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4 <title>zstd 1.3.4 Manual</title>
7 <h1>zstd 1.3.4 Manual</h1>
9 <a name="Contents"></a><h2>Contents</h2>
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">Simple dictionary API</a></li>
16 <li><a href="#Chapter6">Bulk processing dictionary API</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">START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</a></li>
21 <li><a href="#Chapter11">Advanced types</a></li>
22 <li><a href="#Chapter12">Frame size functions</a></li>
23 <li><a href="#Chapter13">Memory management</a></li>
24 <li><a href="#Chapter14">Advanced compression functions</a></li>
25 <li><a href="#Chapter15">Advanced decompression functions</a></li>
26 <li><a href="#Chapter16">Advanced streaming functions</a></li>
27 <li><a href="#Chapter17">Buffer-less and synchronous inner streaming functions</a></li>
28 <li><a href="#Chapter18">Buffer-less streaming compression (synchronous mode)</a></li>
29 <li><a href="#Chapter19">Buffer-less streaming decompression (synchronous mode)</a></li>
30 <li><a href="#Chapter20">New advanced API (experimental)</a></li>
31 <li><a href="#Chapter21">Block level API</a></li>
34 <a name="Chapter1"></a><h2>Introduction</h2><pre>
35 zstd, short for Zstandard, is a fast lossless compression algorithm,
36 targeting real-time compression scenarios at zlib-level and better compression ratios.
37 The zstd compression library provides in-memory compression and decompression functions.
38 The library supports compression levels from 1 up to ZSTD_maxCLevel() which is currently 22.
39 Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
40 Compression can be done in:
41 - a single step (described as Simple API)
42 - a single step, reusing a context (described as Explicit context)
43 - unbounded multiple steps (described as Streaming compression)
44 The compression ratio achievable on small data can be highly improved using a dictionary in:
45 - a single step (described as Simple dictionary API)
46 - a single step, reusing a dictionary (described as Bulk-processing dictionary API)
48 Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
49 Advanced experimental APIs shall never be used with a dynamic library.
50 They are not "stable", their definition may change in the future. Only static linking is allowed.
53 <a name="Chapter2"></a><h2>Version</h2><pre></pre>
55 <pre><b>unsigned ZSTD_versionNumber(void); </b>/**< useful to check dll version */<b>
57 <a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
59 <pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
60 const void* src, size_t srcSize,
61 int compressionLevel);
62 </b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
63 Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
64 @return : compressed size written into `dst` (<= `dstCapacity),
65 or an error code if it fails (which can be tested using ZSTD_isError()).
68 <pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
69 const void* src, size_t compressedSize);
70 </b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
71 `dstCapacity` is an upper bound of originalSize to regenerate.
72 If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
73 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
74 or an errorCode if it fails (which can be tested using ZSTD_isError()).
77 <pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
78 #define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
79 unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
80 </b><p> `src` should point to the start of a ZSTD encoded frame.
81 `srcSize` must be at least as large as the frame header.
82 hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
83 @return : - decompressed size of the frame in `src`, if known
84 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
85 - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
86 note 1 : a 0 return value means the frame is valid but "empty".
87 note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
88 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
89 In which case, it's necessary to use streaming mode to decompress data.
90 Optionally, application can rely on some implicit limit,
91 as ZSTD_decompress() only needs an upper bound of decompressed size.
92 (For example, data could be necessarily cut into blocks <= 16 KB).
93 note 3 : decompressed size is always present when compression is done with ZSTD_compress()
94 note 4 : decompressed size can be very large (64-bits value),
95 potentially larger than what local system can handle as a single memory segment.
96 In which case, it's necessary to use streaming mode to decompress data.
97 note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
98 Always ensure return value fits within application's authorized limits.
99 Each application can set its own limits.
100 note 6 : This function replaces ZSTD_getDecompressedSize()
103 <pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
104 </b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
105 Both functions work the same way, but ZSTD_getDecompressedSize() blends
106 "empty", "unknown" and "error" results to the same return value (0),
107 while ZSTD_getFrameContentSize() gives them separate return values.
108 `src` is the start of a zstd compressed frame.
109 @return : content size to be decompressed, as a 64-bits value _if known and not empty_, 0 otherwise.
112 <h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
113 size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
114 unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
115 const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
116 int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
118 <a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
120 <h3>Compression context</h3><pre> When compressing many times,
121 it is recommended to allocate a context just once, and re-use it for each successive compression operation.
122 This will make workload friendlier for system's memory.
123 Use one context per thread for parallel execution in multi-threaded environments.
124 </pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
125 ZSTD_CCtx* ZSTD_createCCtx(void);
126 size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
128 <pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx,
129 void* dst, size_t dstCapacity,
130 const void* src, size_t srcSize,
131 int compressionLevel);
132 </b><p> Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()).
135 <h3>Decompression context</h3><pre> When decompressing many times,
136 it is recommended to allocate a context only once,
137 and re-use it for each successive compression operation.
