1/*
2 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
3 * All rights reserved.
4 *
5 * This source code is licensed under both the BSD-style license (found in the
6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
7 * in the COPYING file in the root directory of this source tree).
8 * You may select, at your option, one of the above-listed licenses.
9 */
10#if defined (__cplusplus)
11extern "C" {
12#endif
13
14#ifndef ZSTD_H_235446
15#define ZSTD_H_235446
16
17/* ====== Dependency ======*/
18#include <stddef.h> /* size_t */
19
20
21/* ===== ZSTDLIB_API : control library symbols visibility ===== */
22#ifndef ZSTDLIB_VISIBILITY
23# if defined(__GNUC__) && (__GNUC__ >= 4)
24# define ZSTDLIB_VISIBILITY __attribute__ ((visibility ("default")))
25# else
26# define ZSTDLIB_VISIBILITY
27# endif
28#endif
29#if defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
30# define ZSTDLIB_API __declspec(dllexport) ZSTDLIB_VISIBILITY
31#elif defined(ZSTD_DLL_IMPORT) && (ZSTD_DLL_IMPORT==1)
32# define ZSTDLIB_API __declspec(dllimport) ZSTDLIB_VISIBILITY /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
33#else
34# define ZSTDLIB_API ZSTDLIB_VISIBILITY
35#endif
36
37
38/*******************************************************************************
39 Introduction
40
41 zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
42 real-time compression scenarios at zlib-level and better compression ratios.
43 The zstd compression library provides in-memory compression and decompression
44 functions.
45
46 The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
47 which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
48 caution, as they require more memory. The library also offers negative
49 compression levels, which extend the range of speed vs. ratio preferences.
50 The lower the level, the faster the speed (at the cost of compression).
51
52 Compression can be done in:
53 - a single step (described as Simple API)
54 - a single step, reusing a context (described as Explicit context)
55 - unbounded multiple steps (described as Streaming compression)
56
57 The compression ratio achievable on small data can be highly improved using
58 a dictionary. Dictionary compression can be performed in:
59 - a single step (described as Simple dictionary API)
60 - a single step, reusing a dictionary (described as Bulk-processing
61 dictionary API)
62
63 Advanced experimental functions can be accessed using
64 `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
65
66 Advanced experimental APIs should never be used with a dynamically-linked
67 library. They are not "stable"; their definitions or signatures may change in
68 the future. Only static linking is allowed.
69*******************************************************************************/
70
71/*------ Version ------*/
72#define ZSTD_VERSION_MAJOR 1
73#define ZSTD_VERSION_MINOR 3
74#define ZSTD_VERSION_RELEASE 8
75
76#define ZSTD_VERSION_NUMBER (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
77ZSTDLIB_API unsigned ZSTD_versionNumber(void); /**< to check runtime library version */
78
79#define ZSTD_LIB_VERSION ZSTD_VERSION_MAJOR.ZSTD_VERSION_MINOR.ZSTD_VERSION_RELEASE
80#define ZSTD_QUOTE(str) #str
81#define ZSTD_EXPAND_AND_QUOTE(str) ZSTD_QUOTE(str)
82#define ZSTD_VERSION_STRING ZSTD_EXPAND_AND_QUOTE(ZSTD_LIB_VERSION)
83ZSTDLIB_API const char* ZSTD_versionString(void); /* requires v1.3.0+ */
84
85/***************************************
86* Default constant
87***************************************/
88#ifndef ZSTD_CLEVEL_DEFAULT
89# define ZSTD_CLEVEL_DEFAULT 3
90#endif
91
92/***************************************
93* Simple API
94***************************************/
95/*! ZSTD_compress() :
96 * Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
97 * Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
98 * @return : compressed size written into `dst` (<= `dstCapacity),
99 * or an error code if it fails (which can be tested using ZSTD_isError()). */
100ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
101 const void* src, size_t srcSize,
102 int compressionLevel);
103
104/*! ZSTD_decompress() :
105 * `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
106 * `dstCapacity` is an upper bound of originalSize to regenerate.
107 * If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
108 * @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
109 * or an errorCode if it fails (which can be tested using ZSTD_isError()). */
110ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
111 const void* src, size_t compressedSize);
112
113/*! ZSTD_getFrameContentSize() : requires v1.3.0+
114 * `src` should point to the start of a ZSTD encoded frame.
115 * `srcSize` must be at least as large as the frame header.
116 * hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
117 * @return : - decompressed size of `src` frame content, if known
118 * - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
119 * - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
120 * note 1 : a 0 return value means the frame is valid but "empty".
121 * note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
122 * When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
123 * In which case, it's necessary to use streaming mode to decompress data.
124 * Optionally, application can rely on some implicit limit,
125 * as ZSTD_decompress() only needs an upper bound of decompressed size.
126 * (For example, data could be necessarily cut into blocks <= 16 KB).
127 * note 3 : decompressed size is always present when compression is completed using single-pass functions,
128 * such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
129 * note 4 : decompressed size can be very large (64-bits value),
130 * potentially larger than what local system can handle as a single memory segment.
131 * In which case, it's necessary to use streaming mode to decompress data.
132 * note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
133 * Always ensure return value fits within application's authorized limits.
134 * Each application can set its own limits.
135 * note 6 : This function replaces ZSTD_getDecompressedSize() */
136#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
137#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
138ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
139
140/*! ZSTD_getDecompressedSize() :
141 * NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
142 * Both functions work the same way, but ZSTD_getDecompressedSize() blends
143 * "empty", "unknown" and "error" results to the same return value (0),
144 * while ZSTD_getFrameContentSize() gives them separate return values.
145 * @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. */
146ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
147
148
149/*====== Helper functions ======*/
150#define ZSTD_COMPRESSBOUND(srcSize) ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) /* 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 */
151ZSTDLIB_API size_t ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case single-pass scenario */
152ZSTDLIB_API unsigned ZSTD_isError(size_t code); /*!< tells if a `size_t` function result is an error code */
153ZSTDLIB_API const char* ZSTD_getErrorName(size_t code); /*!< provides readable string from an error code */
154ZSTDLIB_API int ZSTD_maxCLevel(void); /*!< maximum compression level available */
155
156
157/***************************************
158* Explicit context
159***************************************/
160/*= Compression context
161 * When compressing many times,
162 * it is recommended to allocate a context just once, and re-use it for each successive compression operation.
163 * This will make workload friendlier for system's memory.
164 * Use one context per thread for parallel execution in multi-threaded environments. */
165typedef struct ZSTD_CCtx_s ZSTD_CCtx;
166ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx(void);
167ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
168
169/*! ZSTD_compressCCtx() :
170 * Same as ZSTD_compress(), using an explicit ZSTD_CCtx
171 * The function will compress at requested compression level,
172 * ignoring any other parameter */
173ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
174 void* dst, size_t dstCapacity,
175 const void* src, size_t srcSize,
176 int compressionLevel);
177
178/*= Decompression context
179 * When decompressing many times,
180 * it is recommended to allocate a context only once,
181 * and re-use it for each successive compression operation.
182 * This will make workload friendlier for system's memory.
183 * Use one context per thread for parallel execution. */
184typedef struct ZSTD_DCtx_s ZSTD_DCtx;
185ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
186ZSTDLIB_API size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
187
188/*! ZSTD_decompressDCtx() :
189 * Same as ZSTD_decompress(),
190 * requires an allocated ZSTD_DCtx.
191 * Compatible with sticky parameters.
192 */
193ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
194 void* dst, size_t dstCapacity,
195 const void* src, size_t srcSize);
196
197
198/**************************
199* Simple dictionary API
200***************************/
201/*! ZSTD_compress_usingDict() :
202 * Compression at an explicit compression level using a Dictionary.
203 * A dictionary can be any arbitrary data segment (also called a prefix),
204 * or a buffer with specified information (see dictBuilder/zdict.h).
205 * Note : This function loads the dictionary, resulting in significant startup delay.
206 * It's intended for a dictionary used only once.
207 * Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. */
208ZSTDLIB_API size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
209 void* dst, size_t dstCapacity,
210 const void* src, size_t srcSize,
211 const void* dict,size_t dictSize,
212 int compressionLevel);
213
214/*! ZSTD_decompress_usingDict() :
215 * Decompression using a known Dictionary.
216 * Dictionary must be identical to the one used during compression.
217 * Note : This function loads the dictionary, resulting in significant startup delay.
218 * It's intended for a dictionary used only once.
219 * Note : When `dict == NULL || dictSize < 8` no dictionary is used. */
220ZSTDLIB_API size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
221 void* dst, size_t dstCapacity,
222 const void* src, size_t srcSize,
223 const void* dict,size_t dictSize);
224
225
226/***********************************
227 * Bulk processing dictionary API
228 **********************************/
229typedef struct ZSTD_CDict_s ZSTD_CDict;
230
231/*! ZSTD_createCDict() :
232 * When compressing multiple messages / blocks using the same dictionary, it's recommended to load it only once.
233 * ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup cost.
234 * ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
235 * `dictBuffer` can be released after ZSTD_CDict creation, because its content is copied within CDict.
