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4 | <title>zstd 1.5.5 Manual</title> |
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6 | <body> |
7 | <h1>zstd 1.5.5 Manual</h1> |
8 | <hr> |
9 | <a name="Contents"></a><h2>Contents</h2> |
10 | <ol> |
11 | <li><a href="#Chapter1">Introduction</a></li> |
12 | <li><a href="#Chapter2">Version</a></li> |
13 | <li><a href="#Chapter3">Simple API</a></li> |
14 | <li><a href="#Chapter4">Explicit context</a></li> |
15 | <li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li> |
16 | <li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li> |
17 | <li><a href="#Chapter7">Streaming</a></li> |
18 | <li><a href="#Chapter8">Streaming compression - HowTo</a></li> |
19 | <li><a href="#Chapter9">Streaming decompression - HowTo</a></li> |
20 | <li><a href="#Chapter10">Simple dictionary API</a></li> |
21 | <li><a href="#Chapter11">Bulk processing dictionary API</a></li> |
22 | <li><a href="#Chapter12">Dictionary helper functions</a></li> |
23 | <li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li> |
24 | <li><a href="#Chapter14">experimental API (static linking only)</a></li> |
25 | <li><a href="#Chapter15">Frame header and size functions</a></li> |
26 | <li><a href="#Chapter16">Memory management</a></li> |
27 | <li><a href="#Chapter17">Advanced compression functions</a></li> |
28 | <li><a href="#Chapter18">Advanced decompression functions</a></li> |
29 | <li><a href="#Chapter19">Advanced streaming functions</a></li> |
30 | <li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li> |
31 | <li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li> |
32 | <li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li> |
33 | <li><a href="#Chapter23">Block level API (DEPRECATED)</a></li> |
34 | </ol> |
35 | <hr> |
36 | <a name="Chapter1"></a><h2>Introduction</h2><pre> |
37 | zstd, short for Zstandard, is a fast lossless compression algorithm, targeting |
38 | real-time compression scenarios at zlib-level and better compression ratios. |
39 | The zstd compression library provides in-memory compression and decompression |
40 | functions. |
41 | |
42 | The library supports regular compression levels from 1 up to ZSTD_maxCLevel(), |
43 | which is currently 22. Levels >= 20, labeled `--ultra`, should be used with |
44 | caution, as they require more memory. The library also offers negative |
45 | compression levels, which extend the range of speed vs. ratio preferences. |
46 | The lower the level, the faster the speed (at the cost of compression). |
47 | |
48 | Compression can be done in: |
49 | - a single step (described as Simple API) |
50 | - a single step, reusing a context (described as Explicit context) |
51 | - unbounded multiple steps (described as Streaming compression) |
52 | |
53 | The compression ratio achievable on small data can be highly improved using |
54 | a dictionary. Dictionary compression can be performed in: |
55 | - a single step (described as Simple dictionary API) |
56 | - a single step, reusing a dictionary (described as Bulk-processing |
57 | dictionary API) |
58 | |
59 | Advanced experimental functions can be accessed using |
60 | `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. |
61 | |
62 | Advanced experimental APIs should never be used with a dynamically-linked |
63 | library. They are not "stable"; their definitions or signatures may change in |
64 | the future. Only static linking is allowed. |
65 | <BR></pre> |
66 | |
67 | <a name="Chapter2"></a><h2>Version</h2><pre></pre> |
68 | |
69 | <pre><b>unsigned ZSTD_versionNumber(void); |
70 | </b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE). |
71 | </p></pre><BR> |
72 | |
73 | <pre><b>const char* ZSTD_versionString(void); |
74 | </b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+. |
75 | </p></pre><BR> |
76 | |
77 | <a name="Chapter3"></a><h2>Simple API</h2><pre></pre> |
78 | |
79 | <pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, |
80 | const void* src, size_t srcSize, |
81 | int compressionLevel); |
82 | </b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. |
83 | NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have |
84 | enough space to successfully compress the data. |
85 | @return : compressed size written into `dst` (<= `dstCapacity), |
86 | or an error code if it fails (which can be tested using ZSTD_isError()). |
87 | </p></pre><BR> |
88 | |
89 | <pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, |
90 | const void* src, size_t compressedSize); |
91 | </b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. |
92 | `dstCapacity` is an upper bound of originalSize to regenerate. |
93 | If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data. |
94 | @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), |
95 | or an errorCode if it fails (which can be tested using ZSTD_isError()). |
96 | </p></pre><BR> |
97 | |
98 | <pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) |
99 | #define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) |
100 | unsigned 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") |
126 | ZSTDLIB_API |
127 | unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); |
128 | </b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). |
129 | Both functions work the same way, but ZSTD_getDecompressedSize() blends |
130 | "empty", "unknown" and "error" results to the same return value (0), |
131 | while ZSTD_getFrameContentSize() gives them separate return values. |
132 | @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. |
133 | </p></pre><BR> |
134 | |
135 | <pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); |
136 | </b><p> `src` should point to the start of a ZSTD frame or skippable frame. |
137 | `srcSize` must be >= first frame size |
138 | @return : the compressed size of the first frame starting at `src`, |
139 | suitable to pass as `srcSize` to `ZSTD_decompress` or similar, |
140 | or an error code if input is invalid |
141 | </p></pre><BR> |
142 | |
143 | <h3>Helper functions</h3><pre></pre><b><pre></b>/* ZSTD_compressBound() :<b> |
144 | * maximum compressed size in worst case single-pass scenario. |
145 | * When invoking `ZSTD_compress()` or any other one-pass compression function, |
146 | * it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize) |
147 | * as it eliminates one potential failure scenario, |
148 | * aka not enough room in dst buffer to write the compressed frame. |
149 | * Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE . |
150 | * In which case, ZSTD_compressBound() will return an error code |
151 | * which can be tested using ZSTD_isError(). |
152 | * |
153 | * ZSTD_COMPRESSBOUND() : |
154 | * same as ZSTD_compressBound(), but as a macro. |
155 | * It can be used to produce constants, which can be useful for static allocation, |
156 | * for example to size a static array on stack. |
157 | * Will produce constant value 0 if srcSize too large. |
158 | */ |
159 | #define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00LLU : 0xFF00FF00U) |
160 | #define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> |
161 | size_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 | */ |
167 | unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> |
168 | const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> |
169 | int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b> |
170 | int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> |
171 | int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b> |
172 | </pre></b><BR> |
173 | <a name="Chapter4"></a><h2>Explicit context</h2><pre></pre> |
174 | |
175 | <h3>Compression context</h3><pre> When compressing many times, |
176 | it is recommended to allocate a context just once, |
177 | and re-use it for each successive compression operation. |
178 | This will make workload friendlier for system's memory. |
179 | Note : re-using context is just a speed / resource optimization. |
180 | It doesn't change the compression ratio, which remains identical. |
181 | Note 2 : In multi-threaded environments, |
182 | use one different context per thread for parallel execution. |
183 | |
184 | </pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; |
185 | ZSTD_CCtx* ZSTD_createCCtx(void); |
186 | size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b> |
187 | </pre></b><BR> |
188 | <pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, |
189 | void* dst, size_t dstCapacity, |
190 | const void* src, size_t srcSize, |
191 | int compressionLevel); |
192 | </b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx. |
193 | Important : in order to behave similarly to `ZSTD_compress()`, |
194 | this function compresses at requested compression level, |
195 | __ignoring any other parameter__ . |
196 | If any advanced parameter was set using the advanced API, |
197 | they will all be reset. Only `compressionLevel` remains. |
198 | |
199 | </p></pre><BR> |
200 | |
201 | <h3>Decompression context</h3><pre> When decompressing many times, |
202 | it is recommended to allocate a context only once, |
203 | and re-use it for each successive compression operation. |
204 | This will make workload friendlier for system's memory. |
205 | Use one context per thread for parallel execution. |
206 | </pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; |
207 | ZSTD_DCtx* ZSTD_createDCtx(void); |
208 | size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b> |
209 | </pre></b><BR> |
210 | <pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, |
211 | void* dst, size_t dstCapacity, |
212 | const void* src, size_t srcSize); |
213 | </b><p> Same as ZSTD_decompress(), |
214 | requires an allocated ZSTD_DCtx. |
215 | Compatible with sticky parameters. |
216 | |
217 | </p></pre><BR> |
218 | |
219 | <a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre> |
220 | |
221 | <pre><b>typedef enum { ZSTD_fast=1, |
222 | ZSTD_dfast=2, |
223 | ZSTD_greedy=3, |
224 | ZSTD_lazy=4, |
225 | ZSTD_lazy2=5, |
226 | ZSTD_btlazy2=6, |
227 | ZSTD_btopt=7, |
228 | ZSTD_btultra=8, |
229 | ZSTD_btultra2=9 |
230 | </b>/* note : new strategies _might_ be added in the future.<b> |
231 | Only the order (from fast to strong) is guaranteed */ |
232 | } ZSTD_strategy; |
233 | </b></pre><BR> |
234 | <pre><b>typedef enum { |
235 | |
236 | </b>/* compression parameters<b> |
237 | * Note: When compressing with a ZSTD_CDict these parameters are superseded |
238 | * by the parameters used to construct the ZSTD_CDict. |
239 | * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */ |
240 | ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b> |
241 | * Note that exact compression parameters are dynamically determined, |
242 | * depending on both compression level and srcSize (when known). |
243 | * Default level is ZSTD_CLEVEL_DEFAULT==3. |
244 | * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. |
245 | * Note 1 : it's possible to pass a negative compression level. |
246 | * Note 2 : setting a level does not automatically set all other compression parameters |
247 | * to default. Setting this will however eventually dynamically impact the compression |
248 | * parameters which have not been manually set. The manually set |
249 | * ones will 'stick'. */ |
250 | </b>/* Advanced compression parameters :<b> |
251 | * It's possible to pin down compression parameters to some specific values. |
252 | * In which case, these values are no longer dynamically selected by the compressor */ |
253 | ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> |
254 | * This will set a memory budget for streaming decompression, |
255 | * with larger values requiring more memory |
256 | * and typically compressing more. |
257 | * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. |
258 | * Special: value 0 means "use default windowLog". |
259 | * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT |
260 | * requires explicitly allowing such size at streaming decompression stage. */ |
261 | ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> |
262 | * Resulting memory usage is (1 << (hashLog+2)). |
263 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. |
264 | * Larger tables improve compression ratio of strategies <= dFast, |
265 | * and improve speed of strategies > dFast. |
266 | * Special: value 0 means "use default hashLog". */ |
267 | ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> |
268 | * Resulting memory usage is (1 << (chainLog+2)). |
269 | * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. |
270 | * Larger tables result in better and slower compression. |
271 | * This parameter is useless for "fast" strategy. |
272 | * It's still useful when using "dfast" strategy, |
273 | * in which case it defines a secondary probe table. |
274 | * Special: value 0 means "use default chainLog". */ |
275 | ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> |
276 | * More attempts result in better and slower compression. |
277 | * This parameter is useless for "fast" and "dFast" strategies. |
278 | * Special: value 0 means "use default searchLog". */ |
279 | ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> |
280 | * Note that Zstandard can still find matches of smaller size, |
281 | * it just tweaks its search algorithm to look for this size and larger. |
282 | * Larger values increase compression and decompression speed, but decrease ratio. |
283 | * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. |
284 | * Note that currently, for all strategies < btopt, effective minimum is 4. |
285 | * , for all strategies > fast, effective maximum is 6. |
286 | * Special: value 0 means "use default minMatchLength". */ |
287 | ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> |
288 | * For strategies btopt, btultra & btultra2: |
289 | * Length of Match considered "good enough" to stop search. |