138 This will make workload friendlier for system's memory.
139 Use one context per thread for parallel execution.
140 </pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
141 ZSTD_DCtx* ZSTD_createDCtx(void);
142 size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
144 <pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx,
145 void* dst, size_t dstCapacity,
146 const void* src, size_t srcSize);
147 </b><p> Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx())
150 <a name="Chapter5"></a><h2>Simple dictionary API</h2><pre></pre>
152 <pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
153 void* dst, size_t dstCapacity,
154 const void* src, size_t srcSize,
155 const void* dict,size_t dictSize,
156 int compressionLevel);
157 </b><p> Compression using a predefined Dictionary (see dictBuilder/zdict.h).
158 Note : This function loads the dictionary, resulting in significant startup delay.
159 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
162 <pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
163 void* dst, size_t dstCapacity,
164 const void* src, size_t srcSize,
165 const void* dict,size_t dictSize);
166 </b><p> Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
167 Dictionary must be identical to the one used during compression.
168 Note : This function loads the dictionary, resulting in significant startup delay.
169 Note : When `dict == NULL || dictSize < 8` no dictionary is used.
172 <a name="Chapter6"></a><h2>Bulk processing dictionary API</h2><pre></pre>
174 <pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
175 int compressionLevel);
176 </b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
177 ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
178 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
179 `dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict
182 <pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
183 </b><p> Function frees memory allocated by ZSTD_createCDict().
186 <pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
187 void* dst, size_t dstCapacity,
188 const void* src, size_t srcSize,
189 const ZSTD_CDict* cdict);
190 </b><p> Compression using a digested Dictionary.
191 Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
192 Note that compression level is decided during dictionary creation.
193 Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
196 <pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
197 </b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
198 dictBuffer can be released after DDict creation, as its content is copied inside DDict
201 <pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
202 </b><p> Function frees memory allocated with ZSTD_createDDict()
205 <pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
206 void* dst, size_t dstCapacity,
207 const void* src, size_t srcSize,
208 const ZSTD_DDict* ddict);
209 </b><p> Decompression using a digested Dictionary.
210 Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
213 <a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
215 <pre><b>typedef struct ZSTD_inBuffer_s {
216 const void* src; </b>/**< start of input buffer */<b>
217 size_t size; </b>/**< size of input buffer */<b>
218 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
221 <pre><b>typedef struct ZSTD_outBuffer_s {
222 void* dst; </b>/**< start of output buffer */<b>
223 size_t size; </b>/**< size of output buffer */<b>
224 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
227 <a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
228 A ZSTD_CStream object is required to track streaming operation.
229 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
230 ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
231 It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
232 since it will play nicer with system's memory, by re-using already allocated memory.
233 Use one separate ZSTD_CStream per thread for parallel execution.
235 Start a new compression by initializing ZSTD_CStream.
236 Use ZSTD_initCStream() to start a new compression operation.
237 Use ZSTD_initCStream_usingDict() or ZSTD_initCStream_usingCDict() for a compression which requires a dictionary (experimental section)
239 Use ZSTD_compressStream() repetitively to consume input stream.
240 The function will automatically update both `pos` fields.
241 Note that it may not consume the entire input, in which case `pos < size`,
242 and it's up to the caller to present again remaining data.
243 @return : a size hint, preferred nb of bytes to use as input for next function call
244 or an error code, which can be tested using ZSTD_isError().
245 Note 1 : it's just a hint, to help latency a little, any other value will work fine.
246 Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
248 At any moment, it's possible to flush whatever data remains within internal buffer, using ZSTD_flushStream().
249 `output->pos` will be updated.
250 Note that some content might still be left within internal buffer if `output->size` is too small.
251 @return : nb of bytes still present within internal buffer (0 if it's empty)
252 or an error code, which can be tested using ZSTD_isError().
254 ZSTD_endStream() instructs to finish a frame.
255 It will perform a flush and write frame epilogue.
256 The epilogue is required for decoders to consider a frame completed.
257 ZSTD_endStream() may not be able to flush full data if `output->size` is too small.
258 In which case, call again ZSTD_endStream() to complete the flush.
259 @return : 0 if frame fully completed and fully flushed,
260 or >0 if some data is still present within internal buffer
261 (value is minimum size estimation for remaining data to flush, but it could be more)
262 or an error code, which can be tested using ZSTD_isError().
267 <pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
269 <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
270 size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
272 <h3>Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
273 size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
274 size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
275 size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
277 <pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
279 <pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */<b>
281 <a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
282 A ZSTD_DStream object is required to track streaming operations.
283 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
284 ZSTD_DStream objects can be re-used multiple times.
286 Use ZSTD_initDStream() to start a new decompression operation,
287 or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
288 @return : recommended first input size
290 Use ZSTD_decompressStream() repetitively to consume your input.
291 The function will update both `pos` fields.
292 If `input.pos < input.size`, some input has not been consumed.
293 It's up to the caller to present again remaining data.
294 If `output.pos < output.size`, decoder has flushed everything it could.
295 @return : 0 when a frame is completely decoded and fully flushed,
296 an error code, which can be tested using ZSTD_isError(),
297 any other value > 0, which means there is still some decoding to do to complete current frame.
