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| 4 | <title>zstd 1.5.6 Manual</title> |
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| 6 | <body> |
| 7 | <h1>zstd 1.5.6 Manual</h1> |
| 8 | <hr> |
| 9 | <a name="Contents"></a><h2>Contents</h2> |
| 10 | <ol> |
| 11 | <li><a href="#Chapter1">Introduction</a></li> |
| 12 | <li><a href="#Chapter2">Version</a></li> |
| 13 | <li><a href="#Chapter3">Simple API</a></li> |
| 14 | <li><a href="#Chapter4">Explicit context</a></li> |
| 15 | <li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li> |
| 16 | <li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li> |
| 17 | <li><a href="#Chapter7">Streaming</a></li> |
| 18 | <li><a href="#Chapter8">Streaming compression - HowTo</a></li> |
| 19 | <li><a href="#Chapter9">Streaming decompression - HowTo</a></li> |
| 20 | <li><a href="#Chapter10">Simple dictionary API</a></li> |
| 21 | <li><a href="#Chapter11">Bulk processing dictionary API</a></li> |
| 22 | <li><a href="#Chapter12">Dictionary helper functions</a></li> |
| 23 | <li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li> |
| 24 | <li><a href="#Chapter14">experimental API (static linking only)</a></li> |
| 25 | <li><a href="#Chapter15">Frame header and size functions</a></li> |
| 26 | <li><a href="#Chapter16">Memory management</a></li> |
| 27 | <li><a href="#Chapter17">Advanced compression functions</a></li> |
| 28 | <li><a href="#Chapter18">Advanced decompression functions</a></li> |
| 29 | <li><a href="#Chapter19">Advanced streaming functions</a></li> |
| 30 | <li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li> |
| 31 | <li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li> |
| 32 | <li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li> |
| 33 | <li><a href="#Chapter23">Block level API (DEPRECATED)</a></li> |
| 34 | </ol> |
| 35 | <hr> |
| 36 | <a name="Chapter1"></a><h2>Introduction</h2><pre> |
| 37 | zstd, short for Zstandard, is a fast lossless compression algorithm, targeting |
| 38 | real-time compression scenarios at zlib-level and better compression ratios. |
| 39 | The zstd compression library provides in-memory compression and decompression |
| 40 | functions. |
| 41 | |
| 42 | The library supports regular compression levels from 1 up to ZSTD_maxCLevel(), |
| 43 | which is currently 22. Levels >= 20, labeled `--ultra`, should be used with |
| 44 | caution, as they require more memory. The library also offers negative |
| 45 | compression levels, which extend the range of speed vs. ratio preferences. |
| 46 | The lower the level, the faster the speed (at the cost of compression). |
| 47 | |
| 48 | Compression can be done in: |
| 49 | - a single step (described as Simple API) |
| 50 | - a single step, reusing a context (described as Explicit context) |
| 51 | - unbounded multiple steps (described as Streaming compression) |
| 52 | |
| 53 | The compression ratio achievable on small data can be highly improved using |
| 54 | a dictionary. Dictionary compression can be performed in: |
| 55 | - a single step (described as Simple dictionary API) |
| 56 | - a single step, reusing a dictionary (described as Bulk-processing |
| 57 | dictionary API) |
| 58 | |
| 59 | Advanced experimental functions can be accessed using |
| 60 | `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. |
| 61 | |
| 62 | Advanced experimental APIs should never be used with a dynamically-linked |
| 63 | library. They are not "stable"; their definitions or signatures may change in |
| 64 | the future. Only static linking is allowed. |
| 65 | <BR></pre> |
| 66 | |
| 67 | <a name="Chapter2"></a><h2>Version</h2><pre></pre> |
| 68 | |
| 69 | <pre><b>unsigned ZSTD_versionNumber(void); |
| 70 | </b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE). |
| 71 | </p></pre><BR> |
| 72 | |
| 73 | <pre><b>const char* ZSTD_versionString(void); |
| 74 | </b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+. |
| 75 | </p></pre><BR> |
| 76 | |
| 77 | <a name="Chapter3"></a><h2>Simple API</h2><pre></pre> |
| 78 | |
| 79 | <pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, |
| 80 | const void* src, size_t srcSize, |
| 81 | int compressionLevel); |
| 82 | </b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. |
| 83 | NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have |
| 84 | enough space to successfully compress the data. |
| 85 | @return : compressed size written into `dst` (<= `dstCapacity), |
| 86 | or an error code if it fails (which can be tested using ZSTD_isError()). |
| 87 | </p></pre><BR> |
| 88 | |
| 89 | <pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, |
| 90 | const void* src, size_t compressedSize); |
| 91 | </b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. |
| 92 | `dstCapacity` is an upper bound of originalSize to regenerate. |
| 93 | If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data. |
| 94 | @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), |
| 95 | or an errorCode if it fails (which can be tested using ZSTD_isError()). |
| 96 | </p></pre><BR> |
| 97 | |
| 98 | <pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) |
| 99 | #define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) |
| 100 | unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); |
| 101 | </b><p> `src` should point to the start of a ZSTD encoded frame. |
| 102 | `srcSize` must be at least as large as the frame header. |
| 103 | hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. |
| 104 | @return : - decompressed size of `src` frame content, if known |
| 105 | - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined |
| 106 | - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) |
| 107 | note 1 : a 0 return value means the frame is valid but "empty". |
| 108 | note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode. |
| 109 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. |
| 110 | In which case, it's necessary to use streaming mode to decompress data. |
| 111 | Optionally, application can rely on some implicit limit, |
| 112 | as ZSTD_decompress() only needs an upper bound of decompressed size. |
| 113 | (For example, data could be necessarily cut into blocks <= 16 KB). |
| 114 | note 3 : decompressed size is always present when compression is completed using single-pass functions, |
| 115 | such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict(). |
| 116 | note 4 : decompressed size can be very large (64-bits value), |
| 117 | potentially larger than what local system can handle as a single memory segment. |
| 118 | In which case, it's necessary to use streaming mode to decompress data. |
| 119 | note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. |
| 120 | Always ensure return value fits within application's authorized limits. |
| 121 | Each application can set its own limits. |
| 122 | note 6 : This function replaces ZSTD_getDecompressedSize() |
| 123 | </p></pre><BR> |
| 124 | |
| 125 | <pre><b>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize") |
| 126 | ZSTDLIB_API |
| 127 | unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); |
| 128 | </b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). |
| 129 | Both functions work the same way, but ZSTD_getDecompressedSize() blends |
| 130 | "empty", "unknown" and "error" results to the same return value (0), |
| 131 | while ZSTD_getFrameContentSize() gives them separate return values. |
| 132 | @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. |
| 133 | </p></pre><BR> |
| 134 | |
| 135 | <pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); |
| 136 | </b><p> `src` should point to the start of a ZSTD frame or skippable frame. |
| 137 | `srcSize` must be >= first frame size |
| 138 | @return : the compressed size of the first frame starting at `src`, |
| 139 | suitable to pass as `srcSize` to `ZSTD_decompress` or similar, |
| 140 | or an error code if input is invalid |
| 141 | </p></pre><BR> |
| 142 | |
| 143 | <h3>Helper functions</h3><pre></pre><b><pre></b>/* ZSTD_compressBound() :<b> |
| 144 | * maximum compressed size in worst case single-pass scenario. |
| 145 | * When invoking `ZSTD_compress()` or any other one-pass compression function, |
| 146 | * it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize) |
| 147 | * as it eliminates one potential failure scenario, |
| 148 | * aka not enough room in dst buffer to write the compressed frame. |
| 149 | * Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE . |
| 150 | * In which case, ZSTD_compressBound() will return an error code |
| 151 | * which can be tested using ZSTD_isError(). |
| 152 | * |
| 153 | * ZSTD_COMPRESSBOUND() : |
| 154 | * same as ZSTD_compressBound(), but as a macro. |
| 155 | * It can be used to produce constants, which can be useful for static allocation, |
| 156 | * for example to size a static array on stack. |
| 157 | * Will produce constant value 0 if srcSize too large. |
| 158 | */ |
| 159 | #define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00ULL : 0xFF00FF00U) |
| 160 | #define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> |
| 161 | size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b> |
| 162 | </b>/* ZSTD_isError() :<b> |
| 163 | * Most ZSTD_* functions returning a size_t value can be tested for error, |
| 164 | * using ZSTD_isError(). |
| 165 | * @return 1 if error, 0 otherwise |
| 166 | */ |
| 167 | unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> |
| 168 | const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> |
| 169 | int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b> |
| 170 | int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> |
| 171 | int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b> |
| 172 | </pre></b><BR> |
| 173 | <a name="Chapter4"></a><h2>Explicit context</h2><pre></pre> |
| 174 | |
| 175 | <h3>Compression context</h3><pre> When compressing many times, |
| 176 | it is recommended to allocate a context just once, |
| 177 | and reuse it for each successive compression operation. |
| 178 | This will make workload friendlier for system's memory. |
| 179 | Note : re-using context is just a speed / resource optimization. |
| 180 | It doesn't change the compression ratio, which remains identical. |
| 181 | Note 2 : In multi-threaded environments, |
| 182 | use one different context per thread for parallel execution. |
| 183 | |
| 184 | </pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; |
| 185 | ZSTD_CCtx* ZSTD_createCCtx(void); |
| 186 | size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b> |
| 187 | </pre></b><BR> |
| 188 | <pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, |
| 189 | void* dst, size_t dstCapacity, |
| 190 | const void* src, size_t srcSize, |
| 191 | int compressionLevel); |
| 192 | </b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx. |
| 193 | Important : in order to mirror `ZSTD_compress()` behavior, |
| 194 | this function compresses at the requested compression level, |
| 195 | __ignoring any other advanced parameter__ . |
| 196 | If any advanced parameter was set using the advanced API, |
| 197 | they will all be reset. Only `compressionLevel` remains. |
| 198 | |
| 199 | </p></pre><BR> |
| 200 | |
| 201 | <h3>Decompression context</h3><pre> When decompressing many times, |
| 202 | it is recommended to allocate a context only once, |
| 203 | and reuse it for each successive compression operation. |
| 204 | This will make workload friendlier for system's memory. |
| 205 | Use one context per thread for parallel execution. |
| 206 | </pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; |
| 207 | ZSTD_DCtx* ZSTD_createDCtx(void); |
| 208 | size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b> |
| 209 | </pre></b><BR> |
| 210 | <pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, |
| 211 | void* dst, size_t dstCapacity, |
| 212 | const void* src, size_t srcSize); |
| 213 | </b><p> Same as ZSTD_decompress(), |
| 214 | requires an allocated ZSTD_DCtx. |
| 215 | Compatible with sticky parameters (see below). |
| 216 | |
| 217 | </p></pre><BR> |
| 218 | |
| 219 | <a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre> |
| 220 | |
| 221 | <pre><b>typedef enum { ZSTD_fast=1, |
| 222 | ZSTD_dfast=2, |
| 223 | ZSTD_greedy=3, |
| 224 | ZSTD_lazy=4, |
| 225 | ZSTD_lazy2=5, |
| 226 | ZSTD_btlazy2=6, |
| 227 | ZSTD_btopt=7, |
| 228 | ZSTD_btultra=8, |
| 229 | ZSTD_btultra2=9 |
| 230 | </b>/* note : new strategies _might_ be added in the future.<b> |
| 231 | Only the order (from fast to strong) is guaranteed */ |
| 232 | } ZSTD_strategy; |
| 233 | </b></pre><BR> |
| 234 | <pre><b>typedef enum { |
| 235 | |
| 236 | </b>/* compression parameters<b> |
| 237 | * Note: When compressing with a ZSTD_CDict these parameters are superseded |
| 238 | * by the parameters used to construct the ZSTD_CDict. |
| 239 | * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */ |
| 240 | ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b> |
| 241 | * Note that exact compression parameters are dynamically determined, |
| 242 | * depending on both compression level and srcSize (when known). |
| 243 | * Default level is ZSTD_CLEVEL_DEFAULT==3. |
| 244 | * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. |
| 245 | * Note 1 : it's possible to pass a negative compression level. |
| 246 | * Note 2 : setting a level does not automatically set all other compression parameters |
| 247 | * to default. Setting this will however eventually dynamically impact the compression |
| 248 | * parameters which have not been manually set. The manually set |
| 249 | * ones will 'stick'. */ |
| 250 | </b>/* Advanced compression parameters :<b> |
| 251 | * It's possible to pin down compression parameters to some specific values. |
| 252 | * In which case, these values are no longer dynamically selected by the compressor */ |
| 253 | ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> |
| 254 | * This will set a memory budget for streaming decompression, |
| 255 | * with larger values requiring more memory |
| 256 | * and typically compressing more. |
| 257 | * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. |
| 258 | * Special: value 0 means "use default windowLog". |
| 259 | * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT |
| 260 | * requires explicitly allowing such size at streaming decompression stage. */ |
| 261 | ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> |
| 262 | * Resulting memory usage is (1 << (hashLog+2)). |
| 263 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. |
| 264 | * Larger tables improve compression ratio of strategies <= dFast, |
| 265 | * and improve speed of strategies > dFast. |
| 266 | * Special: value 0 means "use default hashLog". */ |
| 267 | ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> |
| 268 | * Resulting memory usage is (1 << (chainLog+2)). |
| 269 | * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. |
| 270 | * Larger tables result in better and slower compression. |
