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f535537f 4<title>zstd 1.5.6 Manual</title>
648db22b 5</head>
6<body>
f535537f 7<h1>zstd 1.5.6 Manual</h1>
648db22b 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 */
f535537f 159#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00ULL : 0xFF00FF00U)
648db22b 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,
f535537f 177 and reuse it for each successive compression operation.
648db22b 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.
f535537f 193 Important : in order to mirror `ZSTD_compress()` behavior,
194 this function compresses at the requested compression level,
195 __ignoring any other advanced parameter__ .
648db22b 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,
f535537f 203 and reuse it for each successive compression operation.
648db22b 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.
f535537f 215 Compatible with sticky parameters (see below).
648db22b 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". */
f535537f 299
300 ZSTD_c_targetCBlockSize=130, </b>/* v1.5.6+<b>
301 * Attempts to fit compressed block size into approximatively targetCBlockSize.
302 * Bound by ZSTD_TARGETCBLOCKSIZE_MIN and ZSTD_TARGETCBLOCKSIZE_MAX.
303 * Note that it's not a guarantee, just a convergence target (default:0).
304 * No target when targetCBlockSize == 0.
305 * This is helpful in low bandwidth streaming environments to improve end-to-end latency,
306 * when a client can make use of partial documents (a prominent example being Chrome).
307 * Note: this parameter is stable since v1.5.6.
308 * It was present as an experimental parameter in earlier versions,
309 * but it's not recommended using it with earlier library versions
310 * due to massive performance regressions.
311 */
648db22b 312 </b>/* LDM mode parameters */<b>
313 ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
314 * This parameter is designed to improve compression ratio
315 * for large inputs, by finding large matches at long distance.
316 * It increases memory usage and window size.
317 * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
318 * except when expressly set to a different value.
319 * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
320 * compression strategy >= ZSTD_btopt (== compression level 16+) */
321 ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
322 * Larger values increase memory usage and compression ratio,
323 * but decrease compression speed.
324 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
325 * default: windowlog - 7.
326 * Special: value 0 means "automatically determine hashlog". */
327 ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
328 * Larger/too small values usually decrease compression ratio.
329 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
330 * Special: value 0 means "use default value" (default: 64). */
331 ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
332 * Larger values improve collision resolution but decrease compression speed.
333 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
334 * Special: value 0 means "use default value" (default: 3). */
335 ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
336 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
337 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
338 * Larger values improve compression speed.
339 * Deviating far from default value will likely result in a compression ratio decrease.
340 * Special: value 0 means "automatically determine hashRateLog". */
341
342 </b>/* frame parameters */<b>
343 ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
344 * Content size must be known at the beginning of compression.
345 * This is automatically the case when using ZSTD_compress2(),
346 * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
347 ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
348 ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
349
350 </b>/* multi-threading parameters */<b>
351 </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
352 * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
353 * In a situation where it's unknown if the linked library supports multi-threading or not,
354 * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
355 */
356 ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
357 * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
358 * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
359 * while compression is performed in parallel, within worker thread(s).
360 * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
361 * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
362 * More workers improve speed, but also increase memory usage.
363 * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
364 * compression is performed inside Caller's thread, and all invocations are blocking */
365 ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
366 * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
367 * 0 means default, which is dynamically determined based on compression parameters.
368 * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
369 * The minimum size is automatically and transparently enforced. */
370 ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
371 * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
372 * It helps preserve compression ratio, while each job is compressed in parallel.
373 * This value is enforced only when nbWorkers >= 1.
374 * Larger values increase compression ratio, but decrease speed.
375 * Possible values range from 0 to 9 :
376 * - 0 means "default" : value will be determined by the library, depending on strategy
377 * - 1 means "no overlap"
378 * - 9 means "full overlap", using a full window size.
379 * Each intermediate rank increases/decreases load size by a factor 2 :
380 * 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
381 * default value varies between 6 and 9, depending on strategy */
382
383 </b>/* note : additional experimental parameters are also available<b>
384 * within the experimental section of the API.
385 * At the time of this writing, they include :
386 * ZSTD_c_rsyncable
387 * ZSTD_c_format
388 * ZSTD_c_forceMaxWindow
389 * ZSTD_c_forceAttachDict
390 * ZSTD_c_literalCompressionMode
648db22b 391 * ZSTD_c_srcSizeHint
392 * ZSTD_c_enableDedicatedDictSearch
393 * ZSTD_c_stableInBuffer
394 * ZSTD_c_stableOutBuffer
395 * ZSTD_c_blockDelimiters
396 * ZSTD_c_validateSequences
397 * ZSTD_c_useBlockSplitter
398 * ZSTD_c_useRowMatchFinder
399 * ZSTD_c_prefetchCDictTables
400 * ZSTD_c_enableSeqProducerFallback
401 * ZSTD_c_maxBlockSize
402 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
403 * note : never ever use experimentalParam? names directly;
404 * also, the enums values themselves are unstable and can still change.
405 */
406 ZSTD_c_experimentalParam1=500,
407 ZSTD_c_experimentalParam2=10,
408 ZSTD_c_experimentalParam3=1000,
409 ZSTD_c_experimentalParam4=1001,
410 ZSTD_c_experimentalParam5=1002,
f535537f 411 </b>/* was ZSTD_c_experimentalParam6=1003; is now ZSTD_c_targetCBlockSize */<b>
648db22b 412 ZSTD_c_experimentalParam7=1004,
413 ZSTD_c_experimentalParam8=1005,
414 ZSTD_c_experimentalParam9=1006,
415 ZSTD_c_experimentalParam10=1007,
416 ZSTD_c_experimentalParam11=1008,
417 ZSTD_c_experimentalParam12=1009,
418 ZSTD_c_experimentalParam13=1010,
419 ZSTD_c_experimentalParam14=1011,
420 ZSTD_c_experimentalParam15=1012,
421 ZSTD_c_experimentalParam16=1013,
422 ZSTD_c_experimentalParam17=1014,
423 ZSTD_c_experimentalParam18=1015,
424 ZSTD_c_experimentalParam19=1016
425} ZSTD_cParameter;
426</b></pre><BR>
427<pre><b>typedef struct {
428 size_t error;
429 int lowerBound;
430 int upperBound;
431} ZSTD_bounds;
432</b></pre><BR>
433<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
434</b><p> All parameters must belong to an interval with lower and upper bounds,
435 otherwise they will either trigger an error or be automatically clamped.
436 @return : a structure, ZSTD_bounds, which contains
437 - an error status field, which must be tested using ZSTD_isError()
438 - lower and upper bounds, both inclusive
439
440</p></pre><BR>
441
442<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
443</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
444 All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
445 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
446 Setting a parameter is generally only possible during frame initialization (before starting compression).
447 Exception : when using multi-threading mode (nbWorkers >= 1),
448 the following parameters can be updated _during_ compression (within same frame):
449 => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
450 new parameters will be active for next job only (after a flush()).
451 @return : an error code (which can be tested using ZSTD_isError()).
452
453</p></pre><BR>
454
455<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
456</b><p> Total input data size to be compressed as a single frame.
457 Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
458 This value will also be controlled at end of frame, and trigger an error if not respected.
459 @result : 0, or an error code (which can be tested with ZSTD_isError()).
460 Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
461 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
462 ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
463 Note 2 : pledgedSrcSize is only valid once, for the next frame.
464 It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
465 Note 3 : Whenever all input data is provided and consumed in a single round,
466 for example with ZSTD_compress2(),
467 or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
468 this value is automatically overridden by srcSize instead.
469
470</p></pre><BR>
471
472<pre><b>typedef enum {
473 ZSTD_reset_session_only = 1,
474 ZSTD_reset_parameters = 2,
475 ZSTD_reset_session_and_parameters = 3
476} ZSTD_ResetDirective;
477</b></pre><BR>
478<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
479</b><p> There are 2 different things that can be reset, independently or jointly :
480 - The session : will stop compressing current frame, and make CCtx ready to start a new one.