236 * Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate `dictBuffer` content.
237 * Note : A ZSTD_CDict can be created from an empty dictBuffer, but it is inefficient when used to compress small data. */
238ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
239 int compressionLevel);
240
241/*! ZSTD_freeCDict() :
242 * Function frees memory allocated by ZSTD_createCDict(). */
243ZSTDLIB_API size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
244
245/*! ZSTD_compress_usingCDict() :
246 * Compression using a digested Dictionary.
247 * Recommended when same dictionary is used multiple times.
248 * Note : compression level is _decided at dictionary creation time_,
249 * and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) */
250ZSTDLIB_API size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
251 void* dst, size_t dstCapacity,
252 const void* src, size_t srcSize,
253 const ZSTD_CDict* cdict);
254
255
256typedef struct ZSTD_DDict_s ZSTD_DDict;
257
258/*! ZSTD_createDDict() :
259 * Create a digested dictionary, ready to start decompression operation without startup delay.
260 * dictBuffer can be released after DDict creation, as its content is copied inside DDict. */
261ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
262
263/*! ZSTD_freeDDict() :
264 * Function frees memory allocated with ZSTD_createDDict() */
265ZSTDLIB_API size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
266
267/*! ZSTD_decompress_usingDDict() :
268 * Decompression using a digested Dictionary.
269 * Recommended when same dictionary is used multiple times. */
270ZSTDLIB_API size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
271 void* dst, size_t dstCapacity,
272 const void* src, size_t srcSize,
273 const ZSTD_DDict* ddict);
274
275
276/****************************
277* Streaming
278****************************/
279
280typedef struct ZSTD_inBuffer_s {
281 const void* src; /**< start of input buffer */
282 size_t size; /**< size of input buffer */
283 size_t pos; /**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */
284} ZSTD_inBuffer;
285
286typedef struct ZSTD_outBuffer_s {
287 void* dst; /**< start of output buffer */
288 size_t size; /**< size of output buffer */
289 size_t pos; /**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */
290} ZSTD_outBuffer;
291
292
293
294/*-***********************************************************************
295* Streaming compression - HowTo
296*
297* A ZSTD_CStream object is required to track streaming operation.
298* Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
299* ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
300* It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
301*
302* For parallel execution, use one separate ZSTD_CStream per thread.
303*
304* note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
305*
306* Parameters are sticky : when starting a new compression on the same context,
307* it will re-use the same sticky parameters as previous compression session.
308* When in doubt, it's recommended to fully initialize the context before usage.
309* Use ZSTD_initCStream() to set the parameter to a selected compression level.
310* Use advanced API (ZSTD_CCtx_setParameter(), etc.) to set more specific parameters.
311*
312* Use ZSTD_compressStream() as many times as necessary to consume input stream.
313* The function will automatically update both `pos` fields within `input` and `output`.
314* Note that the function may not consume the entire input,
315* for example, because the output buffer is already full,
316* in which case `input.pos < input.size`.
317* The caller must check if input has been entirely consumed.
318* If not, the caller must make some room to receive more compressed data,
319* and then present again remaining input data.
320* @return : a size hint, preferred nb of bytes to use as input for next function call
321* or an error code, which can be tested using ZSTD_isError().
322* Note 1 : it's just a hint, to help latency a little, any value will work fine.
323* Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
324*
325* At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
326* using ZSTD_flushStream(). `output->pos` will be updated.
327* Note that, if `output->size` is too small, a single invocation of ZSTD_flushStream() might not be enough (return code > 0).
328* In which case, make some room to receive more compressed data, and call again ZSTD_flushStream().
329* @return : 0 if internal buffers are entirely flushed,
330* >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
331* or an error code, which can be tested using ZSTD_isError().
332*
333* ZSTD_endStream() instructs to finish a frame.
334* It will perform a flush and write frame epilogue.
335* The epilogue is required for decoders to consider a frame completed.
336* flush() operation is the same, and follows same rules as ZSTD_flushStream().
337* @return : 0 if frame fully completed and fully flushed,
338* >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
339* or an error code, which can be tested using ZSTD_isError().
340*
341* *******************************************************************/
342
343typedef ZSTD_CCtx ZSTD_CStream; /**< CCtx and CStream are now effectively same object (>= v1.3.0) */
344 /* Continue to distinguish them for compatibility with older versions <= v1.2.0 */
345/*===== ZSTD_CStream management functions =====*/
346ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void);
347ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
348
349/*===== Streaming compression functions =====*/
350ZSTDLIB_API size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
351ZSTDLIB_API size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
352ZSTDLIB_API size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
353ZSTDLIB_API size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
354
355ZSTDLIB_API size_t ZSTD_CStreamInSize(void); /**< recommended size for input buffer */
356ZSTDLIB_API size_t ZSTD_CStreamOutSize(void); /**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */
357
358
359
360/*-***************************************************************************
361* Streaming decompression - HowTo
362*
363* A ZSTD_DStream object is required to track streaming operations.
364* Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
365* ZSTD_DStream objects can be re-used multiple times.
366*
367* Use ZSTD_initDStream() to start a new decompression operation.
368* @return : recommended first input size
369* Alternatively, use advanced API to set specific properties.
370*
371* Use ZSTD_decompressStream() repetitively to consume your input.
372* The function will update both `pos` fields.
373* If `input.pos < input.size`, some input has not been consumed.
374* It's up to the caller to present again remaining data.
375* The function tries to flush all data decoded immediately, respecting output buffer size.
376* If `output.pos < output.size`, decoder has flushed everything it could.
377* But if `output.pos == output.size`, there might be some data left within internal buffers.,
378* In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
379* Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
380* @return : 0 when a frame is completely decoded and fully flushed,
381* or an error code, which can be tested using ZSTD_isError(),
382* or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
383* the return value is a suggested next input size (just a hint for better latency)
384* that will never request more than the remaining frame size.
385* *******************************************************************************/
386
387typedef ZSTD_DCtx ZSTD_DStream; /**< DCtx and DStream are now effectively same object (>= v1.3.0) */
388 /* For compatibility with versions <= v1.2.0, prefer differentiating them. */
389/*===== ZSTD_DStream management functions =====*/
390ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void);
391ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds);
392
393/*===== Streaming decompression functions =====*/
394ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds);
395ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
396
397ZSTDLIB_API size_t ZSTD_DStreamInSize(void); /*!< recommended size for input buffer */
398ZSTDLIB_API size_t ZSTD_DStreamOutSize(void); /*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */
399
400#endif /* ZSTD_H_235446 */
401
402
403
404
405/****************************************************************************************
406 * ADVANCED AND EXPERIMENTAL FUNCTIONS
407 ****************************************************************************************
408 * The definitions in the following section are considered experimental.
409 * They are provided for advanced scenarios.
410 * They should never be used with a dynamic library, as prototypes may change in the future.
411 * Use them only in association with static linking.
412 * ***************************************************************************************/
413
414#if defined(ZSTD_STATIC_LINKING_ONLY) && !defined(ZSTD_H_ZSTD_STATIC_LINKING_ONLY)
415#define ZSTD_H_ZSTD_STATIC_LINKING_ONLY
416
417
418/****************************************************************************************
419 * Candidate API for promotion to stable status
420 ****************************************************************************************
421 * The following symbols and constants form the "staging area" :
422 * they are considered to join "stable API" by v1.4.0.
423 * The proposal is written so that it can be made stable "as is",
424 * though it's still possible to suggest improvements.
425 * Staging is in fact last chance for changes,
426 * the API is locked once reaching "stable" status.
427 * ***************************************************************************************/
428
429
430/* === Constants === */
431
432/* all magic numbers are supposed read/written to/from files/memory using little-endian convention */
433#define ZSTD_MAGICNUMBER 0xFD2FB528 /* valid since v0.8.0 */
434#define ZSTD_MAGIC_DICTIONARY 0xEC30A437 /* valid since v0.7.0 */
435#define ZSTD_MAGIC_SKIPPABLE_START 0x184D2A50 /* all 16 values, from 0x184D2A50 to 0x184D2A5F, signal the beginning of a skippable frame */
436#define ZSTD_MAGIC_SKIPPABLE_MASK 0xFFFFFFF0
437
438#define ZSTD_BLOCKSIZELOG_MAX 17
439#define ZSTD_BLOCKSIZE_MAX (1<<ZSTD_BLOCKSIZELOG_MAX)
440
441
442/* === query limits === */
443
444ZSTDLIB_API int ZSTD_minCLevel(void); /*!< minimum negative compression level allowed */
445
446
447/* === frame size === */
448
449/*! ZSTD_findFrameCompressedSize() :
450 * `src` should point to the start of a ZSTD frame or skippable frame.
451 * `srcSize` must be >= first frame size
452 * @return : the compressed size of the first frame starting at `src`,
453 * suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
454 * or an error code if input is invalid */
455ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
456
457
458/* === Memory management === */
459
460/*! ZSTD_sizeof_*() :
461 * These functions give the _current_ memory usage of selected object.
