 1 : a 0 return value means the frame is valid but "empty".
108 note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
109 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
110 In which case, it's necessary to use streaming mode to decompress data.
111 Optionally, application can rely on some implicit limit,
112 as ZSTD_decompress() only needs an upper bound of decompressed size.
113 (For example, data could be necessarily cut into blocks <= 16 KB).
114 note 3 : decompressed size is always present when compression is completed using single-pass functions,
115 such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
116 note 4 : decompressed size can be very large (64-bits value),
117 potentially larger than what local system can handle as a single memory segment.
118 In which case, it's necessary to use streaming mode to decompress data.
119 note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
120 Always ensure return value fits within application's authorized limits.
121 Each application can set its own limits.
122 note 6 : This function replaces ZSTD_getDecompressedSize()
123</p></pre><BR>
124
125<pre><b>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize")
126ZSTDLIB_API
127unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
128</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
129 Both functions work the same way, but ZSTD_getDecompressedSize() blends
130 "empty", "unknown" and "error" results to the same return value (0),
131 while ZSTD_getFrameContentSize() gives them separate return values.
132 @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise.
133</p></pre><BR>
134
135<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
136</b><p> `src` should point to the start of a ZSTD frame or skippable frame.
137 `srcSize` must be >= first frame size
138 @return : the compressed size of the first frame starting at `src`,
139 suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
140 or an error code if input is invalid
141</p></pre><BR>
142
143<h3>Helper functions</h3><pre></pre><b><pre></b>/* ZSTD_compressBound() :<b>
144 * maximum compressed size in worst case single-pass scenario.
145 * When invoking `ZSTD_compress()` or any other one-pass compression function,
146 * it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize)
147 * as it eliminates one potential failure scenario,
148 * aka not enough room in dst buffer to write the compressed frame.
149 * Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE .
150 * In which case, ZSTD_compressBound() will return an error code
151 * which can be tested using ZSTD_isError().
152 *
153 * ZSTD_COMPRESSBOUND() :
154 * same as ZSTD_compressBound(), but as a macro.
155 * It can be used to produce constants, which can be useful for static allocation,
156 * for example to size a static array on stack.
157 * Will produce constant value 0 if srcSize too large.
158 */
159#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00LLU : 0xFF00FF00U)
160#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
161size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
162</b>/* ZSTD_isError() :<b>
163 * Most ZSTD_* functions returning a size_t value can be tested for error,
164 * using ZSTD_isError().
165 * @return 1 if error, 0 otherwise
166 */
167unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
168const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
169int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b>
170int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
171int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b>
172</pre></b><BR>
173<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
174
175<h3>Compression context</h3><pre> When compressing many times,
176 it is recommended to allocate a context just once,
177 and re-use it for each successive compression operation.
178 This will make workload friendlier for system's memory.
179 Note : re-using context is just a speed / resource optimization.
180 It doesn't change the compression ratio, which remains identical.
181 Note 2 : In multi-threaded environments,
182 use one different context per thread for parallel execution.
183
184</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
185ZSTD_CCtx* ZSTD_createCCtx(void);
186size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b>
187</pre></b><BR>
188<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
189 void* dst, size_t dstCapacity,
190 const void* src, size_t srcSize,
191 int compressionLevel);
192</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
193 Important : in order to behave similarly to `ZSTD_compress()`,
194 this function compresses at requested compression level,
195 __ignoring any other parameter__ .
196 If any advanced parameter was set using the advanced API,
197 they will all be reset. Only `compressionLevel` remains.
198
199</p></pre><BR>
200
201<h3>Decompression context</h3><pre> When decompressing many times,
202 it is recommended to allocate a context only once,
203 and re-use it for each successive compression operation.
204 This will make workload friendlier for system's memory.
205 Use one context per thread for parallel execution.
206</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
207ZSTD_DCtx* ZSTD_createDCtx(void);
208size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b>
209</pre></b><BR>
210<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
211 void* dst, size_t dstCapacity,
212 const void* src, size_t srcSize);
213</b><p> Same as ZSTD_decompress(),
214 requires an allocated ZSTD_DCtx.
215 Compatible with sticky parameters.
216
217</p></pre><BR>
218
219<a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre>
220
221<pre><b>typedef enum { ZSTD_fast=1,
222 ZSTD_dfast=2,
223 ZSTD_greedy=3,
224 ZSTD_lazy=4,
225 ZSTD_lazy2=5,
226 ZSTD_btlazy2=6,
227 ZSTD_btopt=7,
228 ZSTD_btultra=8,
229 ZSTD_btultra2=9
230 </b>/* note : new strategies _might_ be added in the future.<b>
231 Only the order (from fast to strong) is guaranteed */
232} ZSTD_strategy;
233</b></pre><BR>
234<pre><b>typedef enum {
235
236 </b>/* compression parameters<b>
237 * Note: When compressing with a ZSTD_CDict these parameters are superseded
238 * by the parameters used to construct the ZSTD_CDict.
239 * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
240 ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
241 * Note that exact compression parameters are dynamically determined,
242 * depending on both compression level and srcSize (when known).
243 * Default level is ZSTD_CLEVEL_DEFAULT==3.
244 * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
245 * Note 1 : it's possible to pass a negative compression level.
246 * Note 2 : setting a level does not automatically set all other compression parameters
247 * to default. Setting this will however eventually dynamically impact the compression
248 * parameters which have not been manually set. The manually set
249 * ones will 'stick'. */
250 </b>/* Advanced compression parameters :<b>
251 * It's possible to pin down compression parameters to some specific values.
252 * In which case, these values are no longer dynamically selected by the compressor */
253 ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
254 * This will set a memory budget for streaming decompression,
255 * with larger values requiring more memory
256 * and typically compressing more.
257 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
258 * Special: value 0 means "use default windowLog".
259 * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
260 * requires explicitly allowing such size at streaming decompression stage. */
261 ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
262 * Resulting memory usage is (1 << (hashLog+2)).
263 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
264 * Larger tables improve compression ratio of strategies <= dFast,
265 * and improve speed of strategies > dFast.
266 * Special: value 0 means "use default hashLog". */
267 ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b>
268 * Resulting memory usage is (1 << (chainLog+2)).
269 * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
270 * Larger tables result in better and slower compression.
271 * This parameter is useless for "fast" strategy.
272 * It's still useful when using "dfast" strategy,
273 * in which case it defines a secondary probe table.
274 * Special: value 0 means "use default chainLog". */
275 ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
276 * More attempts result in better and slower compression.
277 * This parameter is useless for "fast" and "dFast" strategies.
278 * Special: value 0 means "use default searchLog". */
279 ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b>
280 * Note that Zstandard can still find matches of smaller size,
281 * it just tweaks its search algorithm to look for this size and larger.
282 * Larger values increase compression and decompression speed, but decrease ratio.
283 * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
284 * Note that currently, for all strategies < btopt, effective minimum is 4.
285 * , for all strategies > fast, effective maximum is 6.
286 * Special: value 0 means "use default minMatchLength". */
287 ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
288 * For strategies btopt, btultra & btultra2:
289 * Length of Match considered "good enough" to stop search.
290 * Larger values make compression stronger, and slower.
291 * For strategy fast:
292 * Distance between match sampling.
293 * Larger values make compression faster, and weaker.
294 * Special: value 0 means "use default targetLength". */
295 ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b>
296 * The higher the value of selected strategy, the more complex it is,
297 * resulting in stronger and slower compression.
298 * Special: value 0 means "use default strategy". */
299 </b>/* LDM mode parameters */<b>
300 ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
301 * This parameter is designed to improve compression ratio
302 * for large inputs, by finding large matches at long distance.
303 * It increases memory usage and window size.
304 * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
305 * except when expressly set to a different value.
306 * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
307 * compression strategy >= ZSTD_btopt (== compression level 16+) */
308 ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
309 * Larger values increase memory usage and compression ratio,
310 * but decrease compression speed.
311 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
312 * default: windowlog - 7.
313 * Special: value 0 means "automatically determine hashlog". */
314 ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
315 * Larger/too small values usually decrease compression ratio.
316 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
317 * Special: value 0 means "use default value" (default: 64). */
318 ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
319 * Larger values improve collision resolution but decrease compression speed.
320 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
321 * Special: value 0 means "use default value" (default: 3). */
322 ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
323 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
324 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
325 * Larger values improve compression speed.
326 * Deviating far from default value will likely result in a compression ratio decrease.
327 * Special: value 0 means "automatically determine hashRateLog". */
328
329 </b>/* frame parameters */<b>
330 ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
331 * Content size must be known at the beginning of compression.
332 * This is automatically the case when using ZSTD_compress2(),
333 * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
334 ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
335 ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
336
337 </b>/* multi-threading parameters */<b>
338 </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
339 * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
340 * In a situation where it's unknown if the linked library supports multi-threading or not,
341 * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
342 */
343 ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
344 * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
345 * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
346 * while compression is performed in parallel, within worker thread(s).
347 * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
348 * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
349 * More workers improve speed, but also increase memory usage.
350 * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
351 * compression is performed inside Caller's thread, and all invocations are blocking */
352 ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
353 * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
354 * 0 means default, which is dynamically determined based on compression parameters.
355 * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
356 * The minimum size is automatically and transparently enforced. */
357 ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
358 * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
359 * It helps preserve compression ratio, while each job is compressed in parallel.
360 * This value is enforced only when nbWorkers >= 1.
361 * Larger values increase compression ratio, but decrease speed.
362 * Possible values range from 0 to 9 :
363 * - 0 means "default" : value will be determined by the library, depending on strategy
364 * - 1 means "no overlap"
365 * - 9 means "full overlap", using a full window size.
366 * Each intermediate rank increases/decreases load size by a factor 2 :
367 * 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
368 * default value varies between 6 and 9, depending on strategy */
369
370 </b>/* note : additional experimental parameters are also available<b>
371 * within the experimental section of the API.
372 * At the time of this writing, they include :
373 * ZSTD_c_rsyncable
374 * ZSTD_c_format
375 * ZSTD_c_forceMaxWindow
376 * ZSTD_c_forceAttachDict
377 * ZSTD_c_literalCompressionMode
378 * ZSTD_c_targetCBlockSize
379 * ZSTD_c_srcSizeHint
380 * ZSTD_c_enableDedicatedDictSearch
381 * ZSTD_c_stableInBuffer
382 * ZSTD_c_stableOutBuffer
383 * ZSTD_c_blockDelimiters
384 * ZSTD_c_validateSequences
385 * ZSTD_c_useBlockSplitter
386 * ZSTD_c_useRowMatchFinder
387 * ZSTD_c_prefetchCDictTables
388 * ZSTD_c_enableSeqProducerFallback
389 * ZSTD_c_maxBlockSize
390 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
391 * note : never ever use experimentalParam? names directly;
392 * also, the enums values themselves are unstable and can still change.
393 */
394 ZSTD_c_experimentalParam1=500,
395 ZSTD_c_experimentalParam2=10,
396 ZSTD_c_experimentalParam3=1000,
397 ZSTD_c_experimentalParam4=1001,
398 ZSTD_c_experimentalParam5=1002,
399 ZSTD_c_experimentalParam6=1003,
400 ZSTD_c_experimentalParam7=1004,
401 ZSTD_c_experimentalParam8=1005,
402 ZSTD_c_experimentalParam9=1006,
403 ZSTD_c_experimentalParam10=1007,
404 ZSTD_c_experimentalParam11=1008,
405 ZSTD_c_experimentalParam12=1009,
406 ZSTD_c_experimentalParam13=1010,
407 ZSTD_c_experimentalParam14=1011,
408 ZSTD_c_experimentalParam15=1012,
409 ZSTD_c_experimentalParam16=1013,
410 ZSTD_c_experimentalParam17=1014,
411 ZSTD_c_experimentalParam18=1015,
412 ZSTD_c_experimentalParam19=1016
413} ZSTD_cParameter;
414</b></pre><BR>
415<pre><b>typedef struct {
416 size_t error;
417 int lowerBound;
418 int upperBound;
419} ZSTD_bounds;
420</b></pre><BR>
421<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
422</b><p> All parameters must belong to an interval with lower and upper bounds,
423 otherwise they will either trigger an error or be automatically clamped.
424 @return : a structure, ZSTD_bounds, which contains
425 - an error status field, which must be tested using ZSTD_isError()
426 - lower and upper bounds, both inclusive
427
428</p></pre><BR>
429
430<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
431</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
432 All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
433 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
434 Setting a parameter is generally only possible during frame initialization (before starting compression).
435 Exception : when using multi-threading mode (nbWorkers >= 1),
436 the following parameters can be updated _during_ compression (within same frame):
437 => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
438 new parameters will be active for next job only (after a flush()).
439 @return : an error code (which can be tested using ZSTD_isError()).
440
441</p></pre><BR>
442
443<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
444</b><p> Total input data size to be compressed as a single frame.
445 Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
446 This value will also be controlled at end of frame, and trigger an error if not respected.
447 @result : 0, or an error code (which can be tested with ZSTD_isError()).
448 Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
449 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
450 ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
451 Note 2 : pledgedSrcSize is only valid once, for the next frame.
452 It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
453 Note 3 : Whenever all input data is provided and consumed in a single round,
454 for example with ZSTD_compress2(),
455 or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
456 this value is automatically overridden by srcSize instead.
457
458</p></pre><BR>
459
460<pre><b>typedef enum {
461 ZSTD_reset_session_only = 1,
462 ZSTD_reset_parameters = 2,
463 ZSTD_reset_session_and_parameters = 3
464} ZSTD_ResetDirective;
465</b></pre><BR>
466<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
467</b><p> There are 2 different things that can be reset, independently or jointly :
468 - The session : will stop compressing current frame, and make CCtx ready to start a new one.
469 Useful after an error, or to interrupt any ongoing compression.
470 Any internal data not yet flushed is cancelled.
471 Compression parameters and dictionary remain unchanged.
472 They will be used to compress next frame.
473 Resetting session never fails.
474 - The parameters : changes all parameters back to "default".
475 This also removes any reference to any dictionary or external sequence producer.
476 Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
477 otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
478 - Both : similar to resetting the session, followed by resetting parameters.
479
480</p></pre><BR>
481
482<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
483 void* dst, size_t dstCapacity,
484 const void* src, size_t srcSize);
485</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
486 ZSTD_compress2() always starts a new frame.
487 Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
488 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
489 - The function is always blocking, returns when compression is completed.
490 NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
491 enough space to successfully compress the data, though it is possible it fails for other reasons.
492 @return : compressed size written into `dst` (<= `dstCapacity),
493 or an error code if it fails (which can be tested using ZSTD_isError()).
494
495</p></pre><BR>
496
497<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre>
498
499<pre><b>typedef enum {
500
501 ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
502 * the streaming API will refuse to allocate memory buffer
503 * in order to protect the host from unreasonable memory requirements.
504 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
505 * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
506 * Special: value 0 means "use default maximum windowLog". */
507
508 </b>/* note : additional experimental parameters are also available<b>
509 * within the experimental section of the API.
510 * At the time of this writing, they include :
511 * ZSTD_d_format
512 * ZSTD_d_stableOutBuffer
513 * ZSTD_d_forceIgnoreChecksum
514 * ZSTD_d_refMultipleDDicts
515 * ZSTD_d_disableHuffmanAssembly
516 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
517 * note : never ever use experimentalParam? names directly
518 */
519 ZSTD_d_experimentalParam1=1000,
520 ZSTD_d_experimentalParam2=1001,
521 ZSTD_d_experimentalParam3=1002,
522 ZSTD_d_experimentalParam4=1003,
523 ZSTD_d_experimentalParam5=1004
524
525} ZSTD_dParameter;
526</b></pre><BR>
527<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
528</b><p> All parameters must belong to an interval with lower and upper bounds,
529 otherwise they will either trigger an error or be automatically clamped.
530 @return : a structure, ZSTD_bounds, which contains
531 - an error status field, which must be tested using ZSTD_isError()
532 - both lower and upper bounds, inclusive
533
534</p></pre><BR>
535
536<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
537</b><p> Set one compression parameter, selected by enum ZSTD_dParameter.
538 All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
539 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
540 Setting a parameter is only possible during frame initialization (before starting decompression).
541 @return : 0, or an error code (which can be tested using ZSTD_isError()).
542
543</p></pre><BR>
544
545<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
546</b><p> Return a DCtx to clean state.