290 | * Larger values make compression stronger, and slower. |
291 | * For strategy fast: |
292 | * Distance between match sampling. |
293 | * Larger values make compression faster, and weaker. |
294 | * Special: value 0 means "use default targetLength". */ |
295 | ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> |
296 | * The higher the value of selected strategy, the more complex it is, |
297 | * resulting in stronger and slower compression. |
298 | * Special: value 0 means "use default strategy". */ |
299 | </b>/* LDM mode parameters */<b> |
300 | ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> |
301 | * This parameter is designed to improve compression ratio |
302 | * for large inputs, by finding large matches at long distance. |
303 | * It increases memory usage and window size. |
304 | * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB |
305 | * except when expressly set to a different value. |
306 | * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and |
307 | * compression strategy >= ZSTD_btopt (== compression level 16+) */ |
308 | ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> |
309 | * Larger values increase memory usage and compression ratio, |
310 | * but decrease compression speed. |
311 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX |
312 | * default: windowlog - 7. |
313 | * Special: value 0 means "automatically determine hashlog". */ |
314 | ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> |
315 | * Larger/too small values usually decrease compression ratio. |
316 | * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. |
317 | * Special: value 0 means "use default value" (default: 64). */ |
318 | ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> |
319 | * Larger values improve collision resolution but decrease compression speed. |
320 | * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. |
321 | * Special: value 0 means "use default value" (default: 3). */ |
322 | ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> |
323 | * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). |
324 | * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. |
325 | * Larger values improve compression speed. |
326 | * Deviating far from default value will likely result in a compression ratio decrease. |
327 | * Special: value 0 means "automatically determine hashRateLog". */ |
328 | |
329 | </b>/* frame parameters */<b> |
330 | ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> |
331 | * Content size must be known at the beginning of compression. |
332 | * This is automatically the case when using ZSTD_compress2(), |
333 | * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ |
334 | ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> |
335 | ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> |
336 | |
337 | </b>/* multi-threading parameters */<b> |
338 | </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> |
339 | * Otherwise, trying to set any other value than default (0) will be a no-op and return an error. |
340 | * In a situation where it's unknown if the linked library supports multi-threading or not, |
341 | * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property. |
342 | */ |
343 | ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> |
344 | * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() : |
345 | * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, |
346 | * while compression is performed in parallel, within worker thread(s). |
347 | * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : |
348 | * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). |
349 | * More workers improve speed, but also increase memory usage. |
350 | * Default value is `0`, aka "single-threaded mode" : no worker is spawned, |
351 | * compression is performed inside Caller's thread, and all invocations are blocking */ |
352 | ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> |
353 | * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. |
354 | * 0 means default, which is dynamically determined based on compression parameters. |
355 | * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest. |
356 | * The minimum size is automatically and transparently enforced. */ |
357 | ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> |
358 | * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. |
359 | * It helps preserve compression ratio, while each job is compressed in parallel. |
360 | * This value is enforced only when nbWorkers >= 1. |
361 | * Larger values increase compression ratio, but decrease speed. |
362 | * Possible values range from 0 to 9 : |
363 | * - 0 means "default" : value will be determined by the library, depending on strategy |
364 | * - 1 means "no overlap" |
365 | * - 9 means "full overlap", using a full window size. |
366 | * Each intermediate rank increases/decreases load size by a factor 2 : |
367 | * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default |
368 | * default value varies between 6 and 9, depending on strategy */ |
369 | |
370 | </b>/* note : additional experimental parameters are also available<b> |
371 | * within the experimental section of the API. |
372 | * At the time of this writing, they include : |
373 | * ZSTD_c_rsyncable |
374 | * ZSTD_c_format |
375 | * ZSTD_c_forceMaxWindow |
376 | * ZSTD_c_forceAttachDict |
377 | * ZSTD_c_literalCompressionMode |
378 | * ZSTD_c_targetCBlockSize |
379 | * ZSTD_c_srcSizeHint |
380 | * ZSTD_c_enableDedicatedDictSearch |
381 | * ZSTD_c_stableInBuffer |
382 | * ZSTD_c_stableOutBuffer |
383 | * ZSTD_c_blockDelimiters |
384 | * ZSTD_c_validateSequences |
385 | * ZSTD_c_useBlockSplitter |
386 | * ZSTD_c_useRowMatchFinder |
387 | * ZSTD_c_prefetchCDictTables |
388 | * ZSTD_c_enableSeqProducerFallback |
389 | * ZSTD_c_maxBlockSize |
390 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. |
391 | * note : never ever use experimentalParam? names directly; |
392 | * also, the enums values themselves are unstable and can still change. |
393 | */ |
394 | ZSTD_c_experimentalParam1=500, |
395 | ZSTD_c_experimentalParam2=10, |
396 | ZSTD_c_experimentalParam3=1000, |
397 | ZSTD_c_experimentalParam4=1001, |
398 | ZSTD_c_experimentalParam5=1002, |
399 | ZSTD_c_experimentalParam6=1003, |
400 | ZSTD_c_experimentalParam7=1004, |
401 | ZSTD_c_experimentalParam8=1005, |
402 | ZSTD_c_experimentalParam9=1006, |
403 | ZSTD_c_experimentalParam10=1007, |
404 | ZSTD_c_experimentalParam11=1008, |
405 | ZSTD_c_experimentalParam12=1009, |
406 | ZSTD_c_experimentalParam13=1010, |
407 | ZSTD_c_experimentalParam14=1011, |
408 | ZSTD_c_experimentalParam15=1012, |
409 | ZSTD_c_experimentalParam16=1013, |
410 | ZSTD_c_experimentalParam17=1014, |
411 | ZSTD_c_experimentalParam18=1015, |
412 | ZSTD_c_experimentalParam19=1016 |
413 | } ZSTD_cParameter; |
414 | </b></pre><BR> |
415 | <pre><b>typedef struct { |
416 | size_t error; |
417 | int lowerBound; |
418 | int upperBound; |
419 | } ZSTD_bounds; |
420 | </b></pre><BR> |
421 | <pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); |
422 | </b><p> All parameters must belong to an interval with lower and upper bounds, |
423 | otherwise they will either trigger an error or be automatically clamped. |
424 | @return : a structure, ZSTD_bounds, which contains |
425 | - an error status field, which must be tested using ZSTD_isError() |
426 | - lower and upper bounds, both inclusive |
427 | |
428 | </p></pre><BR> |
429 | |
430 | <pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); |
431 | </b><p> Set one compression parameter, selected by enum ZSTD_cParameter. |
432 | All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). |
433 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). |
434 | Setting a parameter is generally only possible during frame initialization (before starting compression). |
435 | Exception : when using multi-threading mode (nbWorkers >= 1), |
436 | the following parameters can be updated _during_ compression (within same frame): |
437 | => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. |
438 | new parameters will be active for next job only (after a flush()). |
439 | @return : an error code (which can be tested using ZSTD_isError()). |
440 | |
441 | </p></pre><BR> |
442 | |
443 | <pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); |
444 | </b><p> Total input data size to be compressed as a single frame. |
445 | Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. |
446 | This value will also be controlled at end of frame, and trigger an error if not respected. |
447 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
448 | Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. |
449 | In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. |
450 | ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. |
451 | Note 2 : pledgedSrcSize is only valid once, for the next frame. |
452 | It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. |
453 | Note 3 : Whenever all input data is provided and consumed in a single round, |
454 | for example with ZSTD_compress2(), |
455 | or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), |
456 | this value is automatically overridden by srcSize instead. |
457 | |
458 | </p></pre><BR> |
459 | |
460 | <pre><b>typedef enum { |
461 | ZSTD_reset_session_only = 1, |
462 | ZSTD_reset_parameters = 2, |
463 | ZSTD_reset_session_and_parameters = 3 |
464 | } ZSTD_ResetDirective; |
465 | </b></pre><BR> |
466 | <pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); |
467 | </b><p> There are 2 different things that can be reset, independently or jointly : |
468 | - The session : will stop compressing current frame, and make CCtx ready to start a new one. |
469 | Useful after an error, or to interrupt any ongoing compression. |
470 | Any internal data not yet flushed is cancelled. |
471 | Compression parameters and dictionary remain unchanged. |
472 | They will be used to compress next frame. |
473 | Resetting session never fails. |
474 | - The parameters : changes all parameters back to "default". |
475 | This also removes any reference to any dictionary or external sequence producer. |
476 | Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) |
477 | otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) |
478 | - Both : similar to resetting the session, followed by resetting parameters. |
479 | |
480 | </p></pre><BR> |
481 | |
482 | <pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, |
483 | void* dst, size_t dstCapacity, |
484 | const void* src, size_t srcSize); |
485 | </b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. |
486 | ZSTD_compress2() always starts a new frame. |
487 | Should cctx hold data from a previously unfinished frame, everything about it is forgotten. |
488 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() |
489 | - The function is always blocking, returns when compression is completed. |
490 | NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have |
491 | enough space to successfully compress the data, though it is possible it fails for other reasons. |
492 | @return : compressed size written into `dst` (<= `dstCapacity), |
493 | or an error code if it fails (which can be tested using ZSTD_isError()). |
494 | |
495 | </p></pre><BR> |
496 | |
497 | <a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre> |
498 | |
499 | <pre><b>typedef enum { |
500 | |
501 | ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> |
502 | * the streaming API will refuse to allocate memory buffer |
503 | * in order to protect the host from unreasonable memory requirements. |
504 | * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. |
505 | * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). |
506 | * Special: value 0 means "use default maximum windowLog". */ |
507 | |
508 | </b>/* note : additional experimental parameters are also available<b> |
509 | * within the experimental section of the API. |
510 | * At the time of this writing, they include : |
511 | * ZSTD_d_format |
512 | * ZSTD_d_stableOutBuffer |
513 | * ZSTD_d_forceIgnoreChecksum |
514 | * ZSTD_d_refMultipleDDicts |
515 | * ZSTD_d_disableHuffmanAssembly |
516 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. |
517 | * note : never ever use experimentalParam? names directly |
518 | */ |
519 | ZSTD_d_experimentalParam1=1000, |
520 | ZSTD_d_experimentalParam2=1001, |
521 | ZSTD_d_experimentalParam3=1002, |
522 | ZSTD_d_experimentalParam4=1003, |
523 | ZSTD_d_experimentalParam5=1004 |
524 | |
525 | } ZSTD_dParameter; |
526 | </b></pre><BR> |
527 | <pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); |
528 | </b><p> All parameters must belong to an interval with lower and upper bounds, |
529 | otherwise they will either trigger an error or be automatically clamped. |
530 | @return : a structure, ZSTD_bounds, which contains |
531 | - an error status field, which must be tested using ZSTD_isError() |
532 | - both lower and upper bounds, inclusive |
533 | |
534 | </p></pre><BR> |
535 | |
536 | <pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); |
537 | </b><p> Set one compression parameter, selected by enum ZSTD_dParameter. |
538 | All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). |
539 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). |
540 | Setting a parameter is only possible during frame initialization (before starting decompression). |
541 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
542 | |
543 | </p></pre><BR> |
544 | |
545 | <pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); |
546 | </b><p> Return a DCtx to clean state. |
547 | Session and parameters can be reset jointly or separately. |
548 | Parameters can only be reset when no active frame is being decompressed. |
549 | @return : 0, or an error code, which can be tested with ZSTD_isError() |
550 | |