481 Useful after an error, or to interrupt any ongoing compression.
482 Any internal data not yet flushed is cancelled.
483 Compression parameters and dictionary remain unchanged.
484 They will be used to compress next frame.
485 Resetting session never fails.
486 - The parameters : changes all parameters back to "default".
487 This also removes any reference to any dictionary or external sequence producer.
488 Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
489 otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
490 - Both : similar to resetting the session, followed by resetting parameters.
491
492</p></pre><BR>
493
494<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
495 void* dst, size_t dstCapacity,
496 const void* src, size_t srcSize);
497</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
f535537f 498 (note that this entry point doesn't even expose a compression level parameter).
648db22b 499 ZSTD_compress2() always starts a new frame.
500 Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
501 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
502 - The function is always blocking, returns when compression is completed.
503 NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
504 enough space to successfully compress the data, though it is possible it fails for other reasons.
505 @return : compressed size written into `dst` (<= `dstCapacity),
506 or an error code if it fails (which can be tested using ZSTD_isError()).
507
508</p></pre><BR>
509
510<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre>
511
512<pre><b>typedef enum {
513
514 ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
515 * the streaming API will refuse to allocate memory buffer
516 * in order to protect the host from unreasonable memory requirements.
517 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
518 * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
519 * Special: value 0 means "use default maximum windowLog". */
520
521 </b>/* note : additional experimental parameters are also available<b>
522 * within the experimental section of the API.
523 * At the time of this writing, they include :
524 * ZSTD_d_format
525 * ZSTD_d_stableOutBuffer
526 * ZSTD_d_forceIgnoreChecksum
527 * ZSTD_d_refMultipleDDicts
528 * ZSTD_d_disableHuffmanAssembly
f535537f 529 * ZSTD_d_maxBlockSize
648db22b 530 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
531 * note : never ever use experimentalParam? names directly
532 */
533 ZSTD_d_experimentalParam1=1000,
534 ZSTD_d_experimentalParam2=1001,
535 ZSTD_d_experimentalParam3=1002,
536 ZSTD_d_experimentalParam4=1003,
f535537f 537 ZSTD_d_experimentalParam5=1004,
538 ZSTD_d_experimentalParam6=1005
648db22b 539
540} ZSTD_dParameter;
541</b></pre><BR>
542<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
543</b><p> All parameters must belong to an interval with lower and upper bounds,
544 otherwise they will either trigger an error or be automatically clamped.
545 @return : a structure, ZSTD_bounds, which contains
546 - an error status field, which must be tested using ZSTD_isError()
547 - both lower and upper bounds, inclusive
548
549</p></pre><BR>
550
551<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
552</b><p> Set one compression parameter, selected by enum ZSTD_dParameter.
553 All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
554 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
555 Setting a parameter is only possible during frame initialization (before starting decompression).
556 @return : 0, or an error code (which can be tested using ZSTD_isError()).
557
558</p></pre><BR>
559
560<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
561</b><p> Return a DCtx to clean state.
562 Session and parameters can be reset jointly or separately.
563 Parameters can only be reset when no active frame is being decompressed.
564 @return : 0, or an error code, which can be tested with ZSTD_isError()
565
566</p></pre><BR>
567
568<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
569
570<pre><b>typedef struct ZSTD_inBuffer_s {
571 const void* src; </b>/**< start of input buffer */<b>
572 size_t size; </b>/**< size of input buffer */<b>
573 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
574} ZSTD_inBuffer;
575</b></pre><BR>
576<pre><b>typedef struct ZSTD_outBuffer_s {
577 void* dst; </b>/**< start of output buffer */<b>
578 size_t size; </b>/**< size of output buffer */<b>
579 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
580} ZSTD_outBuffer;
581</b></pre><BR>
582<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
583 A ZSTD_CStream object is required to track streaming operation.
584 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
585 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
f535537f 586 It is recommended to reuse ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
648db22b 587
588 For parallel execution, use one separate ZSTD_CStream per thread.
589
590 note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
591
592 Parameters are sticky : when starting a new compression on the same context,
f535537f 593 it will reuse the same sticky parameters as previous compression session.
648db22b 594 When in doubt, it's recommended to fully initialize the context before usage.
595 Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
596 ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
597 set more specific parameters, the pledged source size, or load a dictionary.
598
599 Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
600 consume input stream. The function will automatically update both `pos`
601 fields within `input` and `output`.
602 Note that the function may not consume the entire input, for example, because
603 the output buffer is already full, in which case `input.pos < input.size`.
604 The caller must check if input has been entirely consumed.
605 If not, the caller must make some room to receive more compressed data,
606 and then present again remaining input data.
607 note: ZSTD_e_continue is guaranteed to make some forward progress when called,
608 but doesn't guarantee maximal forward progress. This is especially relevant
609 when compressing with multiple threads. The call won't block if it can
610 consume some input, but if it can't it will wait for some, but not all,
611 output to be flushed.
612 @return : provides a minimum amount of data remaining to be flushed from internal buffers
613 or an error code, which can be tested using ZSTD_isError().
614
615 At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
616 using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
617 Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
618 In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
619 You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
620 operation.
621 note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
622 block until the flush is complete or the output buffer is full.
623 @return : 0 if internal buffers are entirely flushed,
624 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
625 or an error code, which can be tested using ZSTD_isError().
626
627 Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
628 It will perform a flush and write frame epilogue.
629 The epilogue is required for decoders to consider a frame completed.
630 flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
631 You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
632 start a new frame.
633 note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
634 block until the flush is complete or the output buffer is full.
635 @return : 0 if frame fully completed and fully flushed,
636 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
637 or an error code, which can be tested using ZSTD_isError().
638
639
640<BR></pre>
641
642<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
643</b></pre><BR>
644<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
645size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b>
646</pre></b><BR>
647<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
648 ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
649 ZSTD_e_flush=1, </b>/* flush any data provided so far,<b>
650 * it creates (at least) one new block, that can be decoded immediately on reception;
651 * frame will continue: any future data can still reference previously compressed data, improving compression.
652 * note : multithreaded compression will block to flush as much output as possible. */
653 ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b>
654 * note that frame is only closed after compressed data is fully flushed (return value == 0).
655 * After that point, any additional data starts a new frame.
656 * note : each frame is independent (does not reference any content from previous frame).
657 : note : multithreaded compression will block to flush as much output as possible. */
658} ZSTD_EndDirective;
659</pre></b><BR>
660<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
661 ZSTD_outBuffer* output,
662 ZSTD_inBuffer* input,
663 ZSTD_EndDirective endOp);
664</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive.
665 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
666 - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
667 - output->pos must be <= dstCapacity, input->pos must be <= srcSize
668 - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
669 - endOp must be a valid directive
670 - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
671 - 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,
672 and then immediately returns, just indicating that there is some data remaining to be flushed.
673 The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
674 - 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.
675 - @return provides a minimum amount of data remaining to be flushed from internal buffers
676 or an error code, which can be tested using ZSTD_isError().
677 if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
678 This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
679 For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
680 - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
681 only ZSTD_e_end or ZSTD_e_flush operations are allowed.
682 Before starting a new compression job, or changing compression parameters,
683 it is required to fully flush internal buffers.
f535537f 684 - note: if an operation ends with an error, it may leave @cctx in an undefined state.
685 Therefore, it's UB to invoke ZSTD_compressStream2() of ZSTD_compressStream() on such a state.
686 In order to be re-employed after an error, a state must be reset,
687 which can be done explicitly (ZSTD_CCtx_reset()),
688 or is sometimes implied by methods starting a new compression job (ZSTD_initCStream(), ZSTD_compressCCtx())
648db22b 689
690</p></pre><BR>
691
692<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
693</b></pre><BR>
694<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
695</b></pre><BR>
696<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
697</b>/*!<b>
698 * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
699 * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
700 * the next read size (if non-zero and not an error). ZSTD_compressStream2()
701 * returns the minimum nb of bytes left to flush (if non-zero and not an error).
702 */
703size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
704</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
705size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
706</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
707size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
708</b><p>
709 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
710 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
711 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
712
713 Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API
714 to compress with a dictionary.
