xref: /freebsd/sys/contrib/openzfs/module/zstd/lib/zstd.h (revision 10ff414c)
1 /*
2  * BSD 3-Clause Clear License
3  *
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5  * modification, are permitted provided that the following conditions are met:
6  *
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8  * this list of conditions and the following disclaimer.
9  *
10  * 2. Redistributions in binary form must reproduce the above copyright notice,
11  * this list of conditions and the following disclaimer in the documentation
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30 
31 /*
32  * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc. All rights reserved.
33  */
34 
35 #if defined (__cplusplus)
36 extern "C" {
37 #endif
38 
39 #ifndef ZSTD_H_235446
40 #define ZSTD_H_235446
41 
42 /* ======   Dependency   ======*/
43 #include <limits.h>   /* INT_MAX */
44 #include <stddef.h>   /* size_t */
45 
46 
47 /* =====   ZSTDLIB_API : control library symbols visibility   ===== */
48 #ifndef ZSTDLIB_VISIBILITY
49 #  if defined(__GNUC__) && (__GNUC__ >= 4)
50 #    define ZSTDLIB_VISIBILITY __attribute__ ((visibility ("default")))
51 #  else
52 #    define ZSTDLIB_VISIBILITY
53 #  endif
54 #endif
55 #if defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
56 #  define ZSTDLIB_API __declspec(dllexport) ZSTDLIB_VISIBILITY
57 #elif defined(ZSTD_DLL_IMPORT) && (ZSTD_DLL_IMPORT==1)
58 #  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.*/
59 #else
60 #  define ZSTDLIB_API ZSTDLIB_VISIBILITY
61 #endif
62 
63 
64 /*******************************************************************************
65   Introduction
66 
67   zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
68   real-time compression scenarios at zlib-level and better compression ratios.
69   The zstd compression library provides in-memory compression and decompression
70   functions.
71 
72   The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
73   which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
74   caution, as they require more memory. The library also offers negative
75   compression levels, which extend the range of speed vs. ratio preferences.
76   The lower the level, the faster the speed (at the cost of compression).
77 
78   Compression can be done in:
79     - a single step (described as Simple API)
80     - a single step, reusing a context (described as Explicit context)
81     - unbounded multiple steps (described as Streaming compression)
82 
83   The compression ratio achievable on small data can be highly improved using
84   a dictionary. Dictionary compression can be performed in:
85     - a single step (described as Simple dictionary API)
86     - a single step, reusing a dictionary (described as Bulk-processing
87       dictionary API)
88 
89   Advanced experimental functions can be accessed using
90   `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
91 
92   Advanced experimental APIs should never be used with a dynamically-linked
93   library. They are not "stable"; their definitions or signatures may change in
94   the future. Only static linking is allowed.
95 *******************************************************************************/
96 
97 /*------   Version   ------*/
98 #define ZSTD_VERSION_MAJOR    1
99 #define ZSTD_VERSION_MINOR    4
100 #define ZSTD_VERSION_RELEASE  5
101 
102 #define ZSTD_VERSION_NUMBER  (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
103 ZSTDLIB_API unsigned ZSTD_versionNumber(void);   /**< to check runtime library version */
104 
105 #define ZSTD_LIB_VERSION ZSTD_VERSION_MAJOR.ZSTD_VERSION_MINOR.ZSTD_VERSION_RELEASE
106 #define ZSTD_QUOTE(str) #str
107 #define ZSTD_EXPAND_AND_QUOTE(str) ZSTD_QUOTE(str)
108 #define ZSTD_VERSION_STRING ZSTD_EXPAND_AND_QUOTE(ZSTD_LIB_VERSION)
109 ZSTDLIB_API const char* ZSTD_versionString(void);   /* requires v1.3.0+ */
110 
111 /* *************************************
112  *  Default constant
113  ***************************************/
114 #ifndef ZSTD_CLEVEL_DEFAULT
115 #  define ZSTD_CLEVEL_DEFAULT 3
116 #endif
117 
118 /* *************************************
119  *  Constants
120  ***************************************/
121 
122 /* All magic numbers are supposed read/written to/from files/memory using little-endian convention */
123 #define ZSTD_MAGICNUMBER            0xFD2FB528    /* valid since v0.8.0 */
124 #define ZSTD_MAGIC_DICTIONARY       0xEC30A437    /* valid since v0.7.0 */
125 #define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50    /* all 16 values, from 0x184D2A50 to 0x184D2A5F, signal the beginning of a skippable frame */
126 #define ZSTD_MAGIC_SKIPPABLE_MASK   0xFFFFFFF0
127 
128 #define ZSTD_BLOCKSIZELOG_MAX  17
129 #define ZSTD_BLOCKSIZE_MAX     (1<<ZSTD_BLOCKSIZELOG_MAX)
130 
131 
132 
133 /***************************************
134 *  Simple API
135 ***************************************/
136 /*! ZSTD_compress() :
137  *  Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
138  *  Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
139  *  @return : compressed size written into `dst` (<= `dstCapacity),
140  *            or an error code if it fails (which can be tested using ZSTD_isError()). */
141 ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
142                             const void* src, size_t srcSize,
143                                   int compressionLevel);
144 
145 /*! ZSTD_decompress() :
146  *  `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
147  *  `dstCapacity` is an upper bound of originalSize to regenerate.
148  *  If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
149  *  @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
150  *            or an errorCode if it fails (which can be tested using ZSTD_isError()). */
151 ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
152                               const void* src, size_t compressedSize);
153 
154 /*! ZSTD_getFrameContentSize() : requires v1.3.0+
155  *  `src` should point to the start of a ZSTD encoded frame.
156  *  `srcSize` must be at least as large as the frame header.
157  *            hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
158  *  @return : - decompressed size of `src` frame content, if known
159  *            - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
160  *            - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
161  *   note 1 : a 0 return value means the frame is valid but "empty".
162  *   note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
163  *            When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
164  *            In which case, it's necessary to use streaming mode to decompress data.
165  *            Optionally, application can rely on some implicit limit,
166  *            as ZSTD_decompress() only needs an upper bound of decompressed size.
167  *            (For example, data could be necessarily cut into blocks <= 16 KB).