551 | </p></pre><BR> |
552 | |
553 | <a name="Chapter7"></a><h2>Streaming</h2><pre></pre> |
554 | |
555 | <pre><b>typedef struct ZSTD_inBuffer_s { |
556 | const void* src; </b>/**< start of input buffer */<b> |
557 | size_t size; </b>/**< size of input buffer */<b> |
558 | size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> |
559 | } ZSTD_inBuffer; |
560 | </b></pre><BR> |
561 | <pre><b>typedef struct ZSTD_outBuffer_s { |
562 | void* dst; </b>/**< start of output buffer */<b> |
563 | size_t size; </b>/**< size of output buffer */<b> |
564 | size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> |
565 | } ZSTD_outBuffer; |
566 | </b></pre><BR> |
567 | <a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> |
568 | A ZSTD_CStream object is required to track streaming operation. |
569 | Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. |
570 | ZSTD_CStream objects can be reused multiple times on consecutive compression operations. |
571 | It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. |
572 | |
573 | For parallel execution, use one separate ZSTD_CStream per thread. |
574 | |
575 | note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. |
576 | |
577 | Parameters are sticky : when starting a new compression on the same context, |
578 | it will re-use the same sticky parameters as previous compression session. |
579 | When in doubt, it's recommended to fully initialize the context before usage. |
580 | Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), |
581 | ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to |
582 | set more specific parameters, the pledged source size, or load a dictionary. |
583 | |
584 | Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to |
585 | consume input stream. The function will automatically update both `pos` |
586 | fields within `input` and `output`. |
587 | Note that the function may not consume the entire input, for example, because |
588 | the output buffer is already full, in which case `input.pos < input.size`. |
589 | The caller must check if input has been entirely consumed. |
590 | If not, the caller must make some room to receive more compressed data, |
591 | and then present again remaining input data. |
592 | note: ZSTD_e_continue is guaranteed to make some forward progress when called, |
593 | but doesn't guarantee maximal forward progress. This is especially relevant |
594 | when compressing with multiple threads. The call won't block if it can |
595 | consume some input, but if it can't it will wait for some, but not all, |
596 | output to be flushed. |
597 | @return : provides a minimum amount of data remaining to be flushed from internal buffers |
598 | or an error code, which can be tested using ZSTD_isError(). |
599 | |
600 | At any moment, it's possible to flush whatever data might remain stuck within internal buffer, |
601 | using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. |
602 | Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). |
603 | In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. |
604 | You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the |
605 | operation. |
606 | note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will |
607 | block until the flush is complete or the output buffer is full. |
608 | @return : 0 if internal buffers are entirely flushed, |
609 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), |
610 | or an error code, which can be tested using ZSTD_isError(). |
611 | |
612 | Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame. |
613 | It will perform a flush and write frame epilogue. |
614 | The epilogue is required for decoders to consider a frame completed. |
615 | flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. |
616 | You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to |
617 | start a new frame. |
618 | note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will |
619 | block until the flush is complete or the output buffer is full. |
620 | @return : 0 if frame fully completed and fully flushed, |
621 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), |
622 | or an error code, which can be tested using ZSTD_isError(). |
623 | |
624 | |
625 | <BR></pre> |
626 | |
627 | <pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> |
628 | </b></pre><BR> |
629 | <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); |
630 | size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b> |
631 | </pre></b><BR> |
632 | <h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { |
633 | ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> |
634 | ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> |
635 | * it creates (at least) one new block, that can be decoded immediately on reception; |
636 | * frame will continue: any future data can still reference previously compressed data, improving compression. |
637 | * note : multithreaded compression will block to flush as much output as possible. */ |
638 | ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> |
639 | * note that frame is only closed after compressed data is fully flushed (return value == 0). |
640 | * After that point, any additional data starts a new frame. |
641 | * note : each frame is independent (does not reference any content from previous frame). |
642 | : note : multithreaded compression will block to flush as much output as possible. */ |
643 | } ZSTD_EndDirective; |
644 | </pre></b><BR> |
645 | <pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, |
646 | ZSTD_outBuffer* output, |
647 | ZSTD_inBuffer* input, |
648 | ZSTD_EndDirective endOp); |
649 | </b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. |
650 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() |
651 | - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) |
652 | - output->pos must be <= dstCapacity, input->pos must be <= srcSize |
653 | - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. |
654 | - endOp must be a valid directive |
655 | - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. |
656 | - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available, |
657 | and then immediately returns, just indicating that there is some data remaining to be flushed. |
658 | The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. |
659 | - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking. |
660 | - @return provides a minimum amount of data remaining to be flushed from internal buffers |
661 | or an error code, which can be tested using ZSTD_isError(). |
662 | if @return != 0, flush is not fully completed, there is still some data left within internal buffers. |
663 | This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. |
664 | For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. |
665 | - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), |
666 | only ZSTD_e_end or ZSTD_e_flush operations are allowed. |
667 | Before starting a new compression job, or changing compression parameters, |
668 | it is required to fully flush internal buffers. |
669 | |
670 | </p></pre><BR> |
671 | |
672 | <pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> |
673 | </b></pre><BR> |
674 | <pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b> |
675 | </b></pre><BR> |
676 | <pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); |
677 | </b>/*!<b> |
678 | * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue). |
679 | * NOTE: The return value is different. ZSTD_compressStream() returns a hint for |
680 | * the next read size (if non-zero and not an error). ZSTD_compressStream2() |
681 | * returns the minimum nb of bytes left to flush (if non-zero and not an error). |
682 | */ |
683 | size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); |
684 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b> |
685 | size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); |
686 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b> |
687 | size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); |
688 | </b><p> |
689 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
690 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) |
691 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
692 | |
693 | Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API |
694 | to compress with a dictionary. |
695 | |
696 | </p></pre><BR> |
697 | |
698 | <a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> |
699 | A ZSTD_DStream object is required to track streaming operations. |
700 | Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. |
701 | ZSTD_DStream objects can be re-used multiple times. |
702 | |
703 | Use ZSTD_initDStream() to start a new decompression operation. |
704 | @return : recommended first input size |
705 | Alternatively, use advanced API to set specific properties. |
706 | |
707 | Use ZSTD_decompressStream() repetitively to consume your input. |
708 | The function will update both `pos` fields. |
709 | If `input.pos < input.size`, some input has not been consumed. |
710 | It's up to the caller to present again remaining data. |
711 | The function tries to flush all data decoded immediately, respecting output buffer size. |
712 | If `output.pos < output.size`, decoder has flushed everything it could. |
713 | But if `output.pos == output.size`, there might be some data left within internal buffers., |
714 | In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. |
715 | Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. |
716 | @return : 0 when a frame is completely decoded and fully flushed, |
717 | or an error code, which can be tested using ZSTD_isError(), |
718 | or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : |
719 | the return value is a suggested next input size (just a hint for better latency) |
720 | that will never request more than the remaining frame size. |
721 | |
722 | <BR></pre> |
723 | |
724 | <pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> |
725 | </b></pre><BR> |
726 | <h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); |
727 | size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b> |
728 | </pre></b><BR> |
729 | <h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
730 | <pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds); |
731 | </b><p> Initialize/reset DStream state for new decompression operation. |
732 | Call before new decompression operation using same DStream. |
733 | |
734 | Note : This function is redundant with the advanced API and equivalent to: |
735 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
736 | ZSTD_DCtx_refDDict(zds, NULL); |
737 | |
738 | </p></pre><BR> |
739 | |
740 | <pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); |
741 | </b><p> Streaming decompression function. |
742 | Call repetitively to consume full input updating it as necessary. |
743 | Function will update both input and output `pos` fields exposing current state via these fields: |
744 | - `input.pos < input.size`, some input remaining and caller should provide remaining input |
745 | on the next call. |
746 | - `output.pos < output.size`, decoder finished and flushed all remaining buffers. |
747 | - `output.pos == output.size`, potentially uncflushed data present in the internal buffers, |
748 | call ZSTD_decompressStream() again to flush remaining data to output. |
749 | Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX. |
750 | |
751 | @return : 0 when a frame is completely decoded and fully flushed, |
752 | or an error code, which can be tested using ZSTD_isError(), |
753 | or any other value > 0, which means there is some decoding or flushing to do to complete current frame. |
754 | |
755 | </p></pre><BR> |
756 | |
757 | <pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> |
758 | </b></pre><BR> |
759 | <pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> |
760 | </b></pre><BR> |
761 | <a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre> |
762 | |
763 | <pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, |
764 | void* dst, size_t dstCapacity, |
765 | const void* src, size_t srcSize, |
766 | const void* dict,size_t dictSize, |
767 | int compressionLevel); |
768 | </b><p> Compression at an explicit compression level using a Dictionary. |
769 | A dictionary can be any arbitrary data segment (also called a prefix), |
770 | or a buffer with specified information (see zdict.h). |
771 | Note : This function loads the dictionary, resulting in significant startup delay. |
772 | It's intended for a dictionary used only once. |
773 | Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. |
774 | </p></pre><BR> |
775 | |
776 | <pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, |
777 | void* dst, size_t dstCapacity, |
778 | const void* src, size_t srcSize, |
779 | const void* dict,size_t dictSize); |
780 | </b><p> Decompression using a known Dictionary. |
781 | Dictionary must be identical to the one used during compression. |
782 | Note : This function loads the dictionary, resulting in significant startup delay. |
783 | It's intended for a dictionary used only once. |
784 | Note : When `dict == NULL || dictSize < 8` no dictionary is used. |
785 | </p></pre><BR> |
786 | |
787 | <a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> |
788 | |
789 | <pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, |
790 | int compressionLevel); |
791 | </b><p> When compressing multiple messages or blocks using the same dictionary, |
792 | it's recommended to digest the dictionary only once, since it's a costly operation. |
793 | ZSTD_createCDict() will create a state from digesting a dictionary. |
794 | The resulting state can be used for future compression operations with very limited startup cost. |
795 | ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. |
796 | @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict. |
797 | Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content. |
798 | Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer, |
799 | in which case the only thing that it transports is the @compressionLevel. |
800 | This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively, |
801 | expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. |
802 | </p></pre><BR> |
803 | |
804 | <pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); |
805 | </b><p> Function frees memory allocated by ZSTD_createCDict(). |
806 | If a NULL pointer is passed, no operation is performed. |
807 | </p></pre><BR> |
808 | |
809 | <pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, |
810 | void* dst, size_t dstCapacity, |
811 | const void* src, size_t srcSize, |
812 | const ZSTD_CDict* cdict); |
813 | </b><p> Compression using a digested Dictionary. |
814 | Recommended when same dictionary is used multiple times. |
815 | Note : compression level is _decided at dictionary creation time_, |
816 | and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) |
817 | </p></pre><BR> |
818 | |
819 | <pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); |
820 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. |
821 | dictBuffer can be released after DDict creation, as its content is copied inside DDict. |
822 | </p></pre><BR> |
823 | |
824 | <pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); |
825 | </b><p> Function frees memory allocated with ZSTD_createDDict() |
826 | If a NULL pointer is passed, no operation is performed. |
827 | </p></pre><BR> |
828 | |
829 | <pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, |
830 | void* dst, size_t dstCapacity, |
831 | const void* src, size_t srcSize, |
832 | const ZSTD_DDict* ddict); |
833 | </b><p> Decompression using a digested Dictionary. |
834 | Recommended when same dictionary is used multiple times. |
835 | </p></pre><BR> |
836 | |
837 | <a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre> |
838 | |
839 | <pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); |
840 | </b><p> Provides the dictID stored within dictionary. |
841 | if @return == 0, the dictionary is not conformant with Zstandard specification. |
842 | It can still be loaded, but as a content-only dictionary. |
843 | </p></pre><BR> |
844 | |
845 | <pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict); |
846 | </b><p> Provides the dictID of the dictionary loaded into `cdict`. |
847 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. |
848 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries. |
849 | </p></pre><BR> |
850 | |
851 | <pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); |
852 | </b><p> Provides the dictID of the dictionary loaded into `ddict`. |
853 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. |
854 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries. |
855 | </p></pre><BR> |
856 | |
857 | <pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); |
858 | </b><p> Provides the dictID required to decompressed the frame stored within `src`. |
859 | If @return == 0, the dictID could not be decoded. |
860 | This could for one of the following reasons : |
861 | - The frame does not require a dictionary to be decoded (most common case). |
862 | - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information. |
863 | Note : this use case also happens when using a non-conformant dictionary. |
864 | - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). |
865 | - This is not a Zstandard frame. |
866 | When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. |
867 | </p></pre><BR> |
868 | |
869 | <a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre> |
870 | This API allows dictionaries to be used with ZSTD_compress2(), |
871 | ZSTD_compressStream2(), and ZSTD_decompressDCtx(). |
872 | Dictionaries are sticky, they remain valid when same context is re-used, |
873 | they only reset when the context is reset |
874 | with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters. |
875 | In contrast, Prefixes are single-use. |
876 | <BR></pre> |
877 | |
878 | <pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); |
879 | </b><p> Create an internal CDict from `dict` buffer. |
880 | Decompression will have to use same dictionary. |
881 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
882 | Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, |
883 | meaning "return to no-dictionary mode". |
884 | Note 1 : Dictionary is sticky, it will be used for all future compressed frames, |
885 | until parameters are reset, a new dictionary is loaded, or the dictionary |
886 | is explicitly invalidated by loading a NULL dictionary. |
887 | Note 2 : Loading a dictionary involves building tables. |
888 | It's also a CPU consuming operation, with non-negligible impact on latency. |
889 | Tables are dependent on compression parameters, and for this reason, |
890 | compression parameters can no longer be changed after loading a dictionary. |
891 | Note 3 :`dict` content will be copied internally. |
892 | Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. |
893 | In such a case, dictionary buffer must outlive its users. |
894 | Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() |
895 | to precisely select how dictionary content must be interpreted. |
896 | Note 5 : This method does not benefit from LDM (long distance mode). |
897 | If you want to employ LDM on some large dictionary content, |
898 | prefer employing ZSTD_CCtx_refPrefix() described below. |
899 | |
900 | </p></pre><BR> |
901 | |
902 | <pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); |
903 | </b><p> Reference a prepared dictionary, to be used for all future compressed frames. |
904 | Note that compression parameters are enforced from within CDict, |
905 | and supersede any compression parameter previously set within CCtx. |
906 | The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. |
907 | The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. |
908 | The dictionary will remain valid for future compressed frames using same CCtx. |
909 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
910 | Special : Referencing a NULL CDict means "return to no-dictionary mode". |
911 | Note 1 : Currently, only one dictionary can be managed. |
912 | Referencing a new dictionary effectively "discards" any previous one. |
913 | Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. |
914 | </p></pre><BR> |
915 | |
916 | <pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, |
917 | const void* prefix, size_t prefixSize); |
918 | </b><p> Reference a prefix (single-usage dictionary) for next compressed frame. |
919 | A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). |
920 | Decompression will need same prefix to properly regenerate data. |
921 | Compressing with a prefix is similar in outcome as performing a diff and compressing it, |
922 | but performs much faster, especially during decompression (compression speed is tunable with compression level). |
923 | This method is compatible with LDM (long distance mode). |
924 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
925 | Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary |
926 | Note 1 : Prefix buffer is referenced. It **must** outlive compression. |
927 | Its content must remain unmodified during compression. |
928 | Note 2 : If the intention is to diff some large src data blob with some prior version of itself, |
929 | ensure that the window size is large enough to contain the entire source. |
930 | See ZSTD_c_windowLog. |
931 | Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. |
932 | It's a CPU consuming operation, with non-negligible impact on latency. |
933 | If there is a need to use the same prefix multiple times, consider loadDictionary instead. |
934 | Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent). |
935 | Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. |
936 | </p></pre><BR> |
937 | |
938 | <pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); |
939 | </b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames. |
940 | The dictionary remains valid for all future frames, until explicitly invalidated, or |
941 | a new dictionary is loaded. |
942 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
943 | Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, |
944 | meaning "return to no-dictionary mode". |
945 | Note 1 : Loading a dictionary involves building tables, |
946 | which has a non-negligible impact on CPU usage and latency. |
947 | It's recommended to "load once, use many times", to amortize the cost |
948 | Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. |
949 | Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. |
950 | Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of |
951 | how dictionary content is loaded and interpreted. |
952 | |
953 | </p></pre><BR> |
954 | |
955 | <pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); |
956 | </b><p> Reference a prepared dictionary, to be used to decompress next frames. |
957 | The dictionary remains active for decompression of future frames using same DCtx. |
958 | |
959 | If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function |
960 | will store the DDict references in a table, and the DDict used for decompression |
961 | will be determined at decompression time, as per the dict ID in the frame. |
962 | The memory for the table is allocated on the first call to refDDict, and can be |
963 | freed with ZSTD_freeDCtx(). |
964 | |
965 | If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary |
966 | will be managed, and referencing a dictionary effectively "discards" any previous one. |
967 | |
968 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
969 | Special: referencing a NULL DDict means "return to no-dictionary mode". |
970 | Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. |
971 | |
972 | </p></pre><BR> |
973 | |
974 | <pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, |
975 | const void* prefix, size_t prefixSize); |
976 | </b><p> Reference a prefix (single-usage dictionary) to decompress next frame. |
977 | This is the reverse operation of ZSTD_CCtx_refPrefix(), |
978 | and must use the same prefix as the one used during compression. |
979 | Prefix is **only used once**. Reference is discarded at end of frame. |
980 | End of frame is reached when ZSTD_decompressStream() returns 0. |
981 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
982 | Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary |
983 | Note 2 : Prefix buffer is referenced. It **must** outlive decompression. |
984 | Prefix buffer must remain unmodified up to the end of frame, |
985 | reached when ZSTD_decompressStream() returns 0. |
986 | Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent). |
987 | Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) |
988 | Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. |
989 | A full dictionary is more costly, as it requires building tables. |
990 | |
991 | </p></pre><BR> |
992 | |
993 | <pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); |
994 | size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); |
995 | size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); |
996 | size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); |
997 | size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); |
998 | size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); |
999 | </b><p> These functions give the _current_ memory usage of selected object. |
1000 | Note that object memory usage can evolve (increase or decrease) over time. |
1001 | </p></pre><BR> |
1002 | |
1003 | <a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre> |
1004 | The following symbols and constants |
1005 | are not planned to join "stable API" status in the near future. |
1006 | They can still change in future versions. |
1007 | Some of them are planned to remain in the static_only section indefinitely. |
1008 | Some of them might be removed in the future (especially when redundant with existing stable functions) |
1009 | |
1010 | <BR></pre> |
1011 | |
1012 | <pre><b>typedef struct { |
1013 | unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b> |
1014 | * If offset == 0 and matchLength == 0, this sequence represents the last |
1015 | * literals in the block of litLength size. |
1016 | */ |
1017 | |
1018 | unsigned int litLength; </b>/* Literal length of the sequence. */<b> |
1019 | unsigned int matchLength; </b>/* Match length of the sequence. */<b> |
1020 | |
1021 | </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b> |
1022 | * In this case, we will treat the sequence as a marker for a block boundary. |
1023 | */ |
1024 | |
1025 | unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b> |
1026 | * Ranges from [0, 3]. |
1027 | * |
1028 | * Repeat offsets are essentially previous offsets from previous sequences sorted in |
1029 | * recency order. For more detail, see doc/zstd_compression_format.md |
1030 | * |
1031 | * If rep == 0, then 'offset' does not contain a repeat offset. |
1032 | * If rep > 0: |
1033 | * If litLength != 0: |
1034 | * rep == 1 --> offset == repeat_offset_1 |
1035 | * rep == 2 --> offset == repeat_offset_2 |
1036 | * rep == 3 --> offset == repeat_offset_3 |
1037 | * If litLength == 0: |
1038 | * rep == 1 --> offset == repeat_offset_2 |
1039 | * rep == 2 --> offset == repeat_offset_3 |
1040 | * rep == 3 --> offset == repeat_offset_1 - 1 |
1041 | * |
1042 | * Note: This field is optional. ZSTD_generateSequences() will calculate the value of |
1043 | * 'rep', but repeat offsets do not necessarily need to be calculated from an external |
1044 | * sequence provider's perspective. For example, ZSTD_compressSequences() does not |
1045 | * use this 'rep' field at all (as of now). |
1046 | */ |
1047 | } ZSTD_Sequence; |
1048 | </b></pre><BR> |
1049 | <pre><b>typedef struct { |
1050 | unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> |
1051 | unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> |
1052 | unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> |
1053 | unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> |
1054 | unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> |
1055 | unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> |
1056 | ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> |
1057 | } ZSTD_compressionParameters; |
1058 | </b></pre><BR> |
1059 | <pre><b>typedef struct { |
1060 | int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> |
1061 | int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> |
1062 | int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> |
1063 | } ZSTD_frameParameters; |
1064 | </b></pre><BR> |
1065 | <pre><b>typedef struct { |
1066 | ZSTD_compressionParameters cParams; |
1067 | ZSTD_frameParameters fParams; |
1068 | } ZSTD_parameters; |
1069 | </b></pre><BR> |
1070 | <pre><b>typedef enum { |
1071 | ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> |
1072 | ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> |
1073 | ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> |
1074 | } ZSTD_dictContentType_e; |
1075 | </b></pre><BR> |
1076 | <pre><b>typedef enum { |
1077 | ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> |
1078 | ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> |
1079 | } ZSTD_dictLoadMethod_e; |
1080 | </b></pre><BR> |
1081 | <pre><b>typedef enum { |
1082 | ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> |
1083 | ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> |
1084 | * Useful to save 4 bytes per generated frame. |
1085 | * Decoder cannot recognise automatically this format, requiring this instruction. */ |
1086 | } ZSTD_format_e; |
1087 | </b></pre><BR> |
1088 | <pre><b>typedef enum { |
1089 | </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b> |
1090 | ZSTD_d_validateChecksum = 0, |
1091 | ZSTD_d_ignoreChecksum = 1 |
1092 | } ZSTD_forceIgnoreChecksum_e; |
1093 | </b></pre><BR> |
1094 | <pre><b>typedef enum { |
1095 | </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b> |
1096 | ZSTD_rmd_refSingleDDict = 0, |
1097 | ZSTD_rmd_refMultipleDDicts = 1 |
1098 | } ZSTD_refMultipleDDicts_e; |
1099 | </b></pre><BR> |
1100 | <pre><b>typedef enum { |
1101 | </b>/* Note: this enum and the behavior it controls are effectively internal<b> |
1102 | * implementation details of the compressor. They are expected to continue |
1103 | * to evolve and should be considered only in the context of extremely |
1104 | * advanced performance tuning. |
1105 | * |
1106 | * Zstd currently supports the use of a CDict in three ways: |
1107 | * |
1108 | * - The contents of the CDict can be copied into the working context. This |
1109 | * means that the compression can search both the dictionary and input |
1110 | * while operating on a single set of internal tables. This makes |
1111 | * the compression faster per-byte of input. However, the initial copy of |
1112 | * the CDict's tables incurs a fixed cost at the beginning of the |
1113 | * compression. For small compressions (< 8 KB), that copy can dominate |
1114 | * the cost of the compression. |
1115 | * |
1116 | * - The CDict's tables can be used in-place. In this model, compression is |
1117 | * slower per input byte, because the compressor has to search two sets of |
1118 | * tables. However, this model incurs no start-up cost (as long as the |
1119 | * working context's tables can be reused). For small inputs, this can be |
1120 | * faster than copying the CDict's tables. |
1121 | * |
1122 | * - The CDict's tables are not used at all, and instead we use the working |
1123 | * context alone to reload the dictionary and use params based on the source |
1124 | * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict(). |
1125 | * This method is effective when the dictionary sizes are very small relative |
1126 | * to the input size, and the input size is fairly large to begin with. |
1127 | * |
1128 | * Zstd has a simple internal heuristic that selects which strategy to use |
1129 | * at the beginning of a compression. However, if experimentation shows that |
1130 | * Zstd is making poor choices, it is possible to override that choice with |
1131 | * this enum. |
1132 | */ |
1133 | ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> |
1134 | ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> |
1135 | ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> |
1136 | ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b> |
1137 | } ZSTD_dictAttachPref_e; |
1138 | </b></pre><BR> |
1139 | <pre><b>typedef enum { |
1140 | ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> |
1141 | * Negative compression levels will be uncompressed, and positive compression |
1142 | * levels will be compressed. */ |
1143 | ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> |
1144 | * emitted if Huffman compression is not profitable. */ |
1145 | ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b> |
1146 | } ZSTD_literalCompressionMode_e; |
1147 | </b></pre><BR> |
1148 | <pre><b>typedef enum { |
1149 | </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b> |
1150 | * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable |
1151 | * or ZSTD_ps_disable allow for a force enable/disable the feature. |
1152 | */ |
1153 | ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b> |
1154 | ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b> |
1155 | ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b> |
1156 | } ZSTD_paramSwitch_e; |
1157 | </b></pre><BR> |
1158 | <a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre> |
1159 | |
1160 | <pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); |
1161 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
1162 | `srcSize` must be the _exact_ size of this series |
1163 | (i.e. there should be a frame boundary at `src + srcSize`) |
1164 | @return : - decompressed size of all data in all successive frames |
1165 | - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN |
1166 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR |
1167 | |
1168 | note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. |
1169 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. |
1170 | In which case, it's necessary to use streaming mode to decompress data. |
1171 | note 2 : decompressed size is always present when compression is done with ZSTD_compress() |
1172 | note 3 : decompressed size can be very large (64-bits value), |
1173 | potentially larger than what local system can handle as a single memory segment. |
1174 | In which case, it's necessary to use streaming mode to decompress data. |
1175 | note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. |
1176 | Always ensure result fits within application's authorized limits. |
1177 | Each application can set its own limits. |
1178 | note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to |
1179 | read each contained frame header. This is fast as most of the data is skipped, |
1180 | however it does mean that all frame data must be present and valid. |
1181 | </p></pre><BR> |
1182 | |
1183 | <pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize); |
1184 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
1185 | `srcSize` must be the _exact_ size of this series |
1186 | (i.e. there should be a frame boundary at `src + srcSize`) |
1187 | @return : - upper-bound for the decompressed size of all data in all successive frames |
1188 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR |
1189 | |
1190 | note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. |
1191 | note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. |
1192 | in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. |
1193 | note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: |
1194 | upper-bound = # blocks * min(128 KB, Window_Size) |
1195 | |
1196 | </p></pre><BR> |
1197 | |
1198 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); |
1199 | </b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. |
1200 | @return : size of the Frame Header, |
1201 | or an error code (if srcSize is too small) |
1202 | </p></pre><BR> |
1203 | |
1204 | <pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; |
1205 | </b></pre><BR> |
1206 | <pre><b>typedef struct { |
1207 | unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> |
1208 | unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> |
1209 | unsigned blockSizeMax; |
1210 | ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> |
1211 | unsigned headerSize; |
1212 | unsigned dictID; |
1213 | unsigned checksumFlag; |
1214 | unsigned _reserved1; |
1215 | unsigned _reserved2; |
1216 | } ZSTD_frameHeader; |
1217 | </b></pre><BR> |
1218 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> |
1219 | </b>/*! ZSTD_getFrameHeader_advanced() :<b> |
1220 | * same as ZSTD_getFrameHeader(), |
1221 | * with added capability to select a format (like ZSTD_f_zstd1_magicless) */ |
1222 | ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); |
1223 | </b><p> decode Frame Header, or requires larger `srcSize`. |
1224 | @return : 0, `zfhPtr` is correctly filled, |
1225 | >0, `srcSize` is too small, value is wanted `srcSize` amount, |
1226 | or an error code, which can be tested using ZSTD_isError() |
1227 | </p></pre><BR> |
1228 | |
1229 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize); |
1230 | </b><p> Zstd supports in-place decompression, where the input and output buffers overlap. |
1231 | In this case, the output buffer must be at least (Margin + Output_Size) bytes large, |
1232 | and the input buffer must be at the end of the output buffer. |
1233 | |
1234 | _______________________ Output Buffer ________________________ |
1235 | | | |
1236 | | ____ Input Buffer ____| |
1237 | | | | |
1238 | v v v |
1239 | |---------------------------------------|-----------|----------| |
1240 | ^ ^ ^ |
1241 | |___________________ Output_Size ___________________|_ Margin _| |
1242 | |
1243 | NOTE: See also ZSTD_DECOMPRESSION_MARGIN(). |
1244 | NOTE: This applies only to single-pass decompression through ZSTD_decompress() or |
1245 | ZSTD_decompressDCtx(). |
1246 | NOTE: This function supports multi-frame input. |
1247 | |
1248 | @param src The compressed frame(s) |
1249 | @param srcSize The size of the compressed frame(s) |
1250 | @returns The decompression margin or an error that can be checked with ZSTD_isError(). |
1251 | |
1252 | </p></pre><BR> |
1253 | |
1254 | <pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \ |
1255 | ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b> |
1256 | 4 </b>/* checksum */ + \<b> |
1257 | ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b> |
1258 | (blockSize) </b>/* One block of margin */ \<b> |
1259 | )) |
1260 | </b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from |
1261 | the compressed frame, compute it from the original size and the blockSizeLog. |
1262 | See ZSTD_decompressionMargin() for details. |
1263 | |
1264 | WARNING: This macro does not support multi-frame input, the input must be a single |
1265 | zstd frame. If you need that support use the function, or implement it yourself. |
1266 | |
1267 | @param originalSize The original uncompressed size of the data. |
1268 | @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX). |
1269 | Unless you explicitly set the windowLog smaller than |
1270 | ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX. |
1271 | |
1272 | </p></pre><BR> |
1273 | |
1274 | <pre><b>typedef enum { |
1275 | ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b> |
1276 | ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b> |
1277 | } ZSTD_sequenceFormat_e; |
1278 | </b></pre><BR> |
1279 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize); |
1280 | </b><p> `srcSize` : size of the input buffer |
1281 | @return : upper-bound for the number of sequences that can be generated |
1282 | from a buffer of srcSize bytes |
1283 | |
1284 | note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence). |
1285 | |
1286 | </p></pre><BR> |
1287 | |
1288 | <pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer. |
1289 | |
1290 | Each block will end with a dummy sequence |
1291 | with offset == 0, matchLength == 0, and litLength == length of last literals. |
1292 | litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0) |
1293 | simply acts as a block delimiter. |
1294 | |
1295 | @zc can be used to insert custom compression params. |
1296 | This function invokes ZSTD_compress2(). |
1297 | |
1298 | The output of this function can be fed into ZSTD_compressSequences() with CCtx |
1299 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters |
1300 | @return : number of sequences generated |
1301 | |
1302 | </p></pre><BR> |
1303 | |
1304 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize); |
1305 | </b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals |
1306 | by merging them into the literals of the next sequence. |
1307 | |
1308 | As such, the final generated result has no explicit representation of block boundaries, |
1309 | and the final last literals segment is not represented in the sequences. |
1310 | |
1311 | The output of this function can be fed into ZSTD_compressSequences() with CCtx |
1312 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters |
1313 | @return : number of sequences left after merging |
1314 | |
1315 | </p></pre><BR> |
1316 | |
1317 | <pre><b>ZSTDLIB_STATIC_API size_t |
1318 | ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize, |
1319 | const ZSTD_Sequence* inSeqs, size_t inSeqsSize, |
1320 | const void* src, size_t srcSize); |