| 271 | * This parameter is useless for "fast" strategy. |
| 272 | * It's still useful when using "dfast" strategy, |
| 273 | * in which case it defines a secondary probe table. |
| 274 | * Special: value 0 means "use default chainLog". */ |
| 275 | ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> |
| 276 | * More attempts result in better and slower compression. |
| 277 | * This parameter is useless for "fast" and "dFast" strategies. |
| 278 | * Special: value 0 means "use default searchLog". */ |
| 279 | ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> |
| 280 | * Note that Zstandard can still find matches of smaller size, |
| 281 | * it just tweaks its search algorithm to look for this size and larger. |
| 282 | * Larger values increase compression and decompression speed, but decrease ratio. |
| 283 | * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. |
| 284 | * Note that currently, for all strategies < btopt, effective minimum is 4. |
| 285 | * , for all strategies > fast, effective maximum is 6. |
| 286 | * Special: value 0 means "use default minMatchLength". */ |
| 287 | ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> |
| 288 | * For strategies btopt, btultra & btultra2: |
| 289 | * Length of Match considered "good enough" to stop search. |
| 290 | * Larger values make compression stronger, and slower. |
| 291 | * For strategy fast: |
| 292 | * Distance between match sampling. |
| 293 | * Larger values make compression faster, and weaker. |
| 294 | * Special: value 0 means "use default targetLength". */ |
| 295 | ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> |
| 296 | * The higher the value of selected strategy, the more complex it is, |
| 297 | * resulting in stronger and slower compression. |
| 298 | * Special: value 0 means "use default strategy". */ |
| 299 | |
| 300 | ZSTD_c_targetCBlockSize=130, </b>/* v1.5.6+<b> |
| 301 | * Attempts to fit compressed block size into approximatively targetCBlockSize. |
| 302 | * Bound by ZSTD_TARGETCBLOCKSIZE_MIN and ZSTD_TARGETCBLOCKSIZE_MAX. |
| 303 | * Note that it's not a guarantee, just a convergence target (default:0). |
| 304 | * No target when targetCBlockSize == 0. |
| 305 | * This is helpful in low bandwidth streaming environments to improve end-to-end latency, |
| 306 | * when a client can make use of partial documents (a prominent example being Chrome). |
| 307 | * Note: this parameter is stable since v1.5.6. |
| 308 | * It was present as an experimental parameter in earlier versions, |
| 309 | * but it's not recommended using it with earlier library versions |
| 310 | * due to massive performance regressions. |
| 311 | */ |
| 312 | </b>/* LDM mode parameters */<b> |
| 313 | ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> |
| 314 | * This parameter is designed to improve compression ratio |
| 315 | * for large inputs, by finding large matches at long distance. |
| 316 | * It increases memory usage and window size. |
| 317 | * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB |
| 318 | * except when expressly set to a different value. |
| 319 | * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and |
| 320 | * compression strategy >= ZSTD_btopt (== compression level 16+) */ |
| 321 | ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> |
| 322 | * Larger values increase memory usage and compression ratio, |
| 323 | * but decrease compression speed. |
| 324 | * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX |
| 325 | * default: windowlog - 7. |
| 326 | * Special: value 0 means "automatically determine hashlog". */ |
| 327 | ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> |
| 328 | * Larger/too small values usually decrease compression ratio. |
| 329 | * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. |
| 330 | * Special: value 0 means "use default value" (default: 64). */ |
| 331 | ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> |
| 332 | * Larger values improve collision resolution but decrease compression speed. |
| 333 | * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. |
| 334 | * Special: value 0 means "use default value" (default: 3). */ |
| 335 | ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> |
| 336 | * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). |
| 337 | * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. |
| 338 | * Larger values improve compression speed. |
| 339 | * Deviating far from default value will likely result in a compression ratio decrease. |
| 340 | * Special: value 0 means "automatically determine hashRateLog". */ |
| 341 | |
| 342 | </b>/* frame parameters */<b> |
| 343 | ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> |
| 344 | * Content size must be known at the beginning of compression. |
| 345 | * This is automatically the case when using ZSTD_compress2(), |
| 346 | * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ |
| 347 | ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> |
| 348 | ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> |
| 349 | |
| 350 | </b>/* multi-threading parameters */<b> |
| 351 | </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> |
| 352 | * Otherwise, trying to set any other value than default (0) will be a no-op and return an error. |
| 353 | * In a situation where it's unknown if the linked library supports multi-threading or not, |
| 354 | * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property. |
| 355 | */ |
| 356 | ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> |
| 357 | * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() : |
| 358 | * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, |
| 359 | * while compression is performed in parallel, within worker thread(s). |
| 360 | * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : |
| 361 | * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). |
| 362 | * More workers improve speed, but also increase memory usage. |
| 363 | * Default value is `0`, aka "single-threaded mode" : no worker is spawned, |
| 364 | * compression is performed inside Caller's thread, and all invocations are blocking */ |
| 365 | ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> |
| 366 | * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. |
| 367 | * 0 means default, which is dynamically determined based on compression parameters. |
| 368 | * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest. |
| 369 | * The minimum size is automatically and transparently enforced. */ |
| 370 | ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> |
| 371 | * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. |
| 372 | * It helps preserve compression ratio, while each job is compressed in parallel. |
| 373 | * This value is enforced only when nbWorkers >= 1. |
| 374 | * Larger values increase compression ratio, but decrease speed. |
| 375 | * Possible values range from 0 to 9 : |
| 376 | * - 0 means "default" : value will be determined by the library, depending on strategy |
| 377 | * - 1 means "no overlap" |
| 378 | * - 9 means "full overlap", using a full window size. |
| 379 | * Each intermediate rank increases/decreases load size by a factor 2 : |
| 380 | * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default |
| 381 | * default value varies between 6 and 9, depending on strategy */ |
| 382 | |
| 383 | </b>/* note : additional experimental parameters are also available<b> |
| 384 | * within the experimental section of the API. |
| 385 | * At the time of this writing, they include : |
| 386 | * ZSTD_c_rsyncable |
| 387 | * ZSTD_c_format |
| 388 | * ZSTD_c_forceMaxWindow |
| 389 | * ZSTD_c_forceAttachDict |
| 390 | * ZSTD_c_literalCompressionMode |
| 391 | * ZSTD_c_srcSizeHint |
| 392 | * ZSTD_c_enableDedicatedDictSearch |
| 393 | * ZSTD_c_stableInBuffer |
| 394 | * ZSTD_c_stableOutBuffer |
| 395 | * ZSTD_c_blockDelimiters |
| 396 | * ZSTD_c_validateSequences |
| 397 | * ZSTD_c_useBlockSplitter |
| 398 | * ZSTD_c_useRowMatchFinder |
| 399 | * ZSTD_c_prefetchCDictTables |
| 400 | * ZSTD_c_enableSeqProducerFallback |
| 401 | * ZSTD_c_maxBlockSize |
| 402 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. |
| 403 | * note : never ever use experimentalParam? names directly; |
| 404 | * also, the enums values themselves are unstable and can still change. |
| 405 | */ |
| 406 | ZSTD_c_experimentalParam1=500, |
| 407 | ZSTD_c_experimentalParam2=10, |
| 408 | ZSTD_c_experimentalParam3=1000, |
| 409 | ZSTD_c_experimentalParam4=1001, |
| 410 | ZSTD_c_experimentalParam5=1002, |
| 411 | </b>/* was ZSTD_c_experimentalParam6=1003; is now ZSTD_c_targetCBlockSize */<b> |
| 412 | ZSTD_c_experimentalParam7=1004, |
| 413 | ZSTD_c_experimentalParam8=1005, |
| 414 | ZSTD_c_experimentalParam9=1006, |
| 415 | ZSTD_c_experimentalParam10=1007, |
| 416 | ZSTD_c_experimentalParam11=1008, |
| 417 | ZSTD_c_experimentalParam12=1009, |
| 418 | ZSTD_c_experimentalParam13=1010, |
| 419 | ZSTD_c_experimentalParam14=1011, |
| 420 | ZSTD_c_experimentalParam15=1012, |
| 421 | ZSTD_c_experimentalParam16=1013, |
| 422 | ZSTD_c_experimentalParam17=1014, |
| 423 | ZSTD_c_experimentalParam18=1015, |
| 424 | ZSTD_c_experimentalParam19=1016 |
| 425 | } ZSTD_cParameter; |
| 426 | </b></pre><BR> |
| 427 | <pre><b>typedef struct { |
| 428 | size_t error; |
| 429 | int lowerBound; |
| 430 | int upperBound; |
| 431 | } ZSTD_bounds; |
| 432 | </b></pre><BR> |
| 433 | <pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); |
| 434 | </b><p> All parameters must belong to an interval with lower and upper bounds, |
| 435 | otherwise they will either trigger an error or be automatically clamped. |
| 436 | @return : a structure, ZSTD_bounds, which contains |
| 437 | - an error status field, which must be tested using ZSTD_isError() |
| 438 | - lower and upper bounds, both inclusive |
| 439 | |
| 440 | </p></pre><BR> |
| 441 | |
| 442 | <pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); |
| 443 | </b><p> Set one compression parameter, selected by enum ZSTD_cParameter. |
| 444 | All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). |
| 445 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). |
| 446 | Setting a parameter is generally only possible during frame initialization (before starting compression). |
| 447 | Exception : when using multi-threading mode (nbWorkers >= 1), |
| 448 | the following parameters can be updated _during_ compression (within same frame): |
| 449 | => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. |
| 450 | new parameters will be active for next job only (after a flush()). |
| 451 | @return : an error code (which can be tested using ZSTD_isError()). |
| 452 | |
| 453 | </p></pre><BR> |
| 454 | |
| 455 | <pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); |
| 456 | </b><p> Total input data size to be compressed as a single frame. |
| 457 | Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. |
| 458 | This value will also be controlled at end of frame, and trigger an error if not respected. |
| 459 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 460 | Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. |
| 461 | In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. |
| 462 | ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. |
| 463 | Note 2 : pledgedSrcSize is only valid once, for the next frame. |
| 464 | It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. |
| 465 | Note 3 : Whenever all input data is provided and consumed in a single round, |
| 466 | for example with ZSTD_compress2(), |
| 467 | or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), |
| 468 | this value is automatically overridden by srcSize instead. |
| 469 | |
| 470 | </p></pre><BR> |
| 471 | |
| 472 | <pre><b>typedef enum { |
| 473 | ZSTD_reset_session_only = 1, |
| 474 | ZSTD_reset_parameters = 2, |
| 475 | ZSTD_reset_session_and_parameters = 3 |
| 476 | } ZSTD_ResetDirective; |
| 477 | </b></pre><BR> |
| 478 | <pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); |
| 479 | </b><p> There are 2 different things that can be reset, independently or jointly : |
| 480 | - The session : will stop compressing current frame, and make CCtx ready to start a new one. |
| 481 | Useful after an error, or to interrupt any ongoing compression. |
| 482 | Any internal data not yet flushed is cancelled. |
| 483 | Compression parameters and dictionary remain unchanged. |
| 484 | They will be used to compress next frame. |
| 485 | Resetting session never fails. |
| 486 | - The parameters : changes all parameters back to "default". |
| 487 | This also removes any reference to any dictionary or external sequence producer. |
| 488 | Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) |
| 489 | otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) |
| 490 | - Both : similar to resetting the session, followed by resetting parameters. |
| 491 | |
| 492 | </p></pre><BR> |
| 493 | |
| 494 | <pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, |
| 495 | void* dst, size_t dstCapacity, |
| 496 | const void* src, size_t srcSize); |
| 497 | </b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. |
| 498 | (note that this entry point doesn't even expose a compression level parameter). |
| 499 | ZSTD_compress2() always starts a new frame. |
| 500 | Should cctx hold data from a previously unfinished frame, everything about it is forgotten. |
| 501 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() |
| 502 | - The function is always blocking, returns when compression is completed. |
| 503 | NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have |
| 504 | enough space to successfully compress the data, though it is possible it fails for other reasons. |
| 505 | @return : compressed size written into `dst` (<= `dstCapacity), |
| 506 | or an error code if it fails (which can be tested using ZSTD_isError()). |
| 507 | |
| 508 | </p></pre><BR> |
| 509 | |
| 510 | <a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre> |
| 511 | |
| 512 | <pre><b>typedef enum { |
| 513 | |
| 514 | ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> |
| 515 | * the streaming API will refuse to allocate memory buffer |
| 516 | * in order to protect the host from unreasonable memory requirements. |
| 517 | * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. |
| 518 | * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). |
| 519 | * Special: value 0 means "use default maximum windowLog". */ |
| 520 | |
| 521 | </b>/* note : additional experimental parameters are also available<b> |
| 522 | * within the experimental section of the API. |
| 523 | * At the time of this writing, they include : |
| 524 | * ZSTD_d_format |
| 525 | * ZSTD_d_stableOutBuffer |
| 526 | * ZSTD_d_forceIgnoreChecksum |
| 527 | * ZSTD_d_refMultipleDDicts |
| 528 | * ZSTD_d_disableHuffmanAssembly |
| 529 | * ZSTD_d_maxBlockSize |
| 530 | * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. |
| 531 | * note : never ever use experimentalParam? names directly |
| 532 | */ |
