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3 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> | |
9f95a23c | 4 | <title>zstd 1.4.0 Manual</title> |
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5 | </head> |
6 | <body> | |
9f95a23c | 7 | <h1>zstd 1.4.0 Manual</h1> |
7c673cae FG |
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> | |
9f95a23c TL |
13 | <li><a href="#Chapter3">Default constant</a></li> |
14 | <li><a href="#Chapter4">Constants</a></li> | |
15 | <li><a href="#Chapter5">Simple API</a></li> | |
16 | <li><a href="#Chapter6">Explicit context</a></li> | |
17 | <li><a href="#Chapter7">Advanced compression API</a></li> | |
18 | <li><a href="#Chapter8">Advanced decompression API</a></li> | |
19 | <li><a href="#Chapter9">Streaming</a></li> | |
20 | <li><a href="#Chapter10">Streaming compression - HowTo</a></li> | |
21 | <li><a href="#Chapter11">This is a legacy streaming API, and can be replaced by ZSTD_CCtx_reset() and</a></li> | |
22 | <li><a href="#Chapter12">Equivalent to:</a></li> | |
23 | <li><a href="#Chapter13">Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).</a></li> | |
24 | <li><a href="#Chapter14">Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush).</a></li> | |
25 | <li><a href="#Chapter15">Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end).</a></li> | |
26 | <li><a href="#Chapter16">Streaming decompression - HowTo</a></li> | |
27 | <li><a href="#Chapter17">Simple dictionary API</a></li> | |
28 | <li><a href="#Chapter18">Bulk processing dictionary API</a></li> | |
29 | <li><a href="#Chapter19">Dictionary helper functions</a></li> | |
30 | <li><a href="#Chapter20">Advanced dictionary and prefix API</a></li> | |
31 | <li><a href="#Chapter21">ADVANCED AND EXPERIMENTAL FUNCTIONS</a></li> | |
32 | <li><a href="#Chapter22">experimental API (static linking only)</a></li> | |
33 | <li><a href="#Chapter23">Frame size functions</a></li> | |
34 | <li><a href="#Chapter24">ZSTD_decompressBound() :</a></li> | |
35 | <li><a href="#Chapter25">Memory management</a></li> | |
36 | <li><a href="#Chapter26">Advanced compression functions</a></li> | |
37 | <li><a href="#Chapter27">Advanced decompression functions</a></li> | |
38 | <li><a href="#Chapter28">Advanced streaming functions</a></li> | |
39 | <li><a href="#Chapter29">Buffer-less and synchronous inner streaming functions</a></li> | |
40 | <li><a href="#Chapter30">Buffer-less streaming compression (synchronous mode)</a></li> | |
41 | <li><a href="#Chapter31">Buffer-less streaming decompression (synchronous mode)</a></li> | |
42 | <li><a href="#Chapter32">ZSTD_getFrameHeader() :</a></li> | |
43 | <li><a href="#Chapter33">Block level API</a></li> | |
7c673cae FG |
44 | </ol> |
45 | <hr> | |
46 | <a name="Chapter1"></a><h2>Introduction</h2><pre> | |
9f95a23c TL |
47 | zstd, short for Zstandard, is a fast lossless compression algorithm, targeting |
48 | real-time compression scenarios at zlib-level and better compression ratios. | |
49 | The zstd compression library provides in-memory compression and decompression | |
50 | functions. | |
51 | ||
52 | The library supports regular compression levels from 1 up to ZSTD_maxCLevel(), | |
53 | which is currently 22. Levels >= 20, labeled `--ultra`, should be used with | |
54 | caution, as they require more memory. The library also offers negative | |
55 | compression levels, which extend the range of speed vs. ratio preferences. | |
56 | The lower the level, the faster the speed (at the cost of compression). | |
57 | ||
7c673cae FG |
58 | Compression can be done in: |
59 | - a single step (described as Simple API) | |
9f95a23c | 60 | - a single step, reusing a context (described as Explicit context) |
7c673cae | 61 | - unbounded multiple steps (described as Streaming compression) |
9f95a23c TL |
62 | |
63 | The compression ratio achievable on small data can be highly improved using | |
64 | a dictionary. Dictionary compression can be performed in: | |
7c673cae | 65 | - a single step (described as Simple dictionary API) |
9f95a23c TL |
66 | - a single step, reusing a dictionary (described as Bulk-processing |
67 | dictionary API) | |
68 | ||
69 | Advanced experimental functions can be accessed using | |
70 | `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. | |
7c673cae | 71 | |
9f95a23c TL |
72 | Advanced experimental APIs should never be used with a dynamically-linked |
73 | library. They are not "stable"; their definitions or signatures may change in | |
74 | the future. Only static linking is allowed. | |
7c673cae FG |
75 | <BR></pre> |
76 | ||
77 | <a name="Chapter2"></a><h2>Version</h2><pre></pre> | |
78 | ||
9f95a23c | 79 | <pre><b>unsigned ZSTD_versionNumber(void); </b>/**< to check runtime library version */<b> |
7c673cae | 80 | </b></pre><BR> |
9f95a23c TL |
81 | <a name="Chapter3"></a><h2>Default constant</h2><pre></pre> |
82 | ||
83 | <a name="Chapter4"></a><h2>Constants</h2><pre></pre> | |
84 | ||
85 | <a name="Chapter5"></a><h2>Simple API</h2><pre></pre> | |
7c673cae FG |
86 | |
87 | <pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, | |
11fdf7f2 TL |
88 | const void* src, size_t srcSize, |
89 | int compressionLevel); | |
90 | </b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. | |
91 | Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`. | |
92 | @return : compressed size written into `dst` (<= `dstCapacity), | |
93 | or an error code if it fails (which can be tested using ZSTD_isError()). | |
7c673cae FG |
94 | </p></pre><BR> |
95 | ||
96 | <pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, | |
11fdf7f2 TL |
97 | const void* src, size_t compressedSize); |
98 | </b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. | |
99 | `dstCapacity` is an upper bound of originalSize to regenerate. | |
100 | If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data. | |
101 | @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), | |
102 | or an errorCode if it fails (which can be tested using ZSTD_isError()). | |
103 | </p></pre><BR> | |
104 | ||
105 | <pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) | |
106 | #define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) | |
107 | unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); | |
108 | </b><p> `src` should point to the start of a ZSTD encoded frame. | |
109 | `srcSize` must be at least as large as the frame header. | |
110 | hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. | |
9f95a23c | 111 | @return : - decompressed size of `src` frame content, if known |
11fdf7f2 TL |
112 | - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined |
113 | - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) | |
114 | note 1 : a 0 return value means the frame is valid but "empty". | |
115 | note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode. | |
116 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. | |
117 | In which case, it's necessary to use streaming mode to decompress data. | |
118 | Optionally, application can rely on some implicit limit, | |
119 | as ZSTD_decompress() only needs an upper bound of decompressed size. | |
120 | (For example, data could be necessarily cut into blocks <= 16 KB). | |
9f95a23c TL |
121 | note 3 : decompressed size is always present when compression is completed using single-pass functions, |
122 | such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict(). | |
11fdf7f2 TL |
123 | note 4 : decompressed size can be very large (64-bits value), |
124 | potentially larger than what local system can handle as a single memory segment. | |
125 | In which case, it's necessary to use streaming mode to decompress data. | |
126 | note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. | |
127 | Always ensure return value fits within application's authorized limits. | |
128 | Each application can set its own limits. | |
129 | note 6 : This function replaces ZSTD_getDecompressedSize() | |
7c673cae FG |
130 | </p></pre><BR> |
131 | ||
132 | <pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); | |
11fdf7f2 | 133 | </b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). |
9f95a23c TL |
134 | Both functions work the same way, but ZSTD_getDecompressedSize() blends |
135 | "empty", "unknown" and "error" results to the same return value (0), | |
136 | while ZSTD_getFrameContentSize() gives them separate return values. | |
137 | @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. | |
138 | </p></pre><BR> | |
11fdf7f2 | 139 | |
9f95a23c TL |
140 | <pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); |
141 | </b><p> `src` should point to the start of a ZSTD frame or skippable frame. | |
142 | `srcSize` must be >= first frame size | |
143 | @return : the compressed size of the first frame starting at `src`, | |
144 | suitable to pass as `srcSize` to `ZSTD_decompress` or similar, | |
145 | or an error code if input is invalid | |
11fdf7f2 TL |
146 | </p></pre><BR> |
147 | ||
9f95a23c TL |
148 | <h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> |
149 | size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b> | |
7c673cae FG |
150 | unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> |
151 | const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> | |
9f95a23c | 152 | int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed */<b> |
11fdf7f2 TL |
153 | int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> |
154 | </pre></b><BR> | |
9f95a23c | 155 | <a name="Chapter6"></a><h2>Explicit context</h2><pre></pre> |
7c673cae | 156 | |
11fdf7f2 TL |
157 | <h3>Compression context</h3><pre> When compressing many times, |
158 | it is recommended to allocate a context just once, and re-use it for each successive compression operation. | |
159 | This will make workload friendlier for system's memory. | |
160 | Use one context per thread for parallel execution in multi-threaded environments. | |
161 | </pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; | |
162 | ZSTD_CCtx* ZSTD_createCCtx(void); | |
163 | size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); | |
164 | </pre></b><BR> | |
9f95a23c | 165 | <pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, |
11fdf7f2 TL |
166 | void* dst, size_t dstCapacity, |
167 | const void* src, size_t srcSize, | |
168 | int compressionLevel); | |
9f95a23c TL |
169 | </b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx |
170 | The function will compress at requested compression level, | |
171 | ignoring any other parameter | |
7c673cae FG |
172 | </p></pre><BR> |
173 | ||
11fdf7f2 TL |
174 | <h3>Decompression context</h3><pre> When decompressing many times, |
175 | it is recommended to allocate a context only once, | |
176 | and re-use it for each successive compression operation. | |
177 | This will make workload friendlier for system's memory. | |
178 | Use one context per thread for parallel execution. | |
179 | </pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; | |
7c673cae FG |
180 | ZSTD_DCtx* ZSTD_createDCtx(void); |
181 | size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); | |
11fdf7f2 | 182 | </pre></b><BR> |
9f95a23c | 183 | <pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, |
11fdf7f2 TL |
184 | void* dst, size_t dstCapacity, |
185 | const void* src, size_t srcSize); | |
9f95a23c TL |
186 | </b><p> Same as ZSTD_decompress(), |
187 | requires an allocated ZSTD_DCtx. | |
188 | Compatible with sticky parameters. | |
189 | ||
7c673cae FG |
190 | </p></pre><BR> |
191 | ||
9f95a23c TL |
192 | <a name="Chapter7"></a><h2>Advanced compression API</h2><pre></pre> |
193 | ||
194 | <pre><b>typedef enum { ZSTD_fast=1, | |
195 | ZSTD_dfast=2, | |
196 | ZSTD_greedy=3, | |
197 | ZSTD_lazy=4, | |
198 | ZSTD_lazy2=5, | |
199 | ZSTD_btlazy2=6, | |
200 | ZSTD_btopt=7, | |
201 | ZSTD_btultra=8, | |
202 | ZSTD_btultra2=9 | |
203 | </b>/* note : new strategies _might_ be added in the future.<b> | |
204 | Only the order (from fast to strong) is guaranteed */ | |
205 | } ZSTD_strategy; | |
206 | </b></pre><BR> | |
207 | <pre><b>typedef enum { | |
7c673cae | 208 | |
9f95a23c TL |
209 | </b>/* compression parameters<b> |
210 | * Note: When compressing with a ZSTD_CDict these parameters are superseded | |
211 | * by the parameters used to construct the ZSTD_CDict. See ZSTD_CCtx_refCDict() | |
212 | * for more info (superseded-by-cdict). */ | |
213 | ZSTD_c_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b> | |
214 | * Default level is ZSTD_CLEVEL_DEFAULT==3. | |
215 | * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. | |
216 | * Note 1 : it's possible to pass a negative compression level. | |
217 | * Note 2 : setting a level sets all default values of other compression parameters */ | |
218 | ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> | |
219 | * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. | |
220 | * Special: value 0 means "use default windowLog". | |
221 | * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT | |
222 | * requires explicitly allowing such window size at decompression stage if using streaming. */ | |
223 | ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> | |
224 | * Resulting memory usage is (1 << (hashLog+2)). | |
225 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. | |
226 | * Larger tables improve compression ratio of strategies <= dFast, | |
227 | * and improve speed of strategies > dFast. | |
228 | * Special: value 0 means "use default hashLog". */ | |
229 | ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> | |
230 | * Resulting memory usage is (1 << (chainLog+2)). | |
231 | * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. | |
232 | * Larger tables result in better and slower compression. | |
233 | * This parameter is useless when using "fast" strategy. | |
234 | * It's still useful when using "dfast" strategy, | |
235 | * in which case it defines a secondary probe table. | |
236 | * Special: value 0 means "use default chainLog". */ | |
237 | ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> | |
238 | * More attempts result in better and slower compression. | |
239 | * This parameter is useless when using "fast" and "dFast" strategies. | |
240 | * Special: value 0 means "use default searchLog". */ | |
241 | ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> | |
242 | * Note that Zstandard can still find matches of smaller size, | |
243 | * it just tweaks its search algorithm to look for this size and larger. | |
244 | * Larger values increase compression and decompression speed, but decrease ratio. | |
245 | * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. | |
246 | * Note that currently, for all strategies < btopt, effective minimum is 4. | |
247 | * , for all strategies > fast, effective maximum is 6. | |
248 | * Special: value 0 means "use default minMatchLength". */ | |
249 | ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> | |
250 | * For strategies btopt, btultra & btultra2: | |
251 | * Length of Match considered "good enough" to stop search. | |
252 | * Larger values make compression stronger, and slower. | |
253 | * For strategy fast: | |
254 | * Distance between match sampling. | |
255 | * Larger values make compression faster, and weaker. | |
256 | * Special: value 0 means "use default targetLength". */ | |
257 | ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> | |
258 | * The higher the value of selected strategy, the more complex it is, | |
259 | * resulting in stronger and slower compression. | |
260 | * Special: value 0 means "use default strategy". */ | |
261 | ||
262 | </b>/* LDM mode parameters */<b> | |
263 | ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> | |
264 | * This parameter is designed to improve compression ratio | |
265 | * for large inputs, by finding large matches at long distance. | |
266 | * It increases memory usage and window size. | |
267 | * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB | |
268 | * except when expressly set to a different value. */ | |
269 | ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> | |
270 | * Larger values increase memory usage and compression ratio, | |
271 | * but decrease compression speed. | |
272 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX | |
273 | * default: windowlog - 7. | |
274 | * Special: value 0 means "automatically determine hashlog". */ | |
275 | ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> | |
276 | * Larger/too small values usually decrease compression ratio. | |
277 | * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. | |
278 | * Special: value 0 means "use default value" (default: 64). */ | |
279 | ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> | |
280 | * Larger values improve collision resolution but decrease compression speed. | |
281 | * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. | |
282 | * Special: value 0 means "use default value" (default: 3). */ | |
283 | ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> | |
284 | * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). | |
285 | * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. | |
286 | * Larger values improve compression speed. | |
287 | * Deviating far from default value will likely result in a compression ratio decrease. | |
288 | * Special: value 0 means "automatically determine hashRateLog". */ | |
7c673cae | 289 | |
9f95a23c TL |
290 | </b>/* frame parameters */<b> |
291 | ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> | |
292 | * Content size must be known at the beginning of compression. | |
293 | * This is automatically the case when using ZSTD_compress2(), | |
294 | * For streaming variants, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ | |
295 | ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> | |
296 | ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> | |
297 | ||
298 | </b>/* multi-threading parameters */<b> | |
299 | </b>/* These parameters are only useful if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> | |
300 | * They return an error otherwise. */ | |
301 | ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> | |
302 | * When nbWorkers >= 1, triggers asynchronous mode when used with ZSTD_compressStream*() : | |
303 | * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, | |
304 | * while compression work is performed in parallel, within worker threads. | |
305 | * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : | |
306 | * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). | |
307 | * More workers improve speed, but also increase memory usage. | |
308 | * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */ | |
309 | ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> | |
310 | * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. | |
311 | * 0 means default, which is dynamically determined based on compression parameters. | |
312 | * Job size must be a minimum of overlap size, or 1 MB, whichever is largest. | |
313 | * The minimum size is automatically and transparently enforced */ | |
314 | ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> | |
315 | * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. | |
316 | * It helps preserve compression ratio, while each job is compressed in parallel. | |
317 | * This value is enforced only when nbWorkers >= 1. | |
318 | * Larger values increase compression ratio, but decrease speed. | |
319 | * Possible values range from 0 to 9 : | |
320 | * - 0 means "default" : value will be determined by the library, depending on strategy | |
321 | * - 1 means "no overlap" | |
322 | * - 9 means "full overlap", using a full window size. | |
323 | * Each intermediate rank increases/decreases load size by a factor 2 : | |
324 | * 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 | |
325 | * default value varies between 6 and 9, depending on strategy */ | |
326 | ||
327 | </b>/* note : additional experimental parameters are also available<b> | |
328 | * within the experimental section of the API. | |
329 | * At the time of this writing, they include : | |
330 | * ZSTD_c_rsyncable | |
331 | * ZSTD_c_format | |
332 | * ZSTD_c_forceMaxWindow | |
333 | * ZSTD_c_forceAttachDict | |
334 | * ZSTD_c_literalCompressionMode | |
335 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. | |
336 | * note : never ever use experimentalParam? names directly; | |
337 | * also, the enums values themselves are unstable and can still change. | |
338 | */ | |
339 | ZSTD_c_experimentalParam1=500, | |
340 | ZSTD_c_experimentalParam2=10, | |
341 | ZSTD_c_experimentalParam3=1000, | |
342 | ZSTD_c_experimentalParam4=1001, | |
343 | ZSTD_c_experimentalParam5=1002, | |
344 | } ZSTD_cParameter; | |
345 | </b></pre><BR> | |
346 | <pre><b>typedef struct { | |
347 | size_t error; | |
348 | int lowerBound; | |
349 | int upperBound; | |
350 | } ZSTD_bounds; | |
351 | </b></pre><BR> | |
352 | <pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); | |
353 | </b><p> All parameters must belong to an interval with lower and upper bounds, | |
354 | otherwise they will either trigger an error or be automatically clamped. | |
355 | @return : a structure, ZSTD_bounds, which contains | |
356 | - an error status field, which must be tested using ZSTD_isError() | |
357 | - lower and upper bounds, both inclusive | |
358 | ||
7c673cae FG |
359 | </p></pre><BR> |
360 | ||
9f95a23c TL |
361 | <pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); |
362 | </b><p> Set one compression parameter, selected by enum ZSTD_cParameter. | |
363 | All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). | |
364 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). | |
365 | Setting a parameter is generally only possible during frame initialization (before starting compression). | |
366 | Exception : when using multi-threading mode (nbWorkers >= 1), | |
367 | the following parameters can be updated _during_ compression (within same frame): | |
368 | => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. | |
369 | new parameters will be active for next job only (after a flush()). | |
370 | @return : an error code (which can be tested using ZSTD_isError()). | |
371 | ||
372 | </p></pre><BR> | |
7c673cae | 373 | |
9f95a23c TL |
374 | <pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); |
375 | </b><p> Total input data size to be compressed as a single frame. | |
376 | Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. | |
377 | This value will also be controlled at end of frame, and trigger an error if not respected. | |
378 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
379 | Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. | |
380 | In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. | |
381 | ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. | |
382 | Note 2 : pledgedSrcSize is only valid once, for the next frame. | |
383 | It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. | |
384 | Note 3 : Whenever all input data is provided and consumed in a single round, | |
385 | for example with ZSTD_compress2(), | |
386 | or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), | |
387 | this value is automatically overridden by srcSize instead. | |
388 | ||
7c673cae FG |
389 | </p></pre><BR> |
390 | ||
9f95a23c TL |
391 | <pre><b>typedef enum { |
392 | ZSTD_reset_session_only = 1, | |
393 | ZSTD_reset_parameters = 2, | |
394 | ZSTD_reset_session_and_parameters = 3 | |
395 | } ZSTD_ResetDirective; | |
396 | </b></pre><BR> | |