168  *   note 3 : decompressed size is always present when compression is completed using single-pass functions,
169  *            such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
170  *   note 4 : decompressed size can be very large (64-bits value),
171  *            potentially larger than what local system can handle as a single memory segment.
172  *            In which case, it's necessary to use streaming mode to decompress data.
173  *   note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
174  *            Always ensure return value fits within application's authorized limits.
175  *            Each application can set its own limits.
176  *   note 6 : This function replaces ZSTD_getDecompressedSize() */
177 #define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
178 #define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)
179 ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
180 
181 /*! ZSTD_getDecompressedSize() :
182  *  NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
183  *  Both functions work the same way, but ZSTD_getDecompressedSize() blends
184  *  "empty", "unknown" and "error" results to the same return value (0),
185  *  while ZSTD_getFrameContentSize() gives them separate return values.
186  * @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. */
187 ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
188 
189 /*! ZSTD_findFrameCompressedSize() :
190  * `src` should point to the start of a ZSTD frame or skippable frame.
191  * `srcSize` must be >= first frame size
192  * @return : the compressed size of the first frame starting at `src`,
193  *           suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
194  *        or an error code if input is invalid */
195 ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
196 
197 
198 /*======  Helper functions  ======*/
199 #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 */
200 ZSTDLIB_API size_t      ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case single-pass scenario */
201 ZSTDLIB_API unsigned    ZSTD_isError(size_t code);          /*!< tells if a `size_t` function result is an error code */
202 ZSTDLIB_API const char* ZSTD_getErrorName(size_t code);     /*!< provides readable string from an error code */
203 ZSTDLIB_API int         ZSTD_minCLevel(void);               /*!< minimum negative compression level allowed */
204 ZSTDLIB_API int         ZSTD_maxCLevel(void);               /*!< maximum compression level available */
205 
206 
207 /***************************************
208 *  Explicit context
209 ***************************************/
210 /*= Compression context
211  *  When compressing many times,
212  *  it is recommended to allocate a context just once,
213  *  and re-use it for each successive compression operation.
214  *  This will make workload friendlier for system's memory.
215  *  Note : re-using context is just a speed / resource optimization.
216  *         It doesn't change the compression ratio, which remains identical.
217  *  Note 2 : In multi-threaded environments,
218  *         use one different context per thread for parallel execution.
219  */
220 typedef struct ZSTD_CCtx_s ZSTD_CCtx;
221 ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx(void);
222 ZSTDLIB_API size_t     ZSTD_freeCCtx(ZSTD_CCtx* cctx);
223 
224 /*! ZSTD_compressCCtx() :
225  *  Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
226  *  Important : in order to behave similarly to `ZSTD_compress()`,
227  *  this function compresses at requested compression level,
228  *  __ignoring any other parameter__ .
229  *  If any advanced parameter was set using the advanced API,
230  *  they will all be reset. Only `compressionLevel` remains.
231  */
232 ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
233                                      void* dst, size_t dstCapacity,
234                                const void* src, size_t srcSize,
235                                      int compressionLevel);
236 
237 /*= Decompression context
238  *  When decompressing many times,
239  *  it is recommended to allocate a context only once,
240  *  and re-use it for each successive compression operation.
241  *  This will make workload friendlier for system's memory.
242  *  Use one context per thread for parallel execution. */
243 typedef struct ZSTD_DCtx_s ZSTD_DCtx;
244 ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
245 ZSTDLIB_API size_t     ZSTD_freeDCtx(ZSTD_DCtx* dctx);
246 
247 /*! ZSTD_decompressDCtx() :
248  *  Same as ZSTD_decompress(),
249  *  requires an allocated ZSTD_DCtx.
250  *  Compatible with sticky parameters.
251  */
252 ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
253                                        void* dst, size_t dstCapacity,
254                                  const void* src, size_t srcSize);
255 
256 
257 /***************************************
258 *  Advanced compression API
259 ***************************************/
260 
261 /* API design :
262  *   Parameters are pushed one by one into an existing context,
263  *   using ZSTD_CCtx_set*() functions.
264  *   Pushed parameters are sticky : they are valid for next compressed frame, and any subsequent frame.
265  *   "sticky" parameters are applicable to `ZSTD_compress2()` and `ZSTD_compressStream*()` !
266  *   __They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()__ .
267  *
268  *   It's possible to reset all parameters to "default" using ZSTD_CCtx_reset().
269  *
270  *   This API supercedes all other "advanced" API entry points in the experimental section.
271  *   In the future, we expect to remove from experimental API entry points which are redundant with this API.
272  */
273 
274 
275 /* Compression strategies, listed from fastest to strongest */
276 typedef enum { ZSTD_fast=1,
277                ZSTD_dfast=2,
278                ZSTD_greedy=3,
279                ZSTD_lazy=4,
280                ZSTD_lazy2=5,
281                ZSTD_btlazy2=6,
282                ZSTD_btopt=7,
283                ZSTD_btultra=8,
284                ZSTD_btultra2=9
285                /* note : new strategies _might_ be added in the future.
286                          Only the order (from fast to strong) is guaranteed */
287 } ZSTD_strategy;
288 
289 
290 typedef enum {
291 
292     /* compression parameters
293      * Note: When compressing with a ZSTD_CDict these parameters are superseded
294      * by the parameters used to construct the ZSTD_CDict.
295      * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
296     ZSTD_c_compressionLevel=100, /* Set compression parameters according to pre-defined cLevel table.
297                               * Note that exact compression parameters are dynamically determined,
298                               * depending on both compression level and srcSize (when known).
299                               * Default level is ZSTD_CLEVEL_DEFAULT==3.
300                               * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
301                               * Note 1 : it's possible to pass a negative compression level.
302                               * Note 2 : setting a level does not automatically set all other compression parameters
303                               *   to default. Setting this will however eventually dynamically impact the compression
304                               *   parameters which have not been manually set. The manually set
305                               *   ones will 'stick'. */
306     /* Advanced compression parameters :
307      * It's possible to pin down compression parameters to some specific values.