| 533 | ZSTD_d_experimentalParam1=1000, |
| 534 | ZSTD_d_experimentalParam2=1001, |
| 535 | ZSTD_d_experimentalParam3=1002, |
| 536 | ZSTD_d_experimentalParam4=1003, |
| 537 | ZSTD_d_experimentalParam5=1004, |
| 538 | ZSTD_d_experimentalParam6=1005 |
| 539 | |
| 540 | } ZSTD_dParameter; |
| 541 | </b></pre><BR> |
| 542 | <pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); |
| 543 | </b><p> All parameters must belong to an interval with lower and upper bounds, |
| 544 | otherwise they will either trigger an error or be automatically clamped. |
| 545 | @return : a structure, ZSTD_bounds, which contains |
| 546 | - an error status field, which must be tested using ZSTD_isError() |
| 547 | - both lower and upper bounds, inclusive |
| 548 | |
| 549 | </p></pre><BR> |
| 550 | |
| 551 | <pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); |
| 552 | </b><p> Set one compression parameter, selected by enum ZSTD_dParameter. |
| 553 | All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). |
| 554 | Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). |
| 555 | Setting a parameter is only possible during frame initialization (before starting decompression). |
| 556 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
| 557 | |
| 558 | </p></pre><BR> |
| 559 | |
| 560 | <pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); |
| 561 | </b><p> Return a DCtx to clean state. |
| 562 | Session and parameters can be reset jointly or separately. |
| 563 | Parameters can only be reset when no active frame is being decompressed. |
| 564 | @return : 0, or an error code, which can be tested with ZSTD_isError() |
| 565 | |
| 566 | </p></pre><BR> |
| 567 | |
| 568 | <a name="Chapter7"></a><h2>Streaming</h2><pre></pre> |
| 569 | |
| 570 | <pre><b>typedef struct ZSTD_inBuffer_s { |
| 571 | const void* src; </b>/**< start of input buffer */<b> |
| 572 | size_t size; </b>/**< size of input buffer */<b> |
| 573 | size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> |
| 574 | } ZSTD_inBuffer; |
| 575 | </b></pre><BR> |
| 576 | <pre><b>typedef struct ZSTD_outBuffer_s { |
| 577 | void* dst; </b>/**< start of output buffer */<b> |
| 578 | size_t size; </b>/**< size of output buffer */<b> |
| 579 | size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> |
| 580 | } ZSTD_outBuffer; |
| 581 | </b></pre><BR> |
| 582 | <a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> |
| 583 | A ZSTD_CStream object is required to track streaming operation. |
| 584 | Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. |
| 585 | ZSTD_CStream objects can be reused multiple times on consecutive compression operations. |
| 586 | It is recommended to reuse ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. |
| 587 | |
| 588 | For parallel execution, use one separate ZSTD_CStream per thread. |
| 589 | |
| 590 | note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. |
| 591 | |
| 592 | Parameters are sticky : when starting a new compression on the same context, |
| 593 | it will reuse the same sticky parameters as previous compression session. |
| 594 | When in doubt, it's recommended to fully initialize the context before usage. |
| 595 | Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), |
| 596 | ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to |
| 597 | set more specific parameters, the pledged source size, or load a dictionary. |
| 598 | |
| 599 | Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to |
| 600 | consume input stream. The function will automatically update both `pos` |
| 601 | fields within `input` and `output`. |
| 602 | Note that the function may not consume the entire input, for example, because |
| 603 | the output buffer is already full, in which case `input.pos < input.size`. |
| 604 | The caller must check if input has been entirely consumed. |
| 605 | If not, the caller must make some room to receive more compressed data, |
| 606 | and then present again remaining input data. |
| 607 | note: ZSTD_e_continue is guaranteed to make some forward progress when called, |
| 608 | but doesn't guarantee maximal forward progress. This is especially relevant |
| 609 | when compressing with multiple threads. The call won't block if it can |
| 610 | consume some input, but if it can't it will wait for some, but not all, |
| 611 | output to be flushed. |
| 612 | @return : provides a minimum amount of data remaining to be flushed from internal buffers |
| 613 | or an error code, which can be tested using ZSTD_isError(). |
| 614 | |
| 615 | At any moment, it's possible to flush whatever data might remain stuck within internal buffer, |
| 616 | using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. |
| 617 | Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). |
| 618 | In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. |
| 619 | You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the |
| 620 | operation. |
| 621 | note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will |
| 622 | block until the flush is complete or the output buffer is full. |
| 623 | @return : 0 if internal buffers are entirely flushed, |
| 624 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), |
| 625 | or an error code, which can be tested using ZSTD_isError(). |
| 626 | |
| 627 | Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame. |
| 628 | It will perform a flush and write frame epilogue. |
| 629 | The epilogue is required for decoders to consider a frame completed. |
| 630 | flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. |
| 631 | You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to |
| 632 | start a new frame. |
| 633 | note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will |
| 634 | block until the flush is complete or the output buffer is full. |
| 635 | @return : 0 if frame fully completed and fully flushed, |
| 636 | >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), |
| 637 | or an error code, which can be tested using ZSTD_isError(). |
| 638 | |
| 639 | |
| 640 | <BR></pre> |
| 641 | |
| 642 | <pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> |
| 643 | </b></pre><BR> |
| 644 | <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); |
| 645 | size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b> |
| 646 | </pre></b><BR> |
| 647 | <h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { |
| 648 | ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> |
| 649 | ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> |
| 650 | * it creates (at least) one new block, that can be decoded immediately on reception; |
| 651 | * frame will continue: any future data can still reference previously compressed data, improving compression. |
| 652 | * note : multithreaded compression will block to flush as much output as possible. */ |
| 653 | ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> |
| 654 | * note that frame is only closed after compressed data is fully flushed (return value == 0). |
| 655 | * After that point, any additional data starts a new frame. |
| 656 | * note : each frame is independent (does not reference any content from previous frame). |
| 657 | : note : multithreaded compression will block to flush as much output as possible. */ |
| 658 | } ZSTD_EndDirective; |
| 659 | </pre></b><BR> |
| 660 | <pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, |
| 661 | ZSTD_outBuffer* output, |
| 662 | ZSTD_inBuffer* input, |
| 663 | ZSTD_EndDirective endOp); |
| 664 | </b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. |
| 665 | - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() |
| 666 | - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) |
| 667 | - output->pos must be <= dstCapacity, input->pos must be <= srcSize |
| 668 | - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. |
| 669 | - endOp must be a valid directive |
| 670 | - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. |
| 671 | - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available, |
| 672 | and then immediately returns, just indicating that there is some data remaining to be flushed. |
| 673 | The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. |
| 674 | - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking. |
| 675 | - @return provides a minimum amount of data remaining to be flushed from internal buffers |
| 676 | or an error code, which can be tested using ZSTD_isError(). |
| 677 | if @return != 0, flush is not fully completed, there is still some data left within internal buffers. |
| 678 | This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. |
| 679 | For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. |
| 680 | - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), |
| 681 | only ZSTD_e_end or ZSTD_e_flush operations are allowed. |
| 682 | Before starting a new compression job, or changing compression parameters, |
| 683 | it is required to fully flush internal buffers. |
| 684 | - note: if an operation ends with an error, it may leave @cctx in an undefined state. |
| 685 | Therefore, it's UB to invoke ZSTD_compressStream2() of ZSTD_compressStream() on such a state. |
| 686 | In order to be re-employed after an error, a state must be reset, |
| 687 | which can be done explicitly (ZSTD_CCtx_reset()), |
| 688 | or is sometimes implied by methods starting a new compression job (ZSTD_initCStream(), ZSTD_compressCCtx()) |
| 689 | |
| 690 | </p></pre><BR> |
| 691 | |
| 692 | <pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> |
| 693 | </b></pre><BR> |
| 694 | <pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b> |
| 695 | </b></pre><BR> |
| 696 | <pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); |
| 697 | </b>/*!<b> |
| 698 | * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue). |
| 699 | * NOTE: The return value is different. ZSTD_compressStream() returns a hint for |
| 700 | * the next read size (if non-zero and not an error). ZSTD_compressStream2() |
| 701 | * returns the minimum nb of bytes left to flush (if non-zero and not an error). |
| 702 | */ |
| 703 | size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); |
| 704 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b> |
| 705 | size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); |
| 706 | </b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b> |
| 707 | size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); |
| 708 | </b><p> |
| 709 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 710 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) |
| 711 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
| 712 | |
| 713 | Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API |
| 714 | to compress with a dictionary. |
| 715 | |
| 716 | </p></pre><BR> |
| 717 | |
| 718 | <a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> |
| 719 | A ZSTD_DStream object is required to track streaming operations. |
| 720 | Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. |
| 721 | ZSTD_DStream objects can be reused multiple times. |
| 722 | |
| 723 | Use ZSTD_initDStream() to start a new decompression operation. |
| 724 | @return : recommended first input size |
| 725 | Alternatively, use advanced API to set specific properties. |
| 726 | |
| 727 | Use ZSTD_decompressStream() repetitively to consume your input. |
| 728 | The function will update both `pos` fields. |
| 729 | If `input.pos < input.size`, some input has not been consumed. |
| 730 | It's up to the caller to present again remaining data. |
| 731 | The function tries to flush all data decoded immediately, respecting output buffer size. |
| 732 | If `output.pos < output.size`, decoder has flushed everything it could. |
| 733 | But if `output.pos == output.size`, there might be some data left within internal buffers., |
| 734 | In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. |
| 735 | Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. |
| 736 | @return : 0 when a frame is completely decoded and fully flushed, |
| 737 | or an error code, which can be tested using ZSTD_isError(), |
| 738 | or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : |
| 739 | the return value is a suggested next input size (just a hint for better latency) |
| 740 | that will never request more than the remaining frame size. |
| 741 | |
| 742 | <BR></pre> |
| 743 | |
| 744 | <pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> |
| 745 | </b></pre><BR> |
| 746 | <h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); |
| 747 | size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b> |
| 748 | </pre></b><BR> |
| 749 | <h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
| 750 | <pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds); |
| 751 | </b><p> Initialize/reset DStream state for new decompression operation. |
| 752 | Call before new decompression operation using same DStream. |
| 753 | |
| 754 | Note : This function is redundant with the advanced API and equivalent to: |
| 755 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
| 756 | ZSTD_DCtx_refDDict(zds, NULL); |
| 757 | |
| 758 | </p></pre><BR> |
| 759 | |
| 760 | <pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); |
| 761 | </b><p> Streaming decompression function. |
| 762 | Call repetitively to consume full input updating it as necessary. |
| 763 | Function will update both input and output `pos` fields exposing current state via these fields: |
| 764 | - `input.pos < input.size`, some input remaining and caller should provide remaining input |
| 765 | on the next call. |
| 766 | - `output.pos < output.size`, decoder finished and flushed all remaining buffers. |
| 767 | - `output.pos == output.size`, potentially uncflushed data present in the internal buffers, |
| 768 | call ZSTD_decompressStream() again to flush remaining data to output. |
| 769 | Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX. |
| 770 | |
| 771 | @return : 0 when a frame is completely decoded and fully flushed, |
| 772 | or an error code, which can be tested using ZSTD_isError(), |
| 773 | or any other value > 0, which means there is some decoding or flushing to do to complete current frame. |
| 774 | |
| 775 | Note: when an operation returns with an error code, the @zds state may be left in undefined state. |
| 776 | It's UB to invoke `ZSTD_decompressStream()` on such a state. |
| 777 | In order to re-use such a state, it must be first reset, |
| 778 | which can be done explicitly (`ZSTD_DCtx_reset()`), |
| 779 | or is implied for operations starting some new decompression job (`ZSTD_initDStream`, `ZSTD_decompressDCtx()`, `ZSTD_decompress_usingDict()`) |
| 780 | |
| 781 | </p></pre><BR> |
| 782 | |
| 783 | <pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> |
| 784 | </b></pre><BR> |
| 785 | <pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> |
| 786 | </b></pre><BR> |
| 787 | <a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre> |
| 788 | |
| 789 | <pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, |