462 * Note that object memory usage can evolve (increase or decrease) over time. */
463ZSTDLIB_API size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
464ZSTDLIB_API size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
465ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
466ZSTDLIB_API size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
467ZSTDLIB_API size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
468ZSTDLIB_API size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
469
470
471/***************************************
472* Advanced compression API
473***************************************/
474
475/* API design :
476 * Parameters are pushed one by one into an existing context,
477 * using ZSTD_CCtx_set*() functions.
478 * Pushed parameters are sticky : they are valid for next compressed frame, and any subsequent frame.
479 * "sticky" parameters are applicable to `ZSTD_compress2()` and `ZSTD_compressStream*()` !
480 * They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()
481 *
482 * It's possible to reset all parameters to "default" using ZSTD_CCtx_reset().
483 *
484 * This API supercedes all other "advanced" API entry points in the experimental section.
485 * In the future, we expect to remove from experimental API entry points which are redundant with this API.
486 */
487
488
489/* Compression strategies, listed from fastest to strongest */
490typedef enum { ZSTD_fast=1,
491 ZSTD_dfast=2,
492 ZSTD_greedy=3,
493 ZSTD_lazy=4,
494 ZSTD_lazy2=5,
495 ZSTD_btlazy2=6,
496 ZSTD_btopt=7,
497 ZSTD_btultra=8,
498 ZSTD_btultra2=9
499 /* note : new strategies _might_ be added in the future.
500 Only the order (from fast to strong) is guaranteed */
501} ZSTD_strategy;
502
503
504typedef enum {
505
506 /* compression parameters */
507 ZSTD_c_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table
508 * Default level is ZSTD_CLEVEL_DEFAULT==3.
509 * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
510 * Note 1 : it's possible to pass a negative compression level.
511 * Note 2 : setting a level sets all default values of other compression parameters */
512 ZSTD_c_windowLog=101, /* Maximum allowed back-reference distance, expressed as power of 2.
513 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
514 * Special: value 0 means "use default windowLog".
515 * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
516 * requires explicitly allowing such window size at decompression stage if using streaming. */
517 ZSTD_c_hashLog=102, /* Size of the initial probe table, as a power of 2.
518 * Resulting memory usage is (1 << (hashLog+2)).
519 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
520 * Larger tables improve compression ratio of strategies <= dFast,
521 * and improve speed of strategies > dFast.
522 * Special: value 0 means "use default hashLog". */
523 ZSTD_c_chainLog=103, /* Size of the multi-probe search table, as a power of 2.
524 * Resulting memory usage is (1 << (chainLog+2)).
525 * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
526 * Larger tables result in better and slower compression.
527 * This parameter is useless when using "fast" strategy.
528 * It's still useful when using "dfast" strategy,
529 * in which case it defines a secondary probe table.
530 * Special: value 0 means "use default chainLog". */
531 ZSTD_c_searchLog=104, /* Number of search attempts, as a power of 2.
532 * More attempts result in better and slower compression.
533 * This parameter is useless when using "fast" and "dFast" strategies.
534 * Special: value 0 means "use default searchLog". */
535 ZSTD_c_minMatch=105, /* Minimum size of searched matches.
536 * Note that Zstandard can still find matches of smaller size,
537 * it just tweaks its search algorithm to look for this size and larger.
538 * Larger values increase compression and decompression speed, but decrease ratio.
539 * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
540 * Note that currently, for all strategies < btopt, effective minimum is 4.
541 * , for all strategies > fast, effective maximum is 6.
542 * Special: value 0 means "use default minMatchLength". */
543 ZSTD_c_targetLength=106, /* Impact of this field depends on strategy.
544 * For strategies btopt, btultra & btultra2:
545 * Length of Match considered "good enough" to stop search.
546 * Larger values make compression stronger, and slower.
547 * For strategy fast:
548 * Distance between match sampling.
549 * Larger values make compression faster, and weaker.
550 * Special: value 0 means "use default targetLength". */
551 ZSTD_c_strategy=107, /* See ZSTD_strategy enum definition.
552 * The higher the value of selected strategy, the more complex it is,
553 * resulting in stronger and slower compression.
554 * Special: value 0 means "use default strategy". */
555
556 /* LDM mode parameters */
557 ZSTD_c_enableLongDistanceMatching=160, /* Enable long distance matching.
558 * This parameter is designed to improve compression ratio
559 * for large inputs, by finding large matches at long distance.
560 * It increases memory usage and window size.
561 * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
562 * except when expressly set to a different value. */
563 ZSTD_c_ldmHashLog=161, /* Size of the table for long distance matching, as a power of 2.
564 * Larger values increase memory usage and compression ratio,
565 * but decrease compression speed.
566 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
567 * default: windowlog - 7.
568 * Special: value 0 means "automatically determine hashlog". */
569 ZSTD_c_ldmMinMatch=162, /* Minimum match size for long distance matcher.
570 * Larger/too small values usually decrease compression ratio.
571 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
572 * Special: value 0 means "use default value" (default: 64). */
573 ZSTD_c_ldmBucketSizeLog=163, /* Log size of each bucket in the LDM hash table for collision resolution.
574 * Larger values improve collision resolution but decrease compression speed.
575 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
576 * Special: value 0 means "use default value" (default: 3). */
577 ZSTD_c_ldmHashRateLog=164, /* Frequency of inserting/looking up entries into the LDM hash table.
578 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
579 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
580 * Larger values improve compression speed.
581 * Deviating far from default value will likely result in a compression ratio decrease.
582 * Special: value 0 means "automatically determine hashRateLog". */
583
584 /* frame parameters */
585 ZSTD_c_contentSizeFlag=200, /* Content size will be written into frame header _whenever known_ (default:1)
586 * Content size must be known at the beginning of compression.
587 * This is automatically the case when using ZSTD_compress2(),
588 * For streaming variants, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
589 ZSTD_c_checksumFlag=201, /* A 32-bits checksum of content is written at end of frame (default:0) */
590 ZSTD_c_dictIDFlag=202, /* When applicable, dictionary's ID is written into frame header (default:1) */
591
592 /* multi-threading parameters */
593 /* These parameters are only useful if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).
594 * They return an error otherwise. */
595 ZSTD_c_nbWorkers=400, /* Select how many threads will be spawned to compress in parallel.
596 * When nbWorkers >= 1, triggers asynchronous mode when used with ZSTD_compressStream*() :
597 * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
598 * while compression work is performed in parallel, within worker threads.
599 * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
600 * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
601 * More workers improve speed, but also increase memory usage.
602 * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */
603 ZSTD_c_jobSize=401, /* Size of a compression job. This value is enforced only when nbWorkers >= 1.
604 * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
605 * 0 means default, which is dynamically determined based on compression parameters.
606 * Job size must be a minimum of overlap size, or 1 MB, whichever is largest.
607 * The minimum size is automatically and transparently enforced */
608 ZSTD_c_overlapLog=402, /* Control the overlap size, as a fraction of window size.
609 * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
610 * It helps preserve compression ratio, while each job is compressed in parallel.
611 * This value is enforced only when nbWorkers >= 1.
612 * Larger values increase compression ratio, but decrease speed.
613 * Possible values range from 0 to 9 :
614 * - 0 means "default" : value will be determined by the library, depending on strategy
615 * - 1 means "no overlap"
616 * - 9 means "full overlap", using a full window size.
617 * Each intermediate rank increases/decreases load size by a factor 2 :
618 * 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
619 * default value varies between 6 and 9, depending on strategy */
620
621 /* note : additional experimental parameters are also available
622 * within the experimental section of the API.
623 * At the time of this writing, they include :
624 * ZSTD_c_rsyncable
625 * ZSTD_c_format
626 * ZSTD_c_forceMaxWindow
627 * ZSTD_c_forceAttachDict
628 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
629 * note : never ever use experimentalParam? names directly;
630 * also, the enums values themselves are unstable and can still change.
631 */
632 ZSTD_c_experimentalParam1=500,
633 ZSTD_c_experimentalParam2=10,
634 ZSTD_c_experimentalParam3=1000,
635 ZSTD_c_experimentalParam4=1001
636} ZSTD_cParameter;
637
638
639typedef struct {
640 size_t error;
641 int lowerBound;
642 int upperBound;
643} ZSTD_bounds;
644
645/*! ZSTD_cParam_getBounds() :
646 * All parameters must belong to an interval with lower and upper bounds,
647 * otherwise they will either trigger an error or be automatically clamped.
648 * @return : a structure, ZSTD_bounds, which contains
649 * - an error status field, which must be tested using ZSTD_isError()
650 * - lower and upper bounds, both inclusive
651 */
652ZSTDLIB_API ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
653
654/*! ZSTD_CCtx_setParameter() :
655 * Set one compression parameter, selected by enum ZSTD_cParameter.
656 * All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
657 * Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
658 * Setting a parameter is generally only possible during frame initialization (before starting compression).