308      * In which case, these values are no longer dynamically selected by the compressor */
309     ZSTD_c_windowLog=101,    /* Maximum allowed back-reference distance, expressed as power of 2.
310                               * This will set a memory budget for streaming decompression,
311                               * with larger values requiring more memory
312                               * and typically compressing more.
313                               * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
314                               * Special: value 0 means "use default windowLog".
315                               * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
316                               *       requires explicitly allowing such size at streaming decompression stage. */
317     ZSTD_c_hashLog=102,      /* Size of the initial probe table, as a power of 2.
318                               * Resulting memory usage is (1 << (hashLog+2)).
319                               * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
320                               * Larger tables improve compression ratio of strategies <= dFast,
321                               * and improve speed of strategies > dFast.
322                               * Special: value 0 means "use default hashLog". */
323     ZSTD_c_chainLog=103,     /* Size of the multi-probe search table, as a power of 2.
324                               * Resulting memory usage is (1 << (chainLog+2)).
325                               * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
326                               * Larger tables result in better and slower compression.
327                               * This parameter is useless for "fast" strategy.
328                               * It's still useful when using "dfast" strategy,
329                               * in which case it defines a secondary probe table.
330                               * Special: value 0 means "use default chainLog". */
331     ZSTD_c_searchLog=104,    /* Number of search attempts, as a power of 2.
332                               * More attempts result in better and slower compression.
333                               * This parameter is useless for "fast" and "dFast" strategies.
334                               * Special: value 0 means "use default searchLog". */
335     ZSTD_c_minMatch=105,     /* Minimum size of searched matches.
336                               * Note that Zstandard can still find matches of smaller size,
337                               * it just tweaks its search algorithm to look for this size and larger.
338                               * Larger values increase compression and decompression speed, but decrease ratio.
339                               * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
340                               * Note that currently, for all strategies < btopt, effective minimum is 4.
341                               *                    , for all strategies > fast, effective maximum is 6.
342                               * Special: value 0 means "use default minMatchLength". */
343     ZSTD_c_targetLength=106, /* Impact of this field depends on strategy.
344                               * For strategies btopt, btultra & btultra2:
345                               *     Length of Match considered "good enough" to stop search.
346                               *     Larger values make compression stronger, and slower.
347                               * For strategy fast:
348                               *     Distance between match sampling.
349                               *     Larger values make compression faster, and weaker.
350                               * Special: value 0 means "use default targetLength". */
351     ZSTD_c_strategy=107,     /* See ZSTD_strategy enum definition.
352                               * The higher the value of selected strategy, the more complex it is,
353                               * resulting in stronger and slower compression.
354                               * Special: value 0 means "use default strategy". */
355 
356     /* LDM mode parameters */
357     ZSTD_c_enableLongDistanceMatching=160, /* Enable long distance matching.
358                                      * This parameter is designed to improve compression ratio
359                                      * for large inputs, by finding large matches at long distance.
360                                      * It increases memory usage and window size.
361                                      * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
362                                      * except when expressly set to a different value. */
363     ZSTD_c_ldmHashLog=161,   /* Size of the table for long distance matching, as a power of 2.
364                               * Larger values increase memory usage and compression ratio,
365                               * but decrease compression speed.
366                               * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
367                               * default: windowlog - 7.
368                               * Special: value 0 means "automatically determine hashlog". */
369     ZSTD_c_ldmMinMatch=162,  /* Minimum match size for long distance matcher.
370                               * Larger/too small values usually decrease compression ratio.
371                               * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
372                               * Special: value 0 means "use default value" (default: 64). */
373     ZSTD_c_ldmBucketSizeLog=163, /* Log size of each bucket in the LDM hash table for collision resolution.
374                               * Larger values improve collision resolution but decrease compression speed.
375                               * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
376                               * Special: value 0 means "use default value" (default: 3). */
377     ZSTD_c_ldmHashRateLog=164, /* Frequency of inserting/looking up entries into the LDM hash table.
378                               * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
379                               * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
380                               * Larger values improve compression speed.
381                               * Deviating far from default value will likely result in a compression ratio decrease.
382                               * Special: value 0 means "automatically determine hashRateLog". */
383 
384     /* frame parameters */
385     ZSTD_c_contentSizeFlag=200, /* Content size will be written into frame header _whenever known_ (default:1)
386                               * Content size must be known at the beginning of compression.
387                               * This is automatically the case when using ZSTD_compress2(),
388                               * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
389     ZSTD_c_checksumFlag=201, /* A 32-bits checksum of content is written at end of frame (default:0) */
390     ZSTD_c_dictIDFlag=202,   /* When applicable, dictionary's ID is written into frame header (default:1) */
391 
392     /* multi-threading parameters */
393     /* These parameters are only useful if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).
394      * They return an error otherwise. */
395     ZSTD_c_nbWorkers=400,    /* Select how many threads will be spawned to compress in parallel.
396                               * When nbWorkers >= 1, triggers asynchronous mode when used with ZSTD_compressStream*() :
397                               * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
398                               * while compression work is performed in parallel, within worker threads.
399                               * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
400                               *  in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
401                               * More workers improve speed, but also increase memory usage.
402                               * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */
403     ZSTD_c_jobSize=401,      /* Size of a compression job. This value is enforced only when nbWorkers >= 1.
404                               * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
405                               * 0 means default, which is dynamically determined based on compression parameters.
406                               * Job size must be a minimum of overlap size, or 1 MB, whichever is largest.
407                               * The minimum size is automatically and transparently enforced. */
408     ZSTD_c_overlapLog=402,   /* Control the overlap size, as a fraction of window size.
409                               * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
410                               * It helps preserve compression ratio, while each job is compressed in parallel.
411                               * This value is enforced only when nbWorkers >= 1.
412                               * Larger values increase compression ratio, but decrease speed.
413                               * Possible values range from 0 to 9 :
414                               * - 0 means "default" : value will be determined by the library, depending on strategy
415                               * - 1 means "no overlap"
416                               * - 9 means "full overlap", using a full window size.
417                               * Each intermediate rank increases/decreases load size by a factor 2 :
418                               * 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
419                               * default value varies between 6 and 9, depending on strategy */
420 
421     /* note : additional experimental parameters are also available
422      * within the experimental section of the API.