| 790 | void* dst, size_t dstCapacity, |
| 791 | const void* src, size_t srcSize, |
| 792 | const void* dict,size_t dictSize, |
| 793 | int compressionLevel); |
| 794 | </b><p> Compression at an explicit compression level using a Dictionary. |
| 795 | A dictionary can be any arbitrary data segment (also called a prefix), |
| 796 | or a buffer with specified information (see zdict.h). |
| 797 | Note : This function loads the dictionary, resulting in significant startup delay. |
| 798 | It's intended for a dictionary used only once. |
| 799 | Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. |
| 800 | </p></pre><BR> |
| 801 | |
| 802 | <pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, |
| 803 | void* dst, size_t dstCapacity, |
| 804 | const void* src, size_t srcSize, |
| 805 | const void* dict,size_t dictSize); |
| 806 | </b><p> Decompression using a known Dictionary. |
| 807 | Dictionary must be identical to the one used during compression. |
| 808 | Note : This function loads the dictionary, resulting in significant startup delay. |
| 809 | It's intended for a dictionary used only once. |
| 810 | Note : When `dict == NULL || dictSize < 8` no dictionary is used. |
| 811 | </p></pre><BR> |
| 812 | |
| 813 | <a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> |
| 814 | |
| 815 | <pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, |
| 816 | int compressionLevel); |
| 817 | </b><p> When compressing multiple messages or blocks using the same dictionary, |
| 818 | it's recommended to digest the dictionary only once, since it's a costly operation. |
| 819 | ZSTD_createCDict() will create a state from digesting a dictionary. |
| 820 | The resulting state can be used for future compression operations with very limited startup cost. |
| 821 | ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. |
| 822 | @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict. |
| 823 | Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content. |
| 824 | Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer, |
| 825 | in which case the only thing that it transports is the @compressionLevel. |
| 826 | This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively, |
| 827 | expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. |
| 828 | </p></pre><BR> |
| 829 | |
| 830 | <pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); |
| 831 | </b><p> Function frees memory allocated by ZSTD_createCDict(). |
| 832 | If a NULL pointer is passed, no operation is performed. |
| 833 | </p></pre><BR> |
| 834 | |
| 835 | <pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, |
| 836 | void* dst, size_t dstCapacity, |
| 837 | const void* src, size_t srcSize, |
| 838 | const ZSTD_CDict* cdict); |
| 839 | </b><p> Compression using a digested Dictionary. |
| 840 | Recommended when same dictionary is used multiple times. |
| 841 | Note : compression level is _decided at dictionary creation time_, |
| 842 | and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) |
| 843 | </p></pre><BR> |
| 844 | |
| 845 | <pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); |
| 846 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. |
| 847 | dictBuffer can be released after DDict creation, as its content is copied inside DDict. |
| 848 | </p></pre><BR> |
| 849 | |
| 850 | <pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); |
| 851 | </b><p> Function frees memory allocated with ZSTD_createDDict() |
| 852 | If a NULL pointer is passed, no operation is performed. |
| 853 | </p></pre><BR> |
| 854 | |
| 855 | <pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, |
| 856 | void* dst, size_t dstCapacity, |
| 857 | const void* src, size_t srcSize, |
| 858 | const ZSTD_DDict* ddict); |
| 859 | </b><p> Decompression using a digested Dictionary. |
| 860 | Recommended when same dictionary is used multiple times. |
| 861 | </p></pre><BR> |
| 862 | |
| 863 | <a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre> |
| 864 | |
| 865 | <pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); |
| 866 | </b><p> Provides the dictID stored within dictionary. |
| 867 | if @return == 0, the dictionary is not conformant with Zstandard specification. |
| 868 | It can still be loaded, but as a content-only dictionary. |
| 869 | </p></pre><BR> |
| 870 | |
| 871 | <pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict); |
| 872 | </b><p> Provides the dictID of the dictionary loaded into `cdict`. |
| 873 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. |
| 874 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries. |
| 875 | </p></pre><BR> |
| 876 | |
| 877 | <pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); |
| 878 | </b><p> Provides the dictID of the dictionary loaded into `ddict`. |
| 879 | If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. |
| 880 | Non-conformant dictionaries can still be loaded, but as content-only dictionaries. |
| 881 | </p></pre><BR> |
| 882 | |
| 883 | <pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); |
| 884 | </b><p> Provides the dictID required to decompressed the frame stored within `src`. |
| 885 | If @return == 0, the dictID could not be decoded. |
| 886 | This could for one of the following reasons : |
| 887 | - The frame does not require a dictionary to be decoded (most common case). |
| 888 | - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information. |
| 889 | Note : this use case also happens when using a non-conformant dictionary. |
| 890 | - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). |
| 891 | - This is not a Zstandard frame. |
| 892 | When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. |
| 893 | </p></pre><BR> |
| 894 | |
| 895 | <a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre> |
| 896 | This API allows dictionaries to be used with ZSTD_compress2(), |
| 897 | ZSTD_compressStream2(), and ZSTD_decompressDCtx(). |
| 898 | Dictionaries are sticky, they remain valid when same context is reused, |
| 899 | they only reset when the context is reset |
| 900 | with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters. |
| 901 | In contrast, Prefixes are single-use. |
| 902 | <BR></pre> |
| 903 | |
| 904 | <pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); |
| 905 | </b><p> Create an internal CDict from `dict` buffer. |
| 906 | Decompression will have to use same dictionary. |
| 907 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 908 | Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, |
| 909 | meaning "return to no-dictionary mode". |
| 910 | Note 1 : Dictionary is sticky, it will be used for all future compressed frames, |
| 911 | until parameters are reset, a new dictionary is loaded, or the dictionary |
| 912 | is explicitly invalidated by loading a NULL dictionary. |
| 913 | Note 2 : Loading a dictionary involves building tables. |
| 914 | It's also a CPU consuming operation, with non-negligible impact on latency. |
| 915 | Tables are dependent on compression parameters, and for this reason, |
| 916 | compression parameters can no longer be changed after loading a dictionary. |
| 917 | Note 3 :`dict` content will be copied internally. |
| 918 | Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. |
| 919 | In such a case, dictionary buffer must outlive its users. |
| 920 | Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() |
| 921 | to precisely select how dictionary content must be interpreted. |
| 922 | Note 5 : This method does not benefit from LDM (long distance mode). |
| 923 | If you want to employ LDM on some large dictionary content, |
| 924 | prefer employing ZSTD_CCtx_refPrefix() described below. |
| 925 | |
| 926 | </p></pre><BR> |
| 927 | |
| 928 | <pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); |
| 929 | </b><p> Reference a prepared dictionary, to be used for all future compressed frames. |
| 930 | Note that compression parameters are enforced from within CDict, |
| 931 | and supersede any compression parameter previously set within CCtx. |
| 932 | The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. |
| 933 | The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. |
| 934 | The dictionary will remain valid for future compressed frames using same CCtx. |
| 935 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 936 | Special : Referencing a NULL CDict means "return to no-dictionary mode". |
| 937 | Note 1 : Currently, only one dictionary can be managed. |
| 938 | Referencing a new dictionary effectively "discards" any previous one. |
| 939 | Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. |
| 940 | </p></pre><BR> |
| 941 | |
| 942 | <pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, |
| 943 | const void* prefix, size_t prefixSize); |
| 944 | </b><p> Reference a prefix (single-usage dictionary) for next compressed frame. |
| 945 | A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). |
| 946 | Decompression will need same prefix to properly regenerate data. |
| 947 | Compressing with a prefix is similar in outcome as performing a diff and compressing it, |
| 948 | but performs much faster, especially during decompression (compression speed is tunable with compression level). |
| 949 | This method is compatible with LDM (long distance mode). |
| 950 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 951 | Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary |
| 952 | Note 1 : Prefix buffer is referenced. It **must** outlive compression. |
| 953 | Its content must remain unmodified during compression. |
| 954 | Note 2 : If the intention is to diff some large src data blob with some prior version of itself, |
| 955 | ensure that the window size is large enough to contain the entire source. |
| 956 | See ZSTD_c_windowLog. |
| 957 | Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. |
| 958 | It's a CPU consuming operation, with non-negligible impact on latency. |
| 959 | If there is a need to use the same prefix multiple times, consider loadDictionary instead. |
| 960 | Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent). |
| 961 | Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. |
| 962 | </p></pre><BR> |
| 963 | |
| 964 | <pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); |
| 965 | </b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames. |
| 966 | The dictionary remains valid for all future frames, until explicitly invalidated, or |
| 967 | a new dictionary is loaded. |
| 968 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 969 | Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, |
| 970 | meaning "return to no-dictionary mode". |
| 971 | Note 1 : Loading a dictionary involves building tables, |
| 972 | which has a non-negligible impact on CPU usage and latency. |
| 973 | It's recommended to "load once, use many times", to amortize the cost |
| 974 | Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. |
| 975 | Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. |
| 976 | Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of |
| 977 | how dictionary content is loaded and interpreted. |
| 978 | |
| 979 | </p></pre><BR> |
| 980 | |
| 981 | <pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); |
| 982 | </b><p> Reference a prepared dictionary, to be used to decompress next frames. |
| 983 | The dictionary remains active for decompression of future frames using same DCtx. |
| 984 | |
| 985 | If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function |
| 986 | will store the DDict references in a table, and the DDict used for decompression |
| 987 | will be determined at decompression time, as per the dict ID in the frame. |
| 988 | The memory for the table is allocated on the first call to refDDict, and can be |
| 989 | freed with ZSTD_freeDCtx(). |
| 990 | |
| 991 | If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary |
| 992 | will be managed, and referencing a dictionary effectively "discards" any previous one. |
| 993 | |
| 994 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 995 | Special: referencing a NULL DDict means "return to no-dictionary mode". |
| 996 | Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. |
| 997 | |
| 998 | </p></pre><BR> |
| 999 | |
| 1000 | <pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, |
| 1001 | const void* prefix, size_t prefixSize); |
| 1002 | </b><p> Reference a prefix (single-usage dictionary) to decompress next frame. |
| 1003 | This is the reverse operation of ZSTD_CCtx_refPrefix(), |
| 1004 | and must use the same prefix as the one used during compression. |
| 1005 | Prefix is **only used once**. Reference is discarded at end of frame. |
| 1006 | End of frame is reached when ZSTD_decompressStream() returns 0. |
| 1007 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 1008 | Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary |
| 1009 | Note 2 : Prefix buffer is referenced. It **must** outlive decompression. |
| 1010 | Prefix buffer must remain unmodified up to the end of frame, |
| 1011 | reached when ZSTD_decompressStream() returns 0. |
| 1012 | Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent). |
| 1013 | Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) |
| 1014 | Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. |
| 1015 | A full dictionary is more costly, as it requires building tables. |
| 1016 | |
| 1017 | </p></pre><BR> |
| 1018 | |
| 1019 | <pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); |
| 1020 | size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); |
| 1021 | size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); |
| 1022 | size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); |
| 1023 | size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); |
| 1024 | size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); |
| 1025 | </b><p> These functions give the _current_ memory usage of selected object. |
| 1026 | Note that object memory usage can evolve (increase or decrease) over time. |
| 1027 | </p></pre><BR> |
| 1028 | |
| 1029 | <a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre> |
| 1030 | The following symbols and constants |
| 1031 | are not planned to join "stable API" status in the near future. |
| 1032 | They can still change in future versions. |
| 1033 | Some of them are planned to remain in the static_only section indefinitely. |
| 1034 | Some of them might be removed in the future (especially when redundant with existing stable functions) |
| 1035 | |
| 1036 | <BR></pre> |
| 1037 | |
| 1038 | <pre><b>typedef struct { |
| 1039 | unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b> |
| 1040 | * If offset == 0 and matchLength == 0, this sequence represents the last |
| 1041 | * literals in the block of litLength size. |
| 1042 | */ |
| 1043 | |
| 1044 | unsigned int litLength; </b>/* Literal length of the sequence. */<b> |
| 1045 | unsigned int matchLength; </b>/* Match length of the sequence. */<b> |
| 1046 | |
| 1047 | </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b> |
| 1048 | * In this case, we will treat the sequence as a marker for a block boundary. |
| 1049 | */ |
| 1050 | |
| 1051 | unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b> |
| 1052 | * Ranges from [0, 3]. |
| 1053 | * |
| 1054 | * Repeat offsets are essentially previous offsets from previous sequences sorted in |
| 1055 | * recency order. For more detail, see doc/zstd_compression_format.md |
| 1056 | * |
| 1057 | * If rep == 0, then 'offset' does not contain a repeat offset. |
| 1058 | * If rep > 0: |
| 1059 | * If litLength != 0: |
| 1060 | * rep == 1 --> offset == repeat_offset_1 |
| 1061 | * rep == 2 --> offset == repeat_offset_2 |
| 1062 | * rep == 3 --> offset == repeat_offset_3 |
| 1063 | * If litLength == 0: |
| 1064 | * rep == 1 --> offset == repeat_offset_2 |
| 1065 | * rep == 2 --> offset == repeat_offset_3 |
| 1066 | * rep == 3 --> offset == repeat_offset_1 - 1 |
| 1067 | * |
| 1068 | * Note: This field is optional. ZSTD_generateSequences() will calculate the value of |
| 1069 | * 'rep', but repeat offsets do not necessarily need to be calculated from an external |
| 1070 | * sequence provider's perspective. For example, ZSTD_compressSequences() does not |
| 1071 | * use this 'rep' field at all (as of now). |
| 1072 | */ |
| 1073 | } ZSTD_Sequence; |
| 1074 | </b></pre><BR> |
| 1075 | <pre><b>typedef struct { |
| 1076 | unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> |
| 1077 | unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> |
| 1078 | unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> |
| 1079 | unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> |
| 1080 | unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> |
| 1081 | unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> |
| 1082 | ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> |
| 1083 | } ZSTD_compressionParameters; |
| 1084 | </b></pre><BR> |
| 1085 | <pre><b>typedef struct { |
| 1086 | int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> |
| 1087 | int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> |
| 1088 | int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> |
| 1089 | } ZSTD_frameParameters; |
| 1090 | </b></pre><BR> |
| 1091 | <pre><b>typedef struct { |
| 1092 | ZSTD_compressionParameters cParams; |
| 1093 | ZSTD_frameParameters fParams; |
| 1094 | } ZSTD_parameters; |
| 1095 | </b></pre><BR> |
| 1096 | <pre><b>typedef enum { |
| 1097 | ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> |
| 1098 | ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> |
| 1099 | ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> |
| 1100 | } ZSTD_dictContentType_e; |
| 1101 | </b></pre><BR> |
| 1102 | <pre><b>typedef enum { |
| 1103 | ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> |
| 1104 | ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> |
| 1105 | } ZSTD_dictLoadMethod_e; |
| 1106 | </b></pre><BR> |
| 1107 | <pre><b>typedef enum { |
| 1108 | ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> |
| 1109 | ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> |
| 1110 | * Useful to save 4 bytes per generated frame. |
| 1111 | * Decoder cannot recognise automatically this format, requiring this instruction. */ |
| 1112 | } ZSTD_format_e; |
| 1113 | </b></pre><BR> |
| 1114 | <pre><b>typedef enum { |
| 1115 | </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b> |
| 1116 | ZSTD_d_validateChecksum = 0, |
| 1117 | ZSTD_d_ignoreChecksum = 1 |
| 1118 | } ZSTD_forceIgnoreChecksum_e; |
| 1119 | </b></pre><BR> |
| 1120 | <pre><b>typedef enum { |
| 1121 | </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b> |
| 1122 | ZSTD_rmd_refSingleDDict = 0, |
| 1123 | ZSTD_rmd_refMultipleDDicts = 1 |
| 1124 | } ZSTD_refMultipleDDicts_e; |
| 1125 | </b></pre><BR> |
| 1126 | <pre><b>typedef enum { |
| 1127 | </b>/* Note: this enum and the behavior it controls are effectively internal<b> |
| 1128 | * implementation details of the compressor. They are expected to continue |
| 1129 | * to evolve and should be considered only in the context of extremely |
| 1130 | * advanced performance tuning. |
| 1131 | * |
| 1132 | * Zstd currently supports the use of a CDict in three ways: |
| 1133 | * |
| 1134 | * - The contents of the CDict can be copied into the working context. This |
| 1135 | * means that the compression can search both the dictionary and input |
| 1136 | * while operating on a single set of internal tables. This makes |
| 1137 | * the compression faster per-byte of input. However, the initial copy of |
| 1138 | * the CDict's tables incurs a fixed cost at the beginning of the |
| 1139 | * compression. For small compressions (< 8 KB), that copy can dominate |
| 1140 | * the cost of the compression. |
| 1141 | * |
| 1142 | * - The CDict's tables can be used in-place. In this model, compression is |
| 1143 | * slower per input byte, because the compressor has to search two sets of |
| 1144 | * tables. However, this model incurs no start-up cost (as long as the |
| 1145 | * working context's tables can be reused). For small inputs, this can be |
| 1146 | * faster than copying the CDict's tables. |
| 1147 | * |
| 1148 | * - The CDict's tables are not used at all, and instead we use the working |
| 1149 | * context alone to reload the dictionary and use params based on the source |
| 1150 | * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict(). |
| 1151 | * This method is effective when the dictionary sizes are very small relative |
| 1152 | * to the input size, and the input size is fairly large to begin with. |
| 1153 | * |
| 1154 | * Zstd has a simple internal heuristic that selects which strategy to use |
| 1155 | * at the beginning of a compression. However, if experimentation shows that |
| 1156 | * Zstd is making poor choices, it is possible to override that choice with |
| 1157 | * this enum. |
| 1158 | */ |
| 1159 | ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> |
| 1160 | ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> |
| 1161 | ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> |
| 1162 | ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b> |
| 1163 | } ZSTD_dictAttachPref_e; |
| 1164 | </b></pre><BR> |
| 1165 | <pre><b>typedef enum { |
| 1166 | ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> |
| 1167 | * Negative compression levels will be uncompressed, and positive compression |
| 1168 | * levels will be compressed. */ |
| 1169 | ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> |
| 1170 | * emitted if Huffman compression is not profitable. */ |
| 1171 | ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b> |
| 1172 | } ZSTD_literalCompressionMode_e; |
| 1173 | </b></pre><BR> |
| 1174 | <pre><b>typedef enum { |
| 1175 | </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b> |
| 1176 | * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable |
| 1177 | * or ZSTD_ps_disable allow for a force enable/disable the feature. |
| 1178 | */ |
| 1179 | ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b> |
| 1180 | ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b> |
| 1181 | ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b> |
| 1182 | } ZSTD_paramSwitch_e; |
| 1183 | </b></pre><BR> |
| 1184 | <a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre> |
| 1185 | |
| 1186 | <pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); |
| 1187 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
| 1188 | `srcSize` must be the _exact_ size of this series |
| 1189 | (i.e. there should be a frame boundary at `src + srcSize`) |
| 1190 | @return : - decompressed size of all data in all successive frames |
| 1191 | - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN |
| 1192 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR |
| 1193 | |
| 1194 | note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. |
| 1195 | When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. |
| 1196 | In which case, it's necessary to use streaming mode to decompress data. |
| 1197 | note 2 : decompressed size is always present when compression is done with ZSTD_compress() |
| 1198 | note 3 : decompressed size can be very large (64-bits value), |
| 1199 | potentially larger than what local system can handle as a single memory segment. |
| 1200 | In which case, it's necessary to use streaming mode to decompress data. |
| 1201 | note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. |
| 1202 | Always ensure result fits within application's authorized limits. |
| 1203 | Each application can set its own limits. |
| 1204 | note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to |
| 1205 | read each contained frame header. This is fast as most of the data is skipped, |
| 1206 | however it does mean that all frame data must be present and valid. |
| 1207 | </p></pre><BR> |
| 1208 | |
| 1209 | <pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize); |
| 1210 | </b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames |
| 1211 | `srcSize` must be the _exact_ size of this series |
| 1212 | (i.e. there should be a frame boundary at `src + srcSize`) |
| 1213 | @return : - upper-bound for the decompressed size of all data in all successive frames |
| 1214 | - if an error occurred: ZSTD_CONTENTSIZE_ERROR |
| 1215 | |
| 1216 | note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. |
| 1217 | note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. |
| 1218 | in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. |
| 1219 | note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: |
| 1220 | upper-bound = # blocks * min(128 KB, Window_Size) |
| 1221 | |
| 1222 | </p></pre><BR> |
| 1223 | |
| 1224 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); |
| 1225 | </b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. |
| 1226 | @return : size of the Frame Header, |
| 1227 | or an error code (if srcSize is too small) |
| 1228 | </p></pre><BR> |
| 1229 | |
| 1230 | <pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; |
| 1231 | </b></pre><BR> |
| 1232 | <pre><b>typedef struct { |
| 1233 | unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> |
| 1234 | unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> |
| 1235 | unsigned blockSizeMax; |
| 1236 | ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> |
| 1237 | unsigned headerSize; |
| 1238 | unsigned dictID; |
| 1239 | unsigned checksumFlag; |
| 1240 | unsigned _reserved1; |
| 1241 | unsigned _reserved2; |
| 1242 | } ZSTD_frameHeader; |
| 1243 | </b></pre><BR> |
| 1244 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> |
| 1245 | </b>/*! ZSTD_getFrameHeader_advanced() :<b> |
| 1246 | * same as ZSTD_getFrameHeader(), |
| 1247 | * with added capability to select a format (like ZSTD_f_zstd1_magicless) */ |
| 1248 | ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); |
| 1249 | </b><p> decode Frame Header, or requires larger `srcSize`. |
| 1250 | @return : 0, `zfhPtr` is correctly filled, |
| 1251 | >0, `srcSize` is too small, value is wanted `srcSize` amount, |
| 1252 | or an error code, which can be tested using ZSTD_isError() |
| 1253 | </p></pre><BR> |
| 1254 | |
| 1255 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize); |
| 1256 | </b><p> Zstd supports in-place decompression, where the input and output buffers overlap. |
| 1257 | In this case, the output buffer must be at least (Margin + Output_Size) bytes large, |
| 1258 | and the input buffer must be at the end of the output buffer. |
| 1259 | |
| 1260 | _______________________ Output Buffer ________________________ |
| 1261 | | | |
| 1262 | | ____ Input Buffer ____| |
| 1263 | | | | |
| 1264 | v v v |
| 1265 | |---------------------------------------|-----------|----------| |
| 1266 | ^ ^ ^ |
| 1267 | |___________________ Output_Size ___________________|_ Margin _| |
| 1268 | |
| 1269 | NOTE: See also ZSTD_DECOMPRESSION_MARGIN(). |
| 1270 | NOTE: This applies only to single-pass decompression through ZSTD_decompress() or |
| 1271 | ZSTD_decompressDCtx(). |
| 1272 | NOTE: This function supports multi-frame input. |
| 1273 | |
| 1274 | @param src The compressed frame(s) |
| 1275 | @param srcSize The size of the compressed frame(s) |
| 1276 | @returns The decompression margin or an error that can be checked with ZSTD_isError(). |
| 1277 | |
| 1278 | </p></pre><BR> |
| 1279 | |
| 1280 | <pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \ |
| 1281 | ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b> |
| 1282 | 4 </b>/* checksum */ + \<b> |
| 1283 | ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b> |
| 1284 | (blockSize) </b>/* One block of margin */ \<b> |
| 1285 | )) |
| 1286 | </b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from |
| 1287 | the compressed frame, compute it from the original size and the blockSizeLog. |
| 1288 | See ZSTD_decompressionMargin() for details. |
| 1289 | |
| 1290 | WARNING: This macro does not support multi-frame input, the input must be a single |
| 1291 | zstd frame. If you need that support use the function, or implement it yourself. |
| 1292 | |
| 1293 | @param originalSize The original uncompressed size of the data. |
| 1294 | @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX). |
| 1295 | Unless you explicitly set the windowLog smaller than |
| 1296 | ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX. |
| 1297 | |
| 1298 | </p></pre><BR> |
| 1299 | |
| 1300 | <pre><b>typedef enum { |
| 1301 | ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b> |
| 1302 | ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b> |
| 1303 | } ZSTD_sequenceFormat_e; |
| 1304 | </b></pre><BR> |
| 1305 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize); |
| 1306 | </b><p> `srcSize` : size of the input buffer |
| 1307 | @return : upper-bound for the number of sequences that can be generated |
| 1308 | from a buffer of srcSize bytes |
| 1309 | |
| 1310 | note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence). |
| 1311 | |
| 1312 | </p></pre><BR> |
| 1313 | |
| 1314 | <pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer. |
| 1315 | |
| 1316 | Each block will end with a dummy sequence |
| 1317 | with offset == 0, matchLength == 0, and litLength == length of last literals. |
| 1318 | litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0) |
| 1319 | simply acts as a block delimiter. |
| 1320 | |
| 1321 | @zc can be used to insert custom compression params. |
| 1322 | This function invokes ZSTD_compress2(). |
| 1323 | |
| 1324 | The output of this function can be fed into ZSTD_compressSequences() with CCtx |
| 1325 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters |
| 1326 | @return : number of sequences generated |
| 1327 | |
| 1328 | </p></pre><BR> |
| 1329 | |
| 1330 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize); |
| 1331 | </b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals |
| 1332 | by merging them into the literals of the next sequence. |
| 1333 | |
| 1334 | As such, the final generated result has no explicit representation of block boundaries, |
| 1335 | and the final last literals segment is not represented in the sequences. |
| 1336 | |
| 1337 | The output of this function can be fed into ZSTD_compressSequences() with CCtx |
| 1338 | setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters |
| 1339 | @return : number of sequences left after merging |
| 1340 | |
| 1341 | </p></pre><BR> |
| 1342 | |
| 1343 | <pre><b>ZSTDLIB_STATIC_API size_t |
| 1344 | ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize, |
| 1345 | const ZSTD_Sequence* inSeqs, size_t inSeqsSize, |
| 1346 | const void* src, size_t srcSize); |
| 1347 | </b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst. |
| 1348 | @src contains the entire input (not just the literals). |
| 1349 | If @srcSize > sum(sequence.length), the remaining bytes are considered all literals |
| 1350 | If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.) |
| 1351 | The entire source is compressed into a single frame. |
| 1352 | |
| 1353 | The compression behavior changes based on cctx params. In particular: |
| 1354 | If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain |
| 1355 | no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on |
| 1356 | the block size derived from the cctx, and sequences may be split. This is the default setting. |
| 1357 | |
| 1358 | If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain |
| 1359 | block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided. |
| 1360 | |
| 1361 | If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined |
| 1362 | behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for |
| 1363 | specifics regarding offset/matchlength requirements) then the function will bail out and return an error. |
| 1364 | |
| 1365 | In addition to the two adjustable experimental params, there are other important cctx params. |
| 1366 | - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN. |
| 1367 | - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression. |
| 1368 | - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset |
| 1369 | is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md |
| 1370 | |
| 1371 | Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused. |
| 1372 | Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly, |
| 1373 | and cannot emit an RLE block that disagrees with the repcode history |
| 1374 | @return : final compressed size, or a ZSTD error code. |
| 1375 | |
| 1376 | </p></pre><BR> |
| 1377 | |
| 1378 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity, |
| 1379 | const void* src, size_t srcSize, unsigned magicVariant); |
| 1380 | </b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer. |
| 1381 | |
| 1382 | Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number, |
| 1383 | ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15. |
| 1384 | As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so |
| 1385 | the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant. |
| 1386 | |
| 1387 | Returns an error if destination buffer is not large enough, if the source size is not representable |
| 1388 | with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid). |
| 1389 | |
| 1390 | @return : number of bytes written or a ZSTD error. |
| 1391 | |
| 1392 | </p></pre><BR> |
| 1393 | |
| 1394 | <pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant, |
| 1395 | const void* src, size_t srcSize); |
| 1396 | </b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer. |
| 1397 | |
| 1398 | The parameter magicVariant will receive the magicVariant that was supplied when the frame was written, |
| 1399 | i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested |
| 1400 | in the magicVariant. |
| 1401 | |
| 1402 | Returns an error if destination buffer is not large enough, or if the frame is not skippable. |
| 1403 | |
| 1404 | @return : number of bytes written or a ZSTD error. |
| 1405 | |
| 1406 | </p></pre><BR> |
| 1407 | |
| 1408 | <pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size); |
| 1409 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame. |
| 1410 | |
| 1411 | </p></pre><BR> |
| 1412 | |
| 1413 | <a name="Chapter16"></a><h2>Memory management</h2><pre></pre> |
| 1414 | |
| 1415 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int maxCompressionLevel); |
| 1416 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); |
| 1417 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); |
| 1418 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void); |
| 1419 | </b><p> These functions make it possible to estimate memory usage |
| 1420 | of a future {D,C}Ctx, before its creation. |
| 1421 | This is useful in combination with ZSTD_initStatic(), |
| 1422 | which makes it possible to employ a static buffer for ZSTD_CCtx* state. |
| 1423 | |
| 1424 | ZSTD_estimateCCtxSize() will provide a memory budget large enough |
| 1425 | to compress data of any size using one-shot compression ZSTD_compressCCtx() or ZSTD_compress2() |
| 1426 | associated with any compression level up to max specified one. |
| 1427 | The estimate will assume the input may be arbitrarily large, |
| 1428 | which is the worst case. |
| 1429 | |
| 1430 | Note that the size estimation is specific for one-shot compression, |
| 1431 | it is not valid for streaming (see ZSTD_estimateCStreamSize*()) |
| 1432 | nor other potential ways of using a ZSTD_CCtx* state. |
| 1433 | |
| 1434 | When srcSize can be bound by a known and rather "small" value, |
| 1435 | this knowledge can be used to provide a tighter budget estimation |
| 1436 | because the ZSTD_CCtx* state will need less memory for small inputs. |
| 1437 | This tighter estimation can be provided by employing more advanced functions |
| 1438 | ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(), |
| 1439 | and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter(). |
| 1440 | Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits. |
| 1441 | |
| 1442 | Note : only single-threaded compression is supported. |
| 1443 | ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. |
| 1444 | |
| 1445 | </p></pre><BR> |
| 1446 | |
| 1447 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int maxCompressionLevel); |
| 1448 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); |
| 1449 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); |
| 1450 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t maxWindowSize); |
| 1451 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); |
| 1452 | </b><p> ZSTD_estimateCStreamSize() will provide a memory budget large enough for streaming compression |
| 1453 | using any compression level up to the max specified one. |
| 1454 | It will also consider src size to be arbitrarily "large", which is a worst case scenario. |
| 1455 | If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. |
| 1456 | ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. |
| 1457 | ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1. |
| 1458 | Note : CStream size estimation is only correct for single-threaded compression. |
| 1459 | ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. |
| 1460 | Note 2 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time. |
| 1461 | Size estimates assume that no external sequence producer is registered. |
| 1462 | |
| 1463 | ZSTD_DStream memory budget depends on frame's window Size. |
| 1464 | This information can be passed manually, using ZSTD_estimateDStreamSize, |
| 1465 | or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); |
| 1466 | Any frame requesting a window size larger than max specified one will be rejected. |
| 1467 | Note : if streaming is init with function ZSTD_init?Stream_usingDict(), |
| 1468 | an internal ?Dict will be created, which additional size is not estimated here. |
| 1469 | In this case, get total size by adding ZSTD_estimate?DictSize |
| 1470 | |
| 1471 | </p></pre><BR> |
| 1472 | |
| 1473 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); |
| 1474 | ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); |
| 1475 | ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); |
| 1476 | </b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). |
| 1477 | ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). |
| 1478 | Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. |
| 1479 | |
| 1480 | </p></pre><BR> |
| 1481 | |
| 1482 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); |
| 1483 | ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> |
| 1484 | </b><p> Initialize an object using a pre-allocated fixed-size buffer. |
| 1485 | workspace: The memory area to emplace the object into. |
| 1486 | Provided pointer *must be 8-bytes aligned*. |
| 1487 | Buffer must outlive object. |
| 1488 | workspaceSize: Use ZSTD_estimate*Size() to determine |
| 1489 | how large workspace must be to support target scenario. |
| 1490 | @return : pointer to object (same address as workspace, just different type), |
| 1491 | or NULL if error (size too small, incorrect alignment, etc.) |
| 1492 | Note : zstd will never resize nor malloc() when using a static buffer. |
| 1493 | If the object requires more memory than available, |
| 1494 | zstd will just error out (typically ZSTD_error_memory_allocation). |
| 1495 | Note 2 : there is no corresponding "free" function. |
| 1496 | Since workspace is allocated externally, it must be freed externally too. |
| 1497 | Note 3 : cParams : use ZSTD_getCParams() to convert a compression level |
| 1498 | into its associated cParams. |
| 1499 | Limitation 1 : currently not compatible with internal dictionary creation, triggered by |
| 1500 | ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). |
| 1501 | Limitation 2 : static cctx currently not compatible with multi-threading. |
| 1502 | Limitation 3 : static dctx is incompatible with legacy support. |
| 1503 | |
| 1504 | </p></pre><BR> |
| 1505 | |
| 1506 | <pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> |
| 1507 | </b></pre><BR> |
| 1508 | <pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); |
| 1509 | typedef void (*ZSTD_freeFunction) (void* opaque, void* address); |
| 1510 | typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; |
| 1511 | static |
| 1512 | #ifdef __GNUC__ |
| 1513 | __attribute__((__unused__)) |
| 1514 | #endif |
| 1515 | ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> |
| 1516 | </b><p> These prototypes make it possible to pass your own allocation/free functions. |
| 1517 | ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. |
| 1518 | All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. |
| 1519 | |
| 1520 | </p></pre><BR> |
| 1521 | |
| 1522 | <pre><b>typedef struct POOL_ctx_s ZSTD_threadPool; |
| 1523 | ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads); |
| 1524 | ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b> |
| 1525 | ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool); |
| 1526 | </b><p> These prototypes make it possible to share a thread pool among multiple compression contexts. |
| 1527 | This can limit resources for applications with multiple threads where each one uses |
| 1528 | a threaded compression mode (via ZSTD_c_nbWorkers parameter). |
| 1529 | ZSTD_createThreadPool creates a new thread pool with a given number of threads. |
| 1530 | Note that the lifetime of such pool must exist while being used. |
| 1531 | ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value |
| 1532 | to use an internal thread pool). |
| 1533 | ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer. |
| 1534 | |
| 1535 | </p></pre><BR> |
| 1536 | |
| 1537 | <a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre> |
| 1538 | |
| 1539 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); |
| 1540 | </b><p> Create a digested dictionary for compression |
| 1541 | Dictionary content is just referenced, not duplicated. |
| 1542 | As a consequence, `dictBuffer` **must** outlive CDict, |
| 1543 | and its content must remain unmodified throughout the lifetime of CDict. |
| 1544 | note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef |
| 1545 | </p></pre><BR> |
| 1546 | |
| 1547 | <pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); |
| 1548 | </b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. |
| 1549 | `estimatedSrcSize` value is optional, select 0 if not known |
| 1550 | </p></pre><BR> |
| 1551 | |
| 1552 | <pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); |
| 1553 | </b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. |
| 1554 | All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 |
| 1555 | </p></pre><BR> |
| 1556 | |
| 1557 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params); |
| 1558 | </b><p> Ensure param values remain within authorized range. |
| 1559 | @return 0 on success, or an error code (can be checked with ZSTD_isError()) |
| 1560 | </p></pre><BR> |
| 1561 | |
| 1562 | <pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); |
| 1563 | </b><p> optimize params for a given `srcSize` and `dictSize`. |
| 1564 | `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. |
| 1565 | `dictSize` must be `0` when there is no dictionary. |
| 1566 | cPar can be invalid : all parameters will be clamped within valid range in the @return struct. |
| 1567 | This function never fails (wide contract) |
| 1568 | </p></pre><BR> |
| 1569 | |
| 1570 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams); |
| 1571 | </b><p> Set all parameters provided within @p cparams into the working @p cctx. |
| 1572 | Note : if modifying parameters during compression (MT mode only), |
| 1573 | note that changes to the .windowLog parameter will be ignored. |
| 1574 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
| 1575 | On failure, no parameters are updated. |
| 1576 | |
| 1577 | </p></pre><BR> |
| 1578 | |
| 1579 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams); |
| 1580 | </b><p> Set all parameters provided within @p fparams into the working @p cctx. |
| 1581 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
| 1582 | |
| 1583 | </p></pre><BR> |
| 1584 | |
| 1585 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params); |
| 1586 | </b><p> Set all parameters provided within @p params into the working @p cctx. |
| 1587 | @return 0 on success, or an error code (can be checked with ZSTD_isError()). |
| 1588 | |
| 1589 | </p></pre><BR> |
| 1590 | |
| 1591 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2") |
| 1592 | ZSTDLIB_STATIC_API |
| 1593 | size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, |
| 1594 | void* dst, size_t dstCapacity, |
| 1595 | const void* src, size_t srcSize, |
| 1596 | const void* dict,size_t dictSize, |
| 1597 | ZSTD_parameters params); |
| 1598 | </b><p> Note : this function is now DEPRECATED. |
| 1599 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters. |
| 1600 | This prototype will generate compilation warnings. |
| 1601 | </p></pre><BR> |
| 1602 | |
| 1603 | <pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary") |