397 | <pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); | |
398 | </b><p> There are 2 different things that can be reset, independently or jointly : | |
399 | - The session : will stop compressing current frame, and make CCtx ready to start a new one. | |
400 | Useful after an error, or to interrupt any ongoing compression. | |
401 | Any internal data not yet flushed is cancelled. | |
402 | Compression parameters and dictionary remain unchanged. | |
403 | They will be used to compress next frame. | |
404 | Resetting session never fails. | |
405 | - The parameters : changes all parameters back to "default". | |
406 | This removes any reference to any dictionary too. | |
407 | Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) | |
408 | otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) | |
409 | - Both : similar to resetting the session, followed by resetting parameters. | |
410 | ||
7c673cae FG |
411 | </p></pre><BR> |
412 | ||
9f95a23c TL |
413 | <pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, |
414 | void* dst, size_t dstCapacity, | |
415 | const void* src, size_t srcSize); | |
416 | </b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. | |
417 | ZSTD_compress2() always starts a new frame. | |
418 | Should cctx hold data from a previously unfinished frame, everything about it is forgotten. | |
419 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() | |
420 | - The function is always blocking, returns when compression is completed. | |
421 | Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`. | |
422 | @return : compressed size written into `dst` (<= `dstCapacity), | |
423 | or an error code if it fails (which can be tested using ZSTD_isError()). | |
424 | ||
7c673cae FG |
425 | </p></pre><BR> |
426 | ||
9f95a23c TL |
427 | <a name="Chapter8"></a><h2>Advanced decompression API</h2><pre></pre> |
428 | ||
429 | <pre><b>typedef enum { | |
430 | ||
431 | ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> | |
432 | * the streaming API will refuse to allocate memory buffer | |
433 | * in order to protect the host from unreasonable memory requirements. | |
434 | * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. | |
435 | * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). | |
436 | * Special: value 0 means "use default maximum windowLog". */ | |
437 | ||
438 | </b>/* note : additional experimental parameters are also available<b> | |
439 | * within the experimental section of the API. | |
440 | * At the time of this writing, they include : | |
441 | * ZSTD_c_format | |
442 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. | |
443 | * note : never ever use experimentalParam? names directly | |
444 | */ | |
445 | ZSTD_d_experimentalParam1=1000 | |
446 | ||
447 | } ZSTD_dParameter; | |
448 | </b></pre><BR> | |
449 | <pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); | |
450 | </b><p> All parameters must belong to an interval with lower and upper bounds, | |
451 | otherwise they will either trigger an error or be automatically clamped. | |
452 | @return : a structure, ZSTD_bounds, which contains | |
453 | - an error status field, which must be tested using ZSTD_isError() | |
454 | - both lower and upper bounds, inclusive | |
455 | ||
7c673cae FG |
456 | </p></pre><BR> |
457 | ||
9f95a23c TL |
458 | <pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); |
459 | </b><p> Set one compression parameter, selected by enum ZSTD_dParameter. | |
460 | All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). | |
461 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). | |
462 | Setting a parameter is only possible during frame initialization (before starting decompression). | |
463 | @return : 0, or an error code (which can be tested using ZSTD_isError()). | |
464 | ||
7c673cae FG |
465 | </p></pre><BR> |
466 | ||
9f95a23c TL |
467 | <pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); |
468 | </b><p> Return a DCtx to clean state. | |
469 | Session and parameters can be reset jointly or separately. | |
470 | Parameters can only be reset when no active frame is being decompressed. | |
471 | @return : 0, or an error code, which can be tested with ZSTD_isError() | |
472 | ||
7c673cae FG |
473 | </p></pre><BR> |
474 | ||
9f95a23c | 475 | <a name="Chapter9"></a><h2>Streaming</h2><pre></pre> |
7c673cae FG |
476 | |
477 | <pre><b>typedef struct ZSTD_inBuffer_s { | |
478 | const void* src; </b>/**< start of input buffer */<b> | |
479 | size_t size; </b>/**< size of input buffer */<b> | |
480 | size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> | |
481 | } ZSTD_inBuffer; | |
482 | </b></pre><BR> | |
483 | <pre><b>typedef struct ZSTD_outBuffer_s { | |
484 | void* dst; </b>/**< start of output buffer */<b> | |
485 | size_t size; </b>/**< size of output buffer */<b> | |
486 | size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> | |
487 | } ZSTD_outBuffer; | |
488 | </b></pre><BR> | |
9f95a23c | 489 | <a name="Chapter10"></a><h2>Streaming compression - HowTo</h2><pre> |
7c673cae FG |
490 | A ZSTD_CStream object is required to track streaming operation. |
491 | Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. | |
492 | ZSTD_CStream objects can be reused multiple times on consecutive compression operations. | |
9f95a23c TL |
493 | It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. |
494 | ||
495 | For parallel execution, use one separate ZSTD_CStream per thread. | |
496 | ||
497 | note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. | |
498 | ||
499 | Parameters are sticky : when starting a new compression on the same context, | |
500 | it will re-use the same sticky parameters as previous compression session. | |
501 | When in doubt, it's recommended to fully initialize the context before usage. | |
502 | Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), | |
503 | ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to | |
504 | set more specific parameters, the pledged source size, or load a dictionary. | |
505 | ||
506 | Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to | |
507 | consume input stream. The function will automatically update both `pos` | |
508 | fields within `input` and `output`. | |
509 | Note that the function may not consume the entire input, for example, because | |
510 | the output buffer is already full, in which case `input.pos < input.size`. | |
511 | The caller must check if input has been entirely consumed. | |
512 | If not, the caller must make some room to receive more compressed data, | |
513 | and then present again remaining input data. | |
514 | note: ZSTD_e_continue is guaranteed to make some forward progress when called, | |
515 | but doesn't guarantee maximal forward progress. This is especially relevant | |
516 | when compressing with multiple threads. The call won't block if it can | |
517 | consume some input, but if it can't it will wait for some, but not all, | |
518 | output to be flushed. | |
519 | @return : provides a minimum amount of data remaining to be flushed from internal buffers | |
520 | or an error code, which can be tested using ZSTD_isError(). | |
521 | ||
522 | At any moment, it's possible to flush whatever data might remain stuck within internal buffer, | |
523 | using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. | |
524 | Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). | |
525 | In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. | |
526 | You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the | |
527 | operation. | |
528 | note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will | |
529 | block until the flush is complete or the output buffer is full. | |
530 | @return : 0 if internal buffers are entirely flushed, | |
531 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), | |
7c673cae FG |
532 | or an error code, which can be tested using ZSTD_isError(). |
533 | ||
9f95a23c | 534 | Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame. |
7c673cae FG |
535 | It will perform a flush and write frame epilogue. |
536 | The epilogue is required for decoders to consider a frame completed. | |
9f95a23c TL |
537 | flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. |
538 | You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to | |
539 | start a new frame. | |
540 | note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will | |
541 | block until the flush is complete or the output buffer is full. | |
11fdf7f2 | 542 | @return : 0 if frame fully completed and fully flushed, |
9f95a23c | 543 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), |
7c673cae FG |
544 | or an error code, which can be tested using ZSTD_isError(). |
545 | ||
546 | ||
547 | <BR></pre> | |
548 | ||
11fdf7f2 TL |
549 | <pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> |
550 | </b></pre><BR> | |
551 | <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); | |
552 | size_t ZSTD_freeCStream(ZSTD_CStream* zcs); | |
553 | </pre></b><BR> | |
9f95a23c TL |
554 | <h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { |
555 | ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> | |
556 | ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> | |
557 | * it creates (at least) one new block, that can be decoded immediately on reception; | |
558 | * frame will continue: any future data can still reference previously compressed data, improving compression. | |
559 | * note : multithreaded compression will block to flush as much output as possible. */ | |
560 | ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> | |
561 | * note that frame is only closed after compressed data is fully flushed (return value == 0). | |
562 | * After that point, any additional data starts a new frame. | |
563 | * note : each frame is independent (does not reference any content from previous frame). | |
564 | : note : multithreaded compression will block to flush as much output as possible. */ | |
565 | } ZSTD_EndDirective; | |
11fdf7f2 | 566 | </pre></b><BR> |
9f95a23c TL |
567 | <pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, |
568 | ZSTD_outBuffer* output, | |
569 | ZSTD_inBuffer* input, | |
570 | ZSTD_EndDirective endOp); | |
571 | </b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. | |
572 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() | |
573 | - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) | |
574 | - output->pos must be <= dstCapacity, input->pos must be <= srcSize | |
575 | - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. | |
576 | - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. | |
577 | - When nbWorkers>=1, function is non-blocking : it just acquires a copy of input, and distributes jobs to internal worker threads, flush whatever is available, | |
578 | and then immediately returns, just indicating that there is some data remaining to be flushed. | |
579 | The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. | |
580 | - 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. | |
581 | - @return provides a minimum amount of data remaining to be flushed from internal buffers | |
582 | or an error code, which can be tested using ZSTD_isError(). | |
583 | if @return != 0, flush is not fully completed, there is still some data left within internal buffers. | |
584 | This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. | |
585 | For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. | |
586 | - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), | |
587 | only ZSTD_e_end or ZSTD_e_flush operations are allowed. | |
588 | Before starting a new compression job, or changing compression parameters, | |
589 | it is required to fully flush internal buffers. | |
590 | ||
591 | </p></pre><BR> | |
592 | ||
7c673cae FG |
593 | <pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> |
594 | </b></pre><BR> | |
595 | <pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */<b> | |
596 | </b></pre><BR> | |
9f95a23c TL |
597 | <a name="Chapter11"></a><h2>This is a legacy streaming API, and can be replaced by ZSTD_CCtx_reset() and</h2><pre> ZSTD_compressStream2(). It is redundent, but is still fully supported. |
598 | Advanced parameters and dictionary compression can only be used through the | |
599 | new API. | |
600 | <BR></pre> | |
601 | ||
602 | <a name="Chapter12"></a><h2>Equivalent to:</h2><pre> | |
603 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
604 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) | |
605 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); | |
606 | ||
607 | <BR></pre> | |
608 | ||
609 | <a name="Chapter13"></a><h2>Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).</h2><pre> NOTE: The return value is different. ZSTD_compressStream() returns a hint for | |
610 | the next read size (if non-zero and not an error). ZSTD_compressStream2() | |
611 | returns the number of bytes left to flush (if non-zero and not an error). | |
612 | ||
613 | <BR></pre> | |
614 | ||
615 | <a name="Chapter14"></a><h2>Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush).</h2><pre></pre> | |
616 | ||
617 | <a name="Chapter15"></a><h2>Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end).</h2><pre></pre> | |
618 | ||
619 | <a name="Chapter16"></a><h2>Streaming decompression - HowTo</h2><pre> | |
7c673cae FG |
620 | A ZSTD_DStream object is required to track streaming operations. |
621 | Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. | |
622 | ZSTD_DStream objects can be re-used multiple times. | |
623 | ||
9f95a23c TL |
624 | Use ZSTD_initDStream() to start a new decompression operation. |
625 | @return : recommended first input size | |
626 | Alternatively, use advanced API to set specific properties. | |
7c673cae FG |
627 | |
628 | Use ZSTD_decompressStream() repetitively to consume your input. | |
629 | The function will update both `pos` fields. | |
630 | If `input.pos < input.size`, some input has not been consumed. | |
631 | It's up to the caller to present again remaining data. | |
9f95a23c | 632 | The function tries to flush all data decoded immediately, respecting output buffer size. |
7c673cae | 633 | If `output.pos < output.size`, decoder has flushed everything it could. |
9f95a23c TL |
634 | But if `output.pos == output.size`, there might be some data left within internal buffers., |
635 | In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. | |
636 | Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. | |
637 | @return : 0 when a frame is completely decoded and fully flushed, | |
638 | or an error code, which can be tested using ZSTD_isError(), | |
639 | or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : | |
640 | the return value is a suggested next input size (just a hint for better latency) | |
641 | that will never request more than the remaining frame size. | |
7c673cae FG |
642 | |
643 | <BR></pre> | |
644 | ||
11fdf7f2 TL |
645 | <pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> |
646 | </b></pre><BR> | |
647 | <h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); | |
648 | size_t ZSTD_freeDStream(ZSTD_DStream* zds); | |
649 | </pre></b><BR> | |
650 | <h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds); | |
651 | size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); | |
652 | </pre></b><BR> | |
7c673cae FG |
653 | <pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> |
654 | </b></pre><BR> | |
655 | <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> | |
656 | </b></pre><BR> | |
9f95a23c TL |
657 | <a name="Chapter17"></a><h2>Simple dictionary API</h2><pre></pre> |
658 | ||
659 | <pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, | |
660 | void* dst, size_t dstCapacity, | |
661 | const void* src, size_t srcSize, | |
662 | const void* dict,size_t dictSize, | |
663 | int compressionLevel); | |
664 | </b><p> Compression at an explicit compression level using a Dictionary. | |
665 | A dictionary can be any arbitrary data segment (also called a prefix), | |
666 | or a buffer with specified information (see dictBuilder/zdict.h). | |
667 | Note : This function loads the dictionary, resulting in significant startup delay. | |
668 | It's intended for a dictionary used only once. | |
669 | Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. | |
670 | </p></pre><BR> | |
671 | ||
672 | <pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, | |
673 | void* dst, size_t dstCapacity, | |
674 | const void* src, size_t srcSize, | |
675 | const void* dict,size_t dictSize); | |
676 | </b><p> Decompression using a known Dictionary. | |
677 | Dictionary must be identical to the one used during compression. | |
678 | Note : This function loads the dictionary, resulting in significant startup delay. | |
679 | It's intended for a dictionary used only once. | |
680 | Note : When `dict == NULL || dictSize < 8` no dictionary is used. | |
681 | </p></pre><BR> | |
682 | ||
683 | <a name="Chapter18"></a><h2>Bulk processing dictionary API</h2><pre></pre> | |
684 | ||
685 | <pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, | |
686 | int compressionLevel); | |
687 | </b><p> When compressing multiple messages / blocks using the same dictionary, it's recommended to load it only once. | |
688 | ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup cost. | |
689 | ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. | |
690 | `dictBuffer` can be released after ZSTD_CDict creation, because its content is copied within CDict. | |
691 | Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate `dictBuffer` content. | |
692 | Note : A ZSTD_CDict can be created from an empty dictBuffer, but it is inefficient when used to compress small data. | |
693 | </p></pre><BR> | |
694 | ||
695 | <pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); | |
696 | </b><p> Function frees memory allocated by ZSTD_createCDict(). | |
697 | </p></pre><BR> | |
698 | ||
699 | <pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, | |
700 | void* dst, size_t dstCapacity, | |
701 | const void* src, size_t srcSize, | |
702 | const ZSTD_CDict* cdict); | |
703 | </b><p> Compression using a digested Dictionary. | |
704 | Recommended when same dictionary is used multiple times. | |
705 | Note : compression level is _decided at dictionary creation time_, | |
706 | and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) | |
707 | </p></pre><BR> | |
708 | ||
709 | <pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); | |
710 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. | |
711 | dictBuffer can be released after DDict creation, as its content is copied inside DDict. | |
712 | </p></pre><BR> | |
713 | ||
714 | <pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); | |
715 | </b><p> Function frees memory allocated with ZSTD_createDDict() | |
716 | </p></pre><BR> | |
717 | ||
718 | <pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, | |
719 | void* dst, size_t dstCapacity, | |
720 | const void* src, size_t srcSize, | |
721 | const ZSTD_DDict* ddict); | |
722 | </b><p> Decompression using a digested Dictionary. | |
723 | Recommended when same dictionary is used multiple times. | |
724 | </p></pre><BR> | |
725 | ||
726 | <a name="Chapter19"></a><h2>Dictionary helper functions</h2><pre></pre> | |
727 | ||
728 | <pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); | |
729 | </b><p> Provides the dictID stored within dictionary. | |
730 | if @return == 0, the dictionary is not conformant with Zstandard specification. | |
731 | It can still be loaded, but as a content-only dictionary. | |
732 | </p></pre><BR> | |
733 | ||
734 | <pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); | |
735 | </b><p> Provides the dictID of the dictionary loaded into `ddict`. | |
736 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. | |
737 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries. | |
738 | </p></pre><BR> | |
739 | ||
740 | <pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); | |
741 | </b><p> Provides the dictID required to decompressed the frame stored within `src`. | |
742 | If @return == 0, the dictID could not be decoded. | |
743 | This could for one of the following reasons : | |
744 | - The frame does not require a dictionary to be decoded (most common case). | |
745 | - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information. | |
746 | Note : this use case also happens when using a non-conformant dictionary. | |
747 | - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). | |
748 | - This is not a Zstandard frame. | |
749 | When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. | |
750 | </p></pre><BR> | |
751 | ||
752 | <a name="Chapter20"></a><h2>Advanced dictionary and prefix API</h2><pre> | |
753 | This API allows dictionaries to be used with ZSTD_compress2(), | |
754 | ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and | |
755 | only reset with the context is reset with ZSTD_reset_parameters or | |
756 | ZSTD_reset_session_and_parameters. Prefixes are single-use. | |
757 | <BR></pre> | |
758 | ||
759 | <pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); | |
760 | </b><p> Create an internal CDict from `dict` buffer. | |
761 | Decompression will have to use same dictionary. | |
762 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
763 | Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, | |
764 | meaning "return to no-dictionary mode". | |
765 | Note 1 : Dictionary is sticky, it will be used for all future compressed frames. | |
766 | To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters). | |
767 | Note 2 : Loading a dictionary involves building tables. | |
768 | It's also a CPU consuming operation, with non-negligible impact on latency. | |
769 | Tables are dependent on compression parameters, and for this reason, | |
770 | compression parameters can no longer be changed after loading a dictionary. | |
771 | Note 3 :`dict` content will be copied internally. | |
772 | Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. | |
773 | In such a case, dictionary buffer must outlive its users. | |
774 | Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() | |
775 | to precisely select how dictionary content must be interpreted. | |
776 | </p></pre><BR> | |
777 | ||
778 | <pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); | |
779 | </b><p> Reference a prepared dictionary, to be used for all next compressed frames. | |
780 | Note that compression parameters are enforced from within CDict, | |
781 | and supersede any compression parameter previously set within CCtx. | |
782 | The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. | |
783 | The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. | |
784 | The dictionary will remain valid for future compressed frames using same CCtx. | |
785 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
786 | Special : Referencing a NULL CDict means "return to no-dictionary mode". | |
787 | Note 1 : Currently, only one dictionary can be managed. | |
788 | Referencing a new dictionary effectively "discards" any previous one. | |
789 | Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. | |
790 | </p></pre><BR> | |
791 | ||
792 | <pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, | |
793 | const void* prefix, size_t prefixSize); | |
794 | </b><p> Reference a prefix (single-usage dictionary) for next compressed frame. | |
795 | A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). | |
796 | Decompression will need same prefix to properly regenerate data. | |
797 | Compressing with a prefix is similar in outcome as performing a diff and compressing it, | |
798 | but performs much faster, especially during decompression (compression speed is tunable with compression level). | |
799 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
800 | Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary | |
801 | Note 1 : Prefix buffer is referenced. It **must** outlive compression. | |
802 | Its content must remain unmodified during compression. | |
803 | Note 2 : If the intention is to diff some large src data blob with some prior version of itself, | |
804 | ensure that the window size is large enough to contain the entire source. | |
805 | See ZSTD_c_windowLog. | |
806 | Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. | |
807 | It's a CPU consuming operation, with non-negligible impact on latency. | |
808 | If there is a need to use the same prefix multiple times, consider loadDictionary instead. | |
809 | Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dm_rawContent). | |
810 | Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. | |
811 | </p></pre><BR> | |
812 | ||
813 | <pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); | |
814 | </b><p> Create an internal DDict from dict buffer, | |
815 | to be used to decompress next frames. | |
816 | The dictionary remains valid for all future frames, until explicitly invalidated. | |
817 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
818 | Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, | |
819 | meaning "return to no-dictionary mode". | |
820 | Note 1 : Loading a dictionary involves building tables, | |
821 | which has a non-negligible impact on CPU usage and latency. | |
822 | It's recommended to "load once, use many times", to amortize the cost | |
823 | Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. | |
824 | Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. | |
825 | Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of | |
826 | how dictionary content is loaded and interpreted. | |
827 | ||
828 | </p></pre><BR> | |
829 | ||
830 | <pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); | |
831 | </b><p> Reference a prepared dictionary, to be used to decompress next frames. | |
832 | The dictionary remains active for decompression of future frames using same DCtx. | |
833 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
834 | Note 1 : Currently, only one dictionary can be managed. | |
835 | Referencing a new dictionary effectively "discards" any previous one. | |
836 | Special: referencing a NULL DDict means "return to no-dictionary mode". | |
837 | Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. | |
838 | ||
839 | </p></pre><BR> | |
840 | ||
841 | <pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, | |
842 | const void* prefix, size_t prefixSize); | |
843 | </b><p> Reference a prefix (single-usage dictionary) to decompress next frame. | |
844 | This is the reverse operation of ZSTD_CCtx_refPrefix(), | |
845 | and must use the same prefix as the one used during compression. | |
846 | Prefix is **only used once**. Reference is discarded at end of frame. | |
847 | End of frame is reached when ZSTD_decompressStream() returns 0. | |
848 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
849 | Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary | |
850 | Note 2 : Prefix buffer is referenced. It **must** outlive decompression. | |
851 | Prefix buffer must remain unmodified up to the end of frame, | |
852 | reached when ZSTD_decompressStream() returns 0. | |
853 | Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent). | |
854 | Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) | |
855 | Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. | |
856 | A full dictionary is more costly, as it requires building tables. | |
857 | ||
858 | </p></pre><BR> | |
859 | ||
860 | <pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); | |
861 | size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); | |
862 | size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); | |
863 | size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); | |
864 | size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); | |
865 | size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); | |
866 | </b><p> These functions give the _current_ memory usage of selected object. | |
867 | Note that object memory usage can evolve (increase or decrease) over time. | |
868 | </p></pre><BR> | |
869 | ||
870 | <a name="Chapter21"></a><h2>ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> | |
871 | The definitions in the following section are considered experimental. | |
11fdf7f2 | 872 | They are provided for advanced scenarios. |
9f95a23c | 873 | They should never be used with a dynamic library, as prototypes may change in the future. |
7c673cae FG |
874 | Use them only in association with static linking. |
875 | ||
876 | <BR></pre> | |
877 | ||
9f95a23c TL |
878 | <a name="Chapter22"></a><h2>experimental API (static linking only)</h2><pre> |
879 | The following symbols and constants | |
880 | are not planned to join "stable API" status in the near future. | |
881 | They can still change in future versions. | |
882 | Some of them are planned to remain in the static_only section indefinitely. | |
883 | Some of them might be removed in the future (especially when redundant with existing stable functions) | |
884 | ||
885 | <BR></pre> | |
7c673cae | 886 | |
7c673cae | 887 | <pre><b>typedef struct { |
9f95a23c TL |
888 | unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> |
889 | unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> | |
890 | unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> | |
891 | unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> | |
892 | unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> | |
893 | unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> | |
894 | ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> | |
7c673cae FG |
895 | } ZSTD_compressionParameters; |
896 | </b></pre><BR> | |
897 | <pre><b>typedef struct { | |
9f95a23c TL |
898 | int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> |
899 | int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> | |
900 | int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> | |
7c673cae FG |
901 | } ZSTD_frameParameters; |
902 | </b></pre><BR> | |
903 | <pre><b>typedef struct { | |
904 | ZSTD_compressionParameters cParams; | |
905 | ZSTD_frameParameters fParams; | |
906 | } ZSTD_parameters; | |
907 | </b></pre><BR> | |
9f95a23c TL |
908 | <pre><b>typedef enum { |
909 | ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> | |
910 | ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> | |
911 | ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> | |
912 | } ZSTD_dictContentType_e; | |
913 | </b></pre><BR> | |
914 | <pre><b>typedef enum { | |
915 | ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> | |
916 | ZSTD_dlm_byRef = 1, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> | |
917 | } ZSTD_dictLoadMethod_e; | |
918 | </b></pre><BR> | |
919 | <pre><b>typedef enum { | |
920 | </b>/* Opened question : should we have a format ZSTD_f_auto ?<b> | |
921 | * Today, it would mean exactly the same as ZSTD_f_zstd1. | |
922 | * But, in the future, should several formats become supported, | |
923 | * on the compression side, it would mean "default format". | |
924 | * On the decompression side, it would mean "automatic format detection", | |
925 | * so that ZSTD_f_zstd1 would mean "accept *only* zstd frames". | |
926 | * Since meaning is a little different, another option could be to define different enums for compression and decompression. | |
927 | * This question could be kept for later, when there are actually multiple formats to support, | |
928 | * but there is also the question of pinning enum values, and pinning value `0` is especially important */ | |
929 | ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> | |
930 | ZSTD_f_zstd1_magicless = 1, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> | |
931 | * Useful to save 4 bytes per generated frame. | |
932 | * Decoder cannot recognise automatically this format, requiring this instruction. */ | |
933 | } ZSTD_format_e; | |
934 | </b></pre><BR> | |
935 | <pre><b>typedef enum { | |
936 | </b>/* Note: this enum and the behavior it controls are effectively internal<b> | |
937 | * implementation details of the compressor. They are expected to continue | |
938 | * to evolve and should be considered only in the context of extremely | |
939 | * advanced performance tuning. | |
940 | * | |
941 | * Zstd currently supports the use of a CDict in two ways: | |
942 | * | |
943 | * - The contents of the CDict can be copied into the working context. This | |
944 | * means that the compression can search both the dictionary and input | |
945 | * while operating on a single set of internal tables. This makes | |
946 | * the compression faster per-byte of input. However, the initial copy of | |
947 | * the CDict's tables incurs a fixed cost at the beginning of the | |
948 | * compression. For small compressions (< 8 KB), that copy can dominate | |
949 | * the cost of the compression. | |
950 | * | |
951 | * - The CDict's tables can be used in-place. In this model, compression is | |
952 | * slower per input byte, because the compressor has to search two sets of | |
953 | * tables. However, this model incurs no start-up cost (as long as the | |
954 | * working context's tables can be reused). For small inputs, this can be | |
955 | * faster than copying the CDict's tables. | |
956 | * | |
957 | * Zstd has a simple internal heuristic that selects which strategy to use | |
958 | * at the beginning of a compression. However, if experimentation shows that | |
959 | * Zstd is making poor choices, it is possible to override that choice with | |
960 | * this enum. | |
961 | */ | |
962 | ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> | |
963 | ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> | |
964 | ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> | |
965 | } ZSTD_dictAttachPref_e; | |
966 | </b></pre><BR> | |
967 | <pre><b>typedef enum { | |
968 | ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> | |
969 | * Negative compression levels will be uncompressed, and positive compression | |
970 | * levels will be compressed. */ | |
971 | ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> | |
972 | * emitted if Huffman compression is not profitable. */ | |
973 | ZSTD_lcm_uncompressed = 2, </b>/**< Always emit uncompressed literals. */<b> | |
974 | } ZSTD_literalCompressionMode_e; | |
975 | </b></pre><BR> | |
976 | <a name="Chapter23"></a><h2>Frame size functions</h2><pre></pre> | |
11fdf7f2 TL |
977 | |
978 | <pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); | |
9f95a23c | 979 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
11fdf7f2 | 980 | `srcSize` must be the _exact_ size of this series |
9f95a23c | 981 | (i.e. there should be a frame boundary at `src + srcSize`) |
11fdf7f2 TL |
982 | @return : - decompressed size of all data in all successive frames |
983 | - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN | |
984 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR | |
985 | ||
986 | note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. | |
987 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. | |
988 | In which case, it's necessary to use streaming mode to decompress data. | |
989 | note 2 : decompressed size is always present when compression is done with ZSTD_compress() | |
990 | note 3 : decompressed size can be very large (64-bits value), | |
991 | potentially larger than what local system can handle as a single memory segment. | |
992 | In which case, it's necessary to use streaming mode to decompress data. | |
993 | note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. | |
994 | Always ensure result fits within application's authorized limits. | |
995 | Each application can set its own limits. | |
996 | note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to | |
997 | read each contained frame header. This is fast as most of the data is skipped, | |
998 | however it does mean that all frame data must be present and valid. | |
999 | </p></pre><BR> | |
1000 | ||
9f95a23c TL |
1001 | <a name="Chapter24"></a><h2>ZSTD_decompressBound() :</h2><pre> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
1002 | `srcSize` must be the _exact_ size of this series | |
1003 | (i.e. there should be a frame boundary at `src + srcSize`) | |
1004 | @return : - upper-bound for the decompressed size of all data in all successive frames | |
1005 | - if an error occured: ZSTD_CONTENTSIZE_ERROR | |
1006 | ||
1007 | note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. | |
1008 | note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. | |
1009 | in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. | |
1010 | note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: | |
1011 | upper-bound = # blocks * min(128 KB, Window_Size) | |
1012 | ||
1013 | <BR></pre> | |
1014 | ||
11fdf7f2 | 1015 | <pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); |
9f95a23c TL |
1016 | </b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. |
1017 | @return : size of the Frame Header, | |
1018 | or an error code (if srcSize is too small) | |
11fdf7f2 TL |
1019 | </p></pre><BR> |
1020 | ||
9f95a23c | 1021 | <a name="Chapter25"></a><h2>Memory management</h2><pre></pre> |
11fdf7f2 TL |
1022 | |
1023 | <pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel); | |
1024 | size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); | |
1025 | size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); | |
1026 | size_t ZSTD_estimateDCtxSize(void); | |
1027 | </b><p> These functions make it possible to estimate memory usage | |
1028 | of a future {D,C}Ctx, before its creation. | |
1029 | ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one. | |
1030 | It will also consider src size to be arbitrarily "large", which is worst case. | |
1031 | If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation. | |
1032 | ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. | |
9f95a23c TL |
1033 | ZSTD_estimateCCtxSize_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. |
1034 | Note : CCtx size estimation is only correct for single-threaded compression. | |
7c673cae FG |
1035 | </p></pre><BR> |
1036 | ||
11fdf7f2 TL |
1037 | <pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel); |
1038 | size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); | |
1039 | size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); | |
1040 | size_t ZSTD_estimateDStreamSize(size_t windowSize); | |
1041 | size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); | |
1042 | </b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one. | |
1043 | It will also consider src size to be arbitrarily "large", which is worst case. | |
1044 | If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. | |
1045 | ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. | |
9f95a23c TL |
1046 | 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. |
1047 | Note : CStream size estimation is only correct for single-threaded compression. | |
11fdf7f2 TL |
1048 | ZSTD_DStream memory budget depends on window Size. |
1049 | This information can be passed manually, using ZSTD_estimateDStreamSize, | |
1050 | or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); | |
1051 | Note : if streaming is init with function ZSTD_init?Stream_usingDict(), | |
1052 | an internal ?Dict will be created, which additional size is not estimated here. | |
1053 | In this case, get total size by adding ZSTD_estimate?DictSize | |
1054 | </p></pre><BR> | |
1055 | ||
11fdf7f2 TL |
1056 | <pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); |
1057 | size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); | |
1058 | size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); | |
1059 | </b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). | |
9f95a23c TL |
1060 | ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). |
1061 | Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. | |
11fdf7f2 TL |
1062 | |
1063 | </p></pre><BR> | |
1064 | ||
9f95a23c TL |
1065 | <pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); |
1066 | ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> | |
1067 | </b><p> Initialize an object using a pre-allocated fixed-size buffer. | |
1068 | workspace: The memory area to emplace the object into. | |
1069 | Provided pointer *must be 8-bytes aligned*. | |
1070 | Buffer must outlive object. | |
1071 | workspaceSize: Use ZSTD_estimate*Size() to determine | |
1072 | how large workspace must be to support target scenario. | |
1073 | @return : pointer to object (same address as workspace, just different type), | |
1074 | or NULL if error (size too small, incorrect alignment, etc.) | |
1075 | Note : zstd will never resize nor malloc() when using a static buffer. | |
1076 | If the object requires more memory than available, | |
1077 | zstd will just error out (typically ZSTD_error_memory_allocation). | |
1078 | Note 2 : there is no corresponding "free" function. | |
1079 | Since workspace is allocated externally, it must be freed externally too. | |
1080 | Note 3 : cParams : use ZSTD_getCParams() to convert a compression level | |
1081 | into its associated cParams. | |
1082 | Limitation 1 : currently not compatible with internal dictionary creation, triggered by | |
1083 | ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). | |
1084 | Limitation 2 : static cctx currently not compatible with multi-threading. | |
1085 | Limitation 3 : static dctx is incompatible with legacy support. | |
1086 | ||
7c673cae FG |
1087 | </p></pre><BR> |
1088 | ||
9f95a23c TL |
1089 | <pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> |
1090 | </b></pre><BR> | |
1091 | <pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); | |
1092 | typedef void (*ZSTD_freeFunction) (void* opaque, void* address); | |
1093 | typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; | |
1094 | static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> | |
1095 | </b><p> These prototypes make it possible to pass your own allocation/free functions. | |
1096 | ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. | |
1097 | All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. | |
11fdf7f2 TL |
1098 | |
1099 | </p></pre><BR> | |
1100 | ||
9f95a23c TL |
1101 | <a name="Chapter26"></a><h2>Advanced compression functions</h2><pre></pre> |
1102 | ||
11fdf7f2 TL |
1103 | <pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); |
1104 | </b><p> Create a digested dictionary for compression | |
9f95a23c TL |
1105 | Dictionary content is just referenced, not duplicated. |
1106 | As a consequence, `dictBuffer` **must** outlive CDict, | |
1107 | and its content must remain unmodified throughout the lifetime of CDict. | |
7c673cae FG |
1108 | </p></pre><BR> |
1109 | ||
1110 | <pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); | |
9f95a23c TL |
1111 | </b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. |
1112 | `estimatedSrcSize` value is optional, select 0 if not known | |
7c673cae FG |
1113 | </p></pre><BR> |
1114 | ||
1115 | <pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); | |
9f95a23c TL |
1116 | </b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. |
1117 | All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 | |
7c673cae FG |
1118 | </p></pre><BR> |
1119 | ||
1120 | <pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params); | |
9f95a23c TL |
1121 | </b><p> Ensure param values remain within authorized range. |
1122 | @return 0 on success, or an error code (can be checked with ZSTD_isError()) | |
7c673cae FG |
1123 | </p></pre><BR> |
1124 | ||
1125 | <pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); | |
11fdf7f2 | 1126 | </b><p> optimize params for a given `srcSize` and `dictSize`. |
9f95a23c TL |
1127 | `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. |
1128 | `dictSize` must be `0` when there is no dictionary. | |
1129 | cPar can be invalid : all parameters will be clamped within valid range in the @return struct. | |
1130 | This function never fails (wide contract) | |
11fdf7f2 TL |
1131 | </p></pre><BR> |
1132 | ||
9f95a23c TL |
1133 | <pre><b>size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, |
1134 | void* dst, size_t dstCapacity, | |
1135 | const void* src, size_t srcSize, | |
1136 | const void* dict,size_t dictSize, | |
1137 | ZSTD_parameters params); | |
1138 | </b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over compression parameters (by structure) | |
7c673cae FG |
1139 | </p></pre><BR> |
1140 | ||
11fdf7f2 | 1141 | <pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, |
9f95a23c TL |
1142 | void* dst, size_t dstCapacity, |
1143 | const void* src, size_t srcSize, | |
1144 | const ZSTD_CDict* cdict, | |
1145 | ZSTD_frameParameters fParams); | |
1146 | </b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters | |
1147 | </p></pre><BR> | |
1148 | ||
1149 | <pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); | |
1150 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. | |
1151 | It saves some memory, but also requires that `dict` outlives its usage within `cctx` | |
1152 | </p></pre><BR> | |
1153 | ||
1154 | <pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); | |
1155 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over | |
1156 | how to load the dictionary (by copy ? by reference ?) | |
1157 | and how to interpret it (automatic ? force raw mode ? full mode only ?) | |
1158 | </p></pre><BR> | |
1159 | ||
1160 | <pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); | |
1161 | </b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over | |
1162 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) | |
1163 | </p></pre><BR> | |
1164 | ||
1165 | <pre><b>size_t ZSTD_CCtx_getParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); | |
1166 | </b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, | |
1167 | and store it into int* value. | |
1168 | @return : 0, or an error code (which can be tested with ZSTD_isError()). | |
1169 | ||
1170 | </p></pre><BR> | |
1171 | ||
1172 | <pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void); | |
1173 | size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); | |
1174 | </b><p> Quick howto : | |
1175 | - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure | |
1176 | - ZSTD_CCtxParams_setParameter() : Push parameters one by one into | |
1177 | an existing ZSTD_CCtx_params structure. | |
1178 | This is similar to | |
1179 | ZSTD_CCtx_setParameter(). | |
1180 | - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to | |
1181 | an existing CCtx. | |
1182 | These parameters will be applied to | |
1183 | all subsequent frames. | |
1184 | - ZSTD_compressStream2() : Do compression using the CCtx. | |
1185 | - ZSTD_freeCCtxParams() : Free the memory. | |
1186 | ||
1187 | This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() | |
1188 | for static allocation of CCtx for single-threaded compression. | |
1189 | ||
1190 | </p></pre><BR> | |
1191 | ||
1192 | <pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); | |
1193 | </b><p> Reset params to default values. | |
1194 | ||
1195 | </p></pre><BR> | |
1196 | ||
1197 | <pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); | |
1198 | </b><p> Initializes the compression parameters of cctxParams according to | |
1199 | compression level. All other parameters are reset to their default values. | |
1200 | ||
1201 | </p></pre><BR> | |
1202 | ||
1203 | <pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); | |
1204 | </b><p> Initializes the compression and frame parameters of cctxParams according to | |
1205 | params. All other parameters are reset to their default values. | |
1206 | ||
1207 | </p></pre><BR> | |
1208 | ||
1209 | <pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); | |
1210 | </b><p> Similar to ZSTD_CCtx_setParameter. | |
1211 | Set one compression parameter, selected by enum ZSTD_cParameter. | |
1212 | Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams(). | |
1213 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
1214 | ||
1215 | </p></pre><BR> | |
1216 | ||
1217 | <pre><b>size_t ZSTD_CCtxParams_getParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); | |
1218 | </b><p> Similar to ZSTD_CCtx_getParameter. | |
1219 | Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. | |
1220 | @result : 0, or an error code (which can be tested with ZSTD_isError()). | |
1221 | ||
1222 | </p></pre><BR> | |
1223 | ||
1224 | <pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams( | |
1225 | ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); | |
1226 | </b><p> Apply a set of ZSTD_CCtx_params to the compression context. | |
1227 | This can be done even after compression is started, | |
1228 | if nbWorkers==0, this will have no impact until a new compression is started. | |
1229 | if nbWorkers>=1, new parameters will be picked up at next job, | |
1230 | with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). | |
1231 | ||
1232 | </p></pre><BR> | |
1233 | ||
1234 | <pre><b>size_t ZSTD_compressStream2_simpleArgs ( | |
1235 | ZSTD_CCtx* cctx, | |
1236 | void* dst, size_t dstCapacity, size_t* dstPos, | |
1237 | const void* src, size_t srcSize, size_t* srcPos, | |
1238 | ZSTD_EndDirective endOp); | |
1239 | </b><p> Same as ZSTD_compressStream2(), | |
1240 | but using only integral types as arguments. | |
1241 | This variant might be helpful for binders from dynamic languages | |
1242 | which have troubles handling structures containing memory pointers. | |
1243 | ||
7c673cae FG |
1244 | </p></pre><BR> |
1245 | ||
9f95a23c | 1246 | <a name="Chapter27"></a><h2>Advanced decompression functions</h2><pre></pre> |
7c673cae FG |
1247 | |
1248 | <pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size); | |
1249 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. | |
1250 | Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. | |
1251 | Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. | |
1252 | Note 3 : Skippable Frame Identifiers are considered valid. | |
1253 | </p></pre><BR> | |
1254 | ||
11fdf7f2 TL |
1255 | <pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); |
1256 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. | |
1257 | Dictionary content is referenced, and therefore stays in dictBuffer. | |
1258 | It is important that dictBuffer outlives DDict, | |
1259 | it must remain read accessible throughout the lifetime of DDict | |
7c673cae FG |
1260 | </p></pre><BR> |
1261 | ||
9f95a23c TL |
1262 | <pre><b>size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); |
1263 | </b><p> Same as ZSTD_DCtx_loadDictionary(), | |
1264 | but references `dict` content instead of copying it into `dctx`. | |
1265 | This saves memory if `dict` remains around., | |
1266 | However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. | |
7c673cae FG |
1267 | </p></pre><BR> |
1268 | ||
9f95a23c TL |
1269 | <pre><b>size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); |
1270 | </b><p> Same as ZSTD_DCtx_loadDictionary(), | |
1271 | but gives direct control over | |
1272 | how to load the dictionary (by copy ? by reference ?) | |
1273 | and how to interpret it (automatic ? force raw mode ? full mode only ?). | |
7c673cae FG |
1274 | </p></pre><BR> |
1275 | ||
9f95a23c TL |
1276 | <pre><b>size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); |
1277 | </b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over | |
1278 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) | |
7c673cae FG |
1279 | </p></pre><BR> |
1280 | ||
9f95a23c TL |
1281 | <pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); |
1282 | </b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. | |
1283 | This protects a decoder context from reserving too much memory for itself (potential attack scenario). | |
1284 | This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. | |
1285 | By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) | |
1286 | @return : 0, or an error code (which can be tested using ZSTD_isError()). | |
1287 | ||
7c673cae FG |
1288 | </p></pre><BR> |
1289 | ||
9f95a23c TL |
1290 | <pre><b>size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); |
1291 | </b><p> Instruct the decoder context about what kind of data to decode next. | |
1292 | This instruction is mandatory to decode data without a fully-formed header, | |
1293 | such ZSTD_f_zstd1_magicless for example. | |
1294 | @return : 0, or an error code (which can be tested using ZSTD_isError()). | |
1295 | </p></pre><BR> | |
7c673cae | 1296 | |
9f95a23c TL |
1297 | <pre><b>size_t ZSTD_decompressStream_simpleArgs ( |
1298 | ZSTD_DCtx* dctx, | |
1299 | void* dst, size_t dstCapacity, size_t* dstPos, | |
1300 | const void* src, size_t srcSize, size_t* srcPos); | |
1301 | </b><p> Same as ZSTD_decompressStream(), | |
1302 | but using only integral types as arguments. | |
1303 | This can be helpful for binders from dynamic languages | |
1304 | which have troubles handling structures containing memory pointers. | |
1305 | ||
1306 | </p></pre><BR> | |
1307 | ||
1308 | <a name="Chapter28"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. | |
1309 | Once Advanced API reaches "stable" status, | |
1310 | redundant functions will be deprecated, and then at some point removed. | |
1311 | <BR></pre> | |
1312 | ||
1313 | <h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></b>/**! ZSTD_initCStream_srcSize() :<b> | |
1314 | * This function is deprecated, and equivalent to: | |
1315 | * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1316 | * ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) | |
1317 | * ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); | |
1318 | * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); | |
1319 | * | |
1320 | * pledgedSrcSize must be correct. If it is not known at init time, use | |
1321 | * ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, | |
1322 | * "0" also disables frame content size field. It may be enabled in the future. | |
1323 | */ | |
1324 | size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); | |
1325 | </b>/**! ZSTD_initCStream_usingDict() :<b> | |
1326 | * This function is deprecated, and is equivalent to: | |
1327 | * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1328 | * ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); | |
1329 | * ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); | |
1330 | * | |
1331 | * Creates of an internal CDict (incompatible with static CCtx), except if | |
1332 | * dict == NULL or dictSize < 8, in which case no dict is used. | |
1333 | * Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if | |
1334 | * it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. | |
1335 | */ | |
1336 | size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); | |
1337 | </b>/**! ZSTD_initCStream_advanced() :<b> | |
1338 | * This function is deprecated, and is approximately equivalent to: | |
1339 | * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1340 | * ZSTD_CCtx_setZstdParams(zcs, params); // Set the zstd params and leave the rest as-is | |
1341 | * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); | |
1342 | * ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); | |
1343 | * | |
1344 | * pledgedSrcSize must be correct. If srcSize is not known at init time, use | |
1345 | * value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. | |
1346 | */ | |
7c673cae | 1347 | size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize, |
9f95a23c TL |
1348 | ZSTD_parameters params, unsigned long long pledgedSrcSize); |
1349 | </b>/**! ZSTD_initCStream_usingCDict() :<b> | |
1350 | * This function is deprecated, and equivalent to: | |
1351 | * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1352 | * ZSTD_CCtx_refCDict(zcs, cdict); | |
1353 | * | |
1354 | * note : cdict will just be referenced, and must outlive compression session | |
1355 | */ | |
1356 | size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); | |
1357 | </b>/**! ZSTD_initCStream_usingCDict_advanced() :<b> | |
1358 | * This function is deprecated, and is approximately equivalent to: | |
1359 | * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1360 | * ZSTD_CCtx_setZstdFrameParams(zcs, fParams); // Set the zstd frame params and leave the rest as-is | |
1361 | * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); | |
1362 | * ZSTD_CCtx_refCDict(zcs, cdict); | |
1363 | * | |
1364 | * same as ZSTD_initCStream_usingCDict(), with control over frame parameters. | |
1365 | * pledgedSrcSize must be correct. If srcSize is not known at init time, use | |
1366 | * value ZSTD_CONTENTSIZE_UNKNOWN. | |
1367 | */ | |
1368 | size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); | |
11fdf7f2 TL |
1369 | </pre></b><BR> |
1370 | <pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); | |
9f95a23c TL |
1371 | </b><p> This function is deprecated, and is equivalent to: |
1372 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); | |
1373 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); | |
1374 | ||
1375 | start a new frame, using same parameters from previous frame. | |
1376 | This is typically useful to skip dictionary loading stage, since it will re-use it in-place. | |
11fdf7f2 | 1377 | Note that zcs must be init at least once before using ZSTD_resetCStream(). |
9f95a23c | 1378 | If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. |
11fdf7f2 | 1379 | If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. |
9f95a23c TL |
1380 | For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, |
1381 | but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. | |
1382 | @return : 0, or an error code (which can be tested using ZSTD_isError()) | |
1383 | ||
11fdf7f2 TL |
1384 | </p></pre><BR> |
1385 | ||
9f95a23c TL |
1386 | <pre><b>typedef struct { |
1387 | unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> | |
1388 | unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> | |
1389 | unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> | |
1390 | unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> | |
1391 | unsigned currentJobID; </b>/* MT only : latest started job nb */<b> | |
1392 | unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> | |
1393 | } ZSTD_frameProgression; | |
1394 | </b></pre><BR> | |
1395 | <pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); | |
1396 | </b><p> Tell how many bytes are ready to be flushed immediately. | |
1397 | Useful for multithreading scenarios (nbWorkers >= 1). | |
1398 | Probe the oldest active job, defined as oldest job not yet entirely flushed, | |
1399 | and check its output buffer. | |
1400 | @return : amount of data stored in oldest job and ready to be flushed immediately. | |
1401 | if @return == 0, it means either : | |
1402 | + there is no active job (could be checked with ZSTD_frameProgression()), or | |
1403 | + oldest job is still actively compressing data, | |
1404 | but everything it has produced has also been flushed so far, | |
1405 | therefore flush speed is limited by production speed of oldest job | |
1406 | irrespective of the speed of concurrent (and newer) jobs. | |
1407 | ||
1408 | </p></pre><BR> | |
1409 | ||
1410 | <h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: no dictionary will be used if dict == NULL or dictSize < 8 */<b> | |
11fdf7f2 | 1411 | size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict is referenced, it must outlive decompression session */<b> |
7c673cae | 1412 | size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b> |
11fdf7f2 | 1413 | </pre></b><BR> |
9f95a23c | 1414 | <a name="Chapter29"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre> |
7c673cae | 1415 | This is an advanced API, giving full control over buffer management, for users which need direct control over memory. |
11fdf7f2 TL |
1416 | But it's also a complex one, with several restrictions, documented below. |
1417 | Prefer normal streaming API for an easier experience. | |
7c673cae FG |
1418 | |
1419 | <BR></pre> | |
1420 | ||
9f95a23c | 1421 | <a name="Chapter30"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> |
7c673cae FG |
1422 | A ZSTD_CCtx object is required to track streaming operations. |
1423 | Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. | |
1424 | ZSTD_CCtx object can be re-used multiple times within successive compression operations. | |
1425 | ||
1426 | Start by initializing a context. | |
1427 | Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression, | |
1428 | or ZSTD_compressBegin_advanced(), for finer parameter control. | |
1429 | It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx() | |
1430 | ||
1431 | Then, consume your input using ZSTD_compressContinue(). | |
1432 | There are some important considerations to keep in mind when using this advanced function : | |
11fdf7f2 TL |
1433 | - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. |
1434 | - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. | |
7c673cae FG |
1435 | - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. |
1436 | Worst case evaluation is provided by ZSTD_compressBound(). | |
1437 | ZSTD_compressContinue() doesn't guarantee recover after a failed compression. | |
1438 | - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). | |
1439 | It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) | |
1440 | - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. | |
1441 | In which case, it will "discard" the relevant memory section from its history. | |
1442 | ||
1443 | Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. | |
11fdf7f2 TL |
1444 | It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. |
1445 | Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. | |
7c673cae | 1446 | |
11fdf7f2 | 1447 | `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again. |
7c673cae FG |
1448 | <BR></pre> |
1449 | ||
11fdf7f2 | 1450 | <h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); |
7c673cae | 1451 | size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); |
9f95a23c | 1452 | 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> |
11fdf7f2 | 1453 | size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> |
9f95a23c TL |
1454 | size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b> |
1455 | 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> | |
11fdf7f2 | 1456 | </pre></b><BR> |
9f95a23c | 1457 | <a name="Chapter31"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> |
7c673cae FG |
1458 | A ZSTD_DCtx object is required to track streaming operations. |
1459 | Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. | |
1460 | A ZSTD_DCtx object can be re-used multiple times. | |
1461 | ||
11fdf7f2 TL |
1462 | First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). |
1463 | Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. | |
1464 | Data fragment must be large enough to ensure successful decoding. | |
1465 | `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. | |
1466 | @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. | |
7c673cae FG |
1467 | >0 : `srcSize` is too small, please provide at least @result bytes on next attempt. |
1468 | errorCode, which can be tested using ZSTD_isError(). | |
1469 | ||
11fdf7f2 TL |
1470 | It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, |
1471 | such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). | |
1472 | Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. | |
1473 | As a consequence, check that values remain within valid application range. | |
1474 | For example, do not allocate memory blindly, check that `windowSize` is within expectation. | |
1475 | Each application can set its own limits, depending on local restrictions. | |
1476 | For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. | |
1477 | ||
1478 | ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. | |
1479 | ZSTD_decompressContinue() is very sensitive to contiguity, | |
1480 | if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, | |
1481 | or that previous contiguous segment is large enough to properly handle maximum back-reference distance. | |
1482 | There are multiple ways to guarantee this condition. | |
1483 | ||
1484 | The most memory efficient way is to use a round buffer of sufficient size. | |
1485 | Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), | |
1486 | which can @return an error code if required value is too large for current system (in 32-bits mode). | |
1487 | In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, | |
1488 | up to the moment there is not enough room left in the buffer to guarantee decoding another full block, | |
1489 | which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. | |
1490 | At which point, decoding can resume from the beginning of the buffer. | |
1491 | Note that already decoded data stored in the buffer should be flushed before being overwritten. | |
1492 | ||
1493 | There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. | |
1494 | ||
1495 | Finally, if you control the compression process, you can also ignore all buffer size rules, | |
1496 | as long as the encoder and decoder progress in "lock-step", | |
1497 | aka use exactly the same buffer sizes, break contiguity at the same place, etc. | |
1498 | ||
1499 | Once buffers are setup, start decompression, with ZSTD_decompressBegin(). | |
1500 | If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). | |
7c673cae FG |
1501 | |
1502 | Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. | |
1503 | ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). | |
1504 | ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. | |
1505 | ||
11fdf7f2 TL |
1506 | @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). |
1507 | It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. | |
7c673cae FG |
1508 | It can also be an error code, which can be tested with ZSTD_isError(). |
1509 | ||
7c673cae FG |
1510 | A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. |
1511 | Context can then be reset to start a new decompression. | |
1512 | ||
1513 | Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). | |
1514 | This information is not required to properly decode a frame. | |
1515 | ||
11fdf7f2 | 1516 | == Special case : skippable frames |
7c673cae FG |
1517 | |
1518 | Skippable frames allow integration of user-defined data into a flow of concatenated frames. | |
11fdf7f2 TL |
1519 | Skippable frames will be ignored (skipped) by decompressor. |
1520 | The format of skippable frames is as follows : | |
7c673cae FG |
1521 | a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F |
1522 | b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits | |
1523 | c) Frame Content - any content (User Data) of length equal to Frame Size | |
11fdf7f2 TL |
1524 | For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. |
1525 | For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. | |
7c673cae FG |
1526 | <BR></pre> |
1527 | ||
11fdf7f2 TL |
1528 | <h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; |
1529 | typedef struct { | |
1530 | unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> | |
1531 | unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> | |
1532 | unsigned blockSizeMax; | |
1533 | ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> | |
1534 | unsigned headerSize; | |
7c673cae FG |
1535 | unsigned dictID; |
1536 | unsigned checksumFlag; | |
11fdf7f2 | 1537 | } ZSTD_frameHeader; |
11fdf7f2 | 1538 | </pre></b><BR> |
9f95a23c TL |
1539 | <a name="Chapter32"></a><h2>ZSTD_getFrameHeader() :</h2><pre> decode Frame Header, or requires larger `srcSize`. |
1540 | @return : 0, `zfhPtr` is correctly filled, | |
1541 | >0, `srcSize` is too small, value is wanted `srcSize` amount, | |
1542 | or an error code, which can be tested using ZSTD_isError() | |
1543 | <BR></pre> | |
11fdf7f2 | 1544 | |
9f95a23c | 1545 | <pre><b>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> |
11fdf7f2 | 1546 | </b></pre><BR> |
9f95a23c TL |
1547 | <pre><b>size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); |
1548 | 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> | |
1549 | </b><p> same as ZSTD_getFrameHeader(), | |
1550 | with added capability to select a format (like ZSTD_f_zstd1_magicless) | |
11fdf7f2 TL |
1551 | </p></pre><BR> |
1552 | ||
9f95a23c | 1553 | <pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; |
11fdf7f2 | 1554 | </b></pre><BR> |
9f95a23c | 1555 | <a name="Chapter33"></a><h2>Block level API</h2><pre></pre> |
11fdf7f2 TL |
1556 | |
1557 | <pre><b></b><p> Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes). | |
7c673cae FG |
1558 | User will have to take in charge required information to regenerate data, such as compressed and content sizes. |
1559 | ||
1560 | A few rules to respect : | |
1561 | - Compressing and decompressing require a context structure | |
1562 | + Use ZSTD_createCCtx() and ZSTD_createDCtx() | |
1563 | - It is necessary to init context before starting | |
11fdf7f2 TL |
1564 | + compression : any ZSTD_compressBegin*() variant, including with dictionary |
1565 | + decompression : any ZSTD_decompressBegin*() variant, including with dictionary | |
1566 | + copyCCtx() and copyDCtx() can be used too | |
1567 | - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB | |
1568 | + If input is larger than a block size, it's necessary to split input data into multiple blocks | |
9f95a23c | 1569 | + For inputs larger than a single block, really consider using regular ZSTD_compress() instead. |
11fdf7f2 | 1570 | Frame metadata is not that costly, and quickly becomes negligible as source size grows larger. |
7c673cae | 1571 | - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero. |
9f95a23c | 1572 | In which case, nothing is produced into `dst` ! |
7c673cae FG |
1573 | + User must test for such outcome and deal directly with uncompressed data |
1574 | + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!! | |
11fdf7f2 TL |
1575 | + In case of multiple successive blocks, should some of them be uncompressed, |
1576 | decoder must be informed of their existence in order to follow proper history. | |
1577 | Use ZSTD_insertBlock() for such a case. | |
1578 | </p></pre><BR> | |
7c673cae | 1579 | |
11fdf7f2 | 1580 | <h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); |
7c673cae FG |
1581 | size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); |
1582 | size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); | |
9f95a23c | 1583 | 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> |
11fdf7f2 | 1584 | </pre></b><BR> |
7c673cae FG |
1585 | </html> |
1586 | </body> |