659 * Exception : when using multi-threading mode (nbWorkers >= 1),
660 * the following parameters can be updated _during_ compression (within same frame):
661 * => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
662 * new parameters will be active for next job only (after a flush()).
663 * @return : an error code (which can be tested using ZSTD_isError()).
664 */
665ZSTDLIB_API size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
666
667/*! ZSTD_CCtx_setPledgedSrcSize() :
668 * Total input data size to be compressed as a single frame.
669 * Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
670 * This value will also be controlled at end of frame, and trigger an error if not respected.
671 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
672 * Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
673 * In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
674 * ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
675 * Note 2 : pledgedSrcSize is only valid once, for the next frame.
676 * It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
677 * Note 3 : Whenever all input data is provided and consumed in a single round,
678 * for example with ZSTD_compress2(),
679 * or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
680 * this value is automatically overriden by srcSize instead.
681 */
682ZSTDLIB_API size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
683
684/*! ZSTD_CCtx_loadDictionary() :
685 * Create an internal CDict from `dict` buffer.
686 * Decompression will have to use same dictionary.
687 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
688 * Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
689 * meaning "return to no-dictionary mode".
690 * Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
691 * To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
692 * Note 2 : Loading a dictionary involves building tables.
693 * It's also a CPU consuming operation, with non-negligible impact on latency.
694 * Tables are dependent on compression parameters, and for this reason,
695 * compression parameters can no longer be changed after loading a dictionary.
696 * Note 3 :`dict` content will be copied internally.
697 * Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
698 * In such a case, dictionary buffer must outlive its users.
699 * Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
700 * to precisely select how dictionary content must be interpreted. */
701ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
702
703/*! ZSTD_CCtx_refCDict() :
704 * Reference a prepared dictionary, to be used for all next compressed frames.
705 * Note that compression parameters are enforced from within CDict,
706 * and supercede any compression parameter previously set within CCtx.
707 * The dictionary will remain valid for future compressed frames using same CCtx.
708 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
709 * Special : Referencing a NULL CDict means "return to no-dictionary mode".
710 * Note 1 : Currently, only one dictionary can be managed.
711 * Referencing a new dictionary effectively "discards" any previous one.
712 * Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. */
713ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
714
715/*! ZSTD_CCtx_refPrefix() :
716 * Reference a prefix (single-usage dictionary) for next compressed frame.
717 * A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
718 * Decompression will need same prefix to properly regenerate data.
719 * Compressing with a prefix is similar in outcome as performing a diff and compressing it,
720 * but performs much faster, especially during decompression (compression speed is tunable with compression level).
721 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
722 * Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
723 * Note 1 : Prefix buffer is referenced. It **must** outlive compression.
724 * Its content must remain unmodified during compression.
725 * Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
726 * ensure that the window size is large enough to contain the entire source.
727 * See ZSTD_c_windowLog.
728 * Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
729 * It's a CPU consuming operation, with non-negligible impact on latency.
730 * If there is a need to use the same prefix multiple times, consider loadDictionary instead.
731 * Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dm_rawContent).
732 * Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. */
733ZSTDLIB_API size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
734 const void* prefix, size_t prefixSize);
735
736
737typedef enum {
738 ZSTD_reset_session_only = 1,
739 ZSTD_reset_parameters = 2,
740 ZSTD_reset_session_and_parameters = 3
741} ZSTD_ResetDirective;
742
743/*! ZSTD_CCtx_reset() :
744 * There are 2 different things that can be reset, independently or jointly :
745 * - The session : will stop compressing current frame, and make CCtx ready to start a new one.
746 * Useful after an error, or to interrupt any ongoing compression.
747 * Any internal data not yet flushed is cancelled.
748 * Compression parameters and dictionary remain unchanged.
749 * They will be used to compress next frame.
750 * Resetting session never fails.
751 * - The parameters : changes all parameters back to "default".
752 * This removes any reference to any dictionary too.
753 * Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
754 * otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
755 * - Both : similar to resetting the session, followed by resetting parameters.
756 */
757ZSTDLIB_API size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
758
759
760
761/*! ZSTD_compress2() :
762 * Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
763 * ZSTD_compress2() always starts a new frame.
764 * Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
765 * - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
766 * - The function is always blocking, returns when compression is completed.
767 * Hint : compression runs faster if `dstCapacity` >= `ZSTD_compressBound(srcSize)`.
768 * @return : compressed size written into `dst` (<= `dstCapacity),
769 * or an error code if it fails (which can be tested using ZSTD_isError()).
770 */
771ZSTDLIB_API size_t ZSTD_compress2( ZSTD_CCtx* cctx,
772 void* dst, size_t dstCapacity,
773 const void* src, size_t srcSize);
774
775typedef enum {
776 ZSTD_e_continue=0, /* collect more data, encoder decides when to output compressed result, for optimal compression ratio */
777 ZSTD_e_flush=1, /* flush any data provided so far,
778 * it creates (at least) one new block, that can be decoded immediately on reception;
779 * frame will continue: any future data can still reference previously compressed data, improving compression. */
780 ZSTD_e_end=2 /* flush any remaining data _and_ close current frame.
781 * note that frame is only closed after compressed data is fully flushed (return value == 0).
782 * After that point, any additional data starts a new frame.
783 * note : each frame is independent (does not reference any content from previous frame). */
784} ZSTD_EndDirective;
785
786/*! ZSTD_compressStream2() :
787 * Behaves about the same as ZSTD_compressStream, with additional control on end directive.
788 * - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
789 * - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
790 * - outpot->pos must be <= dstCapacity, input->pos must be <= srcSize
791 * - outpot->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
792 * - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
793 * - When nbWorkers>=1, function is non-blocking : it just acquires a copy of input, and distributes jobs to internal worker threads, flush whatever is available,
794 * and then immediately returns, just indicating that there is some data remaining to be flushed.
795 * The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
796 * - 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.
797 * - @return provides a minimum amount of data remaining to be flushed from internal buffers
798 * or an error code, which can be tested using ZSTD_isError().
799 * if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
800 * This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
801 * For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
802 * - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
803 * only ZSTD_e_end or ZSTD_e_flush operations are allowed.
804 * Before starting a new compression job, or changing compression parameters,
805 * it is required to fully flush internal buffers.
806 */
807ZSTDLIB_API size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
808 ZSTD_outBuffer* output,
809 ZSTD_inBuffer* input,
810 ZSTD_EndDirective endOp);
811
812
813
814/* ============================== */
815/* Advanced decompression API */
816/* ============================== */
817
818/* The advanced API pushes parameters one by one into an existing DCtx context.
819 * Parameters are sticky, and remain valid for all following frames
820 * using the same DCtx context.
821 * It's possible to reset parameters to default values using ZSTD_DCtx_reset().
822 * Note : This API is compatible with existing ZSTD_decompressDCtx() and ZSTD_decompressStream().
823 * Therefore, no new decompression function is necessary.
824 */
825
826
827typedef enum {
828
829 ZSTD_d_windowLogMax=100, /* Select a size limit (in power of 2) beyond which
830 * the streaming API will refuse to allocate memory buffer
831 * in order to protect the host from unreasonable memory requirements.
832 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
833 * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) */
834
835 /* note : additional experimental parameters are also available
836 * within the experimental section of the API.
837 * At the time of this writing, they include :
838 * ZSTD_c_format
839 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
840 * note : never ever use experimentalParam? names directly
841 */
842 ZSTD_d_experimentalParam1=1000
843
844} ZSTD_dParameter;
845
846
847/*! ZSTD_dParam_getBounds() :
848 * All parameters must belong to an interval with lower and upper bounds,
849 * otherwise they will either trigger an error or be automatically clamped.
850 * @return : a structure, ZSTD_bounds, which contains
851 * - an error status field, which must be tested using ZSTD_isError()
852 * - both lower and upper bounds, inclusive
853 */
854ZSTDLIB_API ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
855
856/*! ZSTD_DCtx_setParameter() :
857 * Set one compression parameter, selected by enum ZSTD_dParameter.
858 * All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
859 * Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
860 * Setting a parameter is only possible during frame initialization (before starting decompression).
861 * @return : 0, or an error code (which can be tested using ZSTD_isError()).
862 */
863ZSTDLIB_API size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
864
865
866/*! ZSTD_DCtx_loadDictionary() :
867 * Create an internal DDict from dict buffer,
868 * to be used to decompress next frames.
869 * The dictionary remains valid for all future frames, until explicitly invalidated.
870 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
871 * Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
872 * meaning "return to no-dictionary mode".
873 * Note 1 : Loading a dictionary involves building tables,
874 * which has a non-negligible impact on CPU usage and latency.
875 * It's recommended to "load once, use many times", to amortize the cost
876 * Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
877 * Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
878 * Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
879 * how dictionary content is loaded and interpreted.
880 */
881ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
882
883/*! ZSTD_DCtx_refDDict() :
884 * Reference a prepared dictionary, to be used to decompress next frames.
885 * The dictionary remains active for decompression of future frames using same DCtx.
886 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
887 * Note 1 : Currently, only one dictionary can be managed.
888 * Referencing a new dictionary effectively "discards" any previous one.