715
716</p></pre><BR>
717
718<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
719 A ZSTD_DStream object is required to track streaming operations.
720 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
f535537f 721 ZSTD_DStream objects can be reused multiple times.
648db22b 722
723 Use ZSTD_initDStream() to start a new decompression operation.
724 @return : recommended first input size
725 Alternatively, use advanced API to set specific properties.
726
727 Use ZSTD_decompressStream() repetitively to consume your input.
728 The function will update both `pos` fields.
729 If `input.pos < input.size`, some input has not been consumed.
730 It's up to the caller to present again remaining data.
731 The function tries to flush all data decoded immediately, respecting output buffer size.
732 If `output.pos < output.size`, decoder has flushed everything it could.
733 But if `output.pos == output.size`, there might be some data left within internal buffers.,
734 In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
735 Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
736 @return : 0 when a frame is completely decoded and fully flushed,
737 or an error code, which can be tested using ZSTD_isError(),
738 or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
739 the return value is a suggested next input size (just a hint for better latency)
740 that will never request more than the remaining frame size.
741
742<BR></pre>
743
744<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
745</b></pre><BR>
746<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
747size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b>
748</pre></b><BR>
749<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
750<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds);
751</b><p> Initialize/reset DStream state for new decompression operation.
752 Call before new decompression operation using same DStream.
753
754 Note : This function is redundant with the advanced API and equivalent to:
755 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
756 ZSTD_DCtx_refDDict(zds, NULL);
757
758</p></pre><BR>
759
760<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
761</b><p> Streaming decompression function.
762 Call repetitively to consume full input updating it as necessary.
763 Function will update both input and output `pos` fields exposing current state via these fields:
764 - `input.pos < input.size`, some input remaining and caller should provide remaining input
765 on the next call.
766 - `output.pos < output.size`, decoder finished and flushed all remaining buffers.
767 - `output.pos == output.size`, potentially uncflushed data present in the internal buffers,
768 call ZSTD_decompressStream() again to flush remaining data to output.
769 Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX.
770
771 @return : 0 when a frame is completely decoded and fully flushed,
772 or an error code, which can be tested using ZSTD_isError(),
773 or any other value > 0, which means there is some decoding or flushing to do to complete current frame.
f535537f 774
775 Note: when an operation returns with an error code, the @zds state may be left in undefined state.
776 It's UB to invoke `ZSTD_decompressStream()` on such a state.
777 In order to re-use such a state, it must be first reset,
778 which can be done explicitly (`ZSTD_DCtx_reset()`),
779 or is implied for operations starting some new decompression job (`ZSTD_initDStream`, `ZSTD_decompressDCtx()`, `ZSTD_decompress_usingDict()`)
648db22b 780
781</p></pre><BR>
782
783<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
784</b></pre><BR>
785<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>
786</b></pre><BR>
787<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
788
789<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
790 void* dst, size_t dstCapacity,
791 const void* src, size_t srcSize,
792 const void* dict,size_t dictSize,
793 int compressionLevel);
794</b><p> Compression at an explicit compression level using a Dictionary.
795 A dictionary can be any arbitrary data segment (also called a prefix),
796 or a buffer with specified information (see zdict.h).
797 Note : This function loads the dictionary, resulting in significant startup delay.
798 It's intended for a dictionary used only once.
799 Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
800</p></pre><BR>
801
802<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
803 void* dst, size_t dstCapacity,
804 const void* src, size_t srcSize,
805 const void* dict,size_t dictSize);
806</b><p> Decompression using a known Dictionary.
807 Dictionary must be identical to the one used during compression.
808 Note : This function loads the dictionary, resulting in significant startup delay.
809 It's intended for a dictionary used only once.
810 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
811</p></pre><BR>
812
813<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
814
815<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
816 int compressionLevel);
817</b><p> When compressing multiple messages or blocks using the same dictionary,
818 it's recommended to digest the dictionary only once, since it's a costly operation.
819 ZSTD_createCDict() will create a state from digesting a dictionary.
820 The resulting state can be used for future compression operations with very limited startup cost.
821 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
822 @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
823 Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
824 Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
825 in which case the only thing that it transports is the @compressionLevel.
826 This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
827 expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
828</p></pre><BR>
829
830<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
831</b><p> Function frees memory allocated by ZSTD_createCDict().
832 If a NULL pointer is passed, no operation is performed.
833</p></pre><BR>
834
835<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
836 void* dst, size_t dstCapacity,
837 const void* src, size_t srcSize,
838 const ZSTD_CDict* cdict);
839</b><p> Compression using a digested Dictionary.
840 Recommended when same dictionary is used multiple times.
841 Note : compression level is _decided at dictionary creation time_,
842 and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
843</p></pre><BR>
844
845<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
846</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
847 dictBuffer can be released after DDict creation, as its content is copied inside DDict.
848</p></pre><BR>
849
850<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
851</b><p> Function frees memory allocated with ZSTD_createDDict()
852 If a NULL pointer is passed, no operation is performed.
853</p></pre><BR>
854
855<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
856 void* dst, size_t dstCapacity,
857 const void* src, size_t srcSize,
858 const ZSTD_DDict* ddict);
859</b><p> Decompression using a digested Dictionary.
860 Recommended when same dictionary is used multiple times.
861</p></pre><BR>
862
863<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
864
865<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
866</b><p> Provides the dictID stored within dictionary.
867 if @return == 0, the dictionary is not conformant with Zstandard specification.
868 It can still be loaded, but as a content-only dictionary.
869</p></pre><BR>
870
871<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
872</b><p> Provides the dictID of the dictionary loaded into `cdict`.
873 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
874 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
875</p></pre><BR>
876
877<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
878</b><p> Provides the dictID of the dictionary loaded into `ddict`.
879 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
880 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
881</p></pre><BR>
882
883<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
884</b><p> Provides the dictID required to decompressed the frame stored within `src`.
885 If @return == 0, the dictID could not be decoded.
886 This could for one of the following reasons :
887 - The frame does not require a dictionary to be decoded (most common case).
888 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information.
889 Note : this use case also happens when using a non-conformant dictionary.
890 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
891 - This is not a Zstandard frame.
892 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
893</p></pre><BR>
894
895<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre>
896 This API allows dictionaries to be used with ZSTD_compress2(),
897 ZSTD_compressStream2(), and ZSTD_decompressDCtx().
f535537f 898 Dictionaries are sticky, they remain valid when same context is reused,
648db22b 899 they only reset when the context is reset
900 with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters.
901 In contrast, Prefixes are single-use.
902<BR></pre>
903
904<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
905</b><p> Create an internal CDict from `dict` buffer.
906 Decompression will have to use same dictionary.
907 @result : 0, or an error code (which can be tested with ZSTD_isError()).
908 Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
909 meaning "return to no-dictionary mode".
910 Note 1 : Dictionary is sticky, it will be used for all future compressed frames,
911 until parameters are reset, a new dictionary is loaded, or the dictionary
912 is explicitly invalidated by loading a NULL dictionary.
913 Note 2 : Loading a dictionary involves building tables.
914 It's also a CPU consuming operation, with non-negligible impact on latency.
915 Tables are dependent on compression parameters, and for this reason,
916 compression parameters can no longer be changed after loading a dictionary.
917 Note 3 :`dict` content will be copied internally.
918 Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
919 In such a case, dictionary buffer must outlive its users.
920 Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
921 to precisely select how dictionary content must be interpreted.
922 Note 5 : This method does not benefit from LDM (long distance mode).
923 If you want to employ LDM on some large dictionary content,
924 prefer employing ZSTD_CCtx_refPrefix() described below.
925
926</p></pre><BR>
927
928<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
929</b><p> Reference a prepared dictionary, to be used for all future compressed frames.
930 Note that compression parameters are enforced from within CDict,
931 and supersede any compression parameter previously set within CCtx.
932 The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
933 The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
934 The dictionary will remain valid for future compressed frames using same CCtx.
935 @result : 0, or an error code (which can be tested with ZSTD_isError()).