298 The return value is a suggested next input size (a hint to improve latency) that will never load more than the current frame.
302 <pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
304 <h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
305 size_t ZSTD_freeDStream(ZSTD_DStream* zds);
307 <h3>Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream(ZSTD_DStream* zds);
308 size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
310 <pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
312 <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>
314 <a name="Chapter10"></a><h2>START OF ADVANCED AND EXPERIMENTAL FUNCTIONS</h2><pre> The definitions in this section are considered experimental.
315 They should never be used with a dynamic library, as prototypes may change in the future.
316 They are provided for advanced scenarios.
317 Use them only in association with static linking.
321 <a name="Chapter11"></a><h2>Advanced types</h2><pre></pre>
323 <pre><b>typedef enum { ZSTD_fast=1, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2,
324 ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; </b>/* from faster to stronger */<b>
326 <pre><b>typedef struct {
327 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
328 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
329 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
330 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
331 unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
332 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
333 ZSTD_strategy strategy;
334 } ZSTD_compressionParameters;
336 <pre><b>typedef struct {
337 unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
338 unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum at end of frame, for error detection */<b>
339 unsigned noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (if dictionary compression) */<b>
340 } ZSTD_frameParameters;
342 <pre><b>typedef struct {
343 ZSTD_compressionParameters cParams;
344 ZSTD_frameParameters fParams;
347 <pre><b>typedef enum {
348 ZSTD_dct_auto=0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
349 ZSTD_dct_rawContent, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
350 ZSTD_dct_fullDict </b>/* refuses to load a dictionary if it does not respect Zstandard's specification */<b>
351 } ZSTD_dictContentType_e;
353 <pre><b>typedef enum {
354 ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
355 ZSTD_dlm_byRef, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
356 } ZSTD_dictLoadMethod_e;
358 <a name="Chapter12"></a><h2>Frame size functions</h2><pre></pre>
360 <pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
361 </b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
362 `srcSize` must be >= first frame size
363 @return : the compressed size of the first frame starting at `src`,
364 suitable to pass to `ZSTD_decompress` or similar,
365 or an error code if input is invalid
368 <pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
369 </b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
370 `srcSize` must be the _exact_ size of this series
371 (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
372 @return : - decompressed size of all data in all successive frames
373 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
374 - if an error occurred: ZSTD_CONTENTSIZE_ERROR
376 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
377 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
378 In which case, it's necessary to use streaming mode to decompress data.
379 note 2 : decompressed size is always present when compression is done with ZSTD_compress()
380 note 3 : decompressed size can be very large (64-bits value),
381 potentially larger than what local system can handle as a single memory segment.
382 In which case, it's necessary to use streaming mode to decompress data.
383 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
384 Always ensure result fits within application's authorized limits.
385 Each application can set its own limits.
386 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
387 read each contained frame header. This is fast as most of the data is skipped,
388 however it does mean that all frame data must be present and valid.
391 <pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
392 </b><p> `src` should point to the start of a ZSTD frame
393 `srcSize` must be >= ZSTD_frameHeaderSize_prefix.
394 @return : size of the Frame Header
397 <a name="Chapter13"></a><h2>Memory management</h2><pre></pre>
399 <pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
400 size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
401 size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
402 size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
403 size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
404 size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
405 </b><p> These functions give the current memory usage of selected object.
406 Object memory usage can evolve when re-used.
409 <pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
410 size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
411 size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
412 size_t ZSTD_estimateDCtxSize(void);
413 </b><p> These functions make it possible to estimate memory usage
414 of a future {D,C}Ctx, before its creation.
415 ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
416 It will also consider src size to be arbitrarily "large", which is worst case.
417 If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
418 ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
419 ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
420 Note : CCtx size estimation is only correct for single-threaded compression.
423 <pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
424 size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
425 size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
426 size_t ZSTD_estimateDStreamSize(size_t windowSize);
427 size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
428 </b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
429 It will also consider src size to be arbitrarily "large", which is worst case.
430 If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
431 ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
432 ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
433 Note : CStream size estimation is only correct for single-threaded compression.
434 ZSTD_DStream memory budget depends on window Size.
435 This information can be passed manually, using ZSTD_estimateDStreamSize,
436 or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
437 Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
438 an internal ?Dict will be created, which additional size is not estimated here.
439 In this case, get total size by adding ZSTD_estimate?DictSize
442 <pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
443 size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
444 size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
445 </b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
446 ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
447 Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
451 <pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
452 ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
453 </b><p> Initialize an object using a pre-allocated fixed-size buffer.
454 workspace: The memory area to emplace the object into.
455 Provided pointer *must be 8-bytes aligned*.
456 Buffer must outlive object.
457 workspaceSize: Use ZSTD_estimate*Size() to determine
458 how large workspace must be to support target scenario.
459 @return : pointer to object (same address as workspace, just different type),
460 or NULL if error (size too small, incorrect alignment, etc.)