423      * At the time of this writing, they include :
424      * ZSTD_c_rsyncable
425      * ZSTD_c_format
426      * ZSTD_c_forceMaxWindow
427      * ZSTD_c_forceAttachDict
428      * ZSTD_c_literalCompressionMode
429      * ZSTD_c_targetCBlockSize
430      * ZSTD_c_srcSizeHint
431      * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
432      * note : never ever use experimentalParam? names directly;
433      *        also, the enums values themselves are unstable and can still change.
434      */
435      ZSTD_c_experimentalParam1=500,
436      ZSTD_c_experimentalParam2=10,
437      ZSTD_c_experimentalParam3=1000,
438      ZSTD_c_experimentalParam4=1001,
439      ZSTD_c_experimentalParam5=1002,
440      ZSTD_c_experimentalParam6=1003,
441      ZSTD_c_experimentalParam7=1004
442 } ZSTD_cParameter;
443 
444 typedef struct {
445     size_t error;
446     int lowerBound;
447     int upperBound;
448 } ZSTD_bounds;
449 
450 /*! ZSTD_cParam_getBounds() :
451  *  All parameters must belong to an interval with lower and upper bounds,
452  *  otherwise they will either trigger an error or be automatically clamped.
453  * @return : a structure, ZSTD_bounds, which contains
454  *         - an error status field, which must be tested using ZSTD_isError()
455  *         - lower and upper bounds, both inclusive
456  */
457 ZSTDLIB_API ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
458 
459 /*! ZSTD_CCtx_setParameter() :
460  *  Set one compression parameter, selected by enum ZSTD_cParameter.
461  *  All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
462  *  Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
463  *  Setting a parameter is generally only possible during frame initialization (before starting compression).
464  *  Exception : when using multi-threading mode (nbWorkers >= 1),
465  *              the following parameters can be updated _during_ compression (within same frame):
466  *              => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
467  *              new parameters will be active for next job only (after a flush()).
468  * @return : an error code (which can be tested using ZSTD_isError()).
469  */
470 ZSTDLIB_API size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
471 
472 /*! ZSTD_CCtx_setPledgedSrcSize() :
473  *  Total input data size to be compressed as a single frame.
474  *  Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
475  *  This value will also be controlled at end of frame, and trigger an error if not respected.
476  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
477  *  Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
478  *           In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
479  *           ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
480  *  Note 2 : pledgedSrcSize is only valid once, for the next frame.
481  *           It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
482  *  Note 3 : Whenever all input data is provided and consumed in a single round,
483  *           for example with ZSTD_compress2(),
484  *           or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
485  *           this value is automatically overridden by srcSize instead.
486  */
487 ZSTDLIB_API size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
488 
489 typedef enum {
490     ZSTD_reset_session_only = 1,
491     ZSTD_reset_parameters = 2,
492     ZSTD_reset_session_and_parameters = 3
493 } ZSTD_ResetDirective;
494 
495 /*! ZSTD_CCtx_reset() :
496  *  There are 2 different things that can be reset, independently or jointly :
497  *  - The session : will stop compressing current frame, and make CCtx ready to start a new one.
498  *                  Useful after an error, or to interrupt any ongoing compression.
499  *                  Any internal data not yet flushed is cancelled.
500  *                  Compression parameters and dictionary remain unchanged.
501  *                  They will be used to compress next frame.
502  *                  Resetting session never fails.
503  *  - The parameters : changes all parameters back to "default".
504  *                  This removes any reference to any dictionary too.
505  *                  Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
506  *                  otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
507  *  - Both : similar to resetting the session, followed by resetting parameters.
508  */
509 ZSTDLIB_API size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
510 
511 /*! ZSTD_compress2() :
512  *  Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
513  *  ZSTD_compress2() always starts a new frame.
514  *  Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
515  *  - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
516  *  - The function is always blocking, returns when compression is completed.
517  *  Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
518  * @return : compressed size written into `dst` (<= `dstCapacity),
519  *           or an error code if it fails (which can be tested using ZSTD_isError()).
520  */
521 ZSTDLIB_API size_t ZSTD_compress2( ZSTD_CCtx* cctx,
522                                    void* dst, size_t dstCapacity,
523                              const void* src, size_t srcSize);
524 
525 
526 /***************************************
527 *  Advanced decompression API
528 ***************************************/
529 
530 /* The advanced API pushes parameters one by one into an existing DCtx context.
531  * Parameters are sticky, and remain valid for all following frames
532  * using the same DCtx context.
533  * It's possible to reset parameters to default values using ZSTD_DCtx_reset().
534  * Note : This API is compatible with existing ZSTD_decompressDCtx() and ZSTD_decompressStream().
535  *        Therefore, no new decompression function is necessary.
536  */
537 
538 typedef enum {
539 
540     ZSTD_d_windowLogMax=100, /* Select a size limit (in power of 2) beyond which
541                               * the streaming API will refuse to allocate memory buffer
542                               * in order to protect the host from unreasonable memory requirements.
543                               * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
544                               * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
545                               * Special: value 0 means "use default maximum windowLog". */
546 
547     /* note : additional experimental parameters are also available
548      * within the experimental section of the API.
549      * At the time of this writing, they include :
550      * ZSTD_d_format
551      * ZSTD_d_stableOutBuffer
552      * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
553      * note : never ever use experimentalParam? names directly
554      */
555      ZSTD_d_experimentalParam1=1000,
556      ZSTD_d_experimentalParam2=1001
557 
558 } ZSTD_dParameter;
559 
560 /*! ZSTD_dParam_getBounds() :
561  *  All parameters must belong to an interval with lower and upper bounds,
562  *  otherwise they will either trigger an error or be automatically clamped.
563  * @return : a structure, ZSTD_bounds, which contains
564  *         - an error status field, which must be tested using ZSTD_isError()
565  *         - both lower and upper bounds, inclusive
566  */
567 ZSTDLIB_API ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
568 
569 /*! ZSTD_DCtx_setParameter() :
570  *  Set one compression parameter, selected by enum ZSTD_dParameter.
571  *  All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
572  *  Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
573  *  Setting a parameter is only possible during frame initialization (before starting decompression).