547 Session and parameters can be reset jointly or separately.
548 Parameters can only be reset when no active frame is being decompressed.
549 @return : 0, or an error code, which can be tested with ZSTD_isError()
550
551</p></pre><BR>
552
553<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
554
555<pre><b>typedef struct ZSTD_inBuffer_s {
556 const void* src; </b>/**< start of input buffer */<b>
557 size_t size; </b>/**< size of input buffer */<b>
558 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
559} ZSTD_inBuffer;
560</b></pre><BR>
561<pre><b>typedef struct ZSTD_outBuffer_s {
562 void* dst; </b>/**< start of output buffer */<b>
563 size_t size; </b>/**< size of output buffer */<b>
564 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
565} ZSTD_outBuffer;
566</b></pre><BR>
567<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
568 A ZSTD_CStream object is required to track streaming operation.
569 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
570 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
571 It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
572
573 For parallel execution, use one separate ZSTD_CStream per thread.
574
575 note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
576
577 Parameters are sticky : when starting a new compression on the same context,
578 it will re-use the same sticky parameters as previous compression session.
579 When in doubt, it's recommended to fully initialize the context before usage.
580 Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
581 ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
582 set more specific parameters, the pledged source size, or load a dictionary.
583
584 Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
585 consume input stream. The function will automatically update both `pos`
586 fields within `input` and `output`.
587 Note that the function may not consume the entire input, for example, because
588 the output buffer is already full, in which case `input.pos < input.size`.
589 The caller must check if input has been entirely consumed.
590 If not, the caller must make some room to receive more compressed data,
591 and then present again remaining input data.
592 note: ZSTD_e_continue is guaranteed to make some forward progress when called,
593 but doesn't guarantee maximal forward progress. This is especially relevant
594 when compressing with multiple threads. The call won't block if it can
595 consume some input, but if it can't it will wait for some, but not all,
596 output to be flushed.
597 @return : provides a minimum amount of data remaining to be flushed from internal buffers
598 or an error code, which can be tested using ZSTD_isError().
599
600 At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
601 using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
602 Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
603 In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
604 You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
605 operation.
606 note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
607 block until the flush is complete or the output buffer is full.
608 @return : 0 if internal buffers are entirely flushed,
609 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
610 or an error code, which can be tested using ZSTD_isError().
611
612 Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
613 It will perform a flush and write frame epilogue.
614 The epilogue is required for decoders to consider a frame completed.
615 flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
616 You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
617 start a new frame.
618 note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
619 block until the flush is complete or the output buffer is full.
620 @return : 0 if frame fully completed and fully flushed,
621 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
622 or an error code, which can be tested using ZSTD_isError().
623
624
625<BR></pre>
626
627<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
628</b></pre><BR>
629<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
630size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b>
631</pre></b><BR>
632<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
633 ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
634 ZSTD_e_flush=1, </b>/* flush any data provided so far,<b>
635 * it creates (at least) one new block, that can be decoded immediately on reception;
636 * frame will continue: any future data can still reference previously compressed data, improving compression.
637 * note : multithreaded compression will block to flush as much output as possible. */
638 ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b>
639 * note that frame is only closed after compressed data is fully flushed (return value == 0).
640 * After that point, any additional data starts a new frame.
641 * note : each frame is independent (does not reference any content from previous frame).
642 : note : multithreaded compression will block to flush as much output as possible. */
643} ZSTD_EndDirective;
644</pre></b><BR>
645<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
646 ZSTD_outBuffer* output,
647 ZSTD_inBuffer* input,
648 ZSTD_EndDirective endOp);
649</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive.
650 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
651 - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
652 - output->pos must be <= dstCapacity, input->pos must be <= srcSize
653 - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
654 - endOp must be a valid directive
655 - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
656 - 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,
657 and then immediately returns, just indicating that there is some data remaining to be flushed.
658 The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
659 - 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.
660 - @return provides a minimum amount of data remaining to be flushed from internal buffers
661 or an error code, which can be tested using ZSTD_isError().
662 if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
663 This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
664 For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
665 - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
666 only ZSTD_e_end or ZSTD_e_flush operations are allowed.
667 Before starting a new compression job, or changing compression parameters,
668 it is required to fully flush internal buffers.
669
670</p></pre><BR>
671
672<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
673</b></pre><BR>
674<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
675</b></pre><BR>
676<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
677</b>/*!<b>
678 * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
679 * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
680 * the next read size (if non-zero and not an error). ZSTD_compressStream2()
681 * returns the minimum nb of bytes left to flush (if non-zero and not an error).
682 */
683size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
684</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
685size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
686</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
687size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
688</b><p>
689 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
690 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
691 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
692
693 Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API
694 to compress with a dictionary.
695
696</p></pre><BR>
697
698<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
699 A ZSTD_DStream object is required to track streaming operations.
700 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
701 ZSTD_DStream objects can be re-used multiple times.
702
703 Use ZSTD_initDStream() to start a new decompression operation.
704 @return : recommended first input size
705 Alternatively, use advanced API to set specific properties.
706
707 Use ZSTD_decompressStream() repetitively to consume your input.
708 The function will update both `pos` fields.
709 If `input.pos < input.size`, some input has not been consumed.
710 It's up to the caller to present again remaining data.
711 The function tries to flush all data decoded immediately, respecting output buffer size.
712 If `output.pos < output.size`, decoder has flushed everything it could.
713 But if `output.pos == output.size`, there might be some data left within internal buffers.,
714 In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
715 Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
716 @return : 0 when a frame is completely decoded and fully flushed,
717 or an error code, which can be tested using ZSTD_isError(),
718 or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
719 the return value is a suggested next input size (just a hint for better latency)
720 that will never request more than the remaining frame size.
721
722<BR></pre>
723
724<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
725</b></pre><BR>
726<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
727size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b>
728</pre></b><BR>
729<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
730<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds);
731</b><p> Initialize/reset DStream state for new decompression operation.
732 Call before new decompression operation using same DStream.
733
734 Note : This function is redundant with the advanced API and equivalent to:
735 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
736 ZSTD_DCtx_refDDict(zds, NULL);
737
738</p></pre><BR>
739
740<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
741</b><p> Streaming decompression function.
742 Call repetitively to consume full input updating it as necessary.
743 Function will update both input and output `pos` fields exposing current state via these fields:
744 - `input.pos < input.size`, some input remaining and caller should provide remaining input
745 on the next call.
746 - `output.pos < output.size`, decoder finished and flushed all remaining buffers.
747 - `output.pos == output.size`, potentially uncflushed data present in the internal buffers,
748 call ZSTD_decompressStream() again to flush remaining data to output.
749 Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX.
750
751 @return : 0 when a frame is completely decoded and fully flushed,
752 or an error code, which can be tested using ZSTD_isError(),
753 or any other value > 0, which means there is some decoding or flushing to do to complete current frame.
754
755</p></pre><BR>
756
757<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
758</b></pre><BR>
759<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>
760</b></pre><BR>
761<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
762
763<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
764 void* dst, size_t dstCapacity,
765 const void* src, size_t srcSize,
766 const void* dict,size_t dictSize,
767 int compressionLevel);
768</b><p> Compression at an explicit compression level using a Dictionary.
769 A dictionary can be any arbitrary data segment (also called a prefix),
770 or a buffer with specified information (see zdict.h).
771 Note : This function loads the dictionary, resulting in significant startup delay.
772 It's intended for a dictionary used only once.
773 Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
774</p></pre><BR>
775
776<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
777 void* dst, size_t dstCapacity,
778 const void* src, size_t srcSize,
779 const void* dict,size_t dictSize);
780</b><p> Decompression using a known Dictionary.
781 Dictionary must be identical to the one used during compression.
782 Note : This function loads the dictionary, resulting in significant startup delay.
783 It's intended for a dictionary used only once.
784 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
785</p></pre><BR>
786
787<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
788
789<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
790 int compressionLevel);
791</b><p> When compressing multiple messages or blocks using the same dictionary,
792 it's recommended to digest the dictionary only once, since it's a costly operation.
793 ZSTD_createCDict() will create a state from digesting a dictionary.
794 The resulting state can be used for future compression operations with very limited startup cost.
795 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
796 @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
797 Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
798 Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
799 in which case the only thing that it transports is the @compressionLevel.
800 This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
801 expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
802</p></pre><BR>
803
804<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
805</b><p> Function frees memory allocated by ZSTD_createCDict().
806 If a NULL pointer is passed, no operation is performed.
807</p></pre><BR>
808
809<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
810 void* dst, size_t dstCapacity,
811 const void* src, size_t srcSize,
812 const ZSTD_CDict* cdict);
813</b><p> Compression using a digested Dictionary.
814 Recommended when same dictionary is used multiple times.
815 Note : compression level is _decided at dictionary creation time_,
816 and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
817</p></pre><BR>
818
819<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
820</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
821 dictBuffer can be released after DDict creation, as its content is copied inside DDict.
822</p></pre><BR>
823
824<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
825</b><p> Function frees memory allocated with ZSTD_createDDict()
826 If a NULL pointer is passed, no operation is performed.
827</p></pre><BR>
828
829<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
830 void* dst, size_t dstCapacity,
831 const void* src, size_t srcSize,
832 const ZSTD_DDict* ddict);
833</b><p> Decompression using a digested Dictionary.
834 Recommended when same dictionary is used multiple times.
835</p></pre><BR>
836
837<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
838
839<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
840</b><p> Provides the dictID stored within dictionary.
841 if @return == 0, the dictionary is not conformant with Zstandard specification.
842 It can still be loaded, but as a content-only dictionary.
843</p></pre><BR>
844
845<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
846</b><p> Provides the dictID of the dictionary loaded into `cdict`.
847 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
848 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
849</p></pre><BR>
850
851<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
852</b><p> Provides the dictID of the dictionary loaded into `ddict`.
853 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
854 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
855</p></pre><BR>
856
857<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
858</b><p> Provides the dictID required to decompressed the frame stored within `src`.
859 If @return == 0, the dictID could not be decoded.
860 This could for one of the following reasons :
861 - The frame does not require a dictionary to be decoded (most common case).
862 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information.
863 Note : this use case also happens when using a non-conformant dictionary.
864 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
865 - This is not a Zstandard frame.
866 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
867</p></pre><BR>
868
869<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre>
870 This API allows dictionaries to be used with ZSTD_compress2(),
871 ZSTD_compressStream2(), and ZSTD_decompressDCtx().
872 Dictionaries are sticky, they remain valid when same context is re-used,
873 they only reset when the context is reset
874 with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters.
875 In contrast, Prefixes are single-use.
876<BR></pre>
877
878<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
879</b><p> Create an internal CDict from `dict` buffer.
880 Decompression will have to use same dictionary.
881 @result : 0, or an error code (which can be tested with ZSTD_isError()).
882 Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
883 meaning "return to no-dictionary mode".
884 Note 1 : Dictionary is sticky, it will be used for all future compressed frames,
885 until parameters are reset, a new dictionary is loaded, or the dictionary
886 is explicitly invalidated by loading a NULL dictionary.
887 Note 2 : Loading a dictionary involves building tables.
888 It's also a CPU consuming operation, with non-negligible impact on latency.
889 Tables are dependent on compression parameters, and for this reason,
890 compression parameters can no longer be changed after loading a dictionary.
891 Note 3 :`dict` content will be copied internally.
892 Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
893 In such a case, dictionary buffer must outlive its users.
894 Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
895 to precisely select how dictionary content must be interpreted.
896 Note 5 : This method does not benefit from LDM (long distance mode).
897 If you want to employ LDM on some large dictionary content,
898 prefer employing ZSTD_CCtx_refPrefix() described below.
899
900</p></pre><BR>
901
902<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
903</b><p> Reference a prepared dictionary, to be used for all future compressed frames.
904 Note that compression parameters are enforced from within CDict,
905 and supersede any compression parameter previously set within CCtx.
906 The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
907 The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
908 The dictionary will remain valid for future compressed frames using same CCtx.
909 @result : 0, or an error code (which can be tested with ZSTD_isError()).
910 Special : Referencing a NULL CDict means "return to no-dictionary mode".
911 Note 1 : Currently, only one dictionary can be managed.
912 Referencing a new dictionary effectively "discards" any previous one.
913 Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
914</p></pre><BR>
915
916<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
917 const void* prefix, size_t prefixSize);
918</b><p> Reference a prefix (single-usage dictionary) for next compressed frame.
919 A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
920 Decompression will need same prefix to properly regenerate data.
921 Compressing with a prefix is similar in outcome as performing a diff and compressing it,
922 but performs much faster, especially during decompression (compression speed is tunable with compression level).
923 This method is compatible with LDM (long distance mode).
924 @result : 0, or an error code (which can be tested with ZSTD_isError()).
925 Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
926 Note 1 : Prefix buffer is referenced. It **must** outlive compression.
927 Its content must remain unmodified during compression.
928 Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
929 ensure that the window size is large enough to contain the entire source.
930 See ZSTD_c_windowLog.
931 Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
932 It's a CPU consuming operation, with non-negligible impact on latency.
933 If there is a need to use the same prefix multiple times, consider loadDictionary instead.
934 Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
935 Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
936</p></pre><BR>
937
938<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
939</b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames.
940 The dictionary remains valid for all future frames, until explicitly invalidated, or
941 a new dictionary is loaded.
942 @result : 0, or an error code (which can be tested with ZSTD_isError()).
943 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
944 meaning "return to no-dictionary mode".
945 Note 1 : Loading a dictionary involves building tables,
946 which has a non-negligible impact on CPU usage and latency.
947 It's recommended to "load once, use many times", to amortize the cost
948 Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
949 Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
950 Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
951 how dictionary content is loaded and interpreted.
952
953</p></pre><BR>
954
955<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
956</b><p> Reference a prepared dictionary, to be used to decompress next frames.
957 The dictionary remains active for decompression of future frames using same DCtx.
958
959 If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
960 will store the DDict references in a table, and the DDict used for decompression
961 will be determined at decompression time, as per the dict ID in the frame.
962 The memory for the table is allocated on the first call to refDDict, and can be
963 freed with ZSTD_freeDCtx().
964
965 If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary
966 will be managed, and referencing a dictionary effectively "discards" any previous one.
967
968 @result : 0, or an error code (which can be tested with ZSTD_isError()).
969 Special: referencing a NULL DDict means "return to no-dictionary mode".
970 Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
971
972</p></pre><BR>
973
974<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
975 const void* prefix, size_t prefixSize);
976</b><p> Reference a prefix (single-usage dictionary) to decompress next frame.
977 This is the reverse operation of ZSTD_CCtx_refPrefix(),
978 and must use the same prefix as the one used during compression.
979 Prefix is **only used once**. Reference is discarded at end of frame.
980 End of frame is reached when ZSTD_decompressStream() returns 0.
981 @result : 0, or an error code (which can be tested with ZSTD_isError()).
982 Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
983 Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
984 Prefix buffer must remain unmodified up to the end of frame,
985 reached when ZSTD_decompressStream() returns 0.
986 Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
987 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
988 Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
989 A full dictionary is more costly, as it requires building tables.
990
991</p></pre><BR>
992
993<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
994size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
995size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
996size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
997size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
998size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
999</b><p> These functions give the _current_ memory usage of selected object.
1000 Note that object memory usage can evolve (increase or decrease) over time.
1001</p></pre><BR>
1002
1003<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
1004 The following symbols and constants
1005 are not planned to join "stable API" status in the near future.
1006 They can still change in future versions.
1007 Some of them are planned to remain in the static_only section indefinitely.
1008 Some of them might be removed in the future (especially when redundant with existing stable functions)
1009
1010<BR></pre>
1011
1012<pre><b>typedef struct {
1013 unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
1014 * If offset == 0 and matchLength == 0, this sequence represents the last
1015 * literals in the block of litLength size.
1016 */
1017
1018 unsigned int litLength; </b>/* Literal length of the sequence. */<b>
1019 unsigned int matchLength; </b>/* Match length of the sequence. */<b>
1020
1021 </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
1022 * In this case, we will treat the sequence as a marker for a block boundary.
1023 */
1024
1025 unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
1026 * Ranges from [0, 3].
1027 *
1028 * Repeat offsets are essentially previous offsets from previous sequences sorted in
1029 * recency order. For more detail, see doc/zstd_compression_format.md
1030 *
1031 * If rep == 0, then 'offset' does not contain a repeat offset.
1032 * If rep > 0:
1033 * If litLength != 0:
1034 * rep == 1 --> offset == repeat_offset_1
1035 * rep == 2 --> offset == repeat_offset_2
1036 * rep == 3 --> offset == repeat_offset_3
1037 * If litLength == 0:
1038 * rep == 1 --> offset == repeat_offset_2
1039 * rep == 2 --> offset == repeat_offset_3
1040 * rep == 3 --> offset == repeat_offset_1 - 1
1041 *
1042 * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
1043 * 'rep', but repeat offsets do not necessarily need to be calculated from an external
1044 * sequence provider's perspective. For example, ZSTD_compressSequences() does not
1045 * use this 'rep' field at all (as of now).
1046 */
1047} ZSTD_Sequence;
1048</b></pre><BR>
1049<pre><b>typedef struct {
1050 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
1051 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
1052 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
1053 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
1054 unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
1055 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
1056 ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
1057} ZSTD_compressionParameters;
1058</b></pre><BR>
1059<pre><b>typedef struct {
1060 int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
1061 int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
1062 int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
1063} ZSTD_frameParameters;
1064</b></pre><BR>
1065<pre><b>typedef struct {
1066 ZSTD_compressionParameters cParams;
1067 ZSTD_frameParameters fParams;
1068} ZSTD_parameters;
1069</b></pre><BR>
1070<pre><b>typedef enum {
1071 ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
1072 ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
1073 ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
1074} ZSTD_dictContentType_e;
1075</b></pre><BR>
1076<pre><b>typedef enum {
1077 ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
1078 ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
1079} ZSTD_dictLoadMethod_e;
1080</b></pre><BR>
1081<pre><b>typedef enum {
1082 ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
1083 ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
1084 * Useful to save 4 bytes per generated frame.
1085 * Decoder cannot recognise automatically this format, requiring this instruction. */
1086} ZSTD_format_e;
1087</b></pre><BR>
1088<pre><b>typedef enum {
1089 </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
1090 ZSTD_d_validateChecksum = 0,
1091 ZSTD_d_ignoreChecksum = 1
1092} ZSTD_forceIgnoreChecksum_e;
1093</b></pre><BR>
1094<pre><b>typedef enum {
1095 </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
1096 ZSTD_rmd_refSingleDDict = 0,
1097 ZSTD_rmd_refMultipleDDicts = 1
1098} ZSTD_refMultipleDDicts_e;
1099</b></pre><BR>
1100<pre><b>typedef enum {
1101 </b>/* Note: this enum and the behavior it controls are effectively internal<b>
1102 * implementation details of the compressor. They are expected to continue
1103 * to evolve and should be considered only in the context of extremely
1104 * advanced performance tuning.
1105 *
1106 * Zstd currently supports the use of a CDict in three ways:
1107 *
1108 * - The contents of the CDict can be copied into the working context. This
1109 * means that the compression can search both the dictionary and input
1110 * while operating on a single set of internal tables. This makes
1111 * the compression faster per-byte of input. However, the initial copy of
1112 * the CDict's tables incurs a fixed cost at the beginning of the
1113 * compression. For small compressions (< 8 KB), that copy can dominate
1114 * the cost of the compression.
1115 *
1116 * - The CDict's tables can be used in-place. In this model, compression is
1117 * slower per input byte, because the compressor has to search two sets of
1118 * tables. However, this model incurs no start-up cost (as long as the
1119 * working context's tables can be reused). For small inputs, this can be
1120 * faster than copying the CDict's tables.
1121 *
1122 * - The CDict's tables are not used at all, and instead we use the working
1123 * context alone to reload the dictionary and use params based on the source
1124 * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1125 * This method is effective when the dictionary sizes are very small relative
1126 * to the input size, and the input size is fairly large to begin with.
1127 *
1128 * Zstd has a simple internal heuristic that selects which strategy to use
1129 * at the beginning of a compression. However, if experimentation shows that
1130 * Zstd is making poor choices, it is possible to override that choice with
1131 * this enum.
1132 */
1133 ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
1134 ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
1135 ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
1136 ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b>
1137} ZSTD_dictAttachPref_e;
1138</b></pre><BR>
1139<pre><b>typedef enum {
1140 ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b>
1141 * Negative compression levels will be uncompressed, and positive compression
1142 * levels will be compressed. */
1143 ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
1144 * emitted if Huffman compression is not profitable. */
1145 ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
1146} ZSTD_literalCompressionMode_e;
1147</b></pre><BR>
1148<pre><b>typedef enum {
1149 </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b>
1150 * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable
1151 * or ZSTD_ps_disable allow for a force enable/disable the feature.
1152 */
1153 ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b>
1154 ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b>
1155 ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b>
1156} ZSTD_paramSwitch_e;
1157</b></pre><BR>
1158<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre>
1159
1160<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1161</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1162 `srcSize` must be the _exact_ size of this series
1163 (i.e. there should be a frame boundary at `src + srcSize`)
1164 @return : - decompressed size of all data in all successive frames
1165 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1166 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1167
1168 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1169 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1170 In which case, it's necessary to use streaming mode to decompress data.
1171 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1172 note 3 : decompressed size can be very large (64-bits value),
1173 potentially larger than what local system can handle as a single memory segment.
1174 In which case, it's necessary to use streaming mode to decompress data.
1175 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1176 Always ensure result fits within application's authorized limits.
1177 Each application can set its own limits.
1178 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1179 read each contained frame header. This is fast as most of the data is skipped,
1180 however it does mean that all frame data must be present and valid.
1181</p></pre><BR>
1182
1183<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1184</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1185 `srcSize` must be the _exact_ size of this series
1186 (i.e. there should be a frame boundary at `src + srcSize`)
1187 @return : - upper-bound for the decompressed size of all data in all successive frames
1188 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1189
1190 note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1191 note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1192 in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1193 note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1194 upper-bound = # blocks * min(128 KB, Window_Size)
1195
1196</p></pre><BR>
1197
1198<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1199</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1200 @return : size of the Frame Header,
1201 or an error code (if srcSize is too small)
1202</p></pre><BR>
1203
1204<pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
1205</b></pre><BR>
1206<pre><b>typedef struct {
1207 unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
1208 unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
1209 unsigned blockSizeMax;
1210 ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
1211 unsigned headerSize;
1212 unsigned dictID;
1213 unsigned checksumFlag;
1214 unsigned _reserved1;
1215 unsigned _reserved2;
1216} ZSTD_frameHeader;
1217</b></pre><BR>
1218<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
1219</b>/*! ZSTD_getFrameHeader_advanced() :<b>
1220 * same as ZSTD_getFrameHeader(),
1221 * with added capability to select a format (like ZSTD_f_zstd1_magicless) */
1222ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
1223</b><p> decode Frame Header, or requires larger `srcSize`.
1224 @return : 0, `zfhPtr` is correctly filled,
1225 >0, `srcSize` is too small, value is wanted `srcSize` amount,
1226 or an error code, which can be tested using ZSTD_isError()
1227</p></pre><BR>
1228
1229<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize);
1230</b><p> Zstd supports in-place decompression, where the input and output buffers overlap.
1231 In this case, the output buffer must be at least (Margin + Output_Size) bytes large,
1232 and the input buffer must be at the end of the output buffer.
1233
1234 _______________________ Output Buffer ________________________
1235 | |
1236 | ____ Input Buffer ____|
1237 | | |
1238 v v v
1239 |---------------------------------------|-----------|----------|
1240 ^ ^ ^
1241 |___________________ Output_Size ___________________|_ Margin _|
1242
1243 NOTE: See also ZSTD_DECOMPRESSION_MARGIN().
1244 NOTE: This applies only to single-pass decompression through ZSTD_decompress() or
1245 ZSTD_decompressDCtx().
1246 NOTE: This function supports multi-frame input.
1247
1248 @param src The compressed frame(s)
1249 @param srcSize The size of the compressed frame(s)
1250 @returns The decompression margin or an error that can be checked with ZSTD_isError().
1251
1252</p></pre><BR>
1253
1254<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \
1255 ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b>
1256 4 </b>/* checksum */ + \<b>
1257 ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b>
1258 (blockSize) </b>/* One block of margin */ \<b>
1259 ))
1260</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from
1261 the compressed frame, compute it from the original size and the blockSizeLog.
1262 See ZSTD_decompressionMargin() for details.
1263
1264 WARNING: This macro does not support multi-frame input, the input must be a single
1265 zstd frame. If you need that support use the function, or implement it yourself.
1266
1267 @param originalSize The original uncompressed size of the data.
1268 @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX).
1269 Unless you explicitly set the windowLog smaller than
1270 ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX.
1271
1272</p></pre><BR>
1273
1274<pre><b>typedef enum {
1275 ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
1276 ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
1277} ZSTD_sequenceFormat_e;
1278</b></pre><BR>
1279<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize);
1280</b><p> `srcSize` : size of the input buffer
1281 @return : upper-bound for the number of sequences that can be generated
1282 from a buffer of srcSize bytes
1283
1284 note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence).
1285
1286</p></pre><BR>
1287
1288<pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer.
1289
1290 Each block will end with a dummy sequence
1291 with offset == 0, matchLength == 0, and litLength == length of last literals.
1292 litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
1293 simply acts as a block delimiter.
1294
1295 @zc can be used to insert custom compression params.
1296 This function invokes ZSTD_compress2().
1297
1298 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1299 setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
1300 @return : number of sequences generated
1301
1302</p></pre><BR>
1303
1304<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
1305</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
1306 by merging them into the literals of the next sequence.
1307
1308 As such, the final generated result has no explicit representation of block boundaries,
1309 and the final last literals segment is not represented in the sequences.
1310
1311 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1312 setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
1313 @return : number of sequences left after merging
1314
1315</p></pre><BR>
1316
1317<pre><b>ZSTDLIB_STATIC_API size_t
1318ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize,
1319 const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
1320 const void* src, size_t srcSize);
1321</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst.
1322 @src contains the entire input (not just the literals).
1323 If @srcSize > sum(sequence.length), the remaining bytes are considered all literals
1324 If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
1325 The entire source is compressed into a single frame.
1326
1327 The compression behavior changes based on cctx params. In particular:
1328 If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1329 no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
1330 the block size derived from the cctx, and sequences may be split. This is the default setting.
1331
1332 If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1333 block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
1334
1335 If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
1336 behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
1337 specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
1338
1339 In addition to the two adjustable experimental params, there are other important cctx params.
1340 - 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.
1341 - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
1342 - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
1343 is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
1344
1345 Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
1346 Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
1347 and cannot emit an RLE block that disagrees with the repcode history
1348 @return : final compressed size, or a ZSTD error code.
1349
1350</p></pre><BR>
1351
1352<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
1353 const void* src, size_t srcSize, unsigned magicVariant);
1354</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
1355
1356 Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number,
1357 ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
1358 As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
1359 the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
1360
1361 Returns an error if destination buffer is not large enough, if the source size is not representable
1362 with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
1363
1364 @return : number of bytes written or a ZSTD error.
1365
1366</p></pre><BR>
1367
1368<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
1369 const void* src, size_t srcSize);
1370</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
1371
1372 The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
1373 i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested
1374 in the magicVariant.
1375
1376 Returns an error if destination buffer is not large enough, or if the frame is not skippable.
1377
1378 @return : number of bytes written or a ZSTD error.
1379
1380</p></pre><BR>
1381
1382<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
1383</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
1384
1385</p></pre><BR>
1386
1387<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
1388
1389<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
1390ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1391ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1392ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void);
1393</b><p> These functions make it possible to estimate memory usage
1394 of a future {D,C}Ctx, before its creation.
1395
1396 ZSTD_estimateCCtxSize() will provide a memory budget large enough
1397 for any compression level up to selected one.
1398 Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
1399 does not include space for a window buffer.
1400 Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
1401 The estimate will assume the input may be arbitrarily large,
1402 which is the worst case.
1403
1404 When srcSize can be bound by a known and rather "small" value,
1405 this fact can be used to provide a tighter estimation
1406 because the CCtx compression context will need less memory.
1407 This tighter estimation can be provided by more advanced functions
1408 ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1409 and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1410 Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1411
1412 Note : only single-threaded compression is supported.
1413 ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1414
1415 Note 2 : ZSTD_estimateCCtxSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
1416 Size estimates assume that no external sequence producer is registered.
1417
1418</p></pre><BR>
1419
1420<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
1421ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1422ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1423ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
1424ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1425</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1426 It will also consider src size to be arbitrarily "large", which is worst case.
1427 If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1428 ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1429 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.
1430 Note : CStream size estimation is only correct for single-threaded compression.
1431 ZSTD_DStream memory budget depends on window Size.
1432 This information can be passed manually, using ZSTD_estimateDStreamSize,
1433 or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1434 Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1435 an internal ?Dict will be created, which additional size is not estimated here.
1436 In this case, get total size by adding ZSTD_estimate?DictSize
1437 Note 2 : only single-threaded compression is supported.
1438 ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1439 Note 3 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
1440 Size estimates assume that no external sequence producer is registered.
1441
1442</p></pre><BR>
1443
1444<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1445ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1446ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1447</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1448 ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1449 Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1450
1451</p></pre><BR>
1452
1453<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1454ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
1455</b><p> Initialize an object using a pre-allocated fixed-size buffer.
1456 workspace: The memory area to emplace the object into.
1457 Provided pointer *must be 8-bytes aligned*.
1458 Buffer must outlive object.
1459 workspaceSize: Use ZSTD_estimate*Size() to determine
1460 how large workspace must be to support target scenario.
1461 @return : pointer to object (same address as workspace, just different type),
1462 or NULL if error (size too small, incorrect alignment, etc.)
1463 Note : zstd will never resize nor malloc() when using a static buffer.
1464 If the object requires more memory than available,
1465 zstd will just error out (typically ZSTD_error_memory_allocation).
1466 Note 2 : there is no corresponding "free" function.
1467 Since workspace is allocated externally, it must be freed externally too.
1468 Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1469 into its associated cParams.
1470 Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1471 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1472 Limitation 2 : static cctx currently not compatible with multi-threading.
1473 Limitation 3 : static dctx is incompatible with legacy support.
1474
1475</p></pre><BR>
1476
1477<pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
1478</b></pre><BR>
1479<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1480typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
1481typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1482static
1483#ifdef __GNUC__
1484__attribute__((__unused__))
1485#endif
1486ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
1487</b><p> These prototypes make it possible to pass your own allocation/free functions.
1488 ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1489 All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1490
1491</p></pre><BR>
1492
1493<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool;
1494ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads);
1495ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b>
1496ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool);
1497</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts.
1498 This can limit resources for applications with multiple threads where each one uses
1499 a threaded compression mode (via ZSTD_c_nbWorkers parameter).
1500 ZSTD_createThreadPool creates a new thread pool with a given number of threads.
1501 Note that the lifetime of such pool must exist while being used.
1502 ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value
1503 to use an internal thread pool).
1504 ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer.
1505
1506</p></pre><BR>
1507
1508<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
1509
1510<pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1511</b><p> Create a digested dictionary for compression
1512 Dictionary content is just referenced, not duplicated.
1513 As a consequence, `dictBuffer` **must** outlive CDict,
1514 and its content must remain unmodified throughout the lifetime of CDict.
1515 note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
1516</p></pre><BR>
1517
1518<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1519</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1520 `estimatedSrcSize` value is optional, select 0 if not known
1521</p></pre><BR>
1522
1523<pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1524</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1525 All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
1526</p></pre><BR>
1527
1528<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1529</b><p> Ensure param values remain within authorized range.
1530 @return 0 on success, or an error code (can be checked with ZSTD_isError())
1531</p></pre><BR>
1532
1533<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1534</b><p> optimize params for a given `srcSize` and `dictSize`.
1535 `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1536 `dictSize` must be `0` when there is no dictionary.
1537 cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1538 This function never fails (wide contract)
1539</p></pre><BR>
1540
1541<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams);
1542</b><p> Set all parameters provided within @p cparams into the working @p cctx.
1543 Note : if modifying parameters during compression (MT mode only),
1544 note that changes to the .windowLog parameter will be ignored.
1545 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1546 On failure, no parameters are updated.
1547
1548</p></pre><BR>
1549
1550<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams);
1551</b><p> Set all parameters provided within @p fparams into the working @p cctx.
1552 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1553
1554</p></pre><BR>
1555
1556<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params);
1557</b><p> Set all parameters provided within @p params into the working @p cctx.
1558 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1559
1560</p></pre><BR>
1561
1562<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
1563ZSTDLIB_STATIC_API
1564size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1565 void* dst, size_t dstCapacity,
1566 const void* src, size_t srcSize,
1567 const void* dict,size_t dictSize,
1568 ZSTD_parameters params);
1569</b><p> Note : this function is now DEPRECATED.
1570 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1571 This prototype will generate compilation warnings.
1572</p></pre><BR>
1573
1574<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
1575ZSTDLIB_STATIC_API
1576size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1577 void* dst, size_t dstCapacity,
1578 const void* src, size_t srcSize,
1579 const ZSTD_CDict* cdict,
1580 ZSTD_frameParameters fParams);
1581</b><p> Note : this function is now DEPRECATED.
1582 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1583 This prototype will generate compilation warnings.
1584</p></pre><BR>
1585
1586<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1587</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1588 It saves some memory, but also requires that `dict` outlives its usage within `cctx`
1589</p></pre><BR>
1590
1591<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1592</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1593 how to load the dictionary (by copy ? by reference ?)
1594 and how to interpret it (automatic ? force raw mode ? full mode only ?)
1595</p></pre><BR>
1596
1597<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1598</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1599 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1600</p></pre><BR>
1601
1602<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1603</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1604 and store it into int* value.
1605 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1606
1607</p></pre><BR>
1608
1609<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1610ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
1611</b><p> Quick howto :
1612 - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1613 - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1614 an existing ZSTD_CCtx_params structure.
1615 This is similar to
1616 ZSTD_CCtx_setParameter().
1617 - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1618 an existing CCtx.
1619 These parameters will be applied to
1620 all subsequent frames.
1621 - ZSTD_compressStream2() : Do compression using the CCtx.
1622 - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
1623
1624 This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1625 for static allocation of CCtx for single-threaded compression.
1626
1627</p></pre><BR>
1628
1629<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1630</b><p> Reset params to default values.
1631
1632</p></pre><BR>
1633
1634<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1635</b><p> Initializes the compression parameters of cctxParams according to
1636 compression level. All other parameters are reset to their default values.
1637
1638</p></pre><BR>
1639
1640<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1641</b><p> Initializes the compression and frame parameters of cctxParams according to
1642 params. All other parameters are reset to their default values.
1643
1644</p></pre><BR>
1645
1646<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1647</b><p> Similar to ZSTD_CCtx_setParameter.
1648 Set one compression parameter, selected by enum ZSTD_cParameter.
1649 Parameters must be applied to a ZSTD_CCtx using
1650 ZSTD_CCtx_setParametersUsingCCtxParams().
1651 @result : a code representing success or failure (which can be tested with
1652 ZSTD_isError()).
1653
1654</p></pre><BR>
1655
1656<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1657</b><p> Similar to ZSTD_CCtx_getParameter.
1658 Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1659 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1660
1661</p></pre><BR>
1662
1663<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1664 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1665</b><p> Apply a set of ZSTD_CCtx_params to the compression context.
1666 This can be done even after compression is started,
1667 if nbWorkers==0, this will have no impact until a new compression is started.
1668 if nbWorkers>=1, new parameters will be picked up at next job,
1669 with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1670
1671</p></pre><BR>
1672
1673<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs (
1674 ZSTD_CCtx* cctx,
1675 void* dst, size_t dstCapacity, size_t* dstPos,
1676 const void* src, size_t srcSize, size_t* srcPos,
1677 ZSTD_EndDirective endOp);
1678</b><p> Same as ZSTD_compressStream2(),
1679 but using only integral types as arguments.
1680 This variant might be helpful for binders from dynamic languages
1681 which have troubles handling structures containing memory pointers.
1682
1683</p></pre><BR>
1684
1685<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
1686
1687<pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
1688</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
1689 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1690 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1691 Note 3 : Skippable Frame Identifiers are considered valid.
1692</p></pre><BR>
1693
1694<pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1695</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
1696 Dictionary content is referenced, and therefore stays in dictBuffer.
1697 It is important that dictBuffer outlives DDict,
1698 it must remain read accessible throughout the lifetime of DDict
1699</p></pre><BR>
1700
1701<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1702</b><p> Same as ZSTD_DCtx_loadDictionary(),
1703 but references `dict` content instead of copying it into `dctx`.
1704 This saves memory if `dict` remains around.,
1705 However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
1706</p></pre><BR>
1707
1708<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1709</b><p> Same as ZSTD_DCtx_loadDictionary(),
1710 but gives direct control over
1711 how to load the dictionary (by copy ? by reference ?)
1712 and how to interpret it (automatic ? force raw mode ? full mode only ?).
1713</p></pre><BR>
1714
1715<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1716</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1717 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1718</p></pre><BR>
1719
1720<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1721</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1722 This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1723 This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1724 By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1725 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1726
1727</p></pre><BR>
1728
1729<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
1730</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
1731 and store it into int* value.
1732 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1733
1734</p></pre><BR>
1735
1736<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
1737ZSTDLIB_STATIC_API
1738size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1739</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
1740 Instruct the decoder context about what kind of data to decode next.
1741 This instruction is mandatory to decode data without a fully-formed header,
1742 such ZSTD_f_zstd1_magicless for example.
1743 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1744</p></pre><BR>
1745
1746<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs (
1747 ZSTD_DCtx* dctx,
1748 void* dst, size_t dstCapacity, size_t* dstPos,
1749 const void* src, size_t srcSize, size_t* srcPos);
1750</b><p> Same as ZSTD_decompressStream(),
1751 but using only integral types as arguments.
1752 This can be helpful for binders from dynamic languages
1753 which have troubles handling structures containing memory pointers.
1754
1755</p></pre><BR>
1756
1757<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
1758 Once Advanced API reaches "stable" status,
1759 redundant functions will be deprecated, and then at some point removed.
1760<BR></pre>
1761
1762<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
1763<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1764ZSTDLIB_STATIC_API
1765size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
1766 int compressionLevel,
1767 unsigned long long pledgedSrcSize);
1768</b><p> This function is DEPRECATED, and equivalent to:
1769 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1770 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
1771 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1772 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1773
1774 pledgedSrcSize must be correct. If it is not known at init time, use
1775 ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
1776 "0" also disables frame content size field. It may be enabled in the future.
1777 This prototype will generate compilation warnings.
1778
1779</p></pre><BR>
1780
1781<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1782ZSTDLIB_STATIC_API
1783size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
1784 const void* dict, size_t dictSize,
1785 int compressionLevel);
1786</b><p> This function is DEPRECATED, and is equivalent to:
1787 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1788 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1789 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1790
1791 Creates of an internal CDict (incompatible with static CCtx), except if
1792 dict == NULL or dictSize < 8, in which case no dict is used.
1793 Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
1794 it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
1795 This prototype will generate compilation warnings.
1796
1797</p></pre><BR>
1798
1799<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1800ZSTDLIB_STATIC_API
1801size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
1802 const void* dict, size_t dictSize,
1803 ZSTD_parameters params,
1804 unsigned long long pledgedSrcSize);
1805</b><p> This function is DEPRECATED, and is equivalent to:
1806 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1807 ZSTD_CCtx_setParams(zcs, params);
1808 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1809 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1810
1811 dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
1812 pledgedSrcSize must be correct.
1813 If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
1814 This prototype will generate compilation warnings.
1815
1816</p></pre><BR>
1817
1818<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1819ZSTDLIB_STATIC_API
1820size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
1821</b><p> This function is DEPRECATED, and equivalent to:
1822 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1823 ZSTD_CCtx_refCDict(zcs, cdict);
1824
1825 note : cdict will just be referenced, and must outlive compression session
1826 This prototype will generate compilation warnings.
1827
1828</p></pre><BR>
1829
1830<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1831ZSTDLIB_STATIC_API
1832size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
1833 const ZSTD_CDict* cdict,
1834 ZSTD_frameParameters fParams,
1835 unsigned long long pledgedSrcSize);
1836</b><p> This function is DEPRECATED, and is equivalent to:
1837 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1838 ZSTD_CCtx_setFParams(zcs, fParams);
1839 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1840 ZSTD_CCtx_refCDict(zcs, cdict);
1841
1842 same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
1843 pledgedSrcSize must be correct. If srcSize is not known at init time, use
1844 value ZSTD_CONTENTSIZE_UNKNOWN.
1845 This prototype will generate compilation warnings.
1846
1847</p></pre><BR>
1848
1849<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1850ZSTDLIB_STATIC_API
1851size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1852</b><p> This function is DEPRECATED, and is equivalent to:
1853 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1854 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1855 Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
1856 ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
1857 explicitly specified.
1858
1859 start a new frame, using same parameters from previous frame.
1860 This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
1861 Note that zcs must be init at least once before using ZSTD_resetCStream().
1862 If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1863 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1864 For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1865 but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1866 @return : 0, or an error code (which can be tested using ZSTD_isError())
1867 This prototype will generate compilation warnings.
1868
1869</p></pre><BR>
1870
1871<pre><b>typedef struct {
1872 unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
1873 unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
1874 unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
1875 unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
1876 unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
1877 unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
1878} ZSTD_frameProgression;
1879</b></pre><BR>
1880<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1881</b><p> Tell how many bytes are ready to be flushed immediately.
1882 Useful for multithreading scenarios (nbWorkers >= 1).
1883 Probe the oldest active job, defined as oldest job not yet entirely flushed,
1884 and check its output buffer.
1885 @return : amount of data stored in oldest job and ready to be flushed immediately.
1886 if @return == 0, it means either :
1887 + there is no active job (could be checked with ZSTD_frameProgression()), or
1888 + oldest job is still actively compressing data,
1889 but everything it has produced has also been flushed so far,
1890 therefore flush speed is limited by production speed of oldest job
1891 irrespective of the speed of concurrent (and newer) jobs.
1892
1893</p></pre><BR>
1894
1895<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
1896<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions")
1897ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
1898</b><p>
1899 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1900 ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
1901
1902 note: no dictionary will be used if dict == NULL or dictSize < 8
1903
1904</p></pre><BR>
1905
1906<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions")
1907ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
1908</b><p>
1909 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1910 ZSTD_DCtx_refDDict(zds, ddict);
1911
1912 note : ddict is referenced, it must outlive decompression session
1913
1914</p></pre><BR>
1915
1916<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions")
1917ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
1918</b><p>
1919 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1920
1921 re-use decompression parameters from previous init; saves dictionary loading
1922
1923</p></pre><BR>
1924
1925<pre><b>ZSTDLIB_STATIC_API void
1926ZSTD_registerSequenceProducer(
1927 ZSTD_CCtx* cctx,
1928 void* sequenceProducerState,
1929 ZSTD_sequenceProducer_F* sequenceProducer
1930);
1931</b><p> Instruct zstd to use a block-level external sequence producer function.
1932
1933 The sequenceProducerState must be initialized by the caller, and the caller is
1934 responsible for managing its lifetime. This parameter is sticky across
1935 compressions. It will remain set until the user explicitly resets compression
1936 parameters.
1937
1938 Sequence producer registration is considered to be an "advanced parameter",
1939 part of the "advanced API". This means it will only have an effect on compression
1940 APIs which respect advanced parameters, such as compress2() and compressStream2().
1941 Older compression APIs such as compressCCtx(), which predate the introduction of
1942 "advanced parameters", will ignore any external sequence producer setting.
1943
1944 The sequence producer can be "cleared" by registering a NULL function pointer. This
1945 removes all limitations described above in the "LIMITATIONS" section of the API docs.
1946
1947 The user is strongly encouraged to read the full API documentation (above) before
1948 calling this function.
1949</p></pre><BR>
1950
1951<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre>
1952 This API is deprecated, and will be removed in a future version.
1953 It allows streaming (de)compression with user allocated buffers.
1954 However, it is hard to use, and not as well tested as the rest of
1955 our API.
1956
1957 Please use the normal streaming API instead: ZSTD_compressStream2,
1958 and ZSTD_decompressStream.
1959 If there is functionality that you need, but it doesn't provide,
1960 please open an issue on our GitHub.
1961
1962<BR></pre>
1963
1964<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
1965 A ZSTD_CCtx object is required to track streaming operations.
1966 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
1967 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
1968
1969 Start by initializing a context.
1970 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
1971
1972 Then, consume your input using ZSTD_compressContinue().
1973 There are some important considerations to keep in mind when using this advanced function :
1974 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
1975 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
1976 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
1977 Worst case evaluation is provided by ZSTD_compressBound().
1978 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
1979 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
1980 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
1981 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
1982 In which case, it will "discard" the relevant memory section from its history.
1983
1984 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
1985 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
1986 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
1987
1988 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
1989<BR></pre>
1990
1991<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
1992ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
1993ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
1994ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
1995ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
1996ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
1997</pre></b><BR>
1998<pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
1999</b></pre><BR>
2000<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>
2001</b></pre><BR>
2002<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
2003 A ZSTD_DCtx object is required to track streaming operations.
2004 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
2005 A ZSTD_DCtx object can be re-used multiple times.
2006
2007 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
2008 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
2009 Data fragment must be large enough to ensure successful decoding.
2010 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
2011 result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
2012 >0 : `srcSize` is too small, please provide at least result bytes on next attempt.
2013 errorCode, which can be tested using ZSTD_isError().
2014
2015 It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
2016 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
2017 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
2018 As a consequence, check that values remain within valid application range.
2019 For example, do not allocate memory blindly, check that `windowSize` is within expectation.
2020 Each application can set its own limits, depending on local restrictions.
2021 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
2022
2023 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
2024 ZSTD_decompressContinue() is very sensitive to contiguity,
2025 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
2026 or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
2027 There are multiple ways to guarantee this condition.
2028
2029 The most memory efficient way is to use a round buffer of sufficient size.
2030 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
2031 which can return an error code if required value is too large for current system (in 32-bits mode).
2032 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
2033 up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
2034 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
2035 At which point, decoding can resume from the beginning of the buffer.
2036 Note that already decoded data stored in the buffer should be flushed before being overwritten.
2037
2038 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
2039
2040 Finally, if you control the compression process, you can also ignore all buffer size rules,
2041 as long as the encoder and decoder progress in "lock-step",
2042 aka use exactly the same buffer sizes, break contiguity at the same place, etc.
2043
2044 Once buffers are setup, start decompression, with ZSTD_decompressBegin().
2045 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
2046
2047 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
2048 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
2049 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
2050
2051 result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
2052 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
2053 It can also be an error code, which can be tested with ZSTD_isError().
2054
2055 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
2056 Context can then be reset to start a new decompression.
2057
2058 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
2059 This information is not required to properly decode a frame.
2060
2061 == Special case : skippable frames
2062
2063 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
2064 Skippable frames will be ignored (skipped) by decompressor.
2065 The format of skippable frames is as follows :
2066 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
2067 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
2068 c) Frame Content - any content (User Data) of length equal to Frame Size
2069 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
2070 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
2071<BR></pre>
2072
2073<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
2074<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b>
2075</b></pre><BR>
2076<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
2077</b></pre><BR>
2078<a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre>
2079
2080<pre><b></b><p> You can get the frame header down to 2 bytes by setting:
2081 - ZSTD_c_format = ZSTD_f_zstd1_magicless
2082 - ZSTD_c_contentSizeFlag = 0
2083 - ZSTD_c_checksumFlag = 0
2084 - ZSTD_c_dictIDFlag = 0
2085
2086 This API is not as well tested as our normal API, so we recommend not using it.
2087 We will be removing it in a future version. If the normal API doesn't provide
2088 the functionality you need, please open a GitHub issue.
2089
2090 Block functions produce and decode raw zstd blocks, without frame metadata.
2091 Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
2092 But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
2093
2094 A few rules to respect :
2095 - Compressing and decompressing require a context structure
2096 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
2097 - It is necessary to init context before starting
2098 + compression : any ZSTD_compressBegin*() variant, including with dictionary
2099 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
2100 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
2101 + If input is larger than a block size, it's necessary to split input data into multiple blocks
2102 + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
2103 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
2104 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
2105 ===> In which case, nothing is produced into `dst` !
2106 + User __must__ test for such outcome and deal directly with uncompressed data
2107 + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
2108 Doing so would mess up with statistics history, leading to potential data corruption.
2109 + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
2110 + In case of multiple successive blocks, should some of them be uncompressed,
2111 decoder must be informed of their existence in order to follow proper history.
2112 Use ZSTD_insertBlock() for such a case.
2113</p></pre><BR>
2114
2115<h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2116ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
2117ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2118ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2119ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2120ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2121ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2122ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b>
2123</pre></b><BR>
2124</html>
2125</body>
ARM optimized PCSX fork