461 Note : zstd will never resize nor malloc() when using a static buffer.
462 If the object requires more memory than available,
463 zstd will just error out (typically ZSTD_error_memory_allocation).
464 Note 2 : there is no corresponding "free" function.
465 Since workspace is allocated externally, it must be freed externally too.
466 Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
467 into its associated cParams.
468 Limitation 1 : currently not compatible with internal dictionary creation, triggered by
469 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
470 Limitation 2 : static cctx currently not compatible with multi-threading.
471 Limitation 3 : static dctx is incompatible with legacy support.
475 <pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
477 <pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
478 typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
479 typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
480 static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
481 </b><p> These prototypes make it possible to pass your own allocation/free functions.
482 ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
483 All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
487 <a name="Chapter14"></a><h2>Advanced compression functions</h2><pre></pre>
489 <pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
490 </b><p> Create a digested dictionary for compression
491 Dictionary content is simply referenced, and therefore stays in dictBuffer.
492 It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
495 <pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
496 </b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
497 `estimatedSrcSize` value is optional, select 0 if not known
500 <pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
501 </b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
502 All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
505 <pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
506 </b><p> Ensure param values remain within authorized range
509 <pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
510 </b><p> optimize params for a given `srcSize` and `dictSize`.
511 both values are optional, select `0` if unknown.
514 <pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
515 void* dst, size_t dstCapacity,
516 const void* src, size_t srcSize,
517 const void* dict,size_t dictSize,
518 ZSTD_parameters params);
519 </b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
522 <pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
523 void* dst, size_t dstCapacity,
524 const void* src, size_t srcSize,
525 const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
526 </b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
529 <a name="Chapter15"></a><h2>Advanced decompression functions</h2><pre></pre>
531 <pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
532 </b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
533 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
534 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
535 Note 3 : Skippable Frame Identifiers are considered valid.
538 <pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
539 </b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
540 Dictionary content is referenced, and therefore stays in dictBuffer.
541 It is important that dictBuffer outlives DDict,
542 it must remain read accessible throughout the lifetime of DDict
545 <pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
546 </b><p> Provides the dictID stored within dictionary.
547 if @return == 0, the dictionary is not conformant with Zstandard specification.
548 It can still be loaded, but as a content-only dictionary.
551 <pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
552 </b><p> Provides the dictID of the dictionary loaded into `ddict`.
553 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
554 Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
557 <pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
558 </b><p> Provides the dictID required to decompressed the frame stored within `src`.
559 If @return == 0, the dictID could not be decoded.
560 This could for one of the following reasons :
561 - The frame does not require a dictionary to be decoded (most common case).
562 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
563 Note : this use case also happens when using a non-conformant dictionary.
564 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
565 - This is not a Zstandard frame.
566 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
569 <a name="Chapter16"></a><h2>Advanced streaming functions</h2><pre></pre>
571 <h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If it is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, "0" also disables frame content size field. It may be enabled in the future. */<b>
572 size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); </b>/**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.*/<b>
573 size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
574 ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. */<b>
575 size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b>
576 size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters. pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. */<b>
578 <pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
579 </b><p> start a new compression job, using same parameters from previous job.
580 This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
581 Note that zcs must be init at least once before using ZSTD_resetCStream().
582 If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
583 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
584 For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
585 but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
586 @return : 0, or an error code (which can be tested using ZSTD_isError())
589 <pre><b>typedef struct {
590 unsigned long long ingested;
591 unsigned long long consumed;
592 unsigned long long produced;
593 } ZSTD_frameProgression;
595 <h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e;
596 size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue); </b>/* obsolete : this API will be removed in a future version */<b>
597 size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: no dictionary will be used if dict == NULL or dictSize < 8 */<b>
598 size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict is referenced, it must outlive decompression session */<b>
599 size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
601 <a name="Chapter17"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
602 This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
603 But it's also a complex one, with several restrictions, documented below.
604 Prefer normal streaming API for an easier experience.
608 <a name="Chapter18"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
609 A ZSTD_CCtx object is required to track streaming operations.
610 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
611 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
613 Start by initializing a context.
614 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
615 or ZSTD_compressBegin_advanced(), for finer parameter control.
616 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
618 Then, consume your input using ZSTD_compressContinue().
619 There are some important considerations to keep in mind when using this advanced function :
620 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
621 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
622 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
623 Worst case evaluation is provided by ZSTD_compressBound().
624 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
625 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
626 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
627 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
628 In which case, it will "discard" the relevant memory section from its history.
630 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
631 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
632 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
634 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
637 <h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
638 size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
639 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>
640 size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
641 size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b>
642 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>
644 <a name="Chapter19"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
645 A ZSTD_DCtx object is required to track streaming operations.
646 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
647 A ZSTD_DCtx object can be re-used multiple times.
649 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
650 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
651 Data fragment must be large enough to ensure successful decoding.
652 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
653 @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
654 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
655 errorCode, which can be tested using ZSTD_isError().