| 1604 | ZSTDLIB_STATIC_API |
| 1605 | size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, |
| 1606 | void* dst, size_t dstCapacity, |
| 1607 | const void* src, size_t srcSize, |
| 1608 | const ZSTD_CDict* cdict, |
| 1609 | ZSTD_frameParameters fParams); |
| 1610 | </b><p> Note : this function is now DEPRECATED. |
| 1611 | It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters. |
| 1612 | This prototype will generate compilation warnings. |
| 1613 | </p></pre><BR> |
| 1614 | |
| 1615 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); |
| 1616 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. |
| 1617 | It saves some memory, but also requires that `dict` outlives its usage within `cctx` |
| 1618 | </p></pre><BR> |
| 1619 | |
| 1620 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); |
| 1621 | </b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over |
| 1622 | how to load the dictionary (by copy ? by reference ?) |
| 1623 | and how to interpret it (automatic ? force raw mode ? full mode only ?) |
| 1624 | </p></pre><BR> |
| 1625 | |
| 1626 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); |
| 1627 | </b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over |
| 1628 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) |
| 1629 | </p></pre><BR> |
| 1630 | |
| 1631 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); |
| 1632 | </b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, |
| 1633 | and store it into int* value. |
| 1634 | @return : 0, or an error code (which can be tested with ZSTD_isError()). |
| 1635 | |
| 1636 | </p></pre><BR> |
| 1637 | |
| 1638 | <pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void); |
| 1639 | ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b> |
| 1640 | </b><p> Quick howto : |
| 1641 | - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure |
| 1642 | - ZSTD_CCtxParams_setParameter() : Push parameters one by one into |
| 1643 | an existing ZSTD_CCtx_params structure. |
| 1644 | This is similar to |
| 1645 | ZSTD_CCtx_setParameter(). |
| 1646 | - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to |
| 1647 | an existing CCtx. |
| 1648 | These parameters will be applied to |
| 1649 | all subsequent frames. |
| 1650 | - ZSTD_compressStream2() : Do compression using the CCtx. |
| 1651 | - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer. |
| 1652 | |
| 1653 | This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() |
| 1654 | for static allocation of CCtx for single-threaded compression. |
| 1655 | |
| 1656 | </p></pre><BR> |
| 1657 | |
| 1658 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); |
| 1659 | </b><p> Reset params to default values. |
| 1660 | |
| 1661 | </p></pre><BR> |
| 1662 | |
| 1663 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); |
| 1664 | </b><p> Initializes the compression parameters of cctxParams according to |
| 1665 | compression level. All other parameters are reset to their default values. |
| 1666 | |
| 1667 | </p></pre><BR> |
| 1668 | |
| 1669 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); |
| 1670 | </b><p> Initializes the compression and frame parameters of cctxParams according to |
| 1671 | params. All other parameters are reset to their default values. |
| 1672 | |
| 1673 | </p></pre><BR> |
| 1674 | |
| 1675 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); |
| 1676 | </b><p> Similar to ZSTD_CCtx_setParameter. |
| 1677 | Set one compression parameter, selected by enum ZSTD_cParameter. |
| 1678 | Parameters must be applied to a ZSTD_CCtx using |
| 1679 | ZSTD_CCtx_setParametersUsingCCtxParams(). |
| 1680 | @result : a code representing success or failure (which can be tested with |
| 1681 | ZSTD_isError()). |
| 1682 | |
| 1683 | </p></pre><BR> |
| 1684 | |
| 1685 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); |
| 1686 | </b><p> Similar to ZSTD_CCtx_getParameter. |
| 1687 | Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. |
| 1688 | @result : 0, or an error code (which can be tested with ZSTD_isError()). |
| 1689 | |
| 1690 | </p></pre><BR> |
| 1691 | |
| 1692 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams( |
| 1693 | ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); |
| 1694 | </b><p> Apply a set of ZSTD_CCtx_params to the compression context. |
| 1695 | This can be done even after compression is started, |
| 1696 | if nbWorkers==0, this will have no impact until a new compression is started. |
| 1697 | if nbWorkers>=1, new parameters will be picked up at next job, |
| 1698 | with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). |
| 1699 | |
| 1700 | </p></pre><BR> |
| 1701 | |
| 1702 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs ( |
| 1703 | ZSTD_CCtx* cctx, |
| 1704 | void* dst, size_t dstCapacity, size_t* dstPos, |
| 1705 | const void* src, size_t srcSize, size_t* srcPos, |
| 1706 | ZSTD_EndDirective endOp); |
| 1707 | </b><p> Same as ZSTD_compressStream2(), |
| 1708 | but using only integral types as arguments. |
| 1709 | This variant might be helpful for binders from dynamic languages |
| 1710 | which have troubles handling structures containing memory pointers. |
| 1711 | |
| 1712 | </p></pre><BR> |
| 1713 | |
| 1714 | <a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre> |
| 1715 | |
| 1716 | <pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size); |
| 1717 | </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. |
| 1718 | Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. |
| 1719 | Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. |
| 1720 | Note 3 : Skippable Frame Identifiers are considered valid. |
| 1721 | </p></pre><BR> |
| 1722 | |
| 1723 | <pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); |
| 1724 | </b><p> Create a digested dictionary, ready to start decompression operation without startup delay. |
| 1725 | Dictionary content is referenced, and therefore stays in dictBuffer. |
| 1726 | It is important that dictBuffer outlives DDict, |
| 1727 | it must remain read accessible throughout the lifetime of DDict |
| 1728 | </p></pre><BR> |
| 1729 | |
| 1730 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); |
| 1731 | </b><p> Same as ZSTD_DCtx_loadDictionary(), |
| 1732 | but references `dict` content instead of copying it into `dctx`. |
| 1733 | This saves memory if `dict` remains around., |
| 1734 | However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. |
| 1735 | </p></pre><BR> |
| 1736 | |
| 1737 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); |
| 1738 | </b><p> Same as ZSTD_DCtx_loadDictionary(), |
| 1739 | but gives direct control over |
| 1740 | how to load the dictionary (by copy ? by reference ?) |
| 1741 | and how to interpret it (automatic ? force raw mode ? full mode only ?). |
| 1742 | </p></pre><BR> |
| 1743 | |
| 1744 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); |
| 1745 | </b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over |
| 1746 | how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) |
| 1747 | </p></pre><BR> |
| 1748 | |
| 1749 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); |
| 1750 | </b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. |
| 1751 | This protects a decoder context from reserving too much memory for itself (potential attack scenario). |
| 1752 | This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. |
| 1753 | By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) |
| 1754 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
| 1755 | |
| 1756 | </p></pre><BR> |
| 1757 | |
| 1758 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value); |
| 1759 | </b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter, |
| 1760 | and store it into int* value. |
| 1761 | @return : 0, or an error code (which can be tested with ZSTD_isError()). |
| 1762 | |
| 1763 | </p></pre><BR> |
| 1764 | |
| 1765 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead") |
| 1766 | ZSTDLIB_STATIC_API |
| 1767 | size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); |
| 1768 | </b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter(). |
| 1769 | Instruct the decoder context about what kind of data to decode next. |
| 1770 | This instruction is mandatory to decode data without a fully-formed header, |
| 1771 | such ZSTD_f_zstd1_magicless for example. |
| 1772 | @return : 0, or an error code (which can be tested using ZSTD_isError()). |
| 1773 | </p></pre><BR> |
| 1774 | |
| 1775 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs ( |
| 1776 | ZSTD_DCtx* dctx, |
| 1777 | void* dst, size_t dstCapacity, size_t* dstPos, |
| 1778 | const void* src, size_t srcSize, size_t* srcPos); |
| 1779 | </b><p> Same as ZSTD_decompressStream(), |
| 1780 | but using only integral types as arguments. |
| 1781 | This can be helpful for binders from dynamic languages |
| 1782 | which have troubles handling structures containing memory pointers. |
| 1783 | |
| 1784 | </p></pre><BR> |
| 1785 | |
| 1786 | <a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. |
| 1787 | Once Advanced API reaches "stable" status, |
| 1788 | redundant functions will be deprecated, and then at some point removed. |
| 1789 | <BR></pre> |
| 1790 | |
| 1791 | <h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR> |
| 1792 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
| 1793 | ZSTDLIB_STATIC_API |
| 1794 | size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, |
| 1795 | int compressionLevel, |
| 1796 | unsigned long long pledgedSrcSize); |
| 1797 | </b><p> This function is DEPRECATED, and equivalent to: |
| 1798 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1799 | ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) |
| 1800 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
| 1801 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
| 1802 | |
| 1803 | pledgedSrcSize must be correct. If it is not known at init time, use |
| 1804 | ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, |
| 1805 | "0" also disables frame content size field. It may be enabled in the future. |
| 1806 | This prototype will generate compilation warnings. |
| 1807 | |
| 1808 | </p></pre><BR> |
| 1809 | |
| 1810 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
| 1811 | ZSTDLIB_STATIC_API |
| 1812 | size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, |
| 1813 | const void* dict, size_t dictSize, |
| 1814 | int compressionLevel); |
| 1815 | </b><p> This function is DEPRECATED, and is equivalent to: |
| 1816 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1817 | ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); |
| 1818 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); |
| 1819 | |
| 1820 | Creates of an internal CDict (incompatible with static CCtx), except if |
| 1821 | dict == NULL or dictSize < 8, in which case no dict is used. |
| 1822 | Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if |
| 1823 | it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. |
| 1824 | This prototype will generate compilation warnings. |
| 1825 | |
| 1826 | </p></pre><BR> |
| 1827 | |
| 1828 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
| 1829 | ZSTDLIB_STATIC_API |
| 1830 | size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, |
| 1831 | const void* dict, size_t dictSize, |
| 1832 | ZSTD_parameters params, |
| 1833 | unsigned long long pledgedSrcSize); |
| 1834 | </b><p> This function is DEPRECATED, and is equivalent to: |
| 1835 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1836 | ZSTD_CCtx_setParams(zcs, params); |
| 1837 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
| 1838 | ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); |
| 1839 | |
| 1840 | dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy. |
| 1841 | pledgedSrcSize must be correct. |
| 1842 | If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. |
| 1843 | This prototype will generate compilation warnings. |
| 1844 | |
| 1845 | </p></pre><BR> |
| 1846 | |
| 1847 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") |
| 1848 | ZSTDLIB_STATIC_API |
| 1849 | size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); |
| 1850 | </b><p> This function is DEPRECATED, and equivalent to: |
| 1851 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1852 | ZSTD_CCtx_refCDict(zcs, cdict); |
| 1853 | |
| 1854 | note : cdict will just be referenced, and must outlive compression session |
| 1855 | This prototype will generate compilation warnings. |
| 1856 | |
| 1857 | </p></pre><BR> |
| 1858 | |
| 1859 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") |
| 1860 | ZSTDLIB_STATIC_API |
| 1861 | size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, |
| 1862 | const ZSTD_CDict* cdict, |
| 1863 | ZSTD_frameParameters fParams, |
| 1864 | unsigned long long pledgedSrcSize); |
| 1865 | </b><p> This function is DEPRECATED, and is equivalent to: |
| 1866 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1867 | ZSTD_CCtx_setFParams(zcs, fParams); |
| 1868 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
| 1869 | ZSTD_CCtx_refCDict(zcs, cdict); |
| 1870 | |
| 1871 | same as ZSTD_initCStream_usingCDict(), with control over frame parameters. |
| 1872 | pledgedSrcSize must be correct. If srcSize is not known at init time, use |
| 1873 | value ZSTD_CONTENTSIZE_UNKNOWN. |
| 1874 | This prototype will generate compilation warnings. |
| 1875 | |
| 1876 | </p></pre><BR> |
| 1877 | |
| 1878 | <pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") |
| 1879 | ZSTDLIB_STATIC_API |
| 1880 | size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); |
| 1881 | </b><p> This function is DEPRECATED, and is equivalent to: |
| 1882 | ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); |
| 1883 | ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); |
| 1884 | Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but |
| 1885 | ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be |
| 1886 | explicitly specified. |
| 1887 | |
| 1888 | start a new frame, using same parameters from previous frame. |
| 1889 | This is typically useful to skip dictionary loading stage, since it will reuse it in-place. |
| 1890 | Note that zcs must be init at least once before using ZSTD_resetCStream(). |
| 1891 | If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. |
| 1892 | If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. |
| 1893 | For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, |
| 1894 | but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. |
| 1895 | @return : 0, or an error code (which can be tested using ZSTD_isError()) |
| 1896 | This prototype will generate compilation warnings. |
| 1897 | |
| 1898 | </p></pre><BR> |
| 1899 | |
| 1900 | <pre><b>typedef struct { |
| 1901 | unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> |
| 1902 | unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> |
| 1903 | unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> |
| 1904 | unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> |
| 1905 | unsigned currentJobID; </b>/* MT only : latest started job nb */<b> |
| 1906 | unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> |
| 1907 | } ZSTD_frameProgression; |
| 1908 | </b></pre><BR> |
| 1909 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); |
| 1910 | </b><p> Tell how many bytes are ready to be flushed immediately. |
| 1911 | Useful for multithreading scenarios (nbWorkers >= 1). |
| 1912 | Probe the oldest active job, defined as oldest job not yet entirely flushed, |
| 1913 | and check its output buffer. |
| 1914 | @return : amount of data stored in oldest job and ready to be flushed immediately. |
| 1915 | if @return == 0, it means either : |
| 1916 | + there is no active job (could be checked with ZSTD_frameProgression()), or |
| 1917 | + oldest job is still actively compressing data, |
| 1918 | but everything it has produced has also been flushed so far, |
| 1919 | therefore flush speed is limited by production speed of oldest job |
| 1920 | irrespective of the speed of concurrent (and newer) jobs. |
| 1921 | |
| 1922 | </p></pre><BR> |
| 1923 | |
| 1924 | <h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
| 1925 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions") |
| 1926 | ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); |
| 1927 | </b><p> |
| 1928 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
| 1929 | ZSTD_DCtx_loadDictionary(zds, dict, dictSize); |
| 1930 | |
| 1931 | note: no dictionary will be used if dict == NULL or dictSize < 8 |
| 1932 | |
| 1933 | </p></pre><BR> |
| 1934 | |
| 1935 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions") |
| 1936 | ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); |
| 1937 | </b><p> |
| 1938 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
| 1939 | ZSTD_DCtx_refDDict(zds, ddict); |
| 1940 | |
| 1941 | note : ddict is referenced, it must outlive decompression session |
| 1942 | |
| 1943 | </p></pre><BR> |
| 1944 | |
| 1945 | <pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions") |
| 1946 | ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds); |
| 1947 | </b><p> |
| 1948 | ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); |
| 1949 | |
| 1950 | reuse decompression parameters from previous init; saves dictionary loading |
| 1951 | |
| 1952 | </p></pre><BR> |
| 1953 | |
| 1954 | <pre><b>ZSTDLIB_STATIC_API void |
| 1955 | ZSTD_registerSequenceProducer( |
| 1956 | ZSTD_CCtx* cctx, |
| 1957 | void* sequenceProducerState, |
| 1958 | ZSTD_sequenceProducer_F sequenceProducer |
| 1959 | ); |
| 1960 | </b><p> Instruct zstd to use a block-level external sequence producer function. |
| 1961 | |
| 1962 | The sequenceProducerState must be initialized by the caller, and the caller is |
| 1963 | responsible for managing its lifetime. This parameter is sticky across |
| 1964 | compressions. It will remain set until the user explicitly resets compression |
| 1965 | parameters. |
| 1966 | |
| 1967 | Sequence producer registration is considered to be an "advanced parameter", |
| 1968 | part of the "advanced API". This means it will only have an effect on compression |
| 1969 | APIs which respect advanced parameters, such as compress2() and compressStream2(). |
| 1970 | Older compression APIs such as compressCCtx(), which predate the introduction of |
| 1971 | "advanced parameters", will ignore any external sequence producer setting. |
| 1972 | |
| 1973 | The sequence producer can be "cleared" by registering a NULL function pointer. This |
| 1974 | removes all limitations described above in the "LIMITATIONS" section of the API docs. |
| 1975 | |
| 1976 | The user is strongly encouraged to read the full API documentation (above) before |
| 1977 | calling this function. |
| 1978 | </p></pre><BR> |
| 1979 | |
| 1980 | <pre><b>ZSTDLIB_STATIC_API void |
| 1981 | ZSTD_CCtxParams_registerSequenceProducer( |
| 1982 | ZSTD_CCtx_params* params, |
| 1983 | void* sequenceProducerState, |
| 1984 | ZSTD_sequenceProducer_F sequenceProducer |
| 1985 | ); |
| 1986 | </b><p> Same as ZSTD_registerSequenceProducer(), but operates on ZSTD_CCtx_params. |
| 1987 | This is used for accurate size estimation with ZSTD_estimateCCtxSize_usingCCtxParams(), |
| 1988 | which is needed when creating a ZSTD_CCtx with ZSTD_initStaticCCtx(). |
| 1989 | |
| 1990 | If you are using the external sequence producer API in a scenario where ZSTD_initStaticCCtx() |
| 1991 | is required, then this function is for you. Otherwise, you probably don't need it. |
| 1992 | |
| 1993 | See tests/zstreamtest.c for example usage. |
| 1994 | </p></pre><BR> |
| 1995 | |
| 1996 | <a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre> |
| 1997 | This API is deprecated, and will be removed in a future version. |
| 1998 | It allows streaming (de)compression with user allocated buffers. |
| 1999 | However, it is hard to use, and not as well tested as the rest of |
| 2000 | our API. |
| 2001 | |
| 2002 | Please use the normal streaming API instead: ZSTD_compressStream2, |
| 2003 | and ZSTD_decompressStream. |
| 2004 | If there is functionality that you need, but it doesn't provide, |
| 2005 | please open an issue on our GitHub. |
| 2006 | |
| 2007 | <BR></pre> |
| 2008 | |
| 2009 | <a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> |
| 2010 | A ZSTD_CCtx object is required to track streaming operations. |
| 2011 | Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. |
| 2012 | ZSTD_CCtx object can be reused multiple times within successive compression operations. |
| 2013 | |
| 2014 | Start by initializing a context. |
| 2015 | Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression. |
| 2016 | |
| 2017 | Then, consume your input using ZSTD_compressContinue(). |
| 2018 | There are some important considerations to keep in mind when using this advanced function : |
| 2019 | - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. |
| 2020 | - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. |
| 2021 | - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. |
| 2022 | Worst case evaluation is provided by ZSTD_compressBound(). |
| 2023 | ZSTD_compressContinue() doesn't guarantee recover after a failed compression. |
| 2024 | - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). |
| 2025 | It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) |
| 2026 | - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. |
| 2027 | In which case, it will "discard" the relevant memory section from its history. |
| 2028 | |
| 2029 | Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. |
| 2030 | It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. |
| 2031 | Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. |
| 2032 | |
| 2033 | `ZSTD_CCtx` object can be reused (ZSTD_compressBegin()) to compress again. |
| 2034 | <BR></pre> |
| 2035 | |
| 2036 | <h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
| 2037 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); |
| 2038 | ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
| 2039 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); |
| 2040 | ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") |
| 2041 | ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> |
| 2042 | </pre></b><BR> |
| 2043 | <pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b> |
| 2044 | </b></pre><BR> |
| 2045 | <pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b> |
| 2046 | </b></pre><BR> |
| 2047 | <a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> |
| 2048 | A ZSTD_DCtx object is required to track streaming operations. |
| 2049 | Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. |
| 2050 | A ZSTD_DCtx object can be reused multiple times. |
| 2051 | |
| 2052 | First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). |
| 2053 | Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. |
| 2054 | Data fragment must be large enough to ensure successful decoding. |
| 2055 | `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. |
| 2056 | result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. |
| 2057 | >0 : `srcSize` is too small, please provide at least result bytes on next attempt. |
| 2058 | errorCode, which can be tested using ZSTD_isError(). |
| 2059 | |
| 2060 | It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, |
| 2061 | such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). |
| 2062 | Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. |
| 2063 | As a consequence, check that values remain within valid application range. |
| 2064 | For example, do not allocate memory blindly, check that `windowSize` is within expectation. |
| 2065 | Each application can set its own limits, depending on local restrictions. |
| 2066 | For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. |
| 2067 | |
| 2068 | ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. |
| 2069 | ZSTD_decompressContinue() is very sensitive to contiguity, |
| 2070 | if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, |
| 2071 | or that previous contiguous segment is large enough to properly handle maximum back-reference distance. |
| 2072 | There are multiple ways to guarantee this condition. |
| 2073 | |
| 2074 | The most memory efficient way is to use a round buffer of sufficient size. |
| 2075 | Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), |
| 2076 | which can return an error code if required value is too large for current system (in 32-bits mode). |
| 2077 | In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, |
| 2078 | up to the moment there is not enough room left in the buffer to guarantee decoding another full block, |
| 2079 | which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. |
| 2080 | At which point, decoding can resume from the beginning of the buffer. |
| 2081 | Note that already decoded data stored in the buffer should be flushed before being overwritten. |
| 2082 | |
| 2083 | There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. |
| 2084 | |
| 2085 | Finally, if you control the compression process, you can also ignore all buffer size rules, |
| 2086 | as long as the encoder and decoder progress in "lock-step", |
| 2087 | aka use exactly the same buffer sizes, break contiguity at the same place, etc. |
| 2088 | |
| 2089 | Once buffers are setup, start decompression, with ZSTD_decompressBegin(). |
| 2090 | If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). |
| 2091 | |
| 2092 | Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. |
| 2093 | ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). |
| 2094 | ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. |
| 2095 | |
| 2096 | result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). |
| 2097 | It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. |
| 2098 | It can also be an error code, which can be tested with ZSTD_isError(). |
| 2099 | |
| 2100 | A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. |
| 2101 | Context can then be reset to start a new decompression. |
| 2102 | |
| 2103 | Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). |
| 2104 | This information is not required to properly decode a frame. |
| 2105 | |
| 2106 | == Special case : skippable frames |
| 2107 | |
| 2108 | Skippable frames allow integration of user-defined data into a flow of concatenated frames. |
| 2109 | Skippable frames will be ignored (skipped) by decompressor. |
| 2110 | The format of skippable frames is as follows : |
| 2111 | a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F |
| 2112 | b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits |
| 2113 | c) Frame Content - any content (User Data) of length equal to Frame Size |
| 2114 | For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. |
| 2115 | For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. |
| 2116 | <BR></pre> |
| 2117 | |
| 2118 | <h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> |
| 2119 | <pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> |
| 2120 | </b></pre><BR> |
| 2121 | <pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; |
| 2122 | </b></pre><BR> |
| 2123 | <a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre> |
| 2124 | |
| 2125 | <pre><b></b><p> You can get the frame header down to 2 bytes by setting: |
| 2126 | - ZSTD_c_format = ZSTD_f_zstd1_magicless |
| 2127 | - ZSTD_c_contentSizeFlag = 0 |
| 2128 | - ZSTD_c_checksumFlag = 0 |
| 2129 | - ZSTD_c_dictIDFlag = 0 |
| 2130 | |
| 2131 | This API is not as well tested as our normal API, so we recommend not using it. |
| 2132 | We will be removing it in a future version. If the normal API doesn't provide |
| 2133 | the functionality you need, please open a GitHub issue. |
| 2134 | |
| 2135 | Block functions produce and decode raw zstd blocks, without frame metadata. |
| 2136 | Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes). |
| 2137 | But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes. |
| 2138 | |
| 2139 | A few rules to respect : |
| 2140 | - Compressing and decompressing require a context structure |
| 2141 | + Use ZSTD_createCCtx() and ZSTD_createDCtx() |
| 2142 | - It is necessary to init context before starting |
| 2143 | + compression : any ZSTD_compressBegin*() variant, including with dictionary |
| 2144 | + decompression : any ZSTD_decompressBegin*() variant, including with dictionary |
| 2145 | - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB |
| 2146 | + If input is larger than a block size, it's necessary to split input data into multiple blocks |
| 2147 | + For inputs larger than a single block, consider using regular ZSTD_compress() instead. |
| 2148 | Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block. |
| 2149 | - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) ! |
| 2150 | ===> In which case, nothing is produced into `dst` ! |
| 2151 | + User __must__ test for such outcome and deal directly with uncompressed data |
| 2152 | + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0. |
| 2153 | Doing so would mess up with statistics history, leading to potential data corruption. |
| 2154 | + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !! |
| 2155 | + In case of multiple successive blocks, should some of them be uncompressed, |
| 2156 | decoder must be informed of their existence in order to follow proper history. |
| 2157 | Use ZSTD_insertBlock() for such a case. |
| 2158 | </p></pre><BR> |
| 2159 | |
| 2160 | <h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
| 2161 | ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); |
| 2162 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
| 2163 | ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); |
| 2164 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
| 2165 | ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); |
| 2166 | ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") |
| 2167 | ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b> |
| 2168 | </pre></b><BR> |
| 2169 | </html> |
| 2170 | </body> |