889 * Special: referencing a NULL DDict means "return to no-dictionary mode".
890 * Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
891 */
892ZSTDLIB_API size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
893
894/*! ZSTD_DCtx_refPrefix() :
895 * Reference a prefix (single-usage dictionary) to decompress next frame.
896 * This is the reverse operation of ZSTD_CCtx_refPrefix(),
897 * and must use the same prefix as the one used during compression.
898 * Prefix is **only used once**. Reference is discarded at end of frame.
899 * End of frame is reached when ZSTD_decompressStream() returns 0.
900 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
901 * Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
902 * Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
903 * Prefix buffer must remain unmodified up to the end of frame,
904 * reached when ZSTD_decompressStream() returns 0.
905 * Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
906 * Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
907 * Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
908 * A full dictionary is more costly, as it requires building tables.
909 */
910ZSTDLIB_API size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
911 const void* prefix, size_t prefixSize);
912
913/*! ZSTD_DCtx_reset() :
914 * Return a DCtx to clean state.
915 * Session and parameters can be reset jointly or separately.
916 * Parameters can only be reset when no active frame is being decompressed.
917 * @return : 0, or an error code, which can be tested with ZSTD_isError()
918 */
919ZSTDLIB_API size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
920
921
922
923/****************************************************************************************
924 * experimental API (static linking only)
925 ****************************************************************************************
926 * The following symbols and constants
927 * are not planned to join "stable API" status in the near future.
928 * They can still change in future versions.
929 * Some of them are planned to remain in the static_only section indefinitely.
930 * Some of them might be removed in the future (especially when redundant with existing stable functions)
931 * ***************************************************************************************/
932
933#define ZSTD_FRAMEHEADERSIZE_PREFIX 5 /* minimum input size required to query frame header size */
934#define ZSTD_FRAMEHEADERSIZE_MIN 6
935#define ZSTD_FRAMEHEADERSIZE_MAX 18 /* can be useful for static allocation */
936#define ZSTD_SKIPPABLEHEADERSIZE 8
937
938/* compression parameter bounds */
939#define ZSTD_WINDOWLOG_MAX_32 30
940#define ZSTD_WINDOWLOG_MAX_64 31
941#define ZSTD_WINDOWLOG_MAX ((int)(sizeof(size_t) == 4 ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
942#define ZSTD_WINDOWLOG_MIN 10
943#define ZSTD_HASHLOG_MAX ((ZSTD_WINDOWLOG_MAX < 30) ? ZSTD_WINDOWLOG_MAX : 30)
944#define ZSTD_HASHLOG_MIN 6
945#define ZSTD_CHAINLOG_MAX_32 29
946#define ZSTD_CHAINLOG_MAX_64 30
947#define ZSTD_CHAINLOG_MAX ((int)(sizeof(size_t) == 4 ? ZSTD_CHAINLOG_MAX_32 : ZSTD_CHAINLOG_MAX_64))
948#define ZSTD_CHAINLOG_MIN ZSTD_HASHLOG_MIN
949#define ZSTD_SEARCHLOG_MAX (ZSTD_WINDOWLOG_MAX-1)
950#define ZSTD_SEARCHLOG_MIN 1
951#define ZSTD_MINMATCH_MAX 7 /* only for ZSTD_fast, other strategies are limited to 6 */
952#define ZSTD_MINMATCH_MIN 3 /* only for ZSTD_btopt+, faster strategies are limited to 4 */
953#define ZSTD_TARGETLENGTH_MAX ZSTD_BLOCKSIZE_MAX
954#define ZSTD_TARGETLENGTH_MIN 0 /* note : comparing this constant to an unsigned results in a tautological test */
955#define ZSTD_STRATEGY_MIN ZSTD_fast
956#define ZSTD_STRATEGY_MAX ZSTD_btultra2
957
958
959#define ZSTD_OVERLAPLOG_MIN 0
960#define ZSTD_OVERLAPLOG_MAX 9
961
962#define ZSTD_WINDOWLOG_LIMIT_DEFAULT 27 /* by default, the streaming decoder will refuse any frame
963 * requiring larger than (1<<ZSTD_WINDOWLOG_LIMIT_DEFAULT) window size,
964 * to preserve host's memory from unreasonable requirements.
965 * This limit can be overriden using ZSTD_DCtx_setParameter(,ZSTD_d_windowLogMax,).
966 * The limit does not apply for one-pass decoders (such as ZSTD_decompress()), since no additional memory is allocated */
967
968
969/* LDM parameter bounds */
970#define ZSTD_LDM_HASHLOG_MIN ZSTD_HASHLOG_MIN
971#define ZSTD_LDM_HASHLOG_MAX ZSTD_HASHLOG_MAX
972#define ZSTD_LDM_MINMATCH_MIN 4
973#define ZSTD_LDM_MINMATCH_MAX 4096
974#define ZSTD_LDM_BUCKETSIZELOG_MIN 1
975#define ZSTD_LDM_BUCKETSIZELOG_MAX 8
976#define ZSTD_LDM_HASHRATELOG_MIN 0
977#define ZSTD_LDM_HASHRATELOG_MAX (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN)
978
979/* internal */
980#define ZSTD_HASHLOG3_MAX 17
981
982
983/* --- Advanced types --- */
984
985typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;
986
987typedef struct {
988 unsigned windowLog; /**< largest match distance : larger == more compression, more memory needed during decompression */
989 unsigned chainLog; /**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */
990 unsigned hashLog; /**< dispatch table : larger == faster, more memory */
991 unsigned searchLog; /**< nb of searches : larger == more compression, slower */
992 unsigned minMatch; /**< match length searched : larger == faster decompression, sometimes less compression */
993 unsigned targetLength; /**< acceptable match size for optimal parser (only) : larger == more compression, slower */
994 ZSTD_strategy strategy; /**< see ZSTD_strategy definition above */
995} ZSTD_compressionParameters;
996
997typedef struct {
998 int contentSizeFlag; /**< 1: content size will be in frame header (when known) */
999 int checksumFlag; /**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */
1000 int noDictIDFlag; /**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */
1001} ZSTD_frameParameters;
1002
1003typedef struct {
1004 ZSTD_compressionParameters cParams;
1005 ZSTD_frameParameters fParams;
1006} ZSTD_parameters;
1007
1008typedef enum {
1009 ZSTD_dct_auto = 0, /* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */
1010 ZSTD_dct_rawContent = 1, /* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */
1011 ZSTD_dct_fullDict = 2 /* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */
1012} ZSTD_dictContentType_e;
1013
1014typedef enum {
1015 ZSTD_dlm_byCopy = 0, /**< Copy dictionary content internally */
1016 ZSTD_dlm_byRef = 1, /**< Reference dictionary content -- the dictionary buffer must outlive its users. */
1017} ZSTD_dictLoadMethod_e;
1018
1019typedef enum {
1020 /* Opened question : should we have a format ZSTD_f_auto ?
1021 * Today, it would mean exactly the same as ZSTD_f_zstd1.
1022 * But, in the future, should several formats become supported,
1023 * on the compression side, it would mean "default format".
1024 * On the decompression side, it would mean "automatic format detection",
1025 * so that ZSTD_f_zstd1 would mean "accept *only* zstd frames".
1026 * Since meaning is a little different, another option could be to define different enums for compression and decompression.
1027 * This question could be kept for later, when there are actually multiple formats to support,
1028 * but there is also the question of pinning enum values, and pinning value `0` is especially important */
1029 ZSTD_f_zstd1 = 0, /* zstd frame format, specified in zstd_compression_format.md (default) */
1030 ZSTD_f_zstd1_magicless = 1, /* Variant of zstd frame format, without initial 4-bytes magic number.
1031 * Useful to save 4 bytes per generated frame.
1032 * Decoder cannot recognise automatically this format, requiring this instruction. */
1033} ZSTD_format_e;
1034
1035typedef enum {
1036 /* Note: this enum and the behavior it controls are effectively internal
1037 * implementation details of the compressor. They are expected to continue
1038 * to evolve and should be considered only in the context of extremely
1039 * advanced performance tuning.
1040 *
1041 * Zstd currently supports the use of a CDict in two ways:
1042 *
1043 * - The contents of the CDict can be copied into the working context. This
1044 * means that the compression can search both the dictionary and input
1045 * while operating on a single set of internal tables. This makes
1046 * the compression faster per-byte of input. However, the initial copy of
1047 * the CDict's tables incurs a fixed cost at the beginning of the
1048 * compression. For small compressions (< 8 KB), that copy can dominate
1049 * the cost of the compression.
1050 *
1051 * - The CDict's tables can be used in-place. In this model, compression is
1052 * slower per input byte, because the compressor has to search two sets of
1053 * tables. However, this model incurs no start-up cost (as long as the
1054 * working context's tables can be reused). For small inputs, this can be
1055 * faster than copying the CDict's tables.
1056 *
1057 * Zstd has a simple internal heuristic that selects which strategy to use
1058 * at the beginning of a compression. However, if experimentation shows that
1059 * Zstd is making poor choices, it is possible to override that choice with
1060 * this enum.