936 Special : Referencing a NULL CDict means "return to no-dictionary mode".
937 Note 1 : Currently, only one dictionary can be managed.
938 Referencing a new dictionary effectively "discards" any previous one.
939 Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
940</p></pre><BR>
941
942<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
943 const void* prefix, size_t prefixSize);
944</b><p> Reference a prefix (single-usage dictionary) for next compressed frame.
945 A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
946 Decompression will need same prefix to properly regenerate data.
947 Compressing with a prefix is similar in outcome as performing a diff and compressing it,
948 but performs much faster, especially during decompression (compression speed is tunable with compression level).
949 This method is compatible with LDM (long distance mode).
950 @result : 0, or an error code (which can be tested with ZSTD_isError()).
951 Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
952 Note 1 : Prefix buffer is referenced. It **must** outlive compression.
953 Its content must remain unmodified during compression.
954 Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
955 ensure that the window size is large enough to contain the entire source.
956 See ZSTD_c_windowLog.
957 Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
958 It's a CPU consuming operation, with non-negligible impact on latency.
959 If there is a need to use the same prefix multiple times, consider loadDictionary instead.
960 Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
961 Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
962</p></pre><BR>
963
964<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
965</b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames.
966 The dictionary remains valid for all future frames, until explicitly invalidated, or
967 a new dictionary is loaded.
968 @result : 0, or an error code (which can be tested with ZSTD_isError()).
969 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
970 meaning "return to no-dictionary mode".
971 Note 1 : Loading a dictionary involves building tables,
972 which has a non-negligible impact on CPU usage and latency.
973 It's recommended to "load once, use many times", to amortize the cost
974 Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
975 Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
976 Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
977 how dictionary content is loaded and interpreted.
978
979</p></pre><BR>
980
981<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
982</b><p> Reference a prepared dictionary, to be used to decompress next frames.
983 The dictionary remains active for decompression of future frames using same DCtx.
984
985 If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
986 will store the DDict references in a table, and the DDict used for decompression
987 will be determined at decompression time, as per the dict ID in the frame.
988 The memory for the table is allocated on the first call to refDDict, and can be
989 freed with ZSTD_freeDCtx().
990
991 If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary
992 will be managed, and referencing a dictionary effectively "discards" any previous one.
993
994 @result : 0, or an error code (which can be tested with ZSTD_isError()).
995 Special: referencing a NULL DDict means "return to no-dictionary mode".
996 Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
997
998</p></pre><BR>
999
1000<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
1001 const void* prefix, size_t prefixSize);
1002</b><p> Reference a prefix (single-usage dictionary) to decompress next frame.
1003 This is the reverse operation of ZSTD_CCtx_refPrefix(),
1004 and must use the same prefix as the one used during compression.
1005 Prefix is **only used once**. Reference is discarded at end of frame.
1006 End of frame is reached when ZSTD_decompressStream() returns 0.
1007 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1008 Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
1009 Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
1010 Prefix buffer must remain unmodified up to the end of frame,
1011 reached when ZSTD_decompressStream() returns 0.
1012 Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
1013 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
1014 Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
1015 A full dictionary is more costly, as it requires building tables.
1016
1017</p></pre><BR>
1018
1019<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
1020size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
1021size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
1022size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
1023size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
1024size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
1025</b><p> These functions give the _current_ memory usage of selected object.
1026 Note that object memory usage can evolve (increase or decrease) over time.
1027</p></pre><BR>
1028
1029<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
1030 The following symbols and constants
1031 are not planned to join "stable API" status in the near future.
1032 They can still change in future versions.
1033 Some of them are planned to remain in the static_only section indefinitely.
1034 Some of them might be removed in the future (especially when redundant with existing stable functions)
1035
1036<BR></pre>
1037
1038<pre><b>typedef struct {
1039 unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
1040 * If offset == 0 and matchLength == 0, this sequence represents the last
1041 * literals in the block of litLength size.
1042 */
1043
1044 unsigned int litLength; </b>/* Literal length of the sequence. */<b>
1045 unsigned int matchLength; </b>/* Match length of the sequence. */<b>
1046
1047 </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
1048 * In this case, we will treat the sequence as a marker for a block boundary.
1049 */
1050
1051 unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
1052 * Ranges from [0, 3].
1053 *
1054 * Repeat offsets are essentially previous offsets from previous sequences sorted in
1055 * recency order. For more detail, see doc/zstd_compression_format.md
1056 *
1057 * If rep == 0, then 'offset' does not contain a repeat offset.
1058 * If rep > 0:
1059 * If litLength != 0:
1060 * rep == 1 --> offset == repeat_offset_1
1061 * rep == 2 --> offset == repeat_offset_2
1062 * rep == 3 --> offset == repeat_offset_3
1063 * If litLength == 0:
1064 * rep == 1 --> offset == repeat_offset_2
1065 * rep == 2 --> offset == repeat_offset_3
1066 * rep == 3 --> offset == repeat_offset_1 - 1
1067 *
1068 * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
1069 * 'rep', but repeat offsets do not necessarily need to be calculated from an external
1070 * sequence provider's perspective. For example, ZSTD_compressSequences() does not
1071 * use this 'rep' field at all (as of now).
1072 */
1073} ZSTD_Sequence;
1074</b></pre><BR>
1075<pre><b>typedef struct {
1076 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
1077 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
1078 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
1079 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
1080 unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
1081 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
1082 ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
1083} ZSTD_compressionParameters;
1084</b></pre><BR>
1085<pre><b>typedef struct {
1086 int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
1087 int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
1088 int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
1089} ZSTD_frameParameters;
1090</b></pre><BR>
1091<pre><b>typedef struct {
1092 ZSTD_compressionParameters cParams;
1093 ZSTD_frameParameters fParams;
1094} ZSTD_parameters;
1095</b></pre><BR>
1096<pre><b>typedef enum {
1097 ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
1098 ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
1099 ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
1100} ZSTD_dictContentType_e;
1101</b></pre><BR>
1102<pre><b>typedef enum {
1103 ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
1104 ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
1105} ZSTD_dictLoadMethod_e;
1106</b></pre><BR>
1107<pre><b>typedef enum {
1108 ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
1109 ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
1110 * Useful to save 4 bytes per generated frame.
1111 * Decoder cannot recognise automatically this format, requiring this instruction. */
1112} ZSTD_format_e;
1113</b></pre><BR>
1114<pre><b>typedef enum {
1115 </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
1116 ZSTD_d_validateChecksum = 0,
1117 ZSTD_d_ignoreChecksum = 1
1118} ZSTD_forceIgnoreChecksum_e;
1119</b></pre><BR>
1120<pre><b>typedef enum {
1121 </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
1122 ZSTD_rmd_refSingleDDict = 0,
1123 ZSTD_rmd_refMultipleDDicts = 1
1124} ZSTD_refMultipleDDicts_e;
1125</b></pre><BR>
1126<pre><b>typedef enum {
1127 </b>/* Note: this enum and the behavior it controls are effectively internal<b>
1128 * implementation details of the compressor. They are expected to continue
1129 * to evolve and should be considered only in the context of extremely
1130 * advanced performance tuning.
1131 *
1132 * Zstd currently supports the use of a CDict in three ways:
1133 *
1134 * - The contents of the CDict can be copied into the working context. This
1135 * means that the compression can search both the dictionary and input
1136 * while operating on a single set of internal tables. This makes
1137 * the compression faster per-byte of input. However, the initial copy of
1138 * the CDict's tables incurs a fixed cost at the beginning of the
1139 * compression. For small compressions (< 8 KB), that copy can dominate
1140 * the cost of the compression.
1141 *
1142 * - The CDict's tables can be used in-place. In this model, compression is
1143 * slower per input byte, because the compressor has to search two sets of
1144 * tables. However, this model incurs no start-up cost (as long as the
1145 * working context's tables can be reused). For small inputs, this can be
1146 * faster than copying the CDict's tables.
1147 *
1148 * - The CDict's tables are not used at all, and instead we use the working
1149 * context alone to reload the dictionary and use params based on the source
1150 * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1151 * This method is effective when the dictionary sizes are very small relative
1152 * to the input size, and the input size is fairly large to begin with.
1153 *
1154 * Zstd has a simple internal heuristic that selects which strategy to use
1155 * at the beginning of a compression. However, if experimentation shows that
1156 * Zstd is making poor choices, it is possible to override that choice with
1157 * this enum.
1158 */
1159 ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
1160 ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
1161 ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
1162 ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b>
1163} ZSTD_dictAttachPref_e;
1164</b></pre><BR>
1165<pre><b>typedef enum {
1166 ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b>
1167 * Negative compression levels will be uncompressed, and positive compression
1168 * levels will be compressed. */
1169 ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
1170 * emitted if Huffman compression is not profitable. */
1171 ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
1172} ZSTD_literalCompressionMode_e;
1173</b></pre><BR>
1174<pre><b>typedef enum {
1175 </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b>
1176 * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable
1177 * or ZSTD_ps_disable allow for a force enable/disable the feature.
1178 */
1179 ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b>
1180 ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b>
1181 ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b>
1182} ZSTD_paramSwitch_e;
1183</b></pre><BR>
1184<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre>
1185
1186<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1187</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1188 `srcSize` must be the _exact_ size of this series
1189 (i.e. there should be a frame boundary at `src + srcSize`)
1190 @return : - decompressed size of all data in all successive frames
1191 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1192 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1193
1194 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1195 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1196 In which case, it's necessary to use streaming mode to decompress data.
1197 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1198 note 3 : decompressed size can be very large (64-bits value),
1199 potentially larger than what local system can handle as a single memory segment.
1200 In which case, it's necessary to use streaming mode to decompress data.
1201 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1202 Always ensure result fits within application's authorized limits.
1203 Each application can set its own limits.
1204 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1205 read each contained frame header. This is fast as most of the data is skipped,
1206 however it does mean that all frame data must be present and valid.
1207</p></pre><BR>
1208
1209<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1210</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1211 `srcSize` must be the _exact_ size of this series
1212 (i.e. there should be a frame boundary at `src + srcSize`)
1213 @return : - upper-bound for the decompressed size of all data in all successive frames
1214 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1215
1216 note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1217 note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1218 in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1219 note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1220 upper-bound = # blocks * min(128 KB, Window_Size)
1221
1222</p></pre><BR>
1223
1224<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1225</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1226 @return : size of the Frame Header,
1227 or an error code (if srcSize is too small)
1228</p></pre><BR>
1229
1230<pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
1231</b></pre><BR>
1232<pre><b>typedef struct {
1233 unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
1234 unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
1235 unsigned blockSizeMax;
1236 ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
1237 unsigned headerSize;
1238 unsigned dictID;
1239 unsigned checksumFlag;
1240 unsigned _reserved1;
1241 unsigned _reserved2;
1242} ZSTD_frameHeader;
1243</b></pre><BR>
1244<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
1245</b>/*! ZSTD_getFrameHeader_advanced() :<b>
1246 * same as ZSTD_getFrameHeader(),
1247 * with added capability to select a format (like ZSTD_f_zstd1_magicless) */
1248ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
1249</b><p> decode Frame Header, or requires larger `srcSize`.
1250 @return : 0, `zfhPtr` is correctly filled,
1251 >0, `srcSize` is too small, value is wanted `srcSize` amount,
1252 or an error code, which can be tested using ZSTD_isError()
1253</p></pre><BR>
1254
1255<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize);
1256</b><p> Zstd supports in-place decompression, where the input and output buffers overlap.
1257 In this case, the output buffer must be at least (Margin + Output_Size) bytes large,
1258 and the input buffer must be at the end of the output buffer.
1259
1260 _______________________ Output Buffer ________________________
1261 | |
1262 | ____ Input Buffer ____|
1263 | | |
1264 v v v
1265 |---------------------------------------|-----------|----------|
1266 ^ ^ ^
1267 |___________________ Output_Size ___________________|_ Margin _|
1268
1269 NOTE: See also ZSTD_DECOMPRESSION_MARGIN().
1270 NOTE: This applies only to single-pass decompression through ZSTD_decompress() or
1271 ZSTD_decompressDCtx().
1272 NOTE: This function supports multi-frame input.
1273
1274 @param src The compressed frame(s)
1275 @param srcSize The size of the compressed frame(s)
1276 @returns The decompression margin or an error that can be checked with ZSTD_isError().
1277
1278</p></pre><BR>
1279
1280<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \
1281 ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b>
1282 4 </b>/* checksum */ + \<b>
1283 ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b>
1284 (blockSize) </b>/* One block of margin */ \<b>
1285 ))
1286</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from
1287 the compressed frame, compute it from the original size and the blockSizeLog.
1288 See ZSTD_decompressionMargin() for details.
1289
1290 WARNING: This macro does not support multi-frame input, the input must be a single
1291 zstd frame. If you need that support use the function, or implement it yourself.
1292
1293 @param originalSize The original uncompressed size of the data.
1294 @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX).
1295 Unless you explicitly set the windowLog smaller than
1296 ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX.
1297
1298</p></pre><BR>
1299
1300<pre><b>typedef enum {
1301 ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
1302 ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
1303} ZSTD_sequenceFormat_e;
1304</b></pre><BR>
1305<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize);
1306</b><p> `srcSize` : size of the input buffer
1307 @return : upper-bound for the number of sequences that can be generated
1308 from a buffer of srcSize bytes
1309
1310 note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence).
1311
1312</p></pre><BR>
1313
1314<pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer.
1315
1316 Each block will end with a dummy sequence
1317 with offset == 0, matchLength == 0, and litLength == length of last literals.
1318 litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
1319 simply acts as a block delimiter.
1320
1321 @zc can be used to insert custom compression params.
1322 This function invokes ZSTD_compress2().
1323
1324 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1325 setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
1326 @return : number of sequences generated
1327
1328</p></pre><BR>
1329
1330<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
1331</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
1332 by merging them into the literals of the next sequence.
1333
1334 As such, the final generated result has no explicit representation of block boundaries,
1335 and the final last literals segment is not represented in the sequences.
1336
1337 The output of this function can be fed into ZSTD_compressSequences() with CCtx
1338 setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
1339 @return : number of sequences left after merging
1340
1341</p></pre><BR>
1342
1343<pre><b>ZSTDLIB_STATIC_API size_t
1344ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize,
1345 const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
1346 const void* src, size_t srcSize);
1347</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst.
1348 @src contains the entire input (not just the literals).
1349 If @srcSize > sum(sequence.length), the remaining bytes are considered all literals
1350 If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
1351 The entire source is compressed into a single frame.
1352
1353 The compression behavior changes based on cctx params. In particular:
1354 If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1355 no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
1356 the block size derived from the cctx, and sequences may be split. This is the default setting.
1357
1358 If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1359 block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
1360
1361 If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
1362 behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
1363 specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
1364
1365 In addition to the two adjustable experimental params, there are other important cctx params.
1366 - 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.
1367 - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
1368 - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
1369 is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
1370
1371 Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
1372 Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
1373 and cannot emit an RLE block that disagrees with the repcode history
1374 @return : final compressed size, or a ZSTD error code.
1375
1376</p></pre><BR>
1377
1378<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
1379 const void* src, size_t srcSize, unsigned magicVariant);
1380</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
1381
1382 Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number,
1383 ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
1384 As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
1385 the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
1386
1387 Returns an error if destination buffer is not large enough, if the source size is not representable
1388 with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
1389
1390 @return : number of bytes written or a ZSTD error.
1391
1392</p></pre><BR>
1393
1394<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
1395 const void* src, size_t srcSize);
1396</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
1397
1398 The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
1399 i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested
1400 in the magicVariant.
1401
1402 Returns an error if destination buffer is not large enough, or if the frame is not skippable.
1403
1404 @return : number of bytes written or a ZSTD error.