574  * @return : 0, or an error code (which can be tested using ZSTD_isError()).
575  */
576 ZSTDLIB_API size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
577 
578 /*! ZSTD_DCtx_reset() :
579  *  Return a DCtx to clean state.
580  *  Session and parameters can be reset jointly or separately.
581  *  Parameters can only be reset when no active frame is being decompressed.
582  * @return : 0, or an error code, which can be tested with ZSTD_isError()
583  */
584 ZSTDLIB_API size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
585 
586 
587 /****************************
588 *  Streaming
589 ****************************/
590 
591 typedef struct ZSTD_inBuffer_s {
592   const void* src;    /**< start of input buffer */
593   size_t size;        /**< size of input buffer */
594   size_t pos;         /**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */
595 } ZSTD_inBuffer;
596 
597 typedef struct ZSTD_outBuffer_s {
598   void*  dst;         /**< start of output buffer */
599   size_t size;        /**< size of output buffer */
600   size_t pos;         /**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */
601 } ZSTD_outBuffer;
602 
603 
604 
605 /*-***********************************************************************
606 *  Streaming compression - HowTo
607 *
608 *  A ZSTD_CStream object is required to track streaming operation.
609 *  Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
610 *  ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
611 *  It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
612 *
613 *  For parallel execution, use one separate ZSTD_CStream per thread.
614 *
615 *  note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
616 *
617 *  Parameters are sticky : when starting a new compression on the same context,
618 *  it will re-use the same sticky parameters as previous compression session.
619 *  When in doubt, it's recommended to fully initialize the context before usage.
620 *  Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
621 *  ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
622 *  set more specific parameters, the pledged source size, or load a dictionary.
623 *
624 *  Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
625 *  consume input stream. The function will automatically update both `pos`
626 *  fields within `input` and `output`.
627 *  Note that the function may not consume the entire input, for example, because
628 *  the output buffer is already full, in which case `input.pos < input.size`.
629 *  The caller must check if input has been entirely consumed.
630 *  If not, the caller must make some room to receive more compressed data,
631 *  and then present again remaining input data.
632 *  note: ZSTD_e_continue is guaranteed to make some forward progress when called,
633 *        but doesn't guarantee maximal forward progress. This is especially relevant
634 *        when compressing with multiple threads. The call won't block if it can
635 *        consume some input, but if it can't it will wait for some, but not all,
636 *        output to be flushed.
637 * @return : provides a minimum amount of data remaining to be flushed from internal buffers
638 *           or an error code, which can be tested using ZSTD_isError().
639 *
640 *  At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
641 *  using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
642 *  Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
643 *  In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
644 *  You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
645 *  operation.
646 *  note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
647 *        block until the flush is complete or the output buffer is full.
648 *  @return : 0 if internal buffers are entirely flushed,
649 *            >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
650 *            or an error code, which can be tested using ZSTD_isError().
651 *
652 *  Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
653 *  It will perform a flush and write frame epilogue.
654 *  The epilogue is required for decoders to consider a frame completed.
655 *  flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
656 *  You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
657 *  start a new frame.
658 *  note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
659 *        block until the flush is complete or the output buffer is full.
660 *  @return : 0 if frame fully completed and fully flushed,
661 *            >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
662 *            or an error code, which can be tested using ZSTD_isError().
663 *
664 * *******************************************************************/
665 
666 typedef ZSTD_CCtx ZSTD_CStream;  /**< CCtx and CStream are now effectively same object (>= v1.3.0) */
667                                  /* Continue to distinguish them for compatibility with older versions <= v1.2.0 */
668 /*===== ZSTD_CStream management functions =====*/
669 ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void);
670 ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
671 
672 /*===== Streaming compression functions =====*/
673 typedef enum {
674     ZSTD_e_continue=0, /* collect more data, encoder decides when to output compressed result, for optimal compression ratio */
675     ZSTD_e_flush=1,    /* flush any data provided so far,
676                         * it creates (at least) one new block, that can be decoded immediately on reception;
677                         * frame will continue: any future data can still reference previously compressed data, improving compression.
678                         * note : multithreaded compression will block to flush as much output as possible. */
679     ZSTD_e_end=2       /* flush any remaining data _and_ close current frame.
680                         * note that frame is only closed after compressed data is fully flushed (return value == 0).
681                         * After that point, any additional data starts a new frame.
682                         * note : each frame is independent (does not reference any content from previous frame).
683                         : note : multithreaded compression will block to flush as much output as possible. */
684 } ZSTD_EndDirective;
685 
686 /*! ZSTD_compressStream2() :
687  *  Behaves about the same as ZSTD_compressStream, with additional control on end directive.
688  *  - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
689  *  - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
690  *  - output->pos must be <= dstCapacity, input->pos must be <= srcSize
691  *  - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
692  *  - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
693  *  - 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,
694  *                                                  and then immediately returns, just indicating that there is some data remaining to be flushed.
695  *                                                  The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
696  *  - 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.
697  *  - @return provides a minimum amount of data remaining to be flushed from internal buffers
698  *            or an error code, which can be tested using ZSTD_isError().
699  *            if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
700  *            This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
701  *            For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
702  *  - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
703  *            only ZSTD_e_end or ZSTD_e_flush operations are allowed.
704  *            Before starting a new compression job, or changing compression parameters,
705  *            it is required to fully flush internal buffers.
706  */
707 ZSTDLIB_API size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
708                                          ZSTD_outBuffer* output,
709                                          ZSTD_inBuffer* input,
710                                          ZSTD_EndDirective endOp);
711 
712 
713 /* These buffer sizes are softly recommended.
714  * They are not required : ZSTD_compressStream*() happily accepts any buffer size, for both input and output.
715  * Respecting the recommended size just makes it a bit easier for ZSTD_compressStream*(),
716  * reducing the amount of memory shuffling and buffering, resulting in minor performance savings.
717  *
718  * However, note that these recommendations are from the perspective of a C caller program.
719  * If the streaming interface is invoked from some other language,
720  * especially managed ones such as Java or Go, through a foreign function interface such as jni or cgo,
721  * a major performance rule is to reduce crossing such interface to an absolute minimum.
722  * It's not rare that performance ends being spent more into the interface, rather than compression itself.
723  * In which cases, prefer using large buffers, as large as practical,
724  * for both input and output, to reduce the nb of roundtrips.
725  */
726 ZSTDLIB_API size_t ZSTD_CStreamInSize(void);    /**< recommended size for input buffer */
727 ZSTDLIB_API size_t ZSTD_CStreamOutSize(void);   /**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */
728 
729 
730 /* *****************************************************************************
731  * This following is a legacy streaming API.
732  * It can be replaced by ZSTD_CCtx_reset() and ZSTD_compressStream2().
733  * It is redundant, but remains fully supported.
734  * Advanced parameters and dictionary compression can only be used through the
735  * new API.
736  ******************************************************************************/
737 
738 /*!
739  * Equivalent to:
740  *
741  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
742  *     ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
743  *     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
744  */
745 ZSTDLIB_API size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
746 /*!
747  * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
748  * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
749  * the next read size (if non-zero and not an error). ZSTD_compressStream2()
750  * returns the minimum nb of bytes left to flush (if non-zero and not an error).
751  */
752 ZSTDLIB_API size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
753 /*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */
754 ZSTDLIB_API size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
755 /*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */
756 ZSTDLIB_API size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
757 
758 
759 /*-***************************************************************************
760 *  Streaming decompression - HowTo
761 *
762 *  A ZSTD_DStream object is required to track streaming operations.
763 *  Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
764 *  ZSTD_DStream objects can be re-used multiple times.
765 *
766 *  Use ZSTD_initDStream() to start a new decompression operation.
767 * @return : recommended first input size
768 *  Alternatively, use advanced API to set specific properties.
769 *
770 *  Use ZSTD_decompressStream() repetitively to consume your input.
771 *  The function will update both `pos` fields.
772 *  If `input.pos < input.size`, some input has not been consumed.
773 *  It's up to the caller to present again remaining data.
774 *  The function tries to flush all data decoded immediately, respecting output buffer size.
775 *  If `output.pos < output.size`, decoder has flushed everything it could.
776 *  But if `output.pos == output.size`, there might be some data left within internal buffers.,
777 *  In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
778 *  Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
779 * @return : 0 when a frame is completely decoded and fully flushed,
780 *        or an error code, which can be tested using ZSTD_isError(),
781 *        or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
782 *                                the return value is a suggested next input size (just a hint for better latency)
783 *                                that will never request more than the remaining frame size.
784 * *******************************************************************************/
785 
786 typedef ZSTD_DCtx ZSTD_DStream;  /**< DCtx and DStream are now effectively same object (>= v1.3.0) */
787                                  /* For compatibility with versions <= v1.2.0, prefer differentiating them. */
788 /*===== ZSTD_DStream management functions =====*/
789 ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void);
790 ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds);
791 
792 /*===== Streaming decompression functions =====*/
793 
794 /* This function is redundant with the advanced API and equivalent to:
795  *
796  *     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
797  *     ZSTD_DCtx_refDDict(zds, NULL);
798  */
799 ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds);
800 
801 ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
802 
803 ZSTDLIB_API size_t ZSTD_DStreamInSize(void);    /*!< recommended size for input buffer */
804 ZSTDLIB_API size_t ZSTD_DStreamOutSize(void);   /*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */
805 
806 
807 /**************************
808 *  Simple dictionary API
809 ***************************/
810 /*! ZSTD_compress_usingDict() :
811  *  Compression at an explicit compression level using a Dictionary.
812  *  A dictionary can be any arbitrary data segment (also called a prefix),
813  *  or a buffer with specified information (see dictBuilder/zdict.h).
814  *  Note : This function loads the dictionary, resulting in significant startup delay.
815  *         It's intended for a dictionary used only once.
816  *  Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. */
817 ZSTDLIB_API size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
818                                            void* dst, size_t dstCapacity,
819                                      const void* src, size_t srcSize,
820                                      const void* dict,size_t dictSize,
821                                            int compressionLevel);
822 
823 /*! ZSTD_decompress_usingDict() :
824  *  Decompression using a known Dictionary.
825  *  Dictionary must be identical to the one used during compression.
826  *  Note : This function loads the dictionary, resulting in significant startup delay.
827  *         It's intended for a dictionary used only once.
828  *  Note : When `dict == NULL || dictSize < 8` no dictionary is used. */
829 ZSTDLIB_API size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
830                                              void* dst, size_t dstCapacity,
831                                        const void* src, size_t srcSize,
832                                        const void* dict,size_t dictSize);
833 
834 
835 /***********************************
836  *  Bulk processing dictionary API
837  **********************************/
838 typedef struct ZSTD_CDict_s ZSTD_CDict;
839 
840 /*! ZSTD_createCDict() :
841  *  When compressing multiple messages or blocks using the same dictionary,
842  *  it's recommended to digest the dictionary only once, since it's a costly operation.
843  *  ZSTD_createCDict() will create a state from digesting a dictionary.
844  *  The resulting state can be used for future compression operations with very limited startup cost.
845  *  ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
846  * @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
847  *  Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
848  *  Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
849  *      in which case the only thing that it transports is the @compressionLevel.
850  *      This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
851  *      expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. */
852 ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
853                                          int compressionLevel);
854 
855 /*! ZSTD_freeCDict() :
856  *  Function frees memory allocated by ZSTD_createCDict(). */
857 ZSTDLIB_API size_t      ZSTD_freeCDict(ZSTD_CDict* CDict);
858 
859 /*! ZSTD_compress_usingCDict() :
860  *  Compression using a digested Dictionary.
861  *  Recommended when same dictionary is used multiple times.
862  *  Note : compression level is _decided at dictionary creation time_,
863  *     and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) */
864 ZSTDLIB_API size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
865                                             void* dst, size_t dstCapacity,
866                                       const void* src, size_t srcSize,
867                                       const ZSTD_CDict* cdict);
868 
869 
870 typedef struct ZSTD_DDict_s ZSTD_DDict;
871 
872 /*! ZSTD_createDDict() :
873  *  Create a digested dictionary, ready to start decompression operation without startup delay.
874  *  dictBuffer can be released after DDict creation, as its content is copied inside DDict. */
875 ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
876 
877 /*! ZSTD_freeDDict() :
878  *  Function frees memory allocated with ZSTD_createDDict() */
879 ZSTDLIB_API size_t      ZSTD_freeDDict(ZSTD_DDict* ddict);
880 
881 /*! ZSTD_decompress_usingDDict() :
882  *  Decompression using a digested Dictionary.
883  *  Recommended when same dictionary is used multiple times. */
884 ZSTDLIB_API size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
885                                               void* dst, size_t dstCapacity,
886                                         const void* src, size_t srcSize,
887                                         const ZSTD_DDict* ddict);
888 
889 
890 /********************************
891  *  Dictionary helper functions
892  *******************************/
893 
894 /*! ZSTD_getDictID_fromDict() :
895  *  Provides the dictID stored within dictionary.
896  *  if @return == 0, the dictionary is not conformant with Zstandard specification.
897  *  It can still be loaded, but as a content-only dictionary. */
898 ZSTDLIB_API unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
899 
900 /*! ZSTD_getDictID_fromDDict() :
901  *  Provides the dictID of the dictionary loaded into `ddict`.
902  *  If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
903  *  Non-conformant dictionaries can still be loaded, but as content-only dictionaries. */
904 ZSTDLIB_API unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
905 
906 /*! ZSTD_getDictID_fromFrame() :
907  *  Provides the dictID required to decompressed the frame stored within `src`.
908  *  If @return == 0, the dictID could not be decoded.
909  *  This could for one of the following reasons :
910  *  - The frame does not require a dictionary to be decoded (most common case).
911  *  - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
912  *    Note : this use case also happens when using a non-conformant dictionary.
913  *  - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
914  *  - This is not a Zstandard frame.
915  *  When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. */
916 ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
917 
918 
919 /*******************************************************************************
920  * Advanced dictionary and prefix API
921  *
922  * This API allows dictionaries to be used with ZSTD_compress2(),
923  * ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and
924  * only reset with the context is reset with ZSTD_reset_parameters or
925  * ZSTD_reset_session_and_parameters. Prefixes are single-use.
926  ******************************************************************************/
927 
928 
929 /*! ZSTD_CCtx_loadDictionary() :
930  *  Create an internal CDict from `dict` buffer.
931  *  Decompression will have to use same dictionary.
932  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
933  *  Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
934  *           meaning "return to no-dictionary mode".
935  *  Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
936  *           To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
937  *  Note 2 : Loading a dictionary involves building tables.
938  *           It's also a CPU consuming operation, with non-negligible impact on latency.
939  *           Tables are dependent on compression parameters, and for this reason,
940  *           compression parameters can no longer be changed after loading a dictionary.
941  *  Note 3 :`dict` content will be copied internally.
942  *           Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
943  *           In such a case, dictionary buffer must outlive its users.
944  *  Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
945  *           to precisely select how dictionary content must be interpreted. */
946 ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
947 
948 /*! ZSTD_CCtx_refCDict() :
949  *  Reference a prepared dictionary, to be used for all next compressed frames.
950  *  Note that compression parameters are enforced from within CDict,
951  *  and supersede any compression parameter previously set within CCtx.
952  *  The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
953  *  The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
954  *  The dictionary will remain valid for future compressed frames using same CCtx.
955  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
956  *  Special : Referencing a NULL CDict means "return to no-dictionary mode".
957  *  Note 1 : Currently, only one dictionary can be managed.
958  *           Referencing a new dictionary effectively "discards" any previous one.
959  *  Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. */
960 ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
961 
962 /*! ZSTD_CCtx_refPrefix() :
963  *  Reference a prefix (single-usage dictionary) for next compressed frame.
964  *  A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
965  *  Decompression will need same prefix to properly regenerate data.
966  *  Compressing with a prefix is similar in outcome as performing a diff and compressing it,
967  *  but performs much faster, especially during decompression (compression speed is tunable with compression level).
968  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
969  *  Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
970  *  Note 1 : Prefix buffer is referenced. It **must** outlive compression.
971  *           Its content must remain unmodified during compression.
972  *  Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
973  *           ensure that the window size is large enough to contain the entire source.
974  *           See ZSTD_c_windowLog.
975  *  Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
976  *           It's a CPU consuming operation, with non-negligible impact on latency.
977  *           If there is a need to use the same prefix multiple times, consider loadDictionary instead.
978  *  Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
979  *           Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. */
980 ZSTDLIB_API size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
981                                  const void* prefix, size_t prefixSize);
982 
983 /*! ZSTD_DCtx_loadDictionary() :
984  *  Create an internal DDict from dict buffer,
985  *  to be used to decompress next frames.
986  *  The dictionary remains valid for all future frames, until explicitly invalidated.
987  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
988  *  Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
989  *            meaning "return to no-dictionary mode".
990  *  Note 1 : Loading a dictionary involves building tables,
991  *           which has a non-negligible impact on CPU usage and latency.
992  *           It's recommended to "load once, use many times", to amortize the cost
993  *  Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
994  *           Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
995  *  Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
996  *           how dictionary content is loaded and interpreted.
997  */
998 ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
999 
1000 /*! ZSTD_DCtx_refDDict() :
1001  *  Reference a prepared dictionary, to be used to decompress next frames.
1002  *  The dictionary remains active for decompression of future frames using same DCtx.
1003  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1004  *  Note 1 : Currently, only one dictionary can be managed.
1005  *           Referencing a new dictionary effectively "discards" any previous one.
1006  *  Special: referencing a NULL DDict means "return to no-dictionary mode".
1007  *  Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
1008  */
1009 ZSTDLIB_API size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
1010 
1011 /*! ZSTD_DCtx_refPrefix() :
1012  *  Reference a prefix (single-usage dictionary) to decompress next frame.
1013  *  This is the reverse operation of ZSTD_CCtx_refPrefix(),
1014  *  and must use the same prefix as the one used during compression.
1015  *  Prefix is **only used once**. Reference is discarded at end of frame.
1016  *  End of frame is reached when ZSTD_decompressStream() returns 0.
1017  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1018  *  Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
1019  *  Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
1020  *           Prefix buffer must remain unmodified up to the end of frame,
1021  *           reached when ZSTD_decompressStream() returns 0.
1022  *  Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
1023  *           Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
1024  *  Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
1025  *           A full dictionary is more costly, as it requires building tables.
1026  */
1027 ZSTDLIB_API size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
1028                                  const void* prefix, size_t prefixSize);
1029 
1030 /* ===   Memory management   === */
1031 
1032 /*! ZSTD_sizeof_*() :
1033  *  These functions give the _current_ memory usage of selected object.
1034  *  Note that object memory usage can evolve (increase or decrease) over time. */
1035 ZSTDLIB_API size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
1036 ZSTDLIB_API size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
1037 ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
1038 ZSTDLIB_API size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
1039 ZSTDLIB_API size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
1040 ZSTDLIB_API size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
1041 
1042 #endif  /* ZSTD_H_235446 */
1043 
1044 
1045 /* **************************************************************************************
1046  *   ADVANCED AND EXPERIMENTAL FUNCTIONS
1047  ****************************************************************************************
1048  * The definitions in the following section are considered experimental.
1049  * They are provided for advanced scenarios.
1050  * They should never be used with a dynamic library, as prototypes may change in the future.
1051  * Use them only in association with static linking.
1052  * ***************************************************************************************/
1053 
1054 #if defined(ZSTD_STATIC_LINKING_ONLY) && !defined(ZSTD_H_ZSTD_STATIC_LINKING_ONLY)
1055 #define ZSTD_H_ZSTD_STATIC_LINKING_ONLY
1056 
1057 /****************************************************************************************
1058  *   experimental API (static linking only)
1059  ****************************************************************************************
1060  * The following symbols and constants
1061  * are not planned to join "stable API" status in the near future.
1062  * They can still change in future versions.
1063  * Some of them are planned to remain in the static_only section indefinitely.
1064  * Some of them might be removed in the future (especially when redundant with existing stable functions)
1065  * ***************************************************************************************/
1066 
1067 #define ZSTD_FRAMEHEADERSIZE_PREFIX(format) ((format) == ZSTD_f_zstd1 ? 5 : 1)   /* minimum input size required to query frame header size */
1068 #define ZSTD_FRAMEHEADERSIZE_MIN(format)    ((format) == ZSTD_f_zstd1 ? 6 : 2)
1069 #define ZSTD_FRAMEHEADERSIZE_MAX   18   /* can be useful for static allocation */
1070 #define ZSTD_SKIPPABLEHEADERSIZE    8
1071 
1072 /* compression parameter bounds */
1073 #define ZSTD_WINDOWLOG_MAX_32    30
1074 #define ZSTD_WINDOWLOG_MAX_64    31
1075 #define ZSTD_WINDOWLOG_MAX     ((int)(sizeof(size_t) == 4 ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
1076 #define ZSTD_WINDOWLOG_MIN       10
1077 #define ZSTD_HASHLOG_MAX       ((ZSTD_WINDOWLOG_MAX < 30) ? ZSTD_WINDOWLOG_MAX : 30)
1078 #define ZSTD_HASHLOG_MIN          6
1079 #define ZSTD_CHAINLOG_MAX_32     29
1080 #define ZSTD_CHAINLOG_MAX_64     30
1081 #define ZSTD_CHAINLOG_MAX      ((int)(sizeof(size_t) == 4 ? ZSTD_CHAINLOG_MAX_32 : ZSTD_CHAINLOG_MAX_64))
1082 #define ZSTD_CHAINLOG_MIN        ZSTD_HASHLOG_MIN
1083 #define ZSTD_SEARCHLOG_MAX      (ZSTD_WINDOWLOG_MAX-1)
1084 #define ZSTD_SEARCHLOG_MIN        1
1085 #define ZSTD_MINMATCH_MAX         7   /* only for ZSTD_fast, other strategies are limited to 6 */
1086 #define ZSTD_MINMATCH_MIN         3   /* only for ZSTD_btopt+, faster strategies are limited to 4 */
1087 #define ZSTD_TARGETLENGTH_MAX    ZSTD_BLOCKSIZE_MAX
1088 #define ZSTD_TARGETLENGTH_MIN     0   /* note : comparing this constant to an unsigned results in a tautological test */
1089 #define ZSTD_STRATEGY_MIN        ZSTD_fast
1090 #define ZSTD_STRATEGY_MAX        ZSTD_btultra2
1091 
1092 
1093 #define ZSTD_OVERLAPLOG_MIN       0
1094 #define ZSTD_OVERLAPLOG_MAX       9
1095 
1096 #define ZSTD_WINDOWLOG_LIMIT_DEFAULT 27   /* by default, the streaming decoder will refuse any frame
1097                                            * requiring larger than (1<<ZSTD_WINDOWLOG_LIMIT_DEFAULT) window size,
1098                                            * to preserve host's memory from unreasonable requirements.
1099                                            * This limit can be overridden using ZSTD_DCtx_setParameter(,ZSTD_d_windowLogMax,).
1100                                            * The limit does not apply for one-pass decoders (such as ZSTD_decompress()), since no additional memory is allocated */
1101 
1102 
1103 /* LDM parameter bounds */
1104 #define ZSTD_LDM_HASHLOG_MIN      ZSTD_HASHLOG_MIN
1105 #define ZSTD_LDM_HASHLOG_MAX      ZSTD_HASHLOG_MAX
1106 #define ZSTD_LDM_MINMATCH_MIN        4
1107 #define ZSTD_LDM_MINMATCH_MAX     4096
1108 #define ZSTD_LDM_BUCKETSIZELOG_MIN   1
1109 #define ZSTD_LDM_BUCKETSIZELOG_MAX   8
1110 #define ZSTD_LDM_HASHRATELOG_MIN     0
1111 #define ZSTD_LDM_HASHRATELOG_MAX (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN)
1112 
1113 /* Advanced parameter bounds */
1114 #define ZSTD_TARGETCBLOCKSIZE_MIN   64
1115 #define ZSTD_TARGETCBLOCKSIZE_MAX   ZSTD_BLOCKSIZE_MAX
1116 #define ZSTD_SRCSIZEHINT_MIN        0
1117 #define ZSTD_SRCSