1 | <html>
|
---|
2 | <head>
|
---|
3 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
---|
4 | <title>zstd 1.5.0 Manual</title>
|
---|
5 | </head>
|
---|
6 | <body>
|
---|
7 | <h1>zstd 1.5.0 Manual</h1>
|
---|
8 | <hr>
|
---|
9 | <a name="Contents"></a><h2>Contents</h2>
|
---|
10 | <ol>
|
---|
11 | <li><a href="#Chapter1">Introduction</a></li>
|
---|
12 | <li><a href="#Chapter2">Version</a></li>
|
---|
13 | <li><a href="#Chapter3">Simple API</a></li>
|
---|
14 | <li><a href="#Chapter4">Explicit context</a></li>
|
---|
15 | <li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li>
|
---|
16 | <li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li>
|
---|
17 | <li><a href="#Chapter7">Streaming</a></li>
|
---|
18 | <li><a href="#Chapter8">Streaming compression - HowTo</a></li>
|
---|
19 | <li><a href="#Chapter9">Streaming decompression - HowTo</a></li>
|
---|
20 | <li><a href="#Chapter10">Simple dictionary API</a></li>
|
---|
21 | <li><a href="#Chapter11">Bulk processing dictionary API</a></li>
|
---|
22 | <li><a href="#Chapter12">Dictionary helper functions</a></li>
|
---|
23 | <li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li>
|
---|
24 | <li><a href="#Chapter14">experimental API (static linking only)</a></li>
|
---|
25 | <li><a href="#Chapter15">Frame size functions</a></li>
|
---|
26 | <li><a href="#Chapter16">Memory management</a></li>
|
---|
27 | <li><a href="#Chapter17">Advanced compression functions</a></li>
|
---|
28 | <li><a href="#Chapter18">Advanced decompression functions</a></li>
|
---|
29 | <li><a href="#Chapter19">Advanced streaming functions</a></li>
|
---|
30 | <li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions</a></li>
|
---|
31 | <li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
|
---|
32 | <li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
|
---|
33 | <li><a href="#Chapter23">Block level API</a></li>
|
---|
34 | </ol>
|
---|
35 | <hr>
|
---|
36 | <a name="Chapter1"></a><h2>Introduction</h2><pre>
|
---|
37 | zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
|
---|
38 | real-time compression scenarios at zlib-level and better compression ratios.
|
---|
39 | The zstd compression library provides in-memory compression and decompression
|
---|
40 | functions.
|
---|
41 |
|
---|
42 | The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
|
---|
43 | which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
|
---|
44 | caution, as they require more memory. The library also offers negative
|
---|
45 | compression levels, which extend the range of speed vs. ratio preferences.
|
---|
46 | The lower the level, the faster the speed (at the cost of compression).
|
---|
47 |
|
---|
48 | Compression can be done in:
|
---|
49 | - a single step (described as Simple API)
|
---|
50 | - a single step, reusing a context (described as Explicit context)
|
---|
51 | - unbounded multiple steps (described as Streaming compression)
|
---|
52 |
|
---|
53 | The compression ratio achievable on small data can be highly improved using
|
---|
54 | a dictionary. Dictionary compression can be performed in:
|
---|
55 | - a single step (described as Simple dictionary API)
|
---|
56 | - a single step, reusing a dictionary (described as Bulk-processing
|
---|
57 | dictionary API)
|
---|
58 |
|
---|
59 | Advanced experimental functions can be accessed using
|
---|
60 | `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
|
---|
61 |
|
---|
62 | Advanced experimental APIs should never be used with a dynamically-linked
|
---|
63 | library. They are not "stable"; their definitions or signatures may change in
|
---|
64 | the future. Only static linking is allowed.
|
---|
65 | <BR></pre>
|
---|
66 |
|
---|
67 | <a name="Chapter2"></a><h2>Version</h2><pre></pre>
|
---|
68 |
|
---|
69 | <pre><b>unsigned ZSTD_versionNumber(void);
|
---|
70 | </b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
|
---|
71 | </p></pre><BR>
|
---|
72 |
|
---|
73 | <pre><b>const char* ZSTD_versionString(void);
|
---|
74 | </b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+.
|
---|
75 | </p></pre><BR>
|
---|
76 |
|
---|
77 | <a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
|
---|
78 |
|
---|
79 | <pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
|
---|
80 | const void* src, size_t srcSize,
|
---|
81 | int compressionLevel);
|
---|
82 | </b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
|
---|
83 | Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
|
---|
84 | @return : compressed size written into `dst` (<= `dstCapacity),
|
---|
85 | or an error code if it fails (which can be tested using ZSTD_isError()).
|
---|
86 | </p></pre><BR>
|
---|
87 |
|
---|
88 | <pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
|
---|
89 | const void* src, size_t compressedSize);
|
---|
90 | </b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
|
---|
91 | `dstCapacity` is an upper bound of originalSize to regenerate.
|
---|
92 | If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
|
---|
93 | @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
|
---|
94 | or an errorCode if it fails (which can be tested using ZSTD_isError()).
|
---|
95 | </p></pre><BR>
|
---|
96 |
|
---|
97 | <pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
|
---|
98 | #define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
|
---|
99 | unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
|
---|
100 | </b><p> `src` should point to the start of a ZSTD encoded frame.
|
---|
101 | `srcSize` must be at least as large as the frame header.
|
---|
102 | hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
|
---|
103 | @return : - decompressed size of `src` frame content, if known
|
---|
104 | - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
|
---|
105 | - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
|
---|
106 | note 1 : a 0 return value means the frame is valid but "empty".
|
---|
107 | note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
|
---|
108 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
|
---|
109 | In which case, it's necessary to use streaming mode to decompress data.
|
---|
110 | Optionally, application can rely on some implicit limit,
|
---|
111 | as ZSTD_decompress() only needs an upper bound of decompressed size.
|
---|
112 | (For example, data could be necessarily cut into blocks <= 16 KB).
|
---|
113 | note 3 : decompressed size is always present when compression is completed using single-pass functions,
|
---|
114 | such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
|
---|
115 | note 4 : decompressed size can be very large (64-bits value),
|
---|
116 | potentially larger than what local system can handle as a single memory segment.
|
---|
117 | In which case, it's necessary to use streaming mode to decompress data.
|
---|
118 | note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
|
---|
119 | Always ensure return value fits within application's authorized limits.
|
---|
120 | Each application can set its own limits.
|
---|
121 | note 6 : This function replaces ZSTD_getDecompressedSize()
|
---|
122 | </p></pre><BR>
|
---|
123 |
|
---|
124 | <pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
|
---|
125 | </b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
|
---|
126 | Both functions work the same way, but ZSTD_getDecompressedSize() blends
|
---|
127 | "empty", "unknown" and "error" results to the same return value (0),
|
---|
128 | while ZSTD_getFrameContentSize() gives them separate return values.
|
---|
129 | @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise.
|
---|
130 | </p></pre><BR>
|
---|
131 |
|
---|
132 | <pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
|
---|
133 | </b><p> `src` should point to the start of a ZSTD frame or skippable frame.
|
---|
134 | `srcSize` must be >= first frame size
|
---|
135 | @return : the compressed size of the first frame starting at `src`,
|
---|
136 | suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
|
---|
137 | or an error code if input is invalid
|
---|
138 | </p></pre><BR>
|
---|
139 |
|
---|
140 | <h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
|
---|
141 | size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
|
---|
142 | unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
|
---|
143 | const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
|
---|
144 | int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b>
|
---|
145 | int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
|
---|
146 | int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b>
|
---|
147 | </pre></b><BR>
|
---|
148 | <a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
|
---|
149 |
|
---|
150 | <h3>Compression context</h3><pre> When compressing many times,
|
---|
151 | it is recommended to allocate a context just once,
|
---|
152 | and re-use it for each successive compression operation.
|
---|
153 | This will make workload friendlier for system's memory.
|
---|
154 | Note : re-using context is just a speed / resource optimization.
|
---|
155 | It doesn't change the compression ratio, which remains identical.
|
---|
156 | Note 2 : In multi-threaded environments,
|
---|
157 | use one different context per thread for parallel execution.
|
---|
158 |
|
---|
159 | </pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
|
---|
160 | ZSTD_CCtx* ZSTD_createCCtx(void);
|
---|
161 | size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b>
|
---|
162 | </pre></b><BR>
|
---|
163 | <pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
|
---|
164 | void* dst, size_t dstCapacity,
|
---|
165 | const void* src, size_t srcSize,
|
---|
166 | int compressionLevel);
|
---|
167 | </b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
|
---|
168 | Important : in order to behave similarly to `ZSTD_compress()`,
|
---|
169 | this function compresses at requested compression level,
|
---|
170 | __ignoring any other parameter__ .
|
---|
171 | If any advanced parameter was set using the advanced API,
|
---|
172 | they will all be reset. Only `compressionLevel` remains.
|
---|
173 |
|
---|
174 | </p></pre><BR>
|
---|
175 |
|
---|
176 | <h3>Decompression context</h3><pre> When decompressing many times,
|
---|
177 | it is recommended to allocate a context only once,
|
---|
178 | and re-use it for each successive compression operation.
|
---|
179 | This will make workload friendlier for system's memory.
|
---|
180 | Use one context per thread for parallel execution.
|
---|
181 | </pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
|
---|
182 | ZSTD_DCtx* ZSTD_createDCtx(void);
|
---|
183 | size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b>
|
---|
184 | </pre></b><BR>
|
---|
185 | <pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
|
---|
186 | void* dst, size_t dstCapacity,
|
---|
187 | const void* src, size_t srcSize);
|
---|
188 | </b><p> Same as ZSTD_decompress(),
|
---|
189 | requires an allocated ZSTD_DCtx.
|
---|
190 | Compatible with sticky parameters.
|
---|
191 |
|
---|
192 | </p></pre><BR>
|
---|
193 |
|
---|
194 | <a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre>
|
---|
195 |
|
---|
196 | <pre><b>typedef enum { ZSTD_fast=1,
|
---|
197 | ZSTD_dfast=2,
|
---|
198 | ZSTD_greedy=3,
|
---|
199 | ZSTD_lazy=4,
|
---|
200 | ZSTD_lazy2=5,
|
---|
201 | ZSTD_btlazy2=6,
|
---|
202 | ZSTD_btopt=7,
|
---|
203 | ZSTD_btultra=8,
|
---|
204 | ZSTD_btultra2=9
|
---|
205 | </b>/* note : new strategies _might_ be added in the future.<b>
|
---|
206 | Only the order (from fast to strong) is guaranteed */
|
---|
207 | } ZSTD_strategy;
|
---|
208 | </b></pre><BR>
|
---|
209 | <pre><b>typedef enum {
|
---|
210 |
|
---|
211 | </b>/* compression parameters<b>
|
---|
212 | * Note: When compressing with a ZSTD_CDict these parameters are superseded
|
---|
213 | * by the parameters used to construct the ZSTD_CDict.
|
---|
214 | * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
|
---|
215 | ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
|
---|
216 | * Note that exact compression parameters are dynamically determined,
|
---|
217 | * depending on both compression level and srcSize (when known).
|
---|
218 | * Default level is ZSTD_CLEVEL_DEFAULT==3.
|
---|
219 | * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
|
---|
220 | * Note 1 : it's possible to pass a negative compression level.
|
---|
221 | * Note 2 : setting a level does not automatically set all other compression parameters
|
---|
222 | * to default. Setting this will however eventually dynamically impact the compression
|
---|
223 | * parameters which have not been manually set. The manually set
|
---|
224 | * ones will 'stick'. */
|
---|
225 | </b>/* Advanced compression parameters :<b>
|
---|
226 | * It's possible to pin down compression parameters to some specific values.
|
---|
227 | * In which case, these values are no longer dynamically selected by the compressor */
|
---|
228 | ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
|
---|
229 | * This will set a memory budget for streaming decompression,
|
---|
230 | * with larger values requiring more memory
|
---|
231 | * and typically compressing more.
|
---|
232 | * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
|
---|
233 | * Special: value 0 means "use default windowLog".
|
---|
234 | * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
|
---|
235 | * requires explicitly allowing such size at streaming decompression stage. */
|
---|
236 | ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
|
---|
237 | * Resulting memory usage is (1 << (hashLog+2)).
|
---|
238 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
|
---|
239 | * Larger tables improve compression ratio of strategies <= dFast,
|
---|
240 | * and improve speed of strategies > dFast.
|
---|
241 | * Special: value 0 means "use default hashLog". */
|
---|
242 | ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b>
|
---|
243 | * Resulting memory usage is (1 << (chainLog+2)).
|
---|
244 | * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
|
---|
245 | * Larger tables result in better and slower compression.
|
---|
246 | * This parameter is useless for "fast" strategy.
|
---|
247 | * It's still useful when using "dfast" strategy,
|
---|
248 | * in which case it defines a secondary probe table.
|
---|
249 | * Special: value 0 means "use default chainLog". */
|
---|
250 | ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
|
---|
251 | * More attempts result in better and slower compression.
|
---|
252 | * This parameter is useless for "fast" and "dFast" strategies.
|
---|
253 | * Special: value 0 means "use default searchLog". */
|
---|
254 | ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b>
|
---|
255 | * Note that Zstandard can still find matches of smaller size,
|
---|
256 | * it just tweaks its search algorithm to look for this size and larger.
|
---|
257 | * Larger values increase compression and decompression speed, but decrease ratio.
|
---|
258 | * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
|
---|
259 | * Note that currently, for all strategies < btopt, effective minimum is 4.
|
---|
260 | * , for all strategies > fast, effective maximum is 6.
|
---|
261 | * Special: value 0 means "use default minMatchLength". */
|
---|
262 | ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
|
---|
263 | * For strategies btopt, btultra & btultra2:
|
---|
264 | * Length of Match considered "good enough" to stop search.
|
---|
265 | * Larger values make compression stronger, and slower.
|
---|
266 | * For strategy fast:
|
---|
267 | * Distance between match sampling.
|
---|
268 | * Larger values make compression faster, and weaker.
|
---|
269 | * Special: value 0 means "use default targetLength". */
|
---|
270 | ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b>
|
---|
271 | * The higher the value of selected strategy, the more complex it is,
|
---|
272 | * resulting in stronger and slower compression.
|
---|
273 | * Special: value 0 means "use default strategy". */
|
---|
274 | </b>/* LDM mode parameters */<b>
|
---|
275 | ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
|
---|
276 | * This parameter is designed to improve compression ratio
|
---|
277 | * for large inputs, by finding large matches at long distance.
|
---|
278 | * It increases memory usage and window size.
|
---|
279 | * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
|
---|
280 | * except when expressly set to a different value.
|
---|
281 | * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
|
---|
282 | * compression strategy >= ZSTD_btopt (== compression level 16+) */
|
---|
283 | ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
|
---|
284 | * Larger values increase memory usage and compression ratio,
|
---|
285 | * but decrease compression speed.
|
---|
286 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
|
---|
287 | * default: windowlog - 7.
|
---|
288 | * Special: value 0 means "automatically determine hashlog". */
|
---|
289 | ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
|
---|
290 | * Larger/too small values usually decrease compression ratio.
|
---|
291 | * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
|
---|
292 | * Special: value 0 means "use default value" (default: 64). */
|
---|
293 | ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
|
---|
294 | * Larger values improve collision resolution but decrease compression speed.
|
---|
295 | * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
|
---|
296 | * Special: value 0 means "use default value" (default: 3). */
|
---|
297 | ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
|
---|
298 | * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
|
---|
299 | * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
|
---|
300 | * Larger values improve compression speed.
|
---|
301 | * Deviating far from default value will likely result in a compression ratio decrease.
|
---|
302 | * Special: value 0 means "automatically determine hashRateLog". */
|
---|
303 |
|
---|
304 | </b>/* frame parameters */<b>
|
---|
305 | ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
|
---|
306 | * Content size must be known at the beginning of compression.
|
---|
307 | * This is automatically the case when using ZSTD_compress2(),
|
---|
308 | * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
|
---|
309 | ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
|
---|
310 | ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
|
---|
311 |
|
---|
312 | </b>/* multi-threading parameters */<b>
|
---|
313 | </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
|
---|
314 | * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
|
---|
315 | * In a situation where it's unknown if the linked library supports multi-threading or not,
|
---|
316 | * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
|
---|
317 | */
|
---|
318 | ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
|
---|
319 | * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
|
---|
320 | * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
|
---|
321 | * while compression is performed in parallel, within worker thread(s).
|
---|
322 | * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
|
---|
323 | * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
|
---|
324 | * More workers improve speed, but also increase memory usage.
|
---|
325 | * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
|
---|
326 | * compression is performed inside Caller's thread, and all invocations are blocking */
|
---|
327 | ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
|
---|
328 | * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
|
---|
329 | * 0 means default, which is dynamically determined based on compression parameters.
|
---|
330 | * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
|
---|
331 | * The minimum size is automatically and transparently enforced. */
|
---|
332 | ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
|
---|
333 | * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
|
---|
334 | * It helps preserve compression ratio, while each job is compressed in parallel.
|
---|
335 | * This value is enforced only when nbWorkers >= 1.
|
---|
336 | * Larger values increase compression ratio, but decrease speed.
|
---|
337 | * Possible values range from 0 to 9 :
|
---|
338 | * - 0 means "default" : value will be determined by the library, depending on strategy
|
---|
339 | * - 1 means "no overlap"
|
---|
340 | * - 9 means "full overlap", using a full window size.
|
---|
341 | * Each intermediate rank increases/decreases load size by a factor 2 :
|
---|
342 | * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default
|
---|
343 | * default value varies between 6 and 9, depending on strategy */
|
---|
344 |
|
---|
345 | </b>/* note : additional experimental parameters are also available<b>
|
---|
346 | * within the experimental section of the API.
|
---|
347 | * At the time of this writing, they include :
|
---|
348 | * ZSTD_c_rsyncable
|
---|
349 | * ZSTD_c_format
|
---|
350 | * ZSTD_c_forceMaxWindow
|
---|
351 | * ZSTD_c_forceAttachDict
|
---|
352 | * ZSTD_c_literalCompressionMode
|
---|
353 | * ZSTD_c_targetCBlockSize
|
---|
354 | * ZSTD_c_srcSizeHint
|
---|
355 | * ZSTD_c_enableDedicatedDictSearch
|
---|
356 | * ZSTD_c_stableInBuffer
|
---|
357 | * ZSTD_c_stableOutBuffer
|
---|
358 | * ZSTD_c_blockDelimiters
|
---|
359 | * ZSTD_c_validateSequences
|
---|
360 | * ZSTD_c_splitBlocks
|
---|
361 | * ZSTD_c_useRowMatchFinder
|
---|
362 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
|
---|
363 | * note : never ever use experimentalParam? names directly;
|
---|
364 | * also, the enums values themselves are unstable and can still change.
|
---|
365 | */
|
---|
366 | ZSTD_c_experimentalParam1=500,
|
---|
367 | ZSTD_c_experimentalParam2=10,
|
---|
368 | ZSTD_c_experimentalParam3=1000,
|
---|
369 | ZSTD_c_experimentalParam4=1001,
|
---|
370 | ZSTD_c_experimentalParam5=1002,
|
---|
371 | ZSTD_c_experimentalParam6=1003,
|
---|
372 | ZSTD_c_experimentalParam7=1004,
|
---|
373 | ZSTD_c_experimentalParam8=1005,
|
---|
374 | ZSTD_c_experimentalParam9=1006,
|
---|
375 | ZSTD_c_experimentalParam10=1007,
|
---|
376 | ZSTD_c_experimentalParam11=1008,
|
---|
377 | ZSTD_c_experimentalParam12=1009,
|
---|
378 | ZSTD_c_experimentalParam13=1010,
|
---|
379 | ZSTD_c_experimentalParam14=1011,
|
---|
380 | ZSTD_c_experimentalParam15=1012
|
---|
381 | } ZSTD_cParameter;
|
---|
382 | </b></pre><BR>
|
---|
383 | <pre><b>typedef struct {
|
---|
384 | size_t error;
|
---|
385 | int lowerBound;
|
---|
386 | int upperBound;
|
---|
387 | } ZSTD_bounds;
|
---|
388 | </b></pre><BR>
|
---|
389 | <pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
|
---|
390 | </b><p> All parameters must belong to an interval with lower and upper bounds,
|
---|
391 | otherwise they will either trigger an error or be automatically clamped.
|
---|
392 | @return : a structure, ZSTD_bounds, which contains
|
---|
393 | - an error status field, which must be tested using ZSTD_isError()
|
---|
394 | - lower and upper bounds, both inclusive
|
---|
395 |
|
---|
396 | </p></pre><BR>
|
---|
397 |
|
---|
398 | <pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
|
---|
399 | </b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
|
---|
400 | All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
|
---|
401 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
|
---|
402 | Setting a parameter is generally only possible during frame initialization (before starting compression).
|
---|
403 | Exception : when using multi-threading mode (nbWorkers >= 1),
|
---|
404 | the following parameters can be updated _during_ compression (within same frame):
|
---|
405 | => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
|
---|
406 | new parameters will be active for next job only (after a flush()).
|
---|
407 | @return : an error code (which can be tested using ZSTD_isError()).
|
---|
408 |
|
---|
409 | </p></pre><BR>
|
---|
410 |
|
---|
411 | <pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
|
---|
412 | </b><p> Total input data size to be compressed as a single frame.
|
---|
413 | Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
|
---|
414 | This value will also be controlled at end of frame, and trigger an error if not respected.
|
---|
415 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
416 | Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
|
---|
417 | In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
418 | ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
|
---|
419 | Note 2 : pledgedSrcSize is only valid once, for the next frame.
|
---|
420 | It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
421 | Note 3 : Whenever all input data is provided and consumed in a single round,
|
---|
422 | for example with ZSTD_compress2(),
|
---|
423 | or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
|
---|
424 | this value is automatically overridden by srcSize instead.
|
---|
425 |
|
---|
426 | </p></pre><BR>
|
---|
427 |
|
---|
428 | <pre><b>typedef enum {
|
---|
429 | ZSTD_reset_session_only = 1,
|
---|
430 | ZSTD_reset_parameters = 2,
|
---|
431 | ZSTD_reset_session_and_parameters = 3
|
---|
432 | } ZSTD_ResetDirective;
|
---|
433 | </b></pre><BR>
|
---|
434 | <pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
|
---|
435 | </b><p> There are 2 different things that can be reset, independently or jointly :
|
---|
436 | - The session : will stop compressing current frame, and make CCtx ready to start a new one.
|
---|
437 | Useful after an error, or to interrupt any ongoing compression.
|
---|
438 | Any internal data not yet flushed is cancelled.
|
---|
439 | Compression parameters and dictionary remain unchanged.
|
---|
440 | They will be used to compress next frame.
|
---|
441 | Resetting session never fails.
|
---|
442 | - The parameters : changes all parameters back to "default".
|
---|
443 | This removes any reference to any dictionary too.
|
---|
444 | Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
|
---|
445 | otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
|
---|
446 | - Both : similar to resetting the session, followed by resetting parameters.
|
---|
447 |
|
---|
448 | </p></pre><BR>
|
---|
449 |
|
---|
450 | <pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
|
---|
451 | void* dst, size_t dstCapacity,
|
---|
452 | const void* src, size_t srcSize);
|
---|
453 | </b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
|
---|
454 | ZSTD_compress2() always starts a new frame.
|
---|
455 | Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
|
---|
456 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
|
---|
457 | - The function is always blocking, returns when compression is completed.
|
---|
458 | Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
|
---|
459 | @return : compressed size written into `dst` (<= `dstCapacity),
|
---|
460 | or an error code if it fails (which can be tested using ZSTD_isError()).
|
---|
461 |
|
---|
462 | </p></pre><BR>
|
---|
463 |
|
---|
464 | <a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre>
|
---|
465 |
|
---|
466 | <pre><b>typedef enum {
|
---|
467 |
|
---|
468 | ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
|
---|
469 | * the streaming API will refuse to allocate memory buffer
|
---|
470 | * in order to protect the host from unreasonable memory requirements.
|
---|
471 | * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
|
---|
472 | * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
|
---|
473 | * Special: value 0 means "use default maximum windowLog". */
|
---|
474 |
|
---|
475 | </b>/* note : additional experimental parameters are also available<b>
|
---|
476 | * within the experimental section of the API.
|
---|
477 | * At the time of this writing, they include :
|
---|
478 | * ZSTD_d_format
|
---|
479 | * ZSTD_d_stableOutBuffer
|
---|
480 | * ZSTD_d_forceIgnoreChecksum
|
---|
481 | * ZSTD_d_refMultipleDDicts
|
---|
482 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
|
---|
483 | * note : never ever use experimentalParam? names directly
|
---|
484 | */
|
---|
485 | ZSTD_d_experimentalParam1=1000,
|
---|
486 | ZSTD_d_experimentalParam2=1001,
|
---|
487 | ZSTD_d_experimentalParam3=1002,
|
---|
488 | ZSTD_d_experimentalParam4=1003
|
---|
489 |
|
---|
490 | } ZSTD_dParameter;
|
---|
491 | </b></pre><BR>
|
---|
492 | <pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
|
---|
493 | </b><p> All parameters must belong to an interval with lower and upper bounds,
|
---|
494 | otherwise they will either trigger an error or be automatically clamped.
|
---|
495 | @return : a structure, ZSTD_bounds, which contains
|
---|
496 | - an error status field, which must be tested using ZSTD_isError()
|
---|
497 | - both lower and upper bounds, inclusive
|
---|
498 |
|
---|
499 | </p></pre><BR>
|
---|
500 |
|
---|
501 | <pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
|
---|
502 | </b><p> Set one compression parameter, selected by enum ZSTD_dParameter.
|
---|
503 | All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
|
---|
504 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
|
---|
505 | Setting a parameter is only possible during frame initialization (before starting decompression).
|
---|
506 | @return : 0, or an error code (which can be tested using ZSTD_isError()).
|
---|
507 |
|
---|
508 | </p></pre><BR>
|
---|
509 |
|
---|
510 | <pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
|
---|
511 | </b><p> Return a DCtx to clean state.
|
---|
512 | Session and parameters can be reset jointly or separately.
|
---|
513 | Parameters can only be reset when no active frame is being decompressed.
|
---|
514 | @return : 0, or an error code, which can be tested with ZSTD_isError()
|
---|
515 |
|
---|
516 | </p></pre><BR>
|
---|
517 |
|
---|
518 | <a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
|
---|
519 |
|
---|
520 | <pre><b>typedef struct ZSTD_inBuffer_s {
|
---|
521 | const void* src; </b>/**< start of input buffer */<b>
|
---|
522 | size_t size; </b>/**< size of input buffer */<b>
|
---|
523 | size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
|
---|
524 | } ZSTD_inBuffer;
|
---|
525 | </b></pre><BR>
|
---|
526 | <pre><b>typedef struct ZSTD_outBuffer_s {
|
---|
527 | void* dst; </b>/**< start of output buffer */<b>
|
---|
528 | size_t size; </b>/**< size of output buffer */<b>
|
---|
529 | size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
|
---|
530 | } ZSTD_outBuffer;
|
---|
531 | </b></pre><BR>
|
---|
532 | <a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
|
---|
533 | A ZSTD_CStream object is required to track streaming operation.
|
---|
534 | Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
|
---|
535 | ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
|
---|
536 | It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
|
---|
537 |
|
---|
538 | For parallel execution, use one separate ZSTD_CStream per thread.
|
---|
539 |
|
---|
540 | note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
|
---|
541 |
|
---|
542 | Parameters are sticky : when starting a new compression on the same context,
|
---|
543 | it will re-use the same sticky parameters as previous compression session.
|
---|
544 | When in doubt, it's recommended to fully initialize the context before usage.
|
---|
545 | Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
|
---|
546 | ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
|
---|
547 | set more specific parameters, the pledged source size, or load a dictionary.
|
---|
548 |
|
---|
549 | Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
|
---|
550 | consume input stream. The function will automatically update both `pos`
|
---|
551 | fields within `input` and `output`.
|
---|
552 | Note that the function may not consume the entire input, for example, because
|
---|
553 | the output buffer is already full, in which case `input.pos < input.size`.
|
---|
554 | The caller must check if input has been entirely consumed.
|
---|
555 | If not, the caller must make some room to receive more compressed data,
|
---|
556 | and then present again remaining input data.
|
---|
557 | note: ZSTD_e_continue is guaranteed to make some forward progress when called,
|
---|
558 | but doesn't guarantee maximal forward progress. This is especially relevant
|
---|
559 | when compressing with multiple threads. The call won't block if it can
|
---|
560 | consume some input, but if it can't it will wait for some, but not all,
|
---|
561 | output to be flushed.
|
---|
562 | @return : provides a minimum amount of data remaining to be flushed from internal buffers
|
---|
563 | or an error code, which can be tested using ZSTD_isError().
|
---|
564 |
|
---|
565 | At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
|
---|
566 | using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
|
---|
567 | Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
|
---|
568 | In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
|
---|
569 | You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
|
---|
570 | operation.
|
---|
571 | note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
|
---|
572 | block until the flush is complete or the output buffer is full.
|
---|
573 | @return : 0 if internal buffers are entirely flushed,
|
---|
574 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
|
---|
575 | or an error code, which can be tested using ZSTD_isError().
|
---|
576 |
|
---|
577 | Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
|
---|
578 | It will perform a flush and write frame epilogue.
|
---|
579 | The epilogue is required for decoders to consider a frame completed.
|
---|
580 | flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
|
---|
581 | You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
|
---|
582 | start a new frame.
|
---|
583 | note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
|
---|
584 | block until the flush is complete or the output buffer is full.
|
---|
585 | @return : 0 if frame fully completed and fully flushed,
|
---|
586 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
|
---|
587 | or an error code, which can be tested using ZSTD_isError().
|
---|
588 |
|
---|
589 |
|
---|
590 | <BR></pre>
|
---|
591 |
|
---|
592 | <pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
|
---|
593 | </b></pre><BR>
|
---|
594 | <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
|
---|
595 | size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b>
|
---|
596 | </pre></b><BR>
|
---|
597 | <h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
|
---|
598 | ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
|
---|
599 | ZSTD_e_flush=1, </b>/* flush any data provided so far,<b>
|
---|
600 | * it creates (at least) one new block, that can be decoded immediately on reception;
|
---|
601 | * frame will continue: any future data can still reference previously compressed data, improving compression.
|
---|
602 | * note : multithreaded compression will block to flush as much output as possible. */
|
---|
603 | ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b>
|
---|
604 | * note that frame is only closed after compressed data is fully flushed (return value == 0).
|
---|
605 | * After that point, any additional data starts a new frame.
|
---|
606 | * note : each frame is independent (does not reference any content from previous frame).
|
---|
607 | : note : multithreaded compression will block to flush as much output as possible. */
|
---|
608 | } ZSTD_EndDirective;
|
---|
609 | </pre></b><BR>
|
---|
610 | <pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
|
---|
611 | ZSTD_outBuffer* output,
|
---|
612 | ZSTD_inBuffer* input,
|
---|
613 | ZSTD_EndDirective endOp);
|
---|
614 | </b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive.
|
---|
615 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
|
---|
616 | - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
|
---|
617 | - output->pos must be <= dstCapacity, input->pos must be <= srcSize
|
---|
618 | - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
|
---|
619 | - endOp must be a valid directive
|
---|
620 | - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
|
---|
621 | - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available,
|
---|
622 | and then immediately returns, just indicating that there is some data remaining to be flushed.
|
---|
623 | The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
|
---|
624 | - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking.
|
---|
625 | - @return provides a minimum amount of data remaining to be flushed from internal buffers
|
---|
626 | or an error code, which can be tested using ZSTD_isError().
|
---|
627 | if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
|
---|
628 | This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
|
---|
629 | For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
|
---|
630 | - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
|
---|
631 | only ZSTD_e_end or ZSTD_e_flush operations are allowed.
|
---|
632 | Before starting a new compression job, or changing compression parameters,
|
---|
633 | it is required to fully flush internal buffers.
|
---|
634 |
|
---|
635 | </p></pre><BR>
|
---|
636 |
|
---|
637 | <pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
|
---|
638 | </b></pre><BR>
|
---|
639 | <pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
|
---|
640 | </b></pre><BR>
|
---|
641 | <pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
|
---|
642 | </b>/*!<b>
|
---|
643 | * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
|
---|
644 | * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
|
---|
645 | * the next read size (if non-zero and not an error). ZSTD_compressStream2()
|
---|
646 | * returns the minimum nb of bytes left to flush (if non-zero and not an error).
|
---|
647 | */
|
---|
648 | size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
|
---|
649 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
|
---|
650 | size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
|
---|
651 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
|
---|
652 | size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
|
---|
653 | </b><p>
|
---|
654 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
655 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
|
---|
656 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
---|
657 |
|
---|
658 | </p></pre><BR>
|
---|
659 |
|
---|
660 | <a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
|
---|
661 | A ZSTD_DStream object is required to track streaming operations.
|
---|
662 | Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
|
---|
663 | ZSTD_DStream objects can be re-used multiple times.
|
---|
664 |
|
---|
665 | Use ZSTD_initDStream() to start a new decompression operation.
|
---|
666 | @return : recommended first input size
|
---|
667 | Alternatively, use advanced API to set specific properties.
|
---|
668 |
|
---|
669 | Use ZSTD_decompressStream() repetitively to consume your input.
|
---|
670 | The function will update both `pos` fields.
|
---|
671 | If `input.pos < input.size`, some input has not been consumed.
|
---|
672 | It's up to the caller to present again remaining data.
|
---|
673 | The function tries to flush all data decoded immediately, respecting output buffer size.
|
---|
674 | If `output.pos < output.size`, decoder has flushed everything it could.
|
---|
675 | But if `output.pos == output.size`, there might be some data left within internal buffers.,
|
---|
676 | In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
|
---|
677 | Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
|
---|
678 | @return : 0 when a frame is completely decoded and fully flushed,
|
---|
679 | or an error code, which can be tested using ZSTD_isError(),
|
---|
680 | or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
|
---|
681 | the return value is a suggested next input size (just a hint for better latency)
|
---|
682 | that will never request more than the remaining frame size.
|
---|
683 |
|
---|
684 | <BR></pre>
|
---|
685 |
|
---|
686 | <pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
|
---|
687 | </b></pre><BR>
|
---|
688 | <h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
|
---|
689 | size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b>
|
---|
690 | </pre></b><BR>
|
---|
691 | <h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
|
---|
692 | <pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
|
---|
693 | </b></pre><BR>
|
---|
694 | <pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b>
|
---|
695 | </b></pre><BR>
|
---|
696 | <a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
|
---|
697 |
|
---|
698 | <pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
|
---|
699 | void* dst, size_t dstCapacity,
|
---|
700 | const void* src, size_t srcSize,
|
---|
701 | const void* dict,size_t dictSize,
|
---|
702 | int compressionLevel);
|
---|
703 | </b><p> Compression at an explicit compression level using a Dictionary.
|
---|
704 | A dictionary can be any arbitrary data segment (also called a prefix),
|
---|
705 | or a buffer with specified information (see zdict.h).
|
---|
706 | Note : This function loads the dictionary, resulting in significant startup delay.
|
---|
707 | It's intended for a dictionary used only once.
|
---|
708 | Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
|
---|
709 | </p></pre><BR>
|
---|
710 |
|
---|
711 | <pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
|
---|
712 | void* dst, size_t dstCapacity,
|
---|
713 | const void* src, size_t srcSize,
|
---|
714 | const void* dict,size_t dictSize);
|
---|
715 | </b><p> Decompression using a known Dictionary.
|
---|
716 | Dictionary must be identical to the one used during compression.
|
---|
717 | Note : This function loads the dictionary, resulting in significant startup delay.
|
---|
718 | It's intended for a dictionary used only once.
|
---|
719 | Note : When `dict == NULL || dictSize < 8` no dictionary is used.
|
---|
720 | </p></pre><BR>
|
---|
721 |
|
---|
722 | <a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
|
---|
723 |
|
---|
724 | <pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
|
---|
725 | int compressionLevel);
|
---|
726 | </b><p> When compressing multiple messages or blocks using the same dictionary,
|
---|
727 | it's recommended to digest the dictionary only once, since it's a costly operation.
|
---|
728 | ZSTD_createCDict() will create a state from digesting a dictionary.
|
---|
729 | The resulting state can be used for future compression operations with very limited startup cost.
|
---|
730 | ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
|
---|
731 | @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
|
---|
732 | Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
|
---|
733 | Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
|
---|
734 | in which case the only thing that it transports is the @compressionLevel.
|
---|
735 | This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
|
---|
736 | expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
|
---|
737 | </p></pre><BR>
|
---|
738 |
|
---|
739 | <pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
|
---|
740 | </b><p> Function frees memory allocated by ZSTD_createCDict().
|
---|
741 | If a NULL pointer is passed, no operation is performed.
|
---|
742 | </p></pre><BR>
|
---|
743 |
|
---|
744 | <pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
|
---|
745 | void* dst, size_t dstCapacity,
|
---|
746 | const void* src, size_t srcSize,
|
---|
747 | const ZSTD_CDict* cdict);
|
---|
748 | </b><p> Compression using a digested Dictionary.
|
---|
749 | Recommended when same dictionary is used multiple times.
|
---|
750 | Note : compression level is _decided at dictionary creation time_,
|
---|
751 | and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
|
---|
752 | </p></pre><BR>
|
---|
753 |
|
---|
754 | <pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
|
---|
755 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
|
---|
756 | dictBuffer can be released after DDict creation, as its content is copied inside DDict.
|
---|
757 | </p></pre><BR>
|
---|
758 |
|
---|
759 | <pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
|
---|
760 | </b><p> Function frees memory allocated with ZSTD_createDDict()
|
---|
761 | If a NULL pointer is passed, no operation is performed.
|
---|
762 | </p></pre><BR>
|
---|
763 |
|
---|
764 | <pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
|
---|
765 | void* dst, size_t dstCapacity,
|
---|
766 | const void* src, size_t srcSize,
|
---|
767 | const ZSTD_DDict* ddict);
|
---|
768 | </b><p> Decompression using a digested Dictionary.
|
---|
769 | Recommended when same dictionary is used multiple times.
|
---|
770 | </p></pre><BR>
|
---|
771 |
|
---|
772 | <a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
|
---|
773 |
|
---|
774 | <pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
|
---|
775 | </b><p> Provides the dictID stored within dictionary.
|
---|
776 | if @return == 0, the dictionary is not conformant with Zstandard specification.
|
---|
777 | It can still be loaded, but as a content-only dictionary.
|
---|
778 | </p></pre><BR>
|
---|
779 |
|
---|
780 | <pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
|
---|
781 | </b><p> Provides the dictID of the dictionary loaded into `cdict`.
|
---|
782 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
|
---|
783 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
|
---|
784 | </p></pre><BR>
|
---|
785 |
|
---|
786 | <pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
|
---|
787 | </b><p> Provides the dictID of the dictionary loaded into `ddict`.
|
---|
788 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
|
---|
789 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
|
---|
790 | </p></pre><BR>
|
---|
791 |
|
---|
792 | <pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
|
---|
793 | </b><p> Provides the dictID required to decompressed the frame stored within `src`.
|
---|
794 | If @return == 0, the dictID could not be decoded.
|
---|
795 | This could for one of the following reasons :
|
---|
796 | - The frame does not require a dictionary to be decoded (most common case).
|
---|
797 | - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
|
---|
798 | Note : this use case also happens when using a non-conformant dictionary.
|
---|
799 | - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
|
---|
800 | - This is not a Zstandard frame.
|
---|
801 | When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
|
---|
802 | </p></pre><BR>
|
---|
803 |
|
---|
804 | <a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre>
|
---|
805 | This API allows dictionaries to be used with ZSTD_compress2(),
|
---|
806 | ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and
|
---|
807 | only reset with the context is reset with ZSTD_reset_parameters or
|
---|
808 | ZSTD_reset_session_and_parameters. Prefixes are single-use.
|
---|
809 | <BR></pre>
|
---|
810 |
|
---|
811 | <pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
|
---|
812 | </b><p> Create an internal CDict from `dict` buffer.
|
---|
813 | Decompression will have to use same dictionary.
|
---|
814 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
815 | Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
|
---|
816 | meaning "return to no-dictionary mode".
|
---|
817 | Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
|
---|
818 | To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
|
---|
819 | Note 2 : Loading a dictionary involves building tables.
|
---|
820 | It's also a CPU consuming operation, with non-negligible impact on latency.
|
---|
821 | Tables are dependent on compression parameters, and for this reason,
|
---|
822 | compression parameters can no longer be changed after loading a dictionary.
|
---|
823 | Note 3 :`dict` content will be copied internally.
|
---|
824 | Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
|
---|
825 | In such a case, dictionary buffer must outlive its users.
|
---|
826 | Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
|
---|
827 | to precisely select how dictionary content must be interpreted.
|
---|
828 | </p></pre><BR>
|
---|
829 |
|
---|
830 | <pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
|
---|
831 | </b><p> Reference a prepared dictionary, to be used for all next compressed frames.
|
---|
832 | Note that compression parameters are enforced from within CDict,
|
---|
833 | and supersede any compression parameter previously set within CCtx.
|
---|
834 | The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
|
---|
835 | The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
|
---|
836 | The dictionary will remain valid for future compressed frames using same CCtx.
|
---|
837 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
838 | Special : Referencing a NULL CDict means "return to no-dictionary mode".
|
---|
839 | Note 1 : Currently, only one dictionary can be managed.
|
---|
840 | Referencing a new dictionary effectively "discards" any previous one.
|
---|
841 | Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
|
---|
842 | </p></pre><BR>
|
---|
843 |
|
---|
844 | <pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
|
---|
845 | const void* prefix, size_t prefixSize);
|
---|
846 | </b><p> Reference a prefix (single-usage dictionary) for next compressed frame.
|
---|
847 | A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
|
---|
848 | Decompression will need same prefix to properly regenerate data.
|
---|
849 | Compressing with a prefix is similar in outcome as performing a diff and compressing it,
|
---|
850 | but performs much faster, especially during decompression (compression speed is tunable with compression level).
|
---|
851 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
852 | Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
|
---|
853 | Note 1 : Prefix buffer is referenced. It **must** outlive compression.
|
---|
854 | Its content must remain unmodified during compression.
|
---|
855 | Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
|
---|
856 | ensure that the window size is large enough to contain the entire source.
|
---|
857 | See ZSTD_c_windowLog.
|
---|
858 | Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
|
---|
859 | It's a CPU consuming operation, with non-negligible impact on latency.
|
---|
860 | If there is a need to use the same prefix multiple times, consider loadDictionary instead.
|
---|
861 | Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
|
---|
862 | Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
|
---|
863 | </p></pre><BR>
|
---|
864 |
|
---|
865 | <pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
|
---|
866 | </b><p> Create an internal DDict from dict buffer,
|
---|
867 | to be used to decompress next frames.
|
---|
868 | The dictionary remains valid for all future frames, until explicitly invalidated.
|
---|
869 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
870 | Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
|
---|
871 | meaning "return to no-dictionary mode".
|
---|
872 | Note 1 : Loading a dictionary involves building tables,
|
---|
873 | which has a non-negligible impact on CPU usage and latency.
|
---|
874 | It's recommended to "load once, use many times", to amortize the cost
|
---|
875 | Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
|
---|
876 | Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
|
---|
877 | Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
|
---|
878 | how dictionary content is loaded and interpreted.
|
---|
879 |
|
---|
880 | </p></pre><BR>
|
---|
881 |
|
---|
882 | <pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
|
---|
883 | </b><p> Reference a prepared dictionary, to be used to decompress next frames.
|
---|
884 | The dictionary remains active for decompression of future frames using same DCtx.
|
---|
885 |
|
---|
886 | If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
|
---|
887 | will store the DDict references in a table, and the DDict used for decompression
|
---|
888 | will be determined at decompression time, as per the dict ID in the frame.
|
---|
889 | The memory for the table is allocated on the first call to refDDict, and can be
|
---|
890 | freed with ZSTD_freeDCtx().
|
---|
891 |
|
---|
892 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
893 | Note 1 : Currently, only one dictionary can be managed.
|
---|
894 | Referencing a new dictionary effectively "discards" any previous one.
|
---|
895 | Special: referencing a NULL DDict means "return to no-dictionary mode".
|
---|
896 | Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
|
---|
897 |
|
---|
898 | </p></pre><BR>
|
---|
899 |
|
---|
900 | <pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
|
---|
901 | const void* prefix, size_t prefixSize);
|
---|
902 | </b><p> Reference a prefix (single-usage dictionary) to decompress next frame.
|
---|
903 | This is the reverse operation of ZSTD_CCtx_refPrefix(),
|
---|
904 | and must use the same prefix as the one used during compression.
|
---|
905 | Prefix is **only used once**. Reference is discarded at end of frame.
|
---|
906 | End of frame is reached when ZSTD_decompressStream() returns 0.
|
---|
907 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
908 | Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
|
---|
909 | Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
|
---|
910 | Prefix buffer must remain unmodified up to the end of frame,
|
---|
911 | reached when ZSTD_decompressStream() returns 0.
|
---|
912 | Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
|
---|
913 | Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
|
---|
914 | Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
|
---|
915 | A full dictionary is more costly, as it requires building tables.
|
---|
916 |
|
---|
917 | </p></pre><BR>
|
---|
918 |
|
---|
919 | <pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
|
---|
920 | size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
|
---|
921 | size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
|
---|
922 | size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
|
---|
923 | size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
|
---|
924 | size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
|
---|
925 | </b><p> These functions give the _current_ memory usage of selected object.
|
---|
926 | Note that object memory usage can evolve (increase or decrease) over time.
|
---|
927 | </p></pre><BR>
|
---|
928 |
|
---|
929 | <a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
|
---|
930 | The following symbols and constants
|
---|
931 | are not planned to join "stable API" status in the near future.
|
---|
932 | They can still change in future versions.
|
---|
933 | Some of them are planned to remain in the static_only section indefinitely.
|
---|
934 | Some of them might be removed in the future (especially when redundant with existing stable functions)
|
---|
935 |
|
---|
936 | <BR></pre>
|
---|
937 |
|
---|
938 | <pre><b>typedef struct {
|
---|
939 | unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
|
---|
940 | * If offset == 0 and matchLength == 0, this sequence represents the last
|
---|
941 | * literals in the block of litLength size.
|
---|
942 | */
|
---|
943 |
|
---|
944 | unsigned int litLength; </b>/* Literal length of the sequence. */<b>
|
---|
945 | unsigned int matchLength; </b>/* Match length of the sequence. */<b>
|
---|
946 |
|
---|
947 | </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
|
---|
948 | * In this case, we will treat the sequence as a marker for a block boundary.
|
---|
949 | */
|
---|
950 |
|
---|
951 | unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
|
---|
952 | * Ranges from [0, 3].
|
---|
953 | *
|
---|
954 | * Repeat offsets are essentially previous offsets from previous sequences sorted in
|
---|
955 | * recency order. For more detail, see doc/zstd_compression_format.md
|
---|
956 | *
|
---|
957 | * If rep == 0, then 'offset' does not contain a repeat offset.
|
---|
958 | * If rep > 0:
|
---|
959 | * If litLength != 0:
|
---|
960 | * rep == 1 --> offset == repeat_offset_1
|
---|
961 | * rep == 2 --> offset == repeat_offset_2
|
---|
962 | * rep == 3 --> offset == repeat_offset_3
|
---|
963 | * If litLength == 0:
|
---|
964 | * rep == 1 --> offset == repeat_offset_2
|
---|
965 | * rep == 2 --> offset == repeat_offset_3
|
---|
966 | * rep == 3 --> offset == repeat_offset_1 - 1
|
---|
967 | *
|
---|
968 | * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
|
---|
969 | * 'rep', but repeat offsets do not necessarily need to be calculated from an external
|
---|
970 | * sequence provider's perspective. For example, ZSTD_compressSequences() does not
|
---|
971 | * use this 'rep' field at all (as of now).
|
---|
972 | */
|
---|
973 | } ZSTD_Sequence;
|
---|
974 | </b></pre><BR>
|
---|
975 | <pre><b>typedef struct {
|
---|
976 | unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
|
---|
977 | unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
|
---|
978 | unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
|
---|
979 | unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
|
---|
980 | unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
|
---|
981 | unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
|
---|
982 | ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
|
---|
983 | } ZSTD_compressionParameters;
|
---|
984 | </b></pre><BR>
|
---|
985 | <pre><b>typedef struct {
|
---|
986 | int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
|
---|
987 | int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
|
---|
988 | int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
|
---|
989 | } ZSTD_frameParameters;
|
---|
990 | </b></pre><BR>
|
---|
991 | <pre><b>typedef struct {
|
---|
992 | ZSTD_compressionParameters cParams;
|
---|
993 | ZSTD_frameParameters fParams;
|
---|
994 | } ZSTD_parameters;
|
---|
995 | </b></pre><BR>
|
---|
996 | <pre><b>typedef enum {
|
---|
997 | ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
|
---|
998 | ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
|
---|
999 | ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
|
---|
1000 | } ZSTD_dictContentType_e;
|
---|
1001 | </b></pre><BR>
|
---|
1002 | <pre><b>typedef enum {
|
---|
1003 | ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
|
---|
1004 | ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
|
---|
1005 | } ZSTD_dictLoadMethod_e;
|
---|
1006 | </b></pre><BR>
|
---|
1007 | <pre><b>typedef enum {
|
---|
1008 | ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
|
---|
1009 | ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
|
---|
1010 | * Useful to save 4 bytes per generated frame.
|
---|
1011 | * Decoder cannot recognise automatically this format, requiring this instruction. */
|
---|
1012 | } ZSTD_format_e;
|
---|
1013 | </b></pre><BR>
|
---|
1014 | <pre><b>typedef enum {
|
---|
1015 | </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
|
---|
1016 | ZSTD_d_validateChecksum = 0,
|
---|
1017 | ZSTD_d_ignoreChecksum = 1
|
---|
1018 | } ZSTD_forceIgnoreChecksum_e;
|
---|
1019 | </b></pre><BR>
|
---|
1020 | <pre><b>typedef enum {
|
---|
1021 | </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
|
---|
1022 | ZSTD_rmd_refSingleDDict = 0,
|
---|
1023 | ZSTD_rmd_refMultipleDDicts = 1
|
---|
1024 | } ZSTD_refMultipleDDicts_e;
|
---|
1025 | </b></pre><BR>
|
---|
1026 | <pre><b>typedef enum {
|
---|
1027 | </b>/* Note: this enum and the behavior it controls are effectively internal<b>
|
---|
1028 | * implementation details of the compressor. They are expected to continue
|
---|
1029 | * to evolve and should be considered only in the context of extremely
|
---|
1030 | * advanced performance tuning.
|
---|
1031 | *
|
---|
1032 | * Zstd currently supports the use of a CDict in three ways:
|
---|
1033 | *
|
---|
1034 | * - The contents of the CDict can be copied into the working context. This
|
---|
1035 | * means that the compression can search both the dictionary and input
|
---|
1036 | * while operating on a single set of internal tables. This makes
|
---|
1037 | * the compression faster per-byte of input. However, the initial copy of
|
---|
1038 | * the CDict's tables incurs a fixed cost at the beginning of the
|
---|
1039 | * compression. For small compressions (< 8 KB), that copy can dominate
|
---|
1040 | * the cost of the compression.
|
---|
1041 | *
|
---|
1042 | * - The CDict's tables can be used in-place. In this model, compression is
|
---|
1043 | * slower per input byte, because the compressor has to search two sets of
|
---|
1044 | * tables. However, this model incurs no start-up cost (as long as the
|
---|
1045 | * working context's tables can be reused). For small inputs, this can be
|
---|
1046 | * faster than copying the CDict's tables.
|
---|
1047 | *
|
---|
1048 | * - The CDict's tables are not used at all, and instead we use the working
|
---|
1049 | * context alone to reload the dictionary and use params based on the source
|
---|
1050 | * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
|
---|
1051 | * This method is effective when the dictionary sizes are very small relative
|
---|
1052 | * to the input size, and the input size is fairly large to begin with.
|
---|
1053 | *
|
---|
1054 | * Zstd has a simple internal heuristic that selects which strategy to use
|
---|
1055 | * at the beginning of a compression. However, if experimentation shows that
|
---|
1056 | * Zstd is making poor choices, it is possible to override that choice with
|
---|
1057 | * this enum.
|
---|
1058 | */
|
---|
1059 | ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
|
---|
1060 | ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
|
---|
1061 | ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
|
---|
1062 | ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b>
|
---|
1063 | } ZSTD_dictAttachPref_e;
|
---|
1064 | </b></pre><BR>
|
---|
1065 | <pre><b>typedef enum {
|
---|
1066 | ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b>
|
---|
1067 | * Negative compression levels will be uncompressed, and positive compression
|
---|
1068 | * levels will be compressed. */
|
---|
1069 | ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
|
---|
1070 | * emitted if Huffman compression is not profitable. */
|
---|
1071 | ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
|
---|
1072 | } ZSTD_literalCompressionMode_e;
|
---|
1073 | </b></pre><BR>
|
---|
1074 | <pre><b>typedef enum {
|
---|
1075 | ZSTD_urm_auto = 0, </b>/* Automatically determine whether or not we use row matchfinder */<b>
|
---|
1076 | ZSTD_urm_disableRowMatchFinder = 1, </b>/* Never use row matchfinder */<b>
|
---|
1077 | ZSTD_urm_enableRowMatchFinder = 2 </b>/* Always use row matchfinder when applicable */<b>
|
---|
1078 | } ZSTD_useRowMatchFinderMode_e;
|
---|
1079 | </b></pre><BR>
|
---|
1080 | <a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre>
|
---|
1081 |
|
---|
1082 | <pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
|
---|
1083 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
|
---|
1084 | `srcSize` must be the _exact_ size of this series
|
---|
1085 | (i.e. there should be a frame boundary at `src + srcSize`)
|
---|
1086 | @return : - decompressed size of all data in all successive frames
|
---|
1087 | - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
|
---|
1088 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR
|
---|
1089 |
|
---|
1090 | note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
|
---|
1091 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
|
---|
1092 | In which case, it's necessary to use streaming mode to decompress data.
|
---|
1093 | note 2 : decompressed size is always present when compression is done with ZSTD_compress()
|
---|
1094 | note 3 : decompressed size can be very large (64-bits value),
|
---|
1095 | potentially larger than what local system can handle as a single memory segment.
|
---|
1096 | In which case, it's necessary to use streaming mode to decompress data.
|
---|
1097 | note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
|
---|
1098 | Always ensure result fits within application's authorized limits.
|
---|
1099 | Each application can set its own limits.
|
---|
1100 | note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
|
---|
1101 | read each contained frame header. This is fast as most of the data is skipped,
|
---|
1102 | however it does mean that all frame data must be present and valid.
|
---|
1103 | </p></pre><BR>
|
---|
1104 |
|
---|
1105 | <pre><b>unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
|
---|
1106 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
|
---|
1107 | `srcSize` must be the _exact_ size of this series
|
---|
1108 | (i.e. there should be a frame boundary at `src + srcSize`)
|
---|
1109 | @return : - upper-bound for the decompressed size of all data in all successive frames
|
---|
1110 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR
|
---|
1111 |
|
---|
1112 | note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
|
---|
1113 | note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
|
---|
1114 | in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
|
---|
1115 | note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
|
---|
1116 | upper-bound = # blocks * min(128 KB, Window_Size)
|
---|
1117 |
|
---|
1118 | </p></pre><BR>
|
---|
1119 |
|
---|
1120 | <pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
|
---|
1121 | </b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
|
---|
1122 | @return : size of the Frame Header,
|
---|
1123 | or an error code (if srcSize is too small)
|
---|
1124 | </p></pre><BR>
|
---|
1125 |
|
---|
1126 | <pre><b>typedef enum {
|
---|
1127 | ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
|
---|
1128 | ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
|
---|
1129 | } ZSTD_sequenceFormat_e;
|
---|
1130 | </b></pre><BR>
|
---|
1131 | <pre><b></b><p> Generate sequences using ZSTD_compress2, given a source buffer.
|
---|
1132 |
|
---|
1133 | Each block will end with a dummy sequence
|
---|
1134 | with offset == 0, matchLength == 0, and litLength == length of last literals.
|
---|
1135 | litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
|
---|
1136 | simply acts as a block delimiter.
|
---|
1137 |
|
---|
1138 | zc can be used to insert custom compression params.
|
---|
1139 | This function invokes ZSTD_compress2
|
---|
1140 |
|
---|
1141 | The output of this function can be fed into ZSTD_compressSequences() with CCtx
|
---|
1142 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
|
---|
1143 | @return : number of sequences generated
|
---|
1144 |
|
---|
1145 | </p></pre><BR>
|
---|
1146 |
|
---|
1147 | <pre><b>size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
|
---|
1148 | </b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
|
---|
1149 | by merging them into into the literals of the next sequence.
|
---|
1150 |
|
---|
1151 | As such, the final generated result has no explicit representation of block boundaries,
|
---|
1152 | and the final last literals segment is not represented in the sequences.
|
---|
1153 |
|
---|
1154 | The output of this function can be fed into ZSTD_compressSequences() with CCtx
|
---|
1155 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
|
---|
1156 | @return : number of sequences left after merging
|
---|
1157 |
|
---|
1158 | </p></pre><BR>
|
---|
1159 |
|
---|
1160 | <pre><b>size_t ZSTD_compressSequences(ZSTD_CCtx* const cctx, void* dst, size_t dstSize,
|
---|
1161 | const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
|
---|
1162 | const void* src, size_t srcSize);
|
---|
1163 | </b><p> Compress an array of ZSTD_Sequence, generated from the original source buffer, into dst.
|
---|
1164 | If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
|
---|
1165 | The entire source is compressed into a single frame.
|
---|
1166 |
|
---|
1167 | The compression behavior changes based on cctx params. In particular:
|
---|
1168 | If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
|
---|
1169 | no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
|
---|
1170 | the block size derived from the cctx, and sequences may be split. This is the default setting.
|
---|
1171 |
|
---|
1172 | If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
|
---|
1173 | block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
|
---|
1174 |
|
---|
1175 | If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
|
---|
1176 | behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
|
---|
1177 | specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
|
---|
1178 |
|
---|
1179 | In addition to the two adjustable experimental params, there are other important cctx params.
|
---|
1180 | - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN.
|
---|
1181 | - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
|
---|
1182 | - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
|
---|
1183 | is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
|
---|
1184 |
|
---|
1185 | Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
|
---|
1186 | Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
|
---|
1187 | and cannot emit an RLE block that disagrees with the repcode history
|
---|
1188 | @return : final compressed size or a ZSTD error.
|
---|
1189 |
|
---|
1190 | </p></pre><BR>
|
---|
1191 |
|
---|
1192 | <pre><b>size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
|
---|
1193 | const void* src, size_t srcSize, unsigned magicVariant);
|
---|
1194 | </b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
|
---|
1195 |
|
---|
1196 | Skippable frames begin with a a 4-byte magic number. There are 16 possible choices of magic number,
|
---|
1197 | ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
|
---|
1198 | As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
|
---|
1199 | the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
|
---|
1200 |
|
---|
1201 | Returns an error if destination buffer is not large enough, if the source size is not representable
|
---|
1202 | with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
|
---|
1203 |
|
---|
1204 | @return : number of bytes written or a ZSTD error.
|
---|
1205 |
|
---|
1206 | </p></pre><BR>
|
---|
1207 |
|
---|
1208 | <a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
|
---|
1209 |
|
---|
1210 | <pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
|
---|
1211 | size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
|
---|
1212 | size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
|
---|
1213 | size_t ZSTD_estimateDCtxSize(void);
|
---|
1214 | </b><p> These functions make it possible to estimate memory usage
|
---|
1215 | of a future {D,C}Ctx, before its creation.
|
---|
1216 |
|
---|
1217 | ZSTD_estimateCCtxSize() will provide a memory budget large enough
|
---|
1218 | for any compression level up to selected one.
|
---|
1219 | Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
|
---|
1220 | does not include space for a window buffer.
|
---|
1221 | Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
|
---|
1222 | The estimate will assume the input may be arbitrarily large,
|
---|
1223 | which is the worst case.
|
---|
1224 |
|
---|
1225 | When srcSize can be bound by a known and rather "small" value,
|
---|
1226 | this fact can be used to provide a tighter estimation
|
---|
1227 | because the CCtx compression context will need less memory.
|
---|
1228 | This tighter estimation can be provided by more advanced functions
|
---|
1229 | ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
|
---|
1230 | and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
|
---|
1231 | Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
|
---|
1232 |
|
---|
1233 | Note 2 : only single-threaded compression is supported.
|
---|
1234 | ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
|
---|
1235 |
|
---|
1236 | </p></pre><BR>
|
---|
1237 |
|
---|
1238 | <pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
|
---|
1239 | size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
|
---|
1240 | size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
|
---|
1241 | size_t ZSTD_estimateDStreamSize(size_t windowSize);
|
---|
1242 | size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
|
---|
1243 | </b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
|
---|
1244 | It will also consider src size to be arbitrarily "large", which is worst case.
|
---|
1245 | If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
|
---|
1246 | ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
|
---|
1247 | ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
|
---|
1248 | Note : CStream size estimation is only correct for single-threaded compression.
|
---|
1249 | ZSTD_DStream memory budget depends on window Size.
|
---|
1250 | This information can be passed manually, using ZSTD_estimateDStreamSize,
|
---|
1251 | or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
|
---|
1252 | Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
|
---|
1253 | an internal ?Dict will be created, which additional size is not estimated here.
|
---|
1254 | In this case, get total size by adding ZSTD_estimate?DictSize
|
---|
1255 | </p></pre><BR>
|
---|
1256 |
|
---|
1257 | <pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
|
---|
1258 | size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
|
---|
1259 | size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
|
---|
1260 | </b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
|
---|
1261 | ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
|
---|
1262 | Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
|
---|
1263 |
|
---|
1264 | </p></pre><BR>
|
---|
1265 |
|
---|
1266 | <pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
|
---|
1267 | ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
|
---|
1268 | </b><p> Initialize an object using a pre-allocated fixed-size buffer.
|
---|
1269 | workspace: The memory area to emplace the object into.
|
---|
1270 | Provided pointer *must be 8-bytes aligned*.
|
---|
1271 | Buffer must outlive object.
|
---|
1272 | workspaceSize: Use ZSTD_estimate*Size() to determine
|
---|
1273 | how large workspace must be to support target scenario.
|
---|
1274 | @return : pointer to object (same address as workspace, just different type),
|
---|
1275 | or NULL if error (size too small, incorrect alignment, etc.)
|
---|
1276 | Note : zstd will never resize nor malloc() when using a static buffer.
|
---|
1277 | If the object requires more memory than available,
|
---|
1278 | zstd will just error out (typically ZSTD_error_memory_allocation).
|
---|
1279 | Note 2 : there is no corresponding "free" function.
|
---|
1280 | Since workspace is allocated externally, it must be freed externally too.
|
---|
1281 | Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
|
---|
1282 | into its associated cParams.
|
---|
1283 | Limitation 1 : currently not compatible with internal dictionary creation, triggered by
|
---|
1284 | ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
|
---|
1285 | Limitation 2 : static cctx currently not compatible with multi-threading.
|
---|
1286 | Limitation 3 : static dctx is incompatible with legacy support.
|
---|
1287 |
|
---|
1288 | </p></pre><BR>
|
---|
1289 |
|
---|
1290 | <pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
|
---|
1291 | </b></pre><BR>
|
---|
1292 | <pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
|
---|
1293 | typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
|
---|
1294 | typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
|
---|
1295 | static
|
---|
1296 | #ifdef __GNUC__
|
---|
1297 | __attribute__((__unused__))
|
---|
1298 | #endif
|
---|
1299 | ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
|
---|
1300 | </b><p> These prototypes make it possible to pass your own allocation/free functions.
|
---|
1301 | ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
|
---|
1302 | All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
|
---|
1303 |
|
---|
1304 | </p></pre><BR>
|
---|
1305 |
|
---|
1306 | <a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
|
---|
1307 |
|
---|
1308 | <pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
|
---|
1309 | </b><p> Create a digested dictionary for compression
|
---|
1310 | Dictionary content is just referenced, not duplicated.
|
---|
1311 | As a consequence, `dictBuffer` **must** outlive CDict,
|
---|
1312 | and its content must remain unmodified throughout the lifetime of CDict.
|
---|
1313 | note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
|
---|
1314 | </p></pre><BR>
|
---|
1315 |
|
---|
1316 | <pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
|
---|
1317 | </b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
|
---|
1318 | `estimatedSrcSize` value is optional, select 0 if not known
|
---|
1319 | </p></pre><BR>
|
---|
1320 |
|
---|
1321 | <pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
|
---|
1322 | </b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
|
---|
1323 | All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
|
---|
1324 | </p></pre><BR>
|
---|
1325 |
|
---|
1326 | <pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
|
---|
1327 | </b><p> Ensure param values remain within authorized range.
|
---|
1328 | @return 0 on success, or an error code (can be checked with ZSTD_isError())
|
---|
1329 | </p></pre><BR>
|
---|
1330 |
|
---|
1331 | <pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
|
---|
1332 | </b><p> optimize params for a given `srcSize` and `dictSize`.
|
---|
1333 | `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
1334 | `dictSize` must be `0` when there is no dictionary.
|
---|
1335 | cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
|
---|
1336 | This function never fails (wide contract)
|
---|
1337 | </p></pre><BR>
|
---|
1338 |
|
---|
1339 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
|
---|
1340 | size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
|
---|
1341 | void* dst, size_t dstCapacity,
|
---|
1342 | const void* src, size_t srcSize,
|
---|
1343 | const void* dict,size_t dictSize,
|
---|
1344 | ZSTD_parameters params);
|
---|
1345 | </b><p> Note : this function is now DEPRECATED.
|
---|
1346 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
|
---|
1347 | This prototype will generate compilation warnings.
|
---|
1348 | </p></pre><BR>
|
---|
1349 |
|
---|
1350 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
|
---|
1351 | size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
|
---|
1352 | void* dst, size_t dstCapacity,
|
---|
1353 | const void* src, size_t srcSize,
|
---|
1354 | const ZSTD_CDict* cdict,
|
---|
1355 | ZSTD_frameParameters fParams);
|
---|
1356 | </b><p> Note : this function is now DEPRECATED.
|
---|
1357 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
|
---|
1358 | This prototype will generate compilation warnings.
|
---|
1359 | </p></pre><BR>
|
---|
1360 |
|
---|
1361 | <pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
|
---|
1362 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
|
---|
1363 | It saves some memory, but also requires that `dict` outlives its usage within `cctx`
|
---|
1364 | </p></pre><BR>
|
---|
1365 |
|
---|
1366 | <pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
|
---|
1367 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
|
---|
1368 | how to load the dictionary (by copy ? by reference ?)
|
---|
1369 | and how to interpret it (automatic ? force raw mode ? full mode only ?)