1405
1406</p></pre><BR>
1407
1408<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
1409</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
1410
1411</p></pre><BR>
1412
1413<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
1414
f535537f 1415<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int maxCompressionLevel);
648db22b 1416ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1417ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1418ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void);
1419</b><p> These functions make it possible to estimate memory usage
1420 of a future {D,C}Ctx, before its creation.
f535537f 1421 This is useful in combination with ZSTD_initStatic(),
1422 which makes it possible to employ a static buffer for ZSTD_CCtx* state.
648db22b 1423
1424 ZSTD_estimateCCtxSize() will provide a memory budget large enough
f535537f 1425 to compress data of any size using one-shot compression ZSTD_compressCCtx() or ZSTD_compress2()
1426 associated with any compression level up to max specified one.
648db22b 1427 The estimate will assume the input may be arbitrarily large,
1428 which is the worst case.
1429
f535537f 1430 Note that the size estimation is specific for one-shot compression,
1431 it is not valid for streaming (see ZSTD_estimateCStreamSize*())
1432 nor other potential ways of using a ZSTD_CCtx* state.
1433
648db22b 1434 When srcSize can be bound by a known and rather "small" value,
f535537f 1435 this knowledge can be used to provide a tighter budget estimation
1436 because the ZSTD_CCtx* state will need less memory for small inputs.
1437 This tighter estimation can be provided by employing more advanced functions
648db22b 1438 ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1439 and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1440 Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1441
1442 Note : only single-threaded compression is supported.
1443 ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
648db22b 1444
1445</p></pre><BR>
1446
f535537f 1447<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int maxCompressionLevel);
648db22b 1448ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1449ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
f535537f 1450ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t maxWindowSize);
648db22b 1451ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
f535537f 1452</b><p> ZSTD_estimateCStreamSize() will provide a memory budget large enough for streaming compression
1453 using any compression level up to the max specified one.
1454 It will also consider src size to be arbitrarily "large", which is a worst case scenario.
648db22b 1455 If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1456 ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1457 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.
1458 Note : CStream size estimation is only correct for single-threaded compression.
f535537f 1459 ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1460 Note 2 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
1461 Size estimates assume that no external sequence producer is registered.
1462
1463 ZSTD_DStream memory budget depends on frame's window Size.
648db22b 1464 This information can be passed manually, using ZSTD_estimateDStreamSize,
1465 or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
f535537f 1466 Any frame requesting a window size larger than max specified one will be rejected.
648db22b 1467 Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1468 an internal ?Dict will be created, which additional size is not estimated here.
1469 In this case, get total size by adding ZSTD_estimate?DictSize
648db22b 1470
1471</p></pre><BR>
1472
1473<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1474ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1475ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1476</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1477 ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1478 Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1479
1480</p></pre><BR>
1481
1482<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1483ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
1484</b><p> Initialize an object using a pre-allocated fixed-size buffer.
1485 workspace: The memory area to emplace the object into.
1486 Provided pointer *must be 8-bytes aligned*.
1487 Buffer must outlive object.
1488 workspaceSize: Use ZSTD_estimate*Size() to determine
1489 how large workspace must be to support target scenario.
1490 @return : pointer to object (same address as workspace, just different type),
1491 or NULL if error (size too small, incorrect alignment, etc.)
1492 Note : zstd will never resize nor malloc() when using a static buffer.
1493 If the object requires more memory than available,
1494 zstd will just error out (typically ZSTD_error_memory_allocation).
1495 Note 2 : there is no corresponding "free" function.
1496 Since workspace is allocated externally, it must be freed externally too.
1497 Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1498 into its associated cParams.
1499 Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1500 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1501 Limitation 2 : static cctx currently not compatible with multi-threading.
1502 Limitation 3 : static dctx is incompatible with legacy support.
1503
1504</p></pre><BR>
1505
1506<pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
1507</b></pre><BR>
1508<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1509typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
1510typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1511static
1512#ifdef __GNUC__
1513__attribute__((__unused__))
1514#endif
1515ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
1516</b><p> These prototypes make it possible to pass your own allocation/free functions.
1517 ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1518 All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1519
1520</p></pre><BR>
1521
1522<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool;
1523ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads);
1524ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b>
1525ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool);
1526</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts.
1527 This can limit resources for applications with multiple threads where each one uses
1528 a threaded compression mode (via ZSTD_c_nbWorkers parameter).
1529 ZSTD_createThreadPool creates a new thread pool with a given number of threads.
1530 Note that the lifetime of such pool must exist while being used.
1531 ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value
1532 to use an internal thread pool).
1533 ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer.
1534
1535</p></pre><BR>
1536
1537<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
1538
1539<pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1540</b><p> Create a digested dictionary for compression
1541 Dictionary content is just referenced, not duplicated.
1542 As a consequence, `dictBuffer` **must** outlive CDict,
1543 and its content must remain unmodified throughout the lifetime of CDict.
1544 note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
1545</p></pre><BR>
1546
1547<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1548</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1549 `estimatedSrcSize` value is optional, select 0 if not known
1550</p></pre><BR>
1551
1552<pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1553</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1554 All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
1555</p></pre><BR>
1556
1557<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1558</b><p> Ensure param values remain within authorized range.
1559 @return 0 on success, or an error code (can be checked with ZSTD_isError())
1560</p></pre><BR>
1561
1562<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1563</b><p> optimize params for a given `srcSize` and `dictSize`.
1564 `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1565 `dictSize` must be `0` when there is no dictionary.
1566 cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1567 This function never fails (wide contract)
1568</p></pre><BR>
1569
1570<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams);
1571</b><p> Set all parameters provided within @p cparams into the working @p cctx.
1572 Note : if modifying parameters during compression (MT mode only),
1573 note that changes to the .windowLog parameter will be ignored.
1574 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1575 On failure, no parameters are updated.
1576
1577</p></pre><BR>
1578
1579<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams);
1580</b><p> Set all parameters provided within @p fparams into the working @p cctx.
1581 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1582
1583</p></pre><BR>
1584
1585<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params);
1586</b><p> Set all parameters provided within @p params into the working @p cctx.
1587 @return 0 on success, or an error code (can be checked with ZSTD_isError()).
1588
1589</p></pre><BR>
1590
1591<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
1592ZSTDLIB_STATIC_API
1593size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1594 void* dst, size_t dstCapacity,
1595 const void* src, size_t srcSize,
1596 const void* dict,size_t dictSize,
1597 ZSTD_parameters params);
1598</b><p> Note : this function is now DEPRECATED.
1599 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1600 This prototype will generate compilation warnings.
1601</p></pre><BR>
1602
1603<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
1604ZSTDLIB_STATIC_API
1605size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1606 void* dst, size_t dstCapacity,
1607 const void* src, size_t srcSize,
1608 const ZSTD_CDict* cdict,
1609 ZSTD_frameParameters fParams);
1610</b><p> Note : this function is now DEPRECATED.
1611 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1612 This prototype will generate compilation warnings.
1613</p></pre><BR>
1614
1615<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1616</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1617 It saves some memory, but also requires that `dict` outlives its usage within `cctx`
1618</p></pre><BR>
1619
1620<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);
1621</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1622 how to load the dictionary (by copy ? by reference ?)
1623 and how to interpret it (automatic ? force raw mode ? full mode only ?)
1624</p></pre><BR>
1625
1626<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1627</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1628 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1629</p></pre><BR>
1630
1631<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1632</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1633 and store it into int* value.
1634 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1635
1636</p></pre><BR>
1637
1638<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1639ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
1640</b><p> Quick howto :
1641 - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1642 - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1643 an existing ZSTD_CCtx_params structure.
1644 This is similar to
1645 ZSTD_CCtx_setParameter().
1646 - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1647 an existing CCtx.
1648 These parameters will be applied to
1649 all subsequent frames.
1650 - ZSTD_compressStream2() : Do compression using the CCtx.
1651 - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
1652
1653 This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1654 for static allocation of CCtx for single-threaded compression.
1655
1656</p></pre><BR>
1657
1658<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1659</b><p> Reset params to default values.
1660
1661</p></pre><BR>
1662
1663<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1664</b><p> Initializes the compression parameters of cctxParams according to
1665 compression level. All other parameters are reset to their default values.