657 It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
658 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
659 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
660 As a consequence, check that values remain within valid application range.
661 For example, do not allocate memory blindly, check that `windowSize` is within expectation.
662 Each application can set its own limits, depending on local restrictions.
663 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
665 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
666 ZSTD_decompressContinue() is very sensitive to contiguity,
667 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
668 or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
669 There are multiple ways to guarantee this condition.
671 The most memory efficient way is to use a round buffer of sufficient size.
672 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
673 which can @return an error code if required value is too large for current system (in 32-bits mode).
674 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
675 up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
676 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
677 At which point, decoding can resume from the beginning of the buffer.
678 Note that already decoded data stored in the buffer should be flushed before being overwritten.
680 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
682 Finally, if you control the compression process, you can also ignore all buffer size rules,
683 as long as the encoder and decoder progress in "lock-step",
684 aka use exactly the same buffer sizes, break contiguity at the same place, etc.
686 Once buffers are setup, start decompression, with ZSTD_decompressBegin().
687 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
689 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
690 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
691 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
693 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
694 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
695 It can also be an error code, which can be tested with ZSTD_isError().
697 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
698 Context can then be reset to start a new decompression.
700 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
701 This information is not required to properly decode a frame.
703 == Special case : skippable frames
705 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
706 Skippable frames will be ignored (skipped) by decompressor.
707 The format of skippable frames is as follows :
708 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
709 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
710 c) Frame Content - any content (User Data) of length equal to Frame Size
711 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
712 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
715 <h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
717 unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
718 unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
719 unsigned blockSizeMax;
720 ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
723 unsigned checksumFlag;
725 size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
726 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>
728 <pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
730 <a name="Chapter20"></a><h2>New advanced API (experimental)</h2><pre></pre>
732 <pre><b>typedef enum {
733 </b>/* Opened question : should we have a format ZSTD_f_auto ?<b>
734 * Today, it would mean exactly the same as ZSTD_f_zstd1.
735 * But, in the future, should several formats become supported,
736 * on the compression side, it would mean "default format".
737 * On the decompression side, it would mean "automatic format detection",
738 * so that ZSTD_f_zstd1 would mean "accept *only* zstd frames".
739 * Since meaning is a little different, another option could be to define different enums for compression and decompression.
740 * This question could be kept for later, when there are actually multiple formats to support,
741 * but there is also the question of pinning enum values, and pinning value `0` is especially important */
742 ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
743 ZSTD_f_zstd1_magicless, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
744 * Useful to save 4 bytes per generated frame.
745 * Decoder cannot recognise automatically this format, requiring instructions. */
748 <pre><b>typedef enum {
749 </b>/* compression format */<b>
750 ZSTD_p_format = 10, </b>/* See ZSTD_format_e enum definition.<b>
751 * Cast selected format as unsigned for ZSTD_CCtx_setParameter() compatibility. */
753 </b>/* compression parameters */<b>
754 ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
755 * Default level is ZSTD_CLEVEL_DEFAULT==3.
756 * Special: value 0 means "do not change cLevel".
757 * Note 1 : it's possible to pass a negative compression level by casting it to unsigned type.
758 * Note 2 : setting a level sets all default values of other compression parameters.
759 * Note 3 : setting compressionLevel automatically updates ZSTD_p_compressLiterals. */
760 ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
761 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
762 * Special: value 0 means "use default windowLog".
763 * Note: Using a window size greater than ZSTD_MAXWINDOWSIZE_DEFAULT (default: 2^27)
764 * requires explicitly allowing such window size during decompression stage. */
765 ZSTD_p_hashLog, </b>/* Size of the probe table, as a power of 2.<b>
766 * Resulting table size is (1 << (hashLog+2)).
767 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
768 * Larger tables improve compression ratio of strategies <= dFast,
769 * and improve speed of strategies > dFast.
770 * Special: value 0 means "use default hashLog". */
771 ZSTD_p_chainLog, </b>/* Size of the full-search table, as a power of 2.<b>
772 * Resulting table size is (1 << (chainLog+2)).
773 * Larger tables result in better and slower compression.
774 * This parameter is useless when using "fast" strategy.
775 * Special: value 0 means "use default chainLog". */
776 ZSTD_p_searchLog, </b>/* Number of search attempts, as a power of 2.<b>
777 * More attempts result in better and slower compression.
778 * This parameter is useless when using "fast" and "dFast" strategies.
779 * Special: value 0 means "use default searchLog". */
780 ZSTD_p_minMatch, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b>
781 * Larger values make faster compression and decompression, but decrease ratio.
782 * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX.
783 * Note that currently, for all strategies < btopt, effective minimum is 4.
784 * , for all strategies > fast, effective maximum is 6.
785 * Special: value 0 means "use default minMatchLength". */
786 ZSTD_p_targetLength, </b>/* Impact of this field depends on strategy.<b>
787 * For strategies btopt & btultra:
788 * Length of Match considered "good enough" to stop search.
789 * Larger values make compression stronger, and slower.