|
---|
1370 | </p></pre><BR>
|
---|
1371 |
|
---|
1372 | <pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
|
---|
1373 | </b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
|
---|
1374 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
|
---|
1375 | </p></pre><BR>
|
---|
1376 |
|
---|
1377 | <pre><b>size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
|
---|
1378 | </b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter,
|
---|
1379 | and store it into int* value.
|
---|
1380 | @return : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
1381 |
|
---|
1382 | </p></pre><BR>
|
---|
1383 |
|
---|
1384 | <pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
|
---|
1385 | size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
|
---|
1386 | </b><p> Quick howto :
|
---|
1387 | - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
|
---|
1388 | - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
|
---|
1389 | an existing ZSTD_CCtx_params structure.
|
---|
1390 | This is similar to
|
---|
1391 | ZSTD_CCtx_setParameter().
|
---|
1392 | - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
|
---|
1393 | an existing CCtx.
|
---|
1394 | These parameters will be applied to
|
---|
1395 | all subsequent frames.
|
---|
1396 | - ZSTD_compressStream2() : Do compression using the CCtx.
|
---|
1397 | - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
|
---|
1398 |
|
---|
1399 | This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
|
---|
1400 | for static allocation of CCtx for single-threaded compression.
|
---|
1401 |
|
---|
1402 | </p></pre><BR>
|
---|
1403 |
|
---|
1404 | <pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
|
---|
1405 | </b><p> Reset params to default values.
|
---|
1406 |
|
---|
1407 | </p></pre><BR>
|
---|
1408 |
|
---|
1409 | <pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
|
---|
1410 | </b><p> Initializes the compression parameters of cctxParams according to
|
---|
1411 | compression level. All other parameters are reset to their default values.
|
---|
1412 |
|
---|
1413 | </p></pre><BR>
|
---|
1414 |
|
---|
1415 | <pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
|
---|
1416 | </b><p> Initializes the compression and frame parameters of cctxParams according to
|
---|
1417 | params. All other parameters are reset to their default values.
|
---|
1418 |
|
---|
1419 | </p></pre><BR>
|
---|
1420 |
|
---|
1421 | <pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
|
---|
1422 | </b><p> Similar to ZSTD_CCtx_setParameter.
|
---|
1423 | Set one compression parameter, selected by enum ZSTD_cParameter.
|
---|
1424 | Parameters must be applied to a ZSTD_CCtx using
|
---|
1425 | ZSTD_CCtx_setParametersUsingCCtxParams().
|
---|
1426 | @result : a code representing success or failure (which can be tested with
|
---|
1427 | ZSTD_isError()).
|
---|
1428 |
|
---|
1429 | </p></pre><BR>
|
---|
1430 |
|
---|
1431 | <pre><b>size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
|
---|
1432 | </b><p> Similar to ZSTD_CCtx_getParameter.
|
---|
1433 | Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
|
---|
1434 | @result : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
1435 |
|
---|
1436 | </p></pre><BR>
|
---|
1437 |
|
---|
1438 | <pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams(
|
---|
1439 | ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
|
---|
1440 | </b><p> Apply a set of ZSTD_CCtx_params to the compression context.
|
---|
1441 | This can be done even after compression is started,
|
---|
1442 | if nbWorkers==0, this will have no impact until a new compression is started.
|
---|
1443 | if nbWorkers>=1, new parameters will be picked up at next job,
|
---|
1444 | with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
|
---|
1445 |
|
---|
1446 | </p></pre><BR>
|
---|
1447 |
|
---|
1448 | <pre><b>size_t ZSTD_compressStream2_simpleArgs (
|
---|
1449 | ZSTD_CCtx* cctx,
|
---|
1450 | void* dst, size_t dstCapacity, size_t* dstPos,
|
---|
1451 | const void* src, size_t srcSize, size_t* srcPos,
|
---|
1452 | ZSTD_EndDirective endOp);
|
---|
1453 | </b><p> Same as ZSTD_compressStream2(),
|
---|
1454 | but using only integral types as arguments.
|
---|
1455 | This variant might be helpful for binders from dynamic languages
|
---|
1456 | which have troubles handling structures containing memory pointers.
|
---|
1457 |
|
---|
1458 | </p></pre><BR>
|
---|
1459 |
|
---|
1460 | <a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
|
---|
1461 |
|
---|
1462 | <pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
|
---|
1463 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
|
---|
1464 | Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
|
---|
1465 | Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
|
---|
1466 | Note 3 : Skippable Frame Identifiers are considered valid.
|
---|
1467 | </p></pre><BR>
|
---|
1468 |
|
---|
1469 | <pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
|
---|
1470 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
|
---|
1471 | Dictionary content is referenced, and therefore stays in dictBuffer.
|
---|
1472 | It is important that dictBuffer outlives DDict,
|
---|
1473 | it must remain read accessible throughout the lifetime of DDict
|
---|
1474 | </p></pre><BR>
|
---|
1475 |
|
---|
1476 | <pre><b>size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
|
---|
1477 | </b><p> Same as ZSTD_DCtx_loadDictionary(),
|
---|
1478 | but references `dict` content instead of copying it into `dctx`.
|
---|
1479 | This saves memory if `dict` remains around.,
|
---|
1480 | However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
|
---|
1481 | </p></pre><BR>
|
---|
1482 |
|
---|
1483 | <pre><b>size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
|
---|
1484 | </b><p> Same as ZSTD_DCtx_loadDictionary(),
|
---|
1485 | but gives direct control over
|
---|
1486 | how to load the dictionary (by copy ? by reference ?)
|
---|
1487 | and how to interpret it (automatic ? force raw mode ? full mode only ?).
|
---|
1488 | </p></pre><BR>
|
---|
1489 |
|
---|
1490 | <pre><b>size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
|
---|
1491 | </b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over
|
---|
1492 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
|
---|
1493 | </p></pre><BR>
|
---|
1494 |
|
---|
1495 | <pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
|
---|
1496 | </b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
|
---|
1497 | This protects a decoder context from reserving too much memory for itself (potential attack scenario).
|
---|
1498 | This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
|
---|
1499 | By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
|
---|
1500 | @return : 0, or an error code (which can be tested using ZSTD_isError()).
|
---|
1501 |
|
---|
1502 | </p></pre><BR>
|
---|
1503 |
|
---|
1504 | <pre><b>size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
|
---|
1505 | </b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
|
---|
1506 | and store it into int* value.
|
---|
1507 | @return : 0, or an error code (which can be tested with ZSTD_isError()).
|
---|
1508 |
|
---|
1509 | </p></pre><BR>
|
---|
1510 |
|
---|
1511 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
|
---|
1512 | size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
|
---|
1513 | </b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
|
---|
1514 | Instruct the decoder context about what kind of data to decode next.
|
---|
1515 | This instruction is mandatory to decode data without a fully-formed header,
|
---|
1516 | such ZSTD_f_zstd1_magicless for example.
|
---|
1517 | @return : 0, or an error code (which can be tested using ZSTD_isError()).
|
---|
1518 | </p></pre><BR>
|
---|
1519 |
|
---|
1520 | <pre><b>size_t ZSTD_decompressStream_simpleArgs (
|
---|
1521 | ZSTD_DCtx* dctx,
|
---|
1522 | void* dst, size_t dstCapacity, size_t* dstPos,
|
---|
1523 | const void* src, size_t srcSize, size_t* srcPos);
|
---|
1524 | </b><p> Same as ZSTD_decompressStream(),
|
---|
1525 | but using only integral types as arguments.
|
---|
1526 | This can be helpful for binders from dynamic languages
|
---|
1527 | which have troubles handling structures containing memory pointers.
|
---|
1528 |
|
---|
1529 | </p></pre><BR>
|
---|
1530 |
|
---|
1531 | <a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
|
---|
1532 | Once Advanced API reaches "stable" status,
|
---|
1533 | redundant functions will be deprecated, and then at some point removed.
|
---|
1534 | <BR></pre>
|
---|
1535 |
|
---|
1536 | <h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
|
---|
1537 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
---|
1538 | size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
|
---|
1539 | int compressionLevel,
|
---|
1540 | unsigned long long pledgedSrcSize);
|
---|
1541 | </b><p> This function is DEPRECATED, and equivalent to:
|
---|
1542 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1543 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
|
---|
1544 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
---|
1545 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
---|
1546 |
|
---|
1547 | pledgedSrcSize must be correct. If it is not known at init time, use
|
---|
1548 | ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
|
---|
1549 | "0" also disables frame content size field. It may be enabled in the future.
|
---|
1550 | This prototype will generate compilation warnings.
|
---|
1551 |
|
---|
1552 | </p></pre><BR>
|
---|
1553 |
|
---|
1554 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
---|
1555 | size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
|
---|
1556 | const void* dict, size_t dictSize,
|
---|
1557 | int compressionLevel);
|
---|
1558 | </b><p> This function is DEPRECATED, and is equivalent to:
|
---|
1559 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1560 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
---|
1561 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
|
---|
1562 |
|
---|
1563 | Creates of an internal CDict (incompatible with static CCtx), except if
|
---|
1564 | dict == NULL or dictSize < 8, in which case no dict is used.
|
---|
1565 | Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
|
---|
1566 | it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
|
---|
1567 | This prototype will generate compilation warnings.
|
---|
1568 |
|
---|
1569 | </p></pre><BR>
|
---|
1570 |
|
---|
1571 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
---|
1572 | size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
|
---|
1573 | const void* dict, size_t dictSize,
|
---|
1574 | ZSTD_parameters params,
|
---|
1575 | unsigned long long pledgedSrcSize);
|
---|
1576 | </b><p> This function is DEPRECATED, and is approximately equivalent to:
|
---|
1577 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1578 | // Pseudocode: Set each zstd parameter and leave the rest as-is.
|
---|
1579 | for ((param, value) : params) {
|
---|
1580 | ZSTD_CCtx_setParameter(zcs, param, value);
|
---|
1581 | }
|
---|
1582 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
---|
1583 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
|
---|
1584 |
|
---|
1585 | dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
|
---|
1586 | pledgedSrcSize must be correct.
|
---|
1587 | If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
1588 | This prototype will generate compilation warnings.
|
---|
1589 |
|
---|
1590 | </p></pre><BR>
|
---|
1591 |
|
---|
1592 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
|
---|
1593 | size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
|
---|
1594 | </b><p> This function is DEPRECATED, and equivalent to:
|
---|
1595 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1596 | ZSTD_CCtx_refCDict(zcs, cdict);
|
---|
1597 |
|
---|
1598 | note : cdict will just be referenced, and must outlive compression session
|
---|
1599 | This prototype will generate compilation warnings.
|
---|
1600 |
|
---|
1601 | </p></pre><BR>
|
---|
1602 |
|
---|
1603 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
|
---|
1604 | size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
|
---|
1605 | const ZSTD_CDict* cdict,
|
---|
1606 | ZSTD_frameParameters fParams,
|
---|
1607 | unsigned long long pledgedSrcSize);
|
---|
1608 | </b><p> This function is DEPRECATED, and is approximately equivalent to:
|
---|
1609 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1610 | // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
|
---|
1611 | for ((fParam, value) : fParams) {
|
---|
1612 | ZSTD_CCtx_setParameter(zcs, fParam, value);
|
---|
1613 | }
|
---|
1614 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
---|
1615 | ZSTD_CCtx_refCDict(zcs, cdict);
|
---|
1616 |
|
---|
1617 | same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
|
---|
1618 | pledgedSrcSize must be correct. If srcSize is not known at init time, use
|
---|
1619 | value ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
1620 | This prototype will generate compilation warnings.