1061 */
1062 ZSTD_dictDefaultAttach = 0, /* Use the default heuristic. */
1063 ZSTD_dictForceAttach = 1, /* Never copy the dictionary. */
1064 ZSTD_dictForceCopy = 2, /* Always copy the dictionary. */
1065} ZSTD_dictAttachPref_e;
1066
1067
1068/***************************************
1069* Frame size functions
1070***************************************/
1071
1072/*! ZSTD_findDecompressedSize() :
1073 * `src` should point the start of a series of ZSTD encoded and/or skippable frames
1074 * `srcSize` must be the _exact_ size of this series
1075 * (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
1076 * @return : - decompressed size of all data in all successive frames
1077 * - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1078 * - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1079 *
1080 * note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1081 * When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1082 * In which case, it's necessary to use streaming mode to decompress data.
1083 * note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1084 * note 3 : decompressed size can be very large (64-bits value),
1085 * potentially larger than what local system can handle as a single memory segment.
1086 * In which case, it's necessary to use streaming mode to decompress data.
1087 * note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1088 * Always ensure result fits within application's authorized limits.
1089 * Each application can set its own limits.
1090 * note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1091 * read each contained frame header. This is fast as most of the data is skipped,
1092 * however it does mean that all frame data must be present and valid. */
1093ZSTDLIB_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1094
1095/*! ZSTD_frameHeaderSize() :
1096 * srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1097 * @return : size of the Frame Header,
1098 * or an error code (if srcSize is too small) */
1099ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1100
1101
1102/***************************************
1103* Memory management
1104***************************************/
1105
1106/*! ZSTD_estimate*() :
1107 * These functions make it possible to estimate memory usage
1108 * of a future {D,C}Ctx, before its creation.
1109 * ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
1110 * It will also consider src size to be arbitrarily "large", which is worst case.
1111 * If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
1112 * ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1113 * 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_c_nbWorkers is >= 1.
1114 * Note : CCtx size estimation is only correct for single-threaded compression. */
1115ZSTDLIB_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
1116ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1117ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1118ZSTDLIB_API size_t ZSTD_estimateDCtxSize(void);
1119
1120/*! ZSTD_estimateCStreamSize() :
1121 * ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1122 * It will also consider src size to be arbitrarily "large", which is worst case.
1123 * If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1124 * ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1125 * 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_c_nbWorkers is >= 1.
1126 * Note : CStream size estimation is only correct for single-threaded compression.
1127 * ZSTD_DStream memory budget depends on window Size.
1128 * This information can be passed manually, using ZSTD_estimateDStreamSize,
1129 * or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1130 * Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1131 * an internal ?Dict will be created, which additional size is not estimated here.
1132 * In this case, get total size by adding ZSTD_estimate?DictSize */
1133ZSTDLIB_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
1134ZSTDLIB_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1135ZSTDLIB_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1136ZSTDLIB_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
1137ZSTDLIB_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1138
1139/*! ZSTD_estimate?DictSize() :
1140 * ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1141 * ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1142 * Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1143 */
1144ZSTDLIB_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1145ZSTDLIB_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1146ZSTDLIB_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1147
1148/*! ZSTD_initStatic*() :
1149 * Initialize an object using a pre-allocated fixed-size buffer.
1150 * workspace: The memory area to emplace the object into.
1151 * Provided pointer *must be 8-bytes aligned*.
1152 * Buffer must outlive object.
1153 * workspaceSize: Use ZSTD_estimate*Size() to determine
1154 * how large workspace must be to support target scenario.
1155 * @return : pointer to object (same address as workspace, just different type),
1156 * or NULL if error (size too small, incorrect alignment, etc.)
1157 * Note : zstd will never resize nor malloc() when using a static buffer.
1158 * If the object requires more memory than available,
1159 * zstd will just error out (typically ZSTD_error_memory_allocation).
1160 * Note 2 : there is no corresponding "free" function.
1161 * Since workspace is allocated externally, it must be freed externally too.
1162 * Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1163 * into its associated cParams.
1164 * Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1165 * ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1166 * Limitation 2 : static cctx currently not compatible with multi-threading.
1167 * Limitation 3 : static dctx is incompatible with legacy support.
1168 */
1169ZSTDLIB_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1170ZSTDLIB_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); /**< same as ZSTD_initStaticCCtx() */
1171
1172ZSTDLIB_API ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);
1173ZSTDLIB_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); /**< same as ZSTD_initStaticDCtx() */
1174
1175ZSTDLIB_API const ZSTD_CDict* ZSTD_initStaticCDict(
1176 void* workspace, size_t workspaceSize,
1177 const void* dict, size_t dictSize,
1178 ZSTD_dictLoadMethod_e dictLoadMethod,
1179 ZSTD_dictContentType_e dictContentType,
1180 ZSTD_compressionParameters cParams);
1181
1182ZSTDLIB_API const ZSTD_DDict* ZSTD_initStaticDDict(
1183 void* workspace, size_t workspaceSize,
1184 const void* dict, size_t dictSize,
1185 ZSTD_dictLoadMethod_e dictLoadMethod,
1186 ZSTD_dictContentType_e dictContentType);
1187
1188
1189/*! Custom memory allocation :
1190 * These prototypes make it possible to pass your own allocation/free functions.
1191 * ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1192 * All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1193 */
1194typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1195typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
1196typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1197static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; /**< this constant defers to stdlib's functions */
1198
1199ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
1200ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
1201ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
1202ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
1203
1204ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
1205 ZSTD_dictLoadMethod_e dictLoadMethod,
1206 ZSTD_dictContentType_e dictContentType,
1207 ZSTD_compressionParameters cParams,
1208 ZSTD_customMem customMem);
1209
1210ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
1211 ZSTD_dictLoadMethod_e dictLoadMethod,
1212 ZSTD_dictContentType_e dictContentType,
1213 ZSTD_customMem customMem);
1214
1215
1216
1217/***************************************
1218* Advanced compression functions
1219***************************************/
1220
1221/*! ZSTD_createCDict_byReference() :
1222 * Create a digested dictionary for compression
1223 * Dictionary content is just referenced, not duplicated.
1224 * As a consequence, `dictBuffer` **must** outlive CDict,
1225 * and its content must remain unmodified throughout the lifetime of CDict. */
1226ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1227
1228/*! ZSTD_getCParams() :
1229* @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1230* `estimatedSrcSize` value is optional, select 0 if not known */
1231ZSTDLIB_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1232
1233/*! ZSTD_getParams() :
1234* same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1235* All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 */
1236ZSTDLIB_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1237
1238/*! ZSTD_checkCParams() :
1239* Ensure param values remain within authorized range */
1240ZSTDLIB_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1241
1242/*! ZSTD_adjustCParams() :
1243 * optimize params for a given `srcSize` and `dictSize`.
1244 * both values are optional, select `0` if unknown. */
1245ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1246
1247/*! ZSTD_compress_advanced() :
1248 * Same as ZSTD_compress_usingDict(), with fine-tune control over compression parameters (by structure) */
1249ZSTDLIB_API size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1250 void* dst, size_t dstCapacity,
1251 const void* src, size_t srcSize,
1252 const void* dict,size_t dictSize,
1253 ZSTD_parameters params);
1254
1255/*! ZSTD_compress_usingCDict_advanced() :
1256 * Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters */
1257ZSTDLIB_API size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1258 void* dst, size_t dstCapacity,
1259 const void* src, size_t srcSize,
1260 const ZSTD_CDict* cdict,
1261 ZSTD_frameParameters fParams);
1262
1263
1264/*! ZSTD_CCtx_loadDictionary_byReference() :
1265 * Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1266 * It saves some memory, but also requires that `dict` outlives its usage within `cctx` */
1267ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1268
1269/*! ZSTD_CCtx_loadDictionary_advanced() :
1270 * Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1271 * how to load the dictionary (by copy ? by reference ?)
1272 * and how to interpret it (automatic ? force raw mode ? full mode only ?) */
1273ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1274
1275/*! ZSTD_CCtx_refPrefix_advanced() :
1276 * Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1277 * how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
1278ZSTDLIB_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1279
1280/* === experimental parameters === */
1281/* these parameters can be used with ZSTD_setParameter()
1282 * they are not guaranteed to remain supported in the future */
1283
1284 /* Enables rsyncable mode,
1285 * which makes compressed files more rsync friendly
1286 * by adding periodic synchronization points to the compressed data.
1287 * The target average block size is ZSTD_c_jobSize / 2.
1288 * It's possible to modify the job size to increase or decrease
1289 * the granularity of the synchronization point.
1290 * Once the jobSize is smaller than the window size,
1291 * it will result in compression ratio degradation.
1292 * NOTE 1: rsyncable mode only works when multithreading is enabled.
1293 * NOTE 2: rsyncable performs poorly in combination with long range mode,
1294 * since it will decrease the effectiveness of synchronization points,
1295 * though mileage may vary.
1296 * NOTE 3: Rsyncable mode limits maximum compression speed to ~400 MB/s.