791 * Distance between match sampling.
792 * Larger values make compression faster, and weaker.
793 * Special: value 0 means "use default targetLength". */
794 ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b>
795 * Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
796 * The higher the value of selected strategy, the more complex it is,
797 * resulting in stronger and slower compression.
798 * Special: value 0 means "use default strategy". */
800 ZSTD_p_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
801 * This parameter is designed to improve compression ratio
802 * for large inputs, by finding large matches at long distance.
803 * It increases memory usage and window size.
804 * Note: enabling this parameter increases ZSTD_p_windowLog to 128 MB
805 * except when expressly set to a different value. */
806 ZSTD_p_ldmHashLog, </b>/* Size of the table for long distance matching, as a power of 2.<b>
807 * Larger values increase memory usage and compression ratio,
808 * but decrease compression speed.
809 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
810 * default: windowlog - 7.
811 * Special: value 0 means "automatically determine hashlog". */
812 ZSTD_p_ldmMinMatch, </b>/* Minimum match size for long distance matcher.<b>
813 * Larger/too small values usually decrease compression ratio.
814 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
815 * Special: value 0 means "use default value" (default: 64). */
816 ZSTD_p_ldmBucketSizeLog, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
817 * Larger values improve collision resolution but decrease compression speed.
818 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX .
819 * Special: value 0 means "use default value" (default: 3). */
820 ZSTD_p_ldmHashEveryLog, </b>/* Frequency of inserting/looking up entries in the LDM hash table.<b>
821 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
822 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
823 * Larger values improve compression speed.
824 * Deviating far from default value will likely result in a compression ratio decrease.
825 * Special: value 0 means "automatically determine hashEveryLog". */
827 </b>/* frame parameters */<b>
828 ZSTD_p_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
829 * Content size must be known at the beginning of compression,
830 * it is provided using ZSTD_CCtx_setPledgedSrcSize() */
831 ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
832 ZSTD_p_dictIDFlag, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
834 </b>/* multi-threading parameters */<b>
835 </b>/* These parameters are only useful if multi-threading is enabled (ZSTD_MULTITHREAD).<b>
836 * They return an error otherwise. */
837 ZSTD_p_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
838 * When nbWorkers >= 1, triggers asynchronous mode :
839 * ZSTD_compress_generic() consumes some input, flush some output if possible, and immediately gives back control to caller,
840 * while compression work is performed in parallel, within worker threads.
841 * (note : a strong exception to this rule is when first invocation sets ZSTD_e_end : it becomes a blocking call).
842 * More workers improve speed, but also increase memory usage.
843 * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */
844 ZSTD_p_jobSize, </b>/* Size of a compression job. This value is enforced only in non-blocking mode.<b>
845 * Each compression job is completed in parallel, so this value indirectly controls the nb of active threads.
846 * 0 means default, which is dynamically determined based on compression parameters.
847 * Job size must be a minimum of overlapSize, or 1 MB, whichever is largest.
848 * The minimum size is automatically and transparently enforced */
849 ZSTD_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b>
850 * 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */
852 </b>/* =================================================================== */<b>
853 </b>/* experimental parameters - no stability guaranteed */<b>
854 </b>/* =================================================================== */<b>
856 ZSTD_p_compressLiterals=1000, </b>/* control huffman compression of literals (enabled) by default.<b>
857 * disabling it improves speed and decreases compression ratio by a large amount.
858 * note : this setting is automatically updated when changing compression level.
859 * positive compression levels set ZSTD_p_compressLiterals to 1.
860 * negative compression levels set ZSTD_p_compressLiterals to 0. */
862 ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
863 * even when referencing into Dictionary content (default:0) */
867 <pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);
868 </b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
869 Setting a parameter is generally only possible during frame initialization (before starting compression),
870 except for a few exceptions which can be updated during compression: compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
871 Note : when `value` is an enum, cast it to unsigned for proper type checking.
872 @result : informational value (typically, value being set clamped correctly),
873 or an error code (which can be tested with ZSTD_isError()).
876 <pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
877 </b><p> Total input data size to be compressed as a single frame.
878 This value will be controlled at the end, and result in error if not respected.
879 @result : 0, or an error code (which can be tested with ZSTD_isError()).
880 Note 1 : 0 means zero, empty.
881 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
882 ZSTD_CONTENTSIZE_UNKNOWN is default value for any new compression job.
883 Note 2 : If all data is provided and consumed in a single round,
884 this value is overriden by srcSize instead.
887 <pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
888 size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
889 size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
890 </b><p> Create an internal CDict from `dict` buffer.
891 Decompression will have to use same dictionary.
892 @result : 0, or an error code (which can be tested with ZSTD_isError()).
893 Special: Adding a NULL (or 0-size) dictionary invalidates previous dictionary,
894 meaning "return to no-dictionary mode".
895 Note 1 : Dictionary will be used for all future compression jobs.
896 To return to "no-dictionary" situation, load a NULL dictionary
897 Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters.