|
---|
1621 |
|
---|
1622 | </p></pre><BR>
|
---|
1623 |
|
---|
1624 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
---|
1625 | size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
|
---|
1626 | </b><p> This function is DEPRECATED, and is equivalent to:
|
---|
1627 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
---|
1628 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
---|
1629 | Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
|
---|
1630 | ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
|
---|
1631 | explicitly specified.
|
---|
1632 |
|
---|
1633 | start a new frame, using same parameters from previous frame.
|
---|
1634 | This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
|
---|
1635 | Note that zcs must be init at least once before using ZSTD_resetCStream().
|
---|
1636 | If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
|
---|
1637 | If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
|
---|
1638 | For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
|
---|
1639 | but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
|
---|
1640 | @return : 0, or an error code (which can be tested using ZSTD_isError())
|
---|
1641 | This prototype will generate compilation warnings.
|
---|
1642 |
|
---|
1643 | </p></pre><BR>
|
---|
1644 |
|
---|
1645 | <pre><b>typedef struct {
|
---|
1646 | unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
|
---|
1647 | unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
|
---|
1648 | unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
|
---|
1649 | unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
|
---|
1650 | unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
|
---|
1651 | unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
|
---|
1652 | } ZSTD_frameProgression;
|
---|
1653 | </b></pre><BR>
|
---|
1654 | <pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
|
---|
1655 | </b><p> Tell how many bytes are ready to be flushed immediately.
|
---|
1656 | Useful for multithreading scenarios (nbWorkers >= 1).
|
---|
1657 | Probe the oldest active job, defined as oldest job not yet entirely flushed,
|
---|
1658 | and check its output buffer.
|
---|
1659 | @return : amount of data stored in oldest job and ready to be flushed immediately.
|
---|
1660 | if @return == 0, it means either :
|
---|
1661 | + there is no active job (could be checked with ZSTD_frameProgression()), or
|
---|
1662 | + oldest job is still actively compressing data,
|
---|
1663 | but everything it has produced has also been flushed so far,
|
---|
1664 | therefore flush speed is limited by production speed of oldest job
|
---|
1665 | irrespective of the speed of concurrent (and newer) jobs.
|
---|
1666 |
|
---|
1667 | </p></pre><BR>
|
---|
1668 |
|
---|
1669 | <h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
|
---|
1670 | <pre><b>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
|
---|
1671 | </b><p>
|
---|
1672 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
---|
1673 | ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
|
---|
1674 |
|
---|
1675 | note: no dictionary will be used if dict == NULL or dictSize < 8
|
---|
1676 | Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
|
---|
1677 |
|
---|
1678 | </p></pre><BR>
|
---|
1679 |
|
---|
1680 | <pre><b>size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
|
---|
1681 | </b><p>
|
---|
1682 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
---|
1683 | ZSTD_DCtx_refDDict(zds, ddict);
|
---|
1684 |
|
---|
1685 | note : ddict is referenced, it must outlive decompression session
|
---|
1686 | Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
|
---|
1687 |
|
---|
1688 | </p></pre><BR>
|
---|
1689 |
|
---|
1690 | <pre><b>size_t ZSTD_resetDStream(ZSTD_DStream* zds);
|
---|
1691 | </b><p>
|
---|
1692 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
---|
1693 |
|
---|
1694 | re-use decompression parameters from previous init; saves dictionary loading
|
---|
1695 | Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
|
---|
1696 |
|
---|
1697 | </p></pre><BR>
|
---|
1698 |
|
---|
1699 | <a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
|
---|
1700 | This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
|
---|
1701 | But it's also a complex one, with several restrictions, documented below.
|
---|
1702 | Prefer normal streaming API for an easier experience.
|
---|
1703 |
|
---|
1704 | <BR></pre>
|
---|
1705 |
|
---|
1706 | <a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
|
---|
1707 | A ZSTD_CCtx object is required to track streaming operations.
|
---|
1708 | Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
|
---|
1709 | ZSTD_CCtx object can be re-used multiple times within successive compression operations.
|
---|
1710 |
|
---|
1711 | Start by initializing a context.
|
---|
1712 | Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
|
---|
1713 | It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
|
---|
1714 |
|
---|
1715 | Then, consume your input using ZSTD_compressContinue().
|
---|
1716 | There are some important considerations to keep in mind when using this advanced function :
|
---|
1717 | - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
|
---|
1718 | - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
|
---|
1719 | - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
|
---|
1720 | Worst case evaluation is provided by ZSTD_compressBound().
|
---|
1721 | ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
|
---|
1722 | - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
|
---|
1723 | It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
|
---|
1724 | - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
|
---|
1725 | In which case, it will "discard" the relevant memory section from its history.
|
---|
1726 |
|
---|
1727 | Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
|
---|
1728 | It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
|
---|
1729 | Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
|
---|
1730 |
|
---|
1731 | `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
|
---|
1732 | <BR></pre>
|
---|
1733 |
|
---|
1734 | <h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
|
---|
1735 | size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
|
---|
1736 | size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
|
---|
1737 | 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>
|
---|
1738 | </pre></b><BR>
|
---|
1739 | <pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
|
---|
1740 | </b></pre><BR>
|
---|
1741 | <a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
|
---|
1742 | A ZSTD_DCtx object is required to track streaming operations.
|
---|
1743 | Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
|
---|
1744 | A ZSTD_DCtx object can be re-used multiple times.
|
---|
1745 |
|
---|
1746 | First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
|
---|
1747 | Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
|
---|
1748 | Data fragment must be large enough to ensure successful decoding.
|
---|
1749 | `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
|
---|
1750 | @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
|
---|
1751 | >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
|
---|
1752 | errorCode, which can be tested using ZSTD_isError().
|
---|
1753 |
|
---|
1754 | It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
|
---|
1755 | such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
|
---|
1756 | Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
|
---|
1757 | As a consequence, check that values remain within valid application range.
|
---|
1758 | For example, do not allocate memory blindly, check that `windowSize` is within expectation.
|
---|
1759 | Each application can set its own limits, depending on local restrictions.
|
---|
1760 | For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
|
---|
1761 |
|
---|
1762 | ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
|
---|
1763 | ZSTD_decompressContinue() is very sensitive to contiguity,
|
---|
1764 | if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
|
---|
1765 | or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
|
---|
1766 | There are multiple ways to guarantee this condition.
|
---|
1767 |
|
---|
1768 | The most memory efficient way is to use a round buffer of sufficient size.
|
---|
1769 | Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
|
---|
1770 | which can @return an error code if required value is too large for current system (in 32-bits mode).
|
---|
1771 | In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
|
---|
1772 | up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
|
---|
1773 | which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
|
---|
1774 | At which point, decoding can resume from the beginning of the buffer.
|
---|
1775 | Note that already decoded data stored in the buffer should be flushed before being overwritten.
|
---|
1776 |
|
---|
1777 | There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
|
---|
1778 |
|
---|
1779 | Finally, if you control the compression process, you can also ignore all buffer size rules,
|
---|
1780 | as long as the encoder and decoder progress in "lock-step",
|
---|
1781 | aka use exactly the same buffer sizes, break contiguity at the same place, etc.
|
---|
1782 |
|
---|
1783 | Once buffers are setup, start decompression, with ZSTD_decompressBegin().
|
---|
1784 | If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
|
---|
1785 |
|
---|
1786 | Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
|
---|
1787 | ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
|
---|
1788 | ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
|
---|
1789 |
|
---|
1790 | @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
|
---|
1791 | It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
|
---|
1792 | It can also be an error code, which can be tested with ZSTD_isError().
|
---|
1793 |
|
---|
1794 | A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
|
---|
1795 | Context can then be reset to start a new decompression.
|
---|
1796 |
|
---|
1797 | Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
|
---|
1798 | This information is not required to properly decode a frame.
|
---|
1799 |
|
---|
1800 | == Special case : skippable frames
|
---|
1801 |
|
---|
1802 | Skippable frames allow integration of user-defined data into a flow of concatenated frames.
|
---|
1803 | Skippable frames will be ignored (skipped) by decompressor.
|
---|
1804 | The format of skippable frames is as follows :
|
---|
1805 | a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
|
---|
1806 | b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
|
---|
1807 | c) Frame Content - any content (User Data) of length equal to Frame Size
|
---|
1808 | For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
|
---|
1809 | For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
|
---|
1810 | <BR></pre>
|
---|
1811 |
|
---|
1812 | <h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
|
---|
1813 | typedef struct {
|
---|
1814 | unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
|
---|
1815 | unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
|
---|
1816 | unsigned blockSizeMax;
|
---|
1817 | ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
|
---|
1818 | unsigned headerSize;
|
---|
1819 | unsigned dictID;
|
---|
1820 | unsigned checksumFlag;
|
---|
1821 | } ZSTD_frameHeader;
|
---|
1822 | </pre></b><BR>
|
---|
1823 | <pre><b>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
|
---|
1824 | </b>/*! ZSTD_getFrameHeader_advanced() :<b>
|
---|
1825 | * same as ZSTD_getFrameHeader(),
|
---|
1826 | * with added capability to select a format (like ZSTD_f_zstd1_magicless) */
|
---|
1827 | size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
|
---|
1828 | 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>
|
---|
1829 | </b><p> decode Frame Header, or requires larger `srcSize`.
|
---|
1830 | @return : 0, `zfhPtr` is correctly filled,
|
---|
1831 | >0, `srcSize` is too small, value is wanted `srcSize` amount,
|
---|
1832 | or an error code, which can be tested using ZSTD_isError()
|
---|
1833 | </p></pre><BR>
|
---|
1834 |
|
---|
1835 | <pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
|
---|
1836 | </b></pre><BR>
|
---|
1837 | <a name="Chapter23"></a><h2>Block level API</h2><pre></pre>
|
---|
1838 |
|
---|
1839 | <pre><b></b><p> Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
|
---|
1840 | But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
|
---|
1841 |
|
---|
1842 | A few rules to respect :
|
---|
1843 | - Compressing and decompressing require a context structure
|
---|
1844 | + Use ZSTD_createCCtx() and ZSTD_createDCtx()
|
---|
1845 | - It is necessary to init context before starting
|
---|
1846 | + compression : any ZSTD_compressBegin*() variant, including with dictionary
|
---|
1847 | + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
|
---|
1848 | + copyCCtx() and copyDCtx() can be used too
|
---|
1849 | - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
|
---|
1850 | + If input is larger than a block size, it's necessary to split input data into multiple blocks
|
---|
1851 | + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
|
---|
1852 | Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
|
---|
1853 | - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
|
---|
1854 | ===> In which case, nothing is produced into `dst` !
|
---|
1855 | + User __must__ test for such outcome and deal directly with uncompressed data
|
---|
1856 | + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
|
---|
1857 | Doing so would mess up with statistics history, leading to potential data corruption.
|
---|
1858 | + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
|
---|
1859 | + In case of multiple successive blocks, should some of them be uncompressed,
|
---|
1860 | decoder must be informed of their existence in order to follow proper history.
|
---|
1861 | Use ZSTD_insertBlock() for such a case.
|
---|
1862 | </p></pre><BR>
|
---|
1863 |
|
---|
1864 | <h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
|
---|
1865 | size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
|
---|
1866 | size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
|
---|
1867 | 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>
|
---|
1868 | </pre></b><BR>
|
---|
1869 | </html>
|
---|
1870 | </body>
|
---|