1321 | </b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst. |
1322 | @src contains the entire input (not just the literals). |
1323 | If @srcSize > sum(sequence.length), the remaining bytes are considered all literals |
1324 | If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.) |
1325 | The entire source is compressed into a single frame. |
1326 | |
1327 | The compression behavior changes based on cctx params. In particular: |
1328 | If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain |
1329 | no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on |
1330 | the block size derived from the cctx, and sequences may be split. This is the default setting. |
1331 | |
1332 | If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain |
1333 | block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided. |
1334 | |
1335 | If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined |
1336 | behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for |
1337 | specifics regarding offset/matchlength requirements) then the function will bail out and return an error. |
1338 | |
1339 | In addition to the two adjustable experimental params, there are other important cctx params. |
1340 | - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN. |
1341 | - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression. |
1342 | - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset |
1343 | is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md |
1344 | |
1345 | Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused. |
1346 | Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly, |
1347 | and cannot emit an RLE block that disagrees with the repcode history |
1348 | @return : final compressed size, or a ZSTD error code. |
1349 | |
1350 | </p></pre><BR> |
1351 | |
1352 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity, |
1353 | const void* src, size_t srcSize, unsigned magicVariant); |
1354 | </b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer. |
1355 | |
1356 | Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number, |
1357 | ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15. |
1358 | As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so |
1359 | the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant. |
1360 | |
1361 | Returns an error if destination buffer is not large enough, if the source size is not representable |
1362 | with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid). |
1363 | |
1364 | @return : number of bytes written or a ZSTD error. |
1365 | |
1366 | </p></pre><BR> |
1367 | |
1368 | <pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant, |
1369 | const void* src, size_t srcSize); |
1370 | </b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer. |
1371 | |
1372 | The parameter magicVariant will receive the magicVariant that was supplied when the frame was written, |
1373 | i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested |
1374 | in the magicVariant. |
1375 | |
1376 | Returns an error if destination buffer is not large enough, or if the frame is not skippable. |
1377 | |
1378 | @return : number of bytes written or a ZSTD error. |
1379 | |
1380 | </p></pre><BR> |
1381 | |
1382 | <pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size); |
1383 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame. |
1384 | |
1385 | </p></pre><BR> |
1386 | |
1387 | <a name="Chapter16"></a><h2>Memory management</h2><pre></pre> |
1388 | |
1389 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int compressionLevel); |
1390 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); |
1391 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); |
1392 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void); |
1393 | </b><p> These functions make it possible to estimate memory usage |
1394 | of a future {D,C}Ctx, before its creation. |
1395 | |
1396 | ZSTD_estimateCCtxSize() will provide a memory budget large enough |
1397 | for any compression level up to selected one. |
1398 | Note : Unlike ZSTD_estimateCStreamSize*(), this estimate |
1399 | does not include space for a window buffer. |
1400 | Therefore, the estimation is only guaranteed for single-shot compressions, not streaming. |
1401 | The estimate will assume the input may be arbitrarily large, |
1402 | which is the worst case. |
1403 | |
1404 | When srcSize can be bound by a known and rather "small" value, |
1405 | this fact can be used to provide a tighter estimation |
1406 | because the CCtx compression context will need less memory. |
1407 | This tighter estimation can be provided by more advanced functions |
1408 | ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(), |
1409 | and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter(). |
1410 | Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits. |
1411 | |
1412 | Note : only single-threaded compression is supported. |
1413 | ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. |
1414 | |
1415 | Note 2 : ZSTD_estimateCCtxSize* functions are not compatible with the Block-Level Sequence Producer API at this time. |
1416 | Size estimates assume that no external sequence producer is registered. |
1417 | |
1418 | </p></pre><BR> |
1419 | |
1420 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int compressionLevel); |
1421 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); |
1422 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); |
1423 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t windowSize); |
1424 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); |
1425 | </b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one. |
1426 | It will also consider src size to be arbitrarily "large", which is worst case. |
1427 | If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. |
1428 | ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. |
1429 | ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1. |
1430 | Note : CStream size estimation is only correct for single-threaded compression. |
1431 | ZSTD_DStream memory budget depends on window Size. |
1432 | This information can be passed manually, using ZSTD_estimateDStreamSize, |
1433 | or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); |
1434 | Note : if streaming is init with function ZSTD_init?Stream_usingDict(), |
1435 | an internal ?Dict will be created, which additional size is not estimated here. |
1436 | In this case, get total size by adding ZSTD_estimate?DictSize |
1437 | Note 2 : only single-threaded compression is supported. |
1438 | ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. |
1439 | Note 3 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time. |
1440 | Size estimates assume that no external sequence producer is registered. |
1441 | |
1442 | </p></pre><BR> |
1443 | |
1444 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); |
1445 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); |
1446 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); |
1447 | </b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). |
1448 | ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). |
1449 | Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. |
1450 | |
1451 | </p></pre><BR> |
1452 | |
1453 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); |
1454 | ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> |
1455 | </b><p> Initialize an object using a pre-allocated fixed-size buffer. |
1456 | workspace: The memory area to emplace the object into. |
1457 | Provided pointer *must be 8-bytes aligned*. |
1458 | Buffer must outlive object. |
1459 | workspaceSize: Use ZSTD_estimate*Size() to determine |
1460 | how large workspace must be to support target scenario. |
1461 | @return : pointer to object (same address as workspace, just different type), |
1462 | or NULL if error (size too small, incorrect alignment, etc.) |
1463 | Note : zstd will never resize nor malloc() when using a static buffer. |
1464 | If the object requires more memory than available, |
1465 | zstd will just error out (typically ZSTD_error_memory_allocation). |
1466 | Note 2 : there is no corresponding "free" function. |
1467 | Since workspace is allocated externally, it must be freed externally too. |
1468 | Note 3 : cParams : use ZSTD_getCParams() to convert a compression level |
1469 | into its associated cParams. |
1470 | Limitation 1 : currently not compatible with internal dictionary creation, triggered by |
1471 | ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). |
1472 | Limitation 2 : static cctx currently not compatible with multi-threading. |
1473 | Limitation 3 : static dctx is incompatible with legacy support. |
1474 | |
1475 | </p></pre><BR> |
1476 | |
1477 | <pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> |
1478 | </b></pre><BR> |
1479 | <pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); |
1480 | typedef void (*ZSTD_freeFunction) (void* opaque, void* address); |
1481 | typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; |
1482 | static |
1483 | #ifdef __GNUC__ |
1484 | __attribute__((__unused__)) |
1485 | #endif |
1486 | ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> |
1487 | </b><p> These prototypes make it possible to pass your own allocation/free functions. |
1488 | ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. |
1489 | All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. |
1490 | |
1491 | </p></pre><BR> |
1492 | |
1493 | <pre><b>typedef struct POOL_ctx_s ZSTD_threadPool; |
1494 | ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads); |
1495 | ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b> |
1496 | ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool); |
1497 | </b><p> These prototypes make it possible to share a thread pool among multiple compression contexts. |
1498 | This can limit resources for applications with multiple threads where each one uses |
1499 | a threaded compression mode (via ZSTD_c_nbWorkers parameter). |
1500 | ZSTD_createThreadPool creates a new thread pool with a given number of threads. |
1501 | Note that the lifetime of such pool must exist while being used. |
1502 | ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value |
1503 | to use an internal thread pool). |
1504 | ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer. |
1505 | |
1506 | </p></pre><BR> |
1507 | |
1508 | <a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre> |
1509 | |
1510 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); |
1511 | </b><p> Create a digested dictionary for compression |
1512 | Dictionary content is just referenced, not duplicated. |
1513 | As a consequence, `dictBuffer` **must** outlive CDict, |
1514 | and its content must remain unmodified throughout the lifetime of CDict. |
1515 | note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef |
1516 | </p></pre><BR> |
1517 | |
1518 | <pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); |
1519 | </b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. |
1520 | `estimatedSrcSize` value is optional, select 0 if not known |
1521 | </p></pre><BR> |
1522 | |
1523 | <pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); |
1524 | </b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. |
1525 | All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 |
1526 | </p></pre><BR> |
1527 | |
1528 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params); |
1529 | </b><p> Ensure param values remain within authorized range. |
1530 | @return 0 on success, or an error code (can be checked with ZSTD_isError()) |
1531 | </p></pre><BR> |
1532 | |
1533 | <pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); |
1534 | </b><p> optimize params for a given `srcSize` and `dictSize`. |
1535 | `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. |
1536 | `dictSize` must be `0` when there is no dictionary. |
1537 | cPar can be invalid : all parameters will be clamped within valid range in the @return struct. |
1538 | This function never fails (wide contract) |
1539 | </p></pre><BR> |
1540 | |
1541 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams); |
1542 | </b><p> Set all parameters provided within @p cparams into the working @p cctx. |
1543 | Note : if modifying parameters during compression (MT mode only), |
1544 | note that changes to the .windowLog parameter will be ignored. |
1545 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
1546 | On failure, no parameters are updated. |
1547 | |
1548 | </p></pre><BR> |
1549 | |
1550 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams); |
1551 | </b><p> Set all parameters provided within @p fparams into the working @p cctx. |
1552 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
1553 | |
1554 | </p></pre><BR> |
1555 | |
1556 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params); |
1557 | </b><p> Set all parameters provided within @p params into the working @p cctx. |
1558 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
1559 | |
1560 | </p></pre><BR> |
1561 | |
1562 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2") |
1563 | ZSTDLIB_STATIC_API |
1564 | size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, |
1565 | void* dst, size_t dstCapacity, |
1566 | const void* src, size_t srcSize, |
1567 | const void* dict,size_t dictSize, |
1568 | ZSTD_parameters params); |
1569 | </b><p> Note : this function is now DEPRECATED. |
1570 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters. |
1571 | This prototype will generate compilation warnings. |
1572 | </p></pre><BR> |
1573 | |
1574 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary") |
1575 | ZSTDLIB_STATIC_API |
1576 | size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, |
1577 | void* dst, size_t dstCapacity, |
1578 | const void* src, size_t srcSize, |
1579 | const ZSTD_CDict* cdict, |
1580 | ZSTD_frameParameters fParams); |