898 For this reason, compression parameters cannot be changed anymore after loading a dictionary.
899 It's also a CPU consuming operation, with non-negligible impact on latency.
900 Note 3 :`dict` content will be copied internally.
901 Use ZSTD_CCtx_loadDictionary_byReference() to reference dictionary content instead.
902 In such a case, dictionary buffer must outlive its users.
903 Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
904 to precisely select how dictionary content must be interpreted.
907 <pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
908 </b><p> Reference a prepared dictionary, to be used for all next compression jobs.
909 Note that compression parameters are enforced from within CDict,
910 and supercede any compression parameter previously set within CCtx.
911 The dictionary will remain valid for future compression jobs using same CCtx.
912 @result : 0, or an error code (which can be tested with ZSTD_isError()).
913 Special : adding a NULL CDict means "return to no-dictionary mode".
914 Note 1 : Currently, only one dictionary can be managed.
915 Adding a new dictionary effectively "discards" any previous one.
916 Note 2 : CDict is just referenced, its lifetime must outlive CCtx.
919 <pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize);
920 size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
921 </b><p> Reference a prefix (single-usage dictionary) for next compression job.
922 Decompression need same prefix to properly regenerate data.
923 Prefix is **only used once**. Tables are discarded at end of compression job.
924 Subsequent compression jobs will be done without prefix (if none is explicitly referenced).
925 If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict instead.
926 @result : 0, or an error code (which can be tested with ZSTD_isError()).
927 Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
928 Note 1 : Prefix buffer is referenced. It must outlive compression job.
929 Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters.
930 It's a CPU consuming operation, with non-negligible impact on latency.
931 Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
932 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode.
935 <pre><b>void ZSTD_CCtx_reset(ZSTD_CCtx* cctx);
936 </b><p> Return a CCtx to clean state.
937 Useful after an error, or to interrupt an ongoing compression job and start a new one.
938 Any internal data not yet flushed is cancelled.
939 Dictionary (if any) is dropped.
940 All parameters are back to default values.
941 It's possible to modify compression parameters after a reset.
945 <pre><b>typedef enum {
946 ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal conditions */<b>
947 ZSTD_e_flush, </b>/* flush any data provided so far - frame will continue, future data can still reference previous data for better compression */<b>
948 ZSTD_e_end </b>/* flush any remaining data and close current frame. Any additional data starts a new frame. */<b>
951 <pre><b>size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
952 ZSTD_outBuffer* output,
953 ZSTD_inBuffer* input,
954 ZSTD_EndDirective endOp);
955 </b><p> Behave about the same as ZSTD_compressStream. To note :
956 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_setParameter()
957 - Compression parameters cannot be changed once compression is started.
958 - outpot->pos must be <= dstCapacity, input->pos must be <= srcSize
959 - outpot->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
960 - In single-thread mode (default), function is blocking : it completed its job before returning to caller.
961 - In multi-thread mode, function is non-blocking : it just acquires a copy of input, and distribute job to internal worker threads,
962 and then immediately returns, just indicating that there is some data remaining to be flushed.
963 The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
964 - Exception : in multi-threading mode, if the first call requests a ZSTD_e_end directive, it is blocking : it will complete compression before giving back control to caller.
965 - @return provides a minimum amount of data remaining to be flushed from internal buffers
966 or an error code, which can be tested using ZSTD_isError().
967 if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
968 This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
969 For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
970 - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
971 only ZSTD_e_end or ZSTD_e_flush operations are allowed.
972 Before starting a new compression job, or changing compression parameters,
973 it is required to fully flush internal buffers.
977 <pre><b>size_t ZSTD_compress_generic_simpleArgs (
979 void* dst, size_t dstCapacity, size_t* dstPos,
980 const void* src, size_t srcSize, size_t* srcPos,
981 ZSTD_EndDirective endOp);
982 </b><p> Same as ZSTD_compress_generic(),
983 but using only integral types as arguments.
984 Argument list is larger than ZSTD_{in,out}Buffer,
985 but can be helpful for binders from dynamic languages
986 which have troubles handling structures containing memory pointers.
990 <pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
991 size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params);
992 </b><p> Quick howto :
993 - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
994 - ZSTD_CCtxParam_setParameter() : Push parameters one by one into
995 an existing ZSTD_CCtx_params structure.
997 ZSTD_CCtx_setParameter().
998 - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1000 These parameters will be applied to
1001 all subsequent compression jobs.
1002 - ZSTD_compress_generic() : Do compression using the CCtx.
1003 - ZSTD_freeCCtxParams() : Free the memory.
1005 This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1006 for static allocation for single-threaded compression.
1010 <pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1011 </b><p> Reset params to default values.
1015 <pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1016 </b><p> Initializes the compression parameters of cctxParams according to
1017 compression level. All other parameters are reset to their default values.
1021 <pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1022 </b><p> Initializes the compression and frame parameters of cctxParams according to
1023 params. All other parameters are reset to their default values.