1297 * If the selected compression level is already running significantly slower,
1298 * the overall speed won't be significantly impacted.
1299 */
1300 #define ZSTD_c_rsyncable ZSTD_c_experimentalParam1
1301
1302/* Select a compression format.
1303 * The value must be of type ZSTD_format_e.
1304 * See ZSTD_format_e enum definition for details */
1305#define ZSTD_c_format ZSTD_c_experimentalParam2
1306
1307/* Force back-reference distances to remain < windowSize,
1308 * even when referencing into Dictionary content (default:0) */
1309#define ZSTD_c_forceMaxWindow ZSTD_c_experimentalParam3
1310
1311/* Controls whether the contents of a CDict
1312 * are used in place, or copied into the working context.
1313 * Accepts values from the ZSTD_dictAttachPref_e enum.
1314 * See the comments on that enum for an explanation of the feature. */
1315#define ZSTD_c_forceAttachDict ZSTD_c_experimentalParam4
1316
1317/*! ZSTD_CCtx_getParameter() :
1318 * Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1319 * and store it into int* value.
1320 * @return : 0, or an error code (which can be tested with ZSTD_isError()).
1321 */
1322ZSTDLIB_API size_t ZSTD_CCtx_getParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1323
1324
1325/*! ZSTD_CCtx_params :
1326 * Quick howto :
1327 * - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1328 * - ZSTD_CCtxParam_setParameter() : Push parameters one by one into
1329 * an existing ZSTD_CCtx_params structure.
1330 * This is similar to
1331 * ZSTD_CCtx_setParameter().
1332 * - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1333 * an existing CCtx.
1334 * These parameters will be applied to
1335 * all subsequent frames.
1336 * - ZSTD_compressStream2() : Do compression using the CCtx.
1337 * - ZSTD_freeCCtxParams() : Free the memory.
1338 *
1339 * This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1340 * for static allocation of CCtx for single-threaded compression.
1341 */
1342ZSTDLIB_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1343ZSTDLIB_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params);
1344
1345/*! ZSTD_CCtxParams_reset() :
1346 * Reset params to default values.
1347 */
1348ZSTDLIB_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1349
1350/*! ZSTD_CCtxParams_init() :
1351 * Initializes the compression parameters of cctxParams according to
1352 * compression level. All other parameters are reset to their default values.
1353 */
1354ZSTDLIB_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1355
1356/*! ZSTD_CCtxParams_init_advanced() :
1357 * Initializes the compression and frame parameters of cctxParams according to
1358 * params. All other parameters are reset to their default values.
1359 */
1360ZSTDLIB_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1361
1362/*! ZSTD_CCtxParam_setParameter() :
1363 * Similar to ZSTD_CCtx_setParameter.
1364 * Set one compression parameter, selected by enum ZSTD_cParameter.
1365 * Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams().
1366 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1367 */
1368ZSTDLIB_API size_t ZSTD_CCtxParam_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1369
1370/*! ZSTD_CCtxParam_getParameter() :
1371 * Similar to ZSTD_CCtx_getParameter.
1372 * Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1373 * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1374 */
1375ZSTDLIB_API size_t ZSTD_CCtxParam_getParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1376
1377/*! ZSTD_CCtx_setParametersUsingCCtxParams() :
1378 * Apply a set of ZSTD_CCtx_params to the compression context.
1379 * This can be done even after compression is started,
1380 * if nbWorkers==0, this will have no impact until a new compression is started.
1381 * if nbWorkers>=1, new parameters will be picked up at next job,
1382 * with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1383 */
1384ZSTDLIB_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1385 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1386
1387/*! ZSTD_compressStream2_simpleArgs() :
1388 * Same as ZSTD_compressStream2(),
1389 * but using only integral types as arguments.
1390 * This variant might be helpful for binders from dynamic languages
1391 * which have troubles handling structures containing memory pointers.
1392 */
1393ZSTDLIB_API size_t ZSTD_compressStream2_simpleArgs (
1394 ZSTD_CCtx* cctx,
1395 void* dst, size_t dstCapacity, size_t* dstPos,
1396 const void* src, size_t srcSize, size_t* srcPos,
1397 ZSTD_EndDirective endOp);
1398
1399
1400/***************************************
1401* Advanced decompression functions
1402***************************************/
1403
1404/*! ZSTD_isFrame() :
1405 * Tells if the content of `buffer` starts with a valid Frame Identifier.
1406 * Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1407 * Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1408 * Note 3 : Skippable Frame Identifiers are considered valid. */
1409ZSTDLIB_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
1410
1411/*! ZSTD_createDDict_byReference() :
1412 * Create a digested dictionary, ready to start decompression operation without startup delay.
1413 * Dictionary content is referenced, and therefore stays in dictBuffer.
1414 * It is important that dictBuffer outlives DDict,
1415 * it must remain read accessible throughout the lifetime of DDict */
1416ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1417
1418
1419/*! ZSTD_getDictID_fromDict() :
1420 * Provides the dictID stored within dictionary.
1421 * if @return == 0, the dictionary is not conformant with Zstandard specification.
1422 * It can still be loaded, but as a content-only dictionary. */
1423ZSTDLIB_API unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
1424
1425/*! ZSTD_getDictID_fromDDict() :
1426 * Provides the dictID of the dictionary loaded into `ddict`.
1427 * If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
1428 * Non-conformant dictionaries can still be loaded, but as content-only dictionaries. */
1429ZSTDLIB_API unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
1430
1431/*! ZSTD_getDictID_fromFrame() :
1432 * Provides the dictID required to decompressed the frame stored within `src`.
1433 * If @return == 0, the dictID could not be decoded.
1434 * This could for one of the following reasons :
1435 * - The frame does not require a dictionary to be decoded (most common case).
1436 * - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
1437 * Note : this use case also happens when using a non-conformant dictionary.
1438 * - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
1439 * - This is not a Zstandard frame.
1440 * When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. */
1441ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
1442
1443/*! ZSTD_DCtx_loadDictionary_byReference() :
1444 * Same as ZSTD_DCtx_loadDictionary(),
1445 * but references `dict` content instead of copying it into `dctx`.
1446 * This saves memory if `dict` remains around.,
1447 * However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. */
1448ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1449
1450/*! ZSTD_DCtx_loadDictionary_advanced() :
1451 * Same as ZSTD_DCtx_loadDictionary(),
1452 * but gives direct control over
1453 * how to load the dictionary (by copy ? by reference ?)
1454 * and how to interpret it (automatic ? force raw mode ? full mode only ?). */
1455ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1456
1457/*! ZSTD_DCtx_refPrefix_advanced() :
1458 * Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1459 * how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
1460ZSTDLIB_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1461
1462/*! ZSTD_DCtx_setMaxWindowSize() :
1463 * Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1464 * This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1465 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1466 * By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1467 * @return : 0, or an error code (which can be tested using ZSTD_isError()).
1468 */
1469ZSTDLIB_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1470
1471/* ZSTD_d_format
1472 * experimental parameter,
1473 * allowing selection between ZSTD_format_e input compression formats
1474 */
1475#define ZSTD_d_format ZSTD_d_experimentalParam1
1476
1477/*! ZSTD_DCtx_setFormat() :
1478 * Instruct the decoder context about what kind of data to decode next.
1479 * This instruction is mandatory to decode data without a fully-formed header,
1480 * such ZSTD_f_zstd1_magicless for example.
1481 * @return : 0, or an error code (which can be tested using ZSTD_isError()). */
1482ZSTDLIB_API size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1483
1484/*! ZSTD_decompressStream_simpleArgs() :
1485 * Same as ZSTD_decompressStream(),
1486 * but using only integral types as arguments.
1487 * This can be helpful for binders from dynamic languages
1488 * which have troubles handling structures containing memory pointers.
1489 */
1490ZSTDLIB_API size_t ZSTD_decompressStream_simpleArgs (
1491 ZSTD_DCtx* dctx,
1492 void* dst, size_t dstCapacity, size_t* dstPos,
1493 const void* src, size_t srcSize, size_t* srcPos);
1494
1495
1496/********************************************************************
1497* Advanced streaming functions
1498* Warning : most of these functions are now redundant with the Advanced API.
1499* Once Advanced API reaches "stable" status,
1500* redundant functions will be deprecated, and then at some point removed.
1501********************************************************************/
1502
1503/*===== Advanced Streaming compression functions =====*/
1504ZSTDLIB_API size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); /**< 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. */
1505ZSTDLIB_API size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); /**< 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.*/
1506ZSTDLIB_API size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
1507 ZSTD_parameters params, unsigned long long pledgedSrcSize); /**< 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. */
1508ZSTDLIB_API size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); /**< note : cdict will just be referenced, and must outlive compression session */
1509ZSTDLIB_API size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); /**< 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. */
1510
1511/*! ZSTD_resetCStream() :
1512 * start a new frame, using same parameters from previous frame.
1513 * This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
1514 * Note that zcs must be init at least once before using ZSTD_resetCStream().