1666
1667</p></pre><BR>
1668
1669<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1670</b><p> Initializes the compression and frame parameters of cctxParams according to
1671 params. All other parameters are reset to their default values.
1672
1673</p></pre><BR>
1674
1675<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1676</b><p> Similar to ZSTD_CCtx_setParameter.
1677 Set one compression parameter, selected by enum ZSTD_cParameter.
1678 Parameters must be applied to a ZSTD_CCtx using
1679 ZSTD_CCtx_setParametersUsingCCtxParams().
1680 @result : a code representing success or failure (which can be tested with
1681 ZSTD_isError()).
1682
1683</p></pre><BR>
1684
1685<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1686</b><p> Similar to ZSTD_CCtx_getParameter.
1687 Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1688 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1689
1690</p></pre><BR>
1691
1692<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1693 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1694</b><p> Apply a set of ZSTD_CCtx_params to the compression context.
1695 This can be done even after compression is started,
1696 if nbWorkers==0, this will have no impact until a new compression is started.
1697 if nbWorkers>=1, new parameters will be picked up at next job,
1698 with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1699
1700</p></pre><BR>
1701
1702<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs (
1703 ZSTD_CCtx* cctx,
1704 void* dst, size_t dstCapacity, size_t* dstPos,
1705 const void* src, size_t srcSize, size_t* srcPos,
1706 ZSTD_EndDirective endOp);
1707</b><p> Same as ZSTD_compressStream2(),
1708 but using only integral types as arguments.
1709 This variant might be helpful for binders from dynamic languages
1710 which have troubles handling structures containing memory pointers.
1711
1712</p></pre><BR>
1713
1714<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
1715
1716<pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
1717</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
1718 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1719 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1720 Note 3 : Skippable Frame Identifiers are considered valid.
1721</p></pre><BR>
1722
1723<pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1724</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
1725 Dictionary content is referenced, and therefore stays in dictBuffer.
1726 It is important that dictBuffer outlives DDict,
1727 it must remain read accessible throughout the lifetime of DDict
1728</p></pre><BR>
1729
1730<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1731</b><p> Same as ZSTD_DCtx_loadDictionary(),
1732 but references `dict` content instead of copying it into `dctx`.
1733 This saves memory if `dict` remains around.,
1734 However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
1735</p></pre><BR>
1736
1737<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);
1738</b><p> Same as ZSTD_DCtx_loadDictionary(),
1739 but gives direct control over
1740 how to load the dictionary (by copy ? by reference ?)
1741 and how to interpret it (automatic ? force raw mode ? full mode only ?).
1742</p></pre><BR>
1743
1744<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1745</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1746 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1747</p></pre><BR>
1748
1749<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1750</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1751 This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1752 This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1753 By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1754 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1755
1756</p></pre><BR>
1757
1758<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
1759</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
1760 and store it into int* value.
1761 @return : 0, or an error code (which can be tested with ZSTD_isError()).
1762
1763</p></pre><BR>
1764
1765<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
1766ZSTDLIB_STATIC_API
1767size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1768</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
1769 Instruct the decoder context about what kind of data to decode next.
1770 This instruction is mandatory to decode data without a fully-formed header,
1771 such ZSTD_f_zstd1_magicless for example.
1772 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1773</p></pre><BR>
1774
1775<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs (
1776 ZSTD_DCtx* dctx,
1777 void* dst, size_t dstCapacity, size_t* dstPos,
1778 const void* src, size_t srcSize, size_t* srcPos);
1779</b><p> Same as ZSTD_decompressStream(),
1780 but using only integral types as arguments.
1781 This can be helpful for binders from dynamic languages
1782 which have troubles handling structures containing memory pointers.
1783
1784</p></pre><BR>
1785
1786<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
1787 Once Advanced API reaches "stable" status,
1788 redundant functions will be deprecated, and then at some point removed.
1789<BR></pre>
1790
1791<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
1792<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1793ZSTDLIB_STATIC_API
1794size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
1795 int compressionLevel,
1796 unsigned long long pledgedSrcSize);
1797</b><p> This function is DEPRECATED, and equivalent to:
1798 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1799 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
1800 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1801 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1802
1803 pledgedSrcSize must be correct. If it is not known at init time, use
1804 ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
1805 "0" also disables frame content size field. It may be enabled in the future.
1806 This prototype will generate compilation warnings.
1807
1808</p></pre><BR>
1809
1810<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1811ZSTDLIB_STATIC_API
1812size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
1813 const void* dict, size_t dictSize,
1814 int compressionLevel);
1815</b><p> This function is DEPRECATED, and is equivalent to:
1816 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1817 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1818 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1819
1820 Creates of an internal CDict (incompatible with static CCtx), except if
1821 dict == NULL or dictSize < 8, in which case no dict is used.
1822 Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
1823 it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
1824 This prototype will generate compilation warnings.
1825
1826</p></pre><BR>
1827
1828<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1829ZSTDLIB_STATIC_API
1830size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
1831 const void* dict, size_t dictSize,
1832 ZSTD_parameters params,
1833 unsigned long long pledgedSrcSize);
1834</b><p> This function is DEPRECATED, and is equivalent to:
1835 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1836 ZSTD_CCtx_setParams(zcs, params);
1837 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1838 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1839
1840 dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
1841 pledgedSrcSize must be correct.
1842 If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
1843 This prototype will generate compilation warnings.
1844
1845</p></pre><BR>
1846
1847<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1848ZSTDLIB_STATIC_API
1849size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
1850</b><p> This function is DEPRECATED, and equivalent to:
1851 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1852 ZSTD_CCtx_refCDict(zcs, cdict);
1853
1854 note : cdict will just be referenced, and must outlive compression session
1855 This prototype will generate compilation warnings.
1856
1857</p></pre><BR>
1858
1859<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
1860ZSTDLIB_STATIC_API
1861size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
1862 const ZSTD_CDict* cdict,
1863 ZSTD_frameParameters fParams,
1864 unsigned long long pledgedSrcSize);
1865</b><p> This function is DEPRECATED, and is equivalent to:
1866 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1867 ZSTD_CCtx_setFParams(zcs, fParams);
1868 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1869 ZSTD_CCtx_refCDict(zcs, cdict);
1870
1871 same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
1872 pledgedSrcSize must be correct. If srcSize is not known at init time, use
1873 value ZSTD_CONTENTSIZE_UNKNOWN.
1874 This prototype will generate compilation warnings.
1875
1876</p></pre><BR>
1877
1878<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
1879ZSTDLIB_STATIC_API
1880size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1881</b><p> This function is DEPRECATED, and is equivalent to:
1882 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1883 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1884 Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
1885 ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
1886 explicitly specified.
1887
1888 start a new frame, using same parameters from previous frame.
f535537f 1889 This is typically useful to skip dictionary loading stage, since it will reuse it in-place.
648db22b 1890 Note that zcs must be init at least once before using ZSTD_resetCStream().
1891 If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1892 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1893 For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1894 but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1895 @return : 0, or an error code (which can be tested using ZSTD_isError())
1896 This prototype will generate compilation warnings.
1897
1898</p></pre><BR>
1899
1900<pre><b>typedef struct {
1901 unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
1902 unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
1903 unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
1904 unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
1905 unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
1906 unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
1907} ZSTD_frameProgression;
1908</b></pre><BR>
1909<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1910</b><p> Tell how many bytes are ready to be flushed immediately.
1911 Useful for multithreading scenarios (nbWorkers >= 1).
1912 Probe the oldest active job, defined as oldest job not yet entirely flushed,
1913 and check its output buffer.
1914 @return : amount of data stored in oldest job and ready to be flushed immediately.
1915 if @return == 0, it means either :
1916 + there is no active job (could be checked with ZSTD_frameProgression()), or
1917 + oldest job is still actively compressing data,
1918 but everything it has produced has also been flushed so far,
1919 therefore flush speed is limited by production speed of oldest job
1920 irrespective of the speed of concurrent (and newer) jobs.