1027 <pre><b>size_t ZSTD_CCtxParam_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, unsigned value);
1028 </b><p> Similar to ZSTD_CCtx_setParameter.
1029 Set one compression parameter, selected by enum ZSTD_cParameter.
1030 Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams().
1031 Note : when `value` is an enum, cast it to unsigned for proper type checking.
1032 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1036 <pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1037 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1038 </b><p> Apply a set of ZSTD_CCtx_params to the compression context.
1039 This can be done even after compression is started,
1040 if nbWorkers==0, this will have no impact until a new compression is started.
1041 if nbWorkers>=1, new parameters will be picked up at next job,
1042 with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1046 <h3>Advanced parameters for decompression API</h3><pre></pre><b><pre></pre></b><BR>
1047 <pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1048 size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1049 size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1050 </b><p> Create an internal DDict from dict buffer,
1051 to be used to decompress next frames.
1052 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1053 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
1054 meaning "return to no-dictionary mode".
1055 Note 1 : `dict` content will be copied internally.
1056 Use ZSTD_DCtx_loadDictionary_byReference()
1057 to reference dictionary content instead.
1058 In which case, the dictionary buffer must outlive its users.
1059 Note 2 : Loading a dictionary involves building tables,
1060 which has a non-negligible impact on CPU usage and latency.
1061 Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to select
1062 how dictionary content will be interpreted and loaded.
1066 <pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
1067 </b><p> Reference a prepared dictionary, to be used to decompress next frames.
1068 The dictionary remains active for decompression of future frames using same DCtx.
1069 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1070 Note 1 : Currently, only one dictionary can be managed.
1071 Referencing a new dictionary effectively "discards" any previous one.
1072 Special : adding a NULL DDict means "return to no-dictionary mode".
1073 Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
1077 <pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize);
1078 size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1079 </b><p> Reference a prefix (single-usage dictionary) for next compression job.
1080 Prefix is **only used once**. It must be explicitly referenced before each frame.
1081 If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_DDict instead.
1082 @result : 0, or an error code (which can be tested with ZSTD_isError()).
1083 Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
1084 Note 2 : Prefix buffer is referenced. It must outlive compression job.
1085 Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
1086 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode.
1087 Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
1091 <pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1092 </b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1093 This is useful to prevent a decoder context from reserving too much memory for itself (potential attack scenario).
1094 This parameter is only useful in streaming mode, since no internal buffer is allocated in direct mode.
1095 By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_MAX)
1096 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1100 <pre><b>size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1101 </b><p> Instruct the decoder context about what kind of data to decode next.
1102 This instruction is mandatory to decode data without a fully-formed header,
1103 such ZSTD_f_zstd1_magicless for example.
1104 @return : 0, or an error code (which can be tested using ZSTD_isError()).
1108 <pre><b>size_t ZSTD_decompress_generic(ZSTD_DCtx* dctx,
1109 ZSTD_outBuffer* output,
1110 ZSTD_inBuffer* input);
1111 </b><p> Behave the same as ZSTD_decompressStream.
1112 Decompression parameters cannot be changed once decompression is started.
1113 @return : an error code, which can be tested using ZSTD_isError()
1114 if >0, a hint, nb of expected input bytes for next invocation.
1115 `0` means : a frame has just been fully decoded and flushed.
1119 <pre><b>size_t ZSTD_decompress_generic_simpleArgs (
1121 void* dst, size_t dstCapacity, size_t* dstPos,
1122 const void* src, size_t srcSize, size_t* srcPos);
1123 </b><p> Same as ZSTD_decompress_generic(),
1124 but using only integral types as arguments.
1125 Argument list is larger than ZSTD_{in,out}Buffer,
1126 but can be helpful for binders from dynamic languages
1127 which have troubles handling structures containing memory pointers.
1131 <pre><b>void ZSTD_DCtx_reset(ZSTD_DCtx* dctx);
1132 </b><p> Return a DCtx to clean state.
1133 If a decompression was ongoing, any internal data not yet flushed is cancelled.
1134 All parameters are back to default values, including sticky ones.
1135 Dictionary (if any) is dropped.
1136 Parameters can be modified again after a reset.
1140 <a name="Chapter21"></a><h2>Block level API</h2><pre></pre>
1142 <pre><b></b><p> Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
1143 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
1145 A few rules to respect :
1146 - Compressing and decompressing require a context structure
1147 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
1148 - It is necessary to init context before starting
1149 + compression : any ZSTD_compressBegin*() variant, including with dictionary
1150 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
1151 + copyCCtx() and copyDCtx() can be used too
1152 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
1153 + If input is larger than a block size, it's necessary to split input data into multiple blocks
1154 + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead.
1155 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
1156 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
1157 In which case, nothing is produced into `dst`.
1158 + User must test for such outcome and deal directly with uncompressed data
1159 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
1160 + In case of multiple successive blocks, should some of them be uncompressed,
1161 decoder must be informed of their existence in order to follow proper history.
1162 Use ZSTD_insertBlock() for such a case.
1165 <h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
1166 size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1167 size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1168 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>
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