1515 * If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1516 * If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1517 * For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1518 * but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1519 * @return : 0, or an error code (which can be tested using ZSTD_isError())
1520 */
1521ZSTDLIB_API size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1522
1523
1524typedef struct {
1525 unsigned long long ingested; /* nb input bytes read and buffered */
1526 unsigned long long consumed; /* nb input bytes actually compressed */
1527 unsigned long long produced; /* nb of compressed bytes generated and buffered */
1528 unsigned long long flushed; /* nb of compressed bytes flushed : not provided; can be tracked from caller side */
1529 unsigned currentJobID; /* MT only : latest started job nb */
1530 unsigned nbActiveWorkers; /* MT only : nb of workers actively compressing at probe time */
1531} ZSTD_frameProgression;
1532
1533/* ZSTD_getFrameProgression() :
1534 * tells how much data has been ingested (read from input)
1535 * consumed (input actually compressed) and produced (output) for current frame.
1536 * Note : (ingested - consumed) is amount of input data buffered internally, not yet compressed.
1537 * Aggregates progression inside active worker threads.
1538 */
1539ZSTDLIB_API ZSTD_frameProgression ZSTD_getFrameProgression(const ZSTD_CCtx* cctx);
1540
1541/*! ZSTD_toFlushNow() :
1542 * Tell how many bytes are ready to be flushed immediately.
1543 * Useful for multithreading scenarios (nbWorkers >= 1).
1544 * Probe the oldest active job, defined as oldest job not yet entirely flushed,
1545 * and check its output buffer.
1546 * @return : amount of data stored in oldest job and ready to be flushed immediately.
1547 * if @return == 0, it means either :
1548 * + there is no active job (could be checked with ZSTD_frameProgression()), or
1549 * + oldest job is still actively compressing data,
1550 * but everything it has produced has also been flushed so far,
1551 * therefore flush speed is limited by production speed of oldest job
1552 * irrespective of the speed of concurrent (and newer) jobs.
1553 */
1554ZSTDLIB_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1555
1556
1557/*===== Advanced Streaming decompression functions =====*/
1558ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); /**< note: no dictionary will be used if dict == NULL or dictSize < 8 */
1559ZSTDLIB_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); /**< note : ddict is referenced, it must outlive decompression session */
1560ZSTDLIB_API size_t ZSTD_resetDStream(ZSTD_DStream* zds); /**< re-use decompression parameters from previous init; saves dictionary loading */
1561
1562
1563/*********************************************************************
1564* Buffer-less and synchronous inner streaming functions
1565*
1566* This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
1567* But it's also a complex one, with several restrictions, documented below.
1568* Prefer normal streaming API for an easier experience.
1569********************************************************************* */
1570
1571/**
1572 Buffer-less streaming compression (synchronous mode)
1573
1574 A ZSTD_CCtx object is required to track streaming operations.
1575 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
1576 ZSTD_CCtx object can be re-used multiple times within successive compression operations.
1577
1578 Start by initializing a context.
1579 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
1580 or ZSTD_compressBegin_advanced(), for finer parameter control.
1581 It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
1582
1583 Then, consume your input using ZSTD_compressContinue().
1584 There are some important considerations to keep in mind when using this advanced function :
1585 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
1586 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
1587 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
1588 Worst case evaluation is provided by ZSTD_compressBound().
1589 ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
1590 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
1591 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
1592 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
1593 In which case, it will "discard" the relevant memory section from its history.
1594
1595 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
1596 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
1597 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
1598
1599 `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
1600*/
1601
1602/*===== Buffer-less streaming compression functions =====*/
1603ZSTDLIB_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
1604ZSTDLIB_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
1605ZSTDLIB_API size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); /**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */
1606ZSTDLIB_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); /**< note: fails if cdict==NULL */
1607ZSTDLIB_API size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); /* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */
1608ZSTDLIB_API size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); /**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */
1609
1610ZSTDLIB_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1611ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1612
1613
1614/*-
1615 Buffer-less streaming decompression (synchronous mode)
1616
1617 A ZSTD_DCtx object is required to track streaming operations.
1618 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
1619 A ZSTD_DCtx object can be re-used multiple times.
1620
1621 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
1622 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
1623 Data fragment must be large enough to ensure successful decoding.
1624 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
1625 @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
1626 >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
1627 errorCode, which can be tested using ZSTD_isError().
1628
1629 It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
1630 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
1631 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
1632 As a consequence, check that values remain within valid application range.
1633 For example, do not allocate memory blindly, check that `windowSize` is within expectation.
1634 Each application can set its own limits, depending on local restrictions.
1635 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
1636
1637 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
1638 ZSTD_decompressContinue() is very sensitive to contiguity,
1639 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
1640 or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
1641 There are multiple ways to guarantee this condition.
1642
1643 The most memory efficient way is to use a round buffer of sufficient size.
1644 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
1645 which can @return an error code if required value is too large for current system (in 32-bits mode).
1646 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
1647 up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
1648 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
1649 At which point, decoding can resume from the beginning of the buffer.
1650 Note that already decoded data stored in the buffer should be flushed before being overwritten.
1651
1652 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
1653
1654 Finally, if you control the compression process, you can also ignore all buffer size rules,
1655 as long as the encoder and decoder progress in "lock-step",
1656 aka use exactly the same buffer sizes, break contiguity at the same place, etc.
1657
1658 Once buffers are setup, start decompression, with ZSTD_decompressBegin().
1659 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
1660
1661 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
1662 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
1663 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
1664
1665 @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
1666 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
1667 It can also be an error code, which can be tested with ZSTD_isError().
1668
1669 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
1670 Context can then be reset to start a new decompression.
1671
1672 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
1673 This information is not required to properly decode a frame.
1674
1675 == Special case : skippable frames ==
1676
1677 Skippable frames allow integration of user-defined data into a flow of concatenated frames.
1678 Skippable frames will be ignored (skipped) by decompressor.
1679 The format of skippable frames is as follows :
1680 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
1681 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
1682 c) Frame Content - any content (User Data) of length equal to Frame Size
1683 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
1684 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
1685*/
1686
1687/*===== Buffer-less streaming decompression functions =====*/
1688typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
1689typedef struct {
1690 unsigned long long frameContentSize; /* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */
1691 unsigned long long windowSize; /* can be very large, up to <= frameContentSize */
1692 unsigned blockSizeMax;
1693 ZSTD_frameType_e frameType; /* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */
1694 unsigned headerSize;
1695 unsigned dictID;
1696 unsigned checksumFlag;
1697} ZSTD_frameHeader;
1698
1699/** ZSTD_getFrameHeader() :
1700 * decode Frame Header, or requires larger `srcSize`.
1701 * @return : 0, `zfhPtr` is correctly filled,
1702 * >0, `srcSize` is too small, value is wanted `srcSize` amount,
1703 * or an error code, which can be tested using ZSTD_isError() */
1704ZSTDLIB_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); /**< doesn't consume input */
1705/*! ZSTD_getFrameHeader_advanced() :
1706 * same as ZSTD_getFrameHeader(),
1707 * with added capability to select a format (like ZSTD_f_zstd1_magicless) */
1708ZSTDLIB_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
1709ZSTDLIB_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); /**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */
1710
1711ZSTDLIB_API size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
1712ZSTDLIB_API size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1713ZSTDLIB_API size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
1714
1715ZSTDLIB_API size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
1716ZSTDLIB_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1717
1718/* misc */
1719ZSTDLIB_API void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
1720typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
1721ZSTDLIB_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
1722
1723
1724
1725
1726/* ============================ */
1727/** Block level API */
1728/* ============================ */
1729
1730/*!
1731 Block functions produce and decode raw zstd blocks, without frame metadata.
1732 Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
1733 User will have to take in charge required information to regenerate data, such as compressed and content sizes.
1734
1735 A few rules to respect :
1736 - Compressing and decompressing require a context structure
1737 + Use ZSTD_createCCtx() and ZSTD_createDCtx()
1738 - It is necessary to init context before starting
1739 + compression : any ZSTD_compressBegin*() variant, including with dictionary
1740 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
1741 + copyCCtx() and copyDCtx() can be used too
1742 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
1743 + If input is larger than a block size, it's necessary to split input data into multiple blocks
1744 + For inputs larger than a single block, really consider using regular ZSTD_compress() instead.
1745 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
1746 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
1747 In which case, nothing is produced into `dst` !
1748 + User must test for such outcome and deal directly with uncompressed data
1749 + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
1750 + In case of multiple successive blocks, should some of them be uncompressed,
1751 decoder must be informed of their existence in order to follow proper history.
1752 Use ZSTD_insertBlock() for such a case.
1753*/
1754
1755/*===== Raw zstd block functions =====*/
1756ZSTDLIB_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
1757ZSTDLIB_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1758ZSTDLIB_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1759ZSTDLIB_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); /**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */
1760
1761
1762#endif /* ZSTD_H_ZSTD_STATIC_LINKING_ONLY */
1763
1764#if defined (__cplusplus)
1765}
1766#endif
1767