1921
1922</p></pre><BR>
1923
1924<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
1925<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions")
1926ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
1927</b><p>
1928 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1929 ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
1930
1931 note: no dictionary will be used if dict == NULL or dictSize < 8
1932
1933</p></pre><BR>
1934
1935<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions")
1936ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
1937</b><p>
1938 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1939 ZSTD_DCtx_refDDict(zds, ddict);
1940
1941 note : ddict is referenced, it must outlive decompression session
1942
1943</p></pre><BR>
1944
1945<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions")
1946ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
1947</b><p>
1948 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1949
f535537f 1950 reuse decompression parameters from previous init; saves dictionary loading
648db22b 1951
1952</p></pre><BR>
1953
1954<pre><b>ZSTDLIB_STATIC_API void
1955ZSTD_registerSequenceProducer(
1956 ZSTD_CCtx* cctx,
1957 void* sequenceProducerState,
f535537f 1958 ZSTD_sequenceProducer_F sequenceProducer
648db22b 1959);
1960</b><p> Instruct zstd to use a block-level external sequence producer function.
1961
1962 The sequenceProducerState must be initialized by the caller, and the caller is
1963 responsible for managing its lifetime. This parameter is sticky across
1964 compressions. It will remain set until the user explicitly resets compression
1965 parameters.
1966
1967 Sequence producer registration is considered to be an "advanced parameter",
1968 part of the "advanced API". This means it will only have an effect on compression
1969 APIs which respect advanced parameters, such as compress2() and compressStream2().
1970 Older compression APIs such as compressCCtx(), which predate the introduction of
1971 "advanced parameters", will ignore any external sequence producer setting.
1972
1973 The sequence producer can be "cleared" by registering a NULL function pointer. This
1974 removes all limitations described above in the "LIMITATIONS" section of the API docs.
1975
1976 The user is strongly encouraged to read the full API documentation (above) before
1977 calling this function.
1978</p></pre><BR>
1979
f535537f 1980<pre><b>ZSTDLIB_STATIC_API void
1981ZSTD_CCtxParams_registerSequenceProducer(
1982 ZSTD_CCtx_params* params,
1983 void* sequenceProducerState,
1984 ZSTD_sequenceProducer_F sequenceProducer
1985);
1986</b><p> Same as ZSTD_registerSequenceProducer(), but operates on ZSTD_CCtx_params.
1987 This is used for accurate size estimation with ZSTD_estimateCCtxSize_usingCCtxParams(),
1988 which is needed when creating a ZSTD_CCtx with ZSTD_initStaticCCtx().
1989
1990 If you are using the external sequence producer API in a scenario where ZSTD_initStaticCCtx()
1991 is required, then this function is for you. Otherwise, you probably don't need it.
1992
1993 See tests/zstreamtest.c for example usage.
1994</p></pre><BR>
1995
648db22b 1996<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre>
1997 This API is deprecated, and will be removed in a future version.
1998 It allows streaming (de)compression with user allocated buffers.
1999 However, it is hard to use, and not as well tested as the rest of
2000 our API.
2001
2002 Please use the normal streaming API instead: ZSTD_compressStream2,
2003 and ZSTD_decompressStream.
2004 If there is functionality that you need, but it doesn't provide,
2005 please open an issue on our GitHub.
2006
2007<BR></pre>
2008
2009<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
2010 A ZSTD_CCtx object is required to track streaming operations.
2011 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
f535537f 2012 ZSTD_CCtx object can be reused multiple times within successive compression operations.
648db22b 2013
2014 Start by initializing a context.
2015 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
2016
2017 Then, consume your input using ZSTD_compressContinue().
2018 There are some important considerations to keep in mind when using this advanced function :
2019 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
2020 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
2021 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
2022 Worst case evaluation is provided by ZSTD_compressBound().
2023 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
2024 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
2025 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
2026 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
2027 In which case, it will "discard" the relevant memory section from its history.
2028
2029 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
2030 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
2031 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
2032
f535537f 2033 `ZSTD_CCtx` object can be reused (ZSTD_compressBegin()) to compress again.
648db22b 2034<BR></pre>
2035
2036<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.")
2037ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
2038ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
2039ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
2040ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
2041ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
2042</pre></b><BR>
2043<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>
2044</b></pre><BR>
2045<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>
2046</b></pre><BR>
2047<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
2048 A ZSTD_DCtx object is required to track streaming operations.
2049 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
f535537f 2050 A ZSTD_DCtx object can be reused multiple times.
648db22b 2051
2052 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
2053 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
2054 Data fragment must be large enough to ensure successful decoding.
2055 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
2056 result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
2057 >0 : `srcSize` is too small, please provide at least result bytes on next attempt.
2058 errorCode, which can be tested using ZSTD_isError().
2059
2060 It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
2061 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
2062 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
2063 As a consequence, check that values remain within valid application range.
2064 For example, do not allocate memory blindly, check that `windowSize` is within expectation.
2065 Each application can set its own limits, depending on local restrictions.
2066 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
2067
2068 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
2069 ZSTD_decompressContinue() is very sensitive to contiguity,
2070 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
2071 or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
2072 There are multiple ways to guarantee this condition.
2073
2074 The most memory efficient way is to use a round buffer of sufficient size.
2075 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
2076 which can return an error code if required value is too large for current system (in 32-bits mode).
2077 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
2078 up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
2079 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
2080 At which point, decoding can resume from the beginning of the buffer.
2081 Note that already decoded data stored in the buffer should be flushed before being overwritten.
2082
2083 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
2084
2085 Finally, if you control the compression process, you can also ignore all buffer size rules,
2086 as long as the encoder and decoder progress in "lock-step",
2087 aka use exactly the same buffer sizes, break contiguity at the same place, etc.
2088
2089 Once buffers are setup, start decompression, with ZSTD_decompressBegin().
2090 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
2091
2092 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
2093 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
2094 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
2095
2096 result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
2097 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
2098 It can also be an error code, which can be tested with ZSTD_isError().
2099
2100 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
2101 Context can then be reset to start a new decompression.
2102
2103 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
2104 This information is not required to properly decode a frame.
2105
2106 == Special case : skippable frames
2107
2108 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
2109 Skippable frames will be ignored (skipped) by decompressor.
2110 The format of skippable frames is as follows :
2111 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
2112 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
2113 c) Frame Content - any content (User Data) of length equal to Frame Size
2114 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
2115 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
2116<BR></pre>
2117
2118<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
2119<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>
2120</b></pre><BR>
2121<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
2122</b></pre><BR>
2123<a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre>
2124
2125<pre><b></b><p> You can get the frame header down to 2 bytes by setting:
2126 - ZSTD_c_format = ZSTD_f_zstd1_magicless
2127 - ZSTD_c_contentSizeFlag = 0
2128 - ZSTD_c_checksumFlag = 0
2129 - ZSTD_c_dictIDFlag = 0
2130
2131 This API is not as well tested as our normal API, so we recommend not using it.
2132 We will be removing it in a future version. If the normal API doesn't provide
2133 the functionality you need, please open a GitHub issue.
2134
2135 Block functions produce and decode raw zstd blocks, without frame metadata.
2136 Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
2137 But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
2138
2139 A few rules to respect :
2140 - Compressing and decompressing require a context structure
2141 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
2142 - It is necessary to init context before starting
2143 + compression : any ZSTD_compressBegin*() variant, including with dictionary
2144 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
2145 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
2146 + If input is larger than a block size, it's necessary to split input data into multiple blocks
2147 + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
2148 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
2149 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
2150 ===> In which case, nothing is produced into `dst` !
2151 + User __must__ test for such outcome and deal directly with uncompressed data
2152 + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
2153 Doing so would mess up with statistics history, leading to potential data corruption.
2154 + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
2155 + In case of multiple successive blocks, should some of them be uncompressed,
2156 decoder must be informed of their existence in order to follow proper history.
2157 Use ZSTD_insertBlock() for such a case.
2158</p></pre><BR>
2159
2160<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.")
2161ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
2162ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2163ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2164ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2165ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2166ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
2167ZSTDLIB_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>
2168</pre></b><BR>
2169</html>
2170</body>
ARM optimized PCSX fork