1581 | </b><p> Note : this function is now DEPRECATED. |
1582 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters. |
1583 | This prototype will generate compilation warnings. |
1584 | </p></pre><BR> |
1585 | |
1586 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); |
1587 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. |
1588 | It saves some memory, but also requires that `dict` outlives its usage within `cctx` |
1589 | </p></pre><BR> |
1590 | |
1591 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); |
1592 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over |
1593 | how to load the dictionary (by copy ? by reference ?) |
1594 | and how to interpret it (automatic ? force raw mode ? full mode only ?) |
1595 | </p></pre><BR> |
1596 | |
1597 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); |
1598 | </b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over |
1599 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) |
1600 | </p></pre><BR> |
1601 | |
1602 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); |
1603 | </b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, |
1604 | and store it into int* value. |
1605 | @return : 0, or an error code (which can be tested with ZSTD_isError()). |
1606 | |
1607 | </p></pre><BR> |
1608 | |
1609 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void); |
1610 | ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b> |
1611 | </b><p> Quick howto : |
1612 | - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure |
1613 | - ZSTD_CCtxParams_setParameter() : Push parameters one by one into |
1614 | an existing ZSTD_CCtx_params structure. |
1615 | This is similar to |
1616 | ZSTD_CCtx_setParameter(). |
1617 | - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to |
1618 | an existing CCtx. |
1619 | These parameters will be applied to |
1620 | all subsequent frames. |
1621 | - ZSTD_compressStream2() : Do compression using the CCtx. |
1622 | - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer. |
1623 | |
1624 | This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() |
1625 | for static allocation of CCtx for single-threaded compression. |
1626 | |
1627 | </p></pre><BR> |
1628 | |
1629 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); |
1630 | </b><p> Reset params to default values. |
1631 | |
1632 | </p></pre><BR> |
1633 | |
1634 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); |
1635 | </b><p> Initializes the compression parameters of cctxParams according to |
1636 | compression level. All other parameters are reset to their default values. |
1637 | |
1638 | </p></pre><BR> |
1639 | |
1640 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); |
1641 | </b><p> Initializes the compression and frame parameters of cctxParams according to |
1642 | params. All other parameters are reset to their default values. |
1643 | |
1644 | </p></pre><BR> |
1645 | |
1646 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); |
1647 | </b><p> Similar to ZSTD_CCtx_setParameter. |
1648 | Set one compression parameter, selected by enum ZSTD_cParameter. |
1649 | Parameters must be applied to a ZSTD_CCtx using |
1650 | ZSTD_CCtx_setParametersUsingCCtxParams(). |
1651 | @result : a code representing success or failure (which can be tested with |
1652 | ZSTD_isError()). |
1653 | |
1654 | </p></pre><BR> |
1655 | |
1656 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); |
1657 | </b><p> Similar to ZSTD_CCtx_getParameter. |
1658 | Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. |
1659 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
1660 | |
1661 | </p></pre><BR> |
1662 | |
1663 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams( |
1664 | ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); |
1665 | </b><p> Apply a set of ZSTD_CCtx_params to the compression context. |
1666 | This can be done even after compression is started, |
1667 | if nbWorkers==0, this will have no impact until a new compression is started. |
1668 | if nbWorkers>=1, new parameters will be picked up at next job, |
1669 | with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). |
1670 | |
1671 | </p></pre><BR> |
1672 | |
1673 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs ( |
1674 | ZSTD_CCtx* cctx, |
1675 | void* dst, size_t dstCapacity, size_t* dstPos, |
1676 | const void* src, size_t srcSize, size_t* srcPos, |
1677 | ZSTD_EndDirective endOp); |
1678 | </b><p> Same as ZSTD_compressStream2(), |
1679 | but using only integral types as arguments. |
1680 | This variant might be helpful for binders from dynamic languages |
1681 | which have troubles handling structures containing memory pointers. |
1682 | |
1683 | </p></pre><BR> |
1684 | |
1685 | <a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre> |
1686 | |
1687 | <pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size); |
1688 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. |
1689 | Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. |
1690 | Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. |
1691 | Note 3 : Skippable Frame Identifiers are considered valid. |
1692 | </p></pre><BR> |
1693 | |
1694 | <pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); |
1695 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. |
1696 | Dictionary content is referenced, and therefore stays in dictBuffer. |
1697 | It is important that dictBuffer outlives DDict, |
1698 | it must remain read accessible throughout the lifetime of DDict |
1699 | </p></pre><BR> |
1700 | |
1701 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); |
1702 | </b><p> Same as ZSTD_DCtx_loadDictionary(), |
1703 | but references `dict` content instead of copying it into `dctx`. |
1704 | This saves memory if `dict` remains around., |
1705 | However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. |
1706 | </p></pre><BR> |
1707 | |
1708 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); |
1709 | </b><p> Same as ZSTD_DCtx_loadDictionary(), |
1710 | but gives direct control over |
1711 | how to load the dictionary (by copy ? by reference ?) |
1712 | and how to interpret it (automatic ? force raw mode ? full mode only ?). |
1713 | </p></pre><BR> |
1714 | |
1715 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); |
1716 | </b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over |
1717 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) |
1718 | </p></pre><BR> |
1719 | |
1720 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); |
1721 | </b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. |
1722 | This protects a decoder context from reserving too much memory for itself (potential attack scenario). |
1723 | This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. |
1724 | By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) |
1725 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
1726 | |
1727 | </p></pre><BR> |
1728 | |
1729 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value); |
1730 | </b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter, |
1731 | and store it into int* value. |
1732 | @return : 0, or an error code (which can be tested with ZSTD_isError()). |
1733 | |
1734 | </p></pre><BR> |
1735 | |
1736 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead") |
1737 | ZSTDLIB_STATIC_API |
1738 | size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); |
1739 | </b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter(). |
1740 | Instruct the decoder context about what kind of data to decode next. |
1741 | This instruction is mandatory to decode data without a fully-formed header, |
1742 | such ZSTD_f_zstd1_magicless for example. |
1743 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
1744 | </p></pre><BR> |
1745 | |
1746 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs ( |
1747 | ZSTD_DCtx* dctx, |
1748 | void* dst, size_t dstCapacity, size_t* dstPos, |
1749 | const void* src, size_t srcSize, size_t* srcPos); |
1750 | </b><p> Same as ZSTD_decompressStream(), |
1751 | but using only integral types as arguments. |
1752 | This can be helpful for binders from dynamic languages |
1753 | which have troubles handling structures containing memory pointers. |
1754 | |
1755 | </p></pre><BR> |
1756 | |
1757 | <a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. |
1758 | Once Advanced API reaches "stable" status, |
1759 | redundant functions will be deprecated, and then at some point removed. |
1760 | <BR></pre> |
1761 | |
1762 | <h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR> |
1763 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
1764 | ZSTDLIB_STATIC_API |
1765 | size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, |
1766 | int compressionLevel, |
1767 | unsigned long long pledgedSrcSize); |
1768 | </b><p> This function is DEPRECATED, and equivalent to: |
1769 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1770 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) |
1771 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
1772 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
1773 | |
1774 | pledgedSrcSize must be correct. If it is not known at init time, use |
1775 | ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, |
1776 | "0" also disables frame content size field. It may be enabled in the future. |
1777 | This prototype will generate compilation warnings. |
1778 | |
1779 | </p></pre><BR> |
1780 | |
1781 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
1782 | ZSTDLIB_STATIC_API |
1783 | size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, |
1784 | const void* dict, size_t dictSize, |
1785 | int compressionLevel); |
1786 | </b><p> This function is DEPRECATED, and is equivalent to: |
1787 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1788 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
1789 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); |
1790 | |
1791 | Creates of an internal CDict (incompatible with static CCtx), except if |
1792 | dict == NULL or dictSize < 8, in which case no dict is used. |
1793 | Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if |
1794 | it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. |
1795 | This prototype will generate compilation warnings. |
1796 | |
1797 | </p></pre><BR> |
1798 | |
1799 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
1800 | ZSTDLIB_STATIC_API |
1801 | size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, |
1802 | const void* dict, size_t dictSize, |
1803 | ZSTD_parameters params, |
1804 | unsigned long long pledgedSrcSize); |
1805 | </b><p> This function is DEPRECATED, and is equivalent to: |
1806 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1807 | ZSTD_CCtx_setParams(zcs, params); |
1808 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
1809 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); |
1810 | |
1811 | dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy. |
1812 | pledgedSrcSize must be correct. |
1813 | If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. |
1814 | This prototype will generate compilation warnings. |
1815 | |
1816 | </p></pre><BR> |
1817 | |
1818 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") |
1819 | ZSTDLIB_STATIC_API |
1820 | size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); |
1821 | </b><p> This function is DEPRECATED, and equivalent to: |
1822 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1823 | ZSTD_CCtx_refCDict(zcs, cdict); |
1824 | |
1825 | note : cdict will just be referenced, and must outlive compression session |
1826 | This prototype will generate compilation warnings. |
1827 | |
1828 | </p></pre><BR> |
1829 | |
1830 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") |
1831 | ZSTDLIB_STATIC_API |
1832 | size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, |
1833 | const ZSTD_CDict* cdict, |
1834 | ZSTD_frameParameters fParams, |
1835 | unsigned long long pledgedSrcSize); |
1836 | </b><p> This function is DEPRECATED, and is equivalent to: |
1837 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1838 | ZSTD_CCtx_setFParams(zcs, fParams); |
1839 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
1840 | ZSTD_CCtx_refCDict(zcs, cdict); |
1841 | |
1842 | same as ZSTD_initCStream_usingCDict(), with control over frame parameters. |
1843 | pledgedSrcSize must be correct. If srcSize is not known at init time, use |
1844 | value ZSTD_CONTENTSIZE_UNKNOWN. |
1845 | This prototype will generate compilation warnings. |
1846 | |
1847 | </p></pre><BR> |
1848 | |
1849 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
1850 | ZSTDLIB_STATIC_API |
1851 | size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); |
1852 | </b><p> This function is DEPRECATED, and is equivalent to: |
1853 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
1854 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
1855 | Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but |
1856 | ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be |
1857 | explicitly specified. |
1858 | |
1859 | start a new frame, using same parameters from previous frame. |
1860 | This is typically useful to skip dictionary loading stage, since it will re-use it in-place. |
1861 | Note that zcs must be init at least once before using ZSTD_resetCStream(). |
1862 | If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. |
1863 | If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. |
1864 | For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, |
1865 | but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. |
1866 | @return : 0, or an error code (which can be tested using ZSTD_isError()) |
1867 | This prototype will generate compilation warnings. |
1868 | |
1869 | </p></pre><BR> |
1870 | |
1871 | <pre><b>typedef struct { |
1872 | unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> |
1873 | unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> |
1874 | unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> |
1875 | unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> |
1876 | unsigned currentJobID; </b>/* MT only : latest started job nb */<b> |
1877 | unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> |
1878 | } ZSTD_frameProgression; |
1879 | </b></pre><BR> |
1880 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); |
1881 | </b><p> Tell how many bytes are ready to be flushed immediately. |
1882 | Useful for multithreading scenarios (nbWorkers >= 1). |
1883 | Probe the oldest active job, defined as oldest job not yet entirely flushed, |
1884 | and check its output buffer. |
1885 | @return : amount of data stored in oldest job and ready to be flushed immediately. |
1886 | if @return == 0, it means either : |
1887 | + there is no active job (could be checked with ZSTD_frameProgression()), or |
1888 | + oldest job is still actively compressing data, |
1889 | but everything it has produced has also been flushed so far, |
1890 | therefore flush speed is limited by production speed of oldest job |
1891 | irrespective of the speed of concurrent (and newer) jobs. |
1892 | |
1893 | </p></pre><BR> |
1894 | |
1895 | <h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
1896 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions") |
1897 | ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); |
1898 | </b><p> |
1899 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
1900 | ZSTD_DCtx_loadDictionary(zds, dict, dictSize); |
1901 | |
1902 | note: no dictionary will be used if dict == NULL or dictSize < 8 |
1903 | |
1904 | </p></pre><BR> |
1905 | |
1906 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions") |
1907 | ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); |
1908 | </b><p> |
1909 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
1910 | ZSTD_DCtx_refDDict(zds, ddict); |
1911 | |
1912 | note : ddict is referenced, it must outlive decompression session |
1913 | |
1914 | </p></pre><BR> |
1915 | |
1916 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions") |
1917 | ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds); |
1918 | </b><p> |
1919 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
1920 | |
1921 | re-use decompression parameters from previous init; saves dictionary loading |
1922 | |
1923 | </p></pre><BR> |
1924 | |
1925 | <pre><b>ZSTDLIB_STATIC_API void |
1926 | ZSTD_registerSequenceProducer( |
1927 | ZSTD_CCtx* cctx, |
1928 | void* sequenceProducerState, |
1929 | ZSTD_sequenceProducer_F* sequenceProducer |
1930 | ); |
1931 | </b><p> Instruct zstd to use a block-level external sequence producer function. |
1932 | |
1933 | The sequenceProducerState must be initialized by the caller, and the caller is |
1934 | responsible for managing its lifetime. This parameter is sticky across |
1935 | compressions. It will remain set until the user explicitly resets compression |
1936 | parameters. |
1937 | |
1938 | Sequence producer registration is considered to be an "advanced parameter", |
1939 | part of the "advanced API". This means it will only have an effect on compression |
1940 | APIs which respect advanced parameters, such as compress2() and compressStream2(). |
1941 | Older compression APIs such as compressCCtx(), which predate the introduction of |
1942 | "advanced parameters", will ignore any external sequence producer setting. |
1943 | |
1944 | The sequence producer can be "cleared" by registering a NULL function pointer. This |
1945 | removes all limitations described above in the "LIMITATIONS" section of the API docs. |
1946 | |
1947 | The user is strongly encouraged to read the full API documentation (above) before |
1948 | calling this function. |
1949 | </p></pre><BR> |
1950 | |
1951 | <a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre> |
1952 | This API is deprecated, and will be removed in a future version. |
1953 | It allows streaming (de)compression with user allocated buffers. |
1954 | However, it is hard to use, and not as well tested as the rest of |
1955 | our API. |
1956 | |
1957 | Please use the normal streaming API instead: ZSTD_compressStream2, |
1958 | and ZSTD_decompressStream. |
1959 | If there is functionality that you need, but it doesn't provide, |
1960 | please open an issue on our GitHub. |
1961 | |
1962 | <BR></pre> |
1963 | |
1964 | <a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> |
1965 | A ZSTD_CCtx object is required to track streaming operations. |
1966 | Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. |
1967 | ZSTD_CCtx object can be re-used multiple times within successive compression operations. |
1968 | |
1969 | Start by initializing a context. |
1970 | Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression. |
1971 | |
1972 | Then, consume your input using ZSTD_compressContinue(). |
1973 | There are some important considerations to keep in mind when using this advanced function : |
1974 | - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. |
1975 | - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. |
1976 | - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. |
1977 | Worst case evaluation is provided by ZSTD_compressBound(). |
1978 | ZSTD_compressContinue() doesn't guarantee recover after a failed compression. |
1979 | - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). |
1980 | It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) |
1981 | - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. |
1982 | In which case, it will "discard" the relevant memory section from its history. |
1983 | |
1984 | Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. |
1985 | It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. |
1986 | Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. |
1987 | |
1988 | `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again. |
1989 | <BR></pre> |
1990 | |
1991 | <h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
1992 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); |
1993 | ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
1994 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); |
1995 | ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
1996 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> |
1997 | </pre></b><BR> |
1998 | <pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b> |
1999 | </b></pre><BR> |
2000 | <pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b> |
2001 | </b></pre><BR> |
2002 | <a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> |
2003 | A ZSTD_DCtx object is required to track streaming operations. |
2004 | Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. |
2005 | A ZSTD_DCtx object can be re-used multiple times. |
2006 | |
2007 | First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). |
2008 | Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. |
2009 | Data fragment must be large enough to ensure successful decoding. |
2010 | `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. |
2011 | result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. |
2012 | >0 : `srcSize` is too small, please provide at least result bytes on next attempt. |
2013 | errorCode, which can be tested using ZSTD_isError(). |
2014 | |
2015 | It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, |
2016 | such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). |
2017 | Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. |
2018 | As a consequence, check that values remain within valid application range. |
2019 | For example, do not allocate memory blindly, check that `windowSize` is within expectation. |
2020 | Each application can set its own limits, depending on local restrictions. |
2021 | For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. |
2022 | |
2023 | ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. |
2024 | ZSTD_decompressContinue() is very sensitive to contiguity, |
2025 | if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, |
2026 | or that previous contiguous segment is large enough to properly handle maximum back-reference distance. |
2027 | There are multiple ways to guarantee this condition. |
2028 | |
2029 | The most memory efficient way is to use a round buffer of sufficient size. |
2030 | Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), |
2031 | which can return an error code if required value is too large for current system (in 32-bits mode). |
2032 | In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, |
2033 | up to the moment there is not enough room left in the buffer to guarantee decoding another full block, |
2034 | which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. |
2035 | At which point, decoding can resume from the beginning of the buffer. |
2036 | Note that already decoded data stored in the buffer should be flushed before being overwritten. |
2037 | |
2038 | There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. |
2039 | |
2040 | Finally, if you control the compression process, you can also ignore all buffer size rules, |
2041 | as long as the encoder and decoder progress in "lock-step", |
2042 | aka use exactly the same buffer sizes, break contiguity at the same place, etc. |
2043 | |
2044 | Once buffers are setup, start decompression, with ZSTD_decompressBegin(). |
2045 | If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). |
2046 | |
2047 | Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. |
2048 | ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). |
2049 | ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. |
2050 | |
2051 | result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). |
2052 | It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. |
2053 | It can also be an error code, which can be tested with ZSTD_isError(). |
2054 | |
2055 | A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. |
2056 | Context can then be reset to start a new decompression. |
2057 | |
2058 | Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). |
2059 | This information is not required to properly decode a frame. |
2060 | |
2061 | == Special case : skippable frames |
2062 | |
2063 | Skippable frames allow integration of user-defined data into a flow of concatenated frames. |
2064 | Skippable frames will be ignored (skipped) by decompressor. |
2065 | The format of skippable frames is as follows : |
2066 | a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F |
2067 | b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits |
2068 | c) Frame Content - any content (User Data) of length equal to Frame Size |
2069 | For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. |
2070 | For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. |
2071 | <BR></pre> |
2072 | |
2073 | <h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
2074 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> |
2075 | </b></pre><BR> |
2076 | <pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; |
2077 | </b></pre><BR> |
2078 | <a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre> |
2079 | |
2080 | <pre><b></b><p> You can get the frame header down to 2 bytes by setting: |
2081 | - ZSTD_c_format = ZSTD_f_zstd1_magicless |
2082 | - ZSTD_c_contentSizeFlag = 0 |
2083 | - ZSTD_c_checksumFlag = 0 |
2084 | - ZSTD_c_dictIDFlag = 0 |
2085 | |
2086 | This API is not as well tested as our normal API, so we recommend not using it. |
2087 | We will be removing it in a future version. If the normal API doesn't provide |
2088 | the functionality you need, please open a GitHub issue. |
2089 | |
2090 | Block functions produce and decode raw zstd blocks, without frame metadata. |
2091 | Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes). |
2092 | But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes. |
2093 | |
2094 | A few rules to respect : |
2095 | - Compressing and decompressing require a context structure |
2096 | + Use ZSTD_createCCtx() and ZSTD_createDCtx() |
2097 | - It is necessary to init context before starting |
2098 | + compression : any ZSTD_compressBegin*() variant, including with dictionary |
2099 | + decompression : any ZSTD_decompressBegin*() variant, including with dictionary |
2100 | - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB |
2101 | + If input is larger than a block size, it's necessary to split input data into multiple blocks |
2102 | + For inputs larger than a single block, consider using regular ZSTD_compress() instead. |
2103 | Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block. |
2104 | - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) ! |
2105 | ===> In which case, nothing is produced into `dst` ! |
2106 | + User __must__ test for such outcome and deal directly with uncompressed data |
2107 | + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0. |
2108 | Doing so would mess up with statistics history, leading to potential data corruption. |
2109 | + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !! |
2110 | + In case of multiple successive blocks, should some of them be uncompressed, |
2111 | decoder must be informed of their existence in order to follow proper history. |
2112 | Use ZSTD_insertBlock() for such a case. |
2113 | </p></pre><BR> |
2114 | |
2115 | <h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
2116 | ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); |
2117 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
2118 | ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); |
2119 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
2120 | ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); |
2121 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
2122 | ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b> |
2123 | </pre></b><BR> |
2124 | </html> |
2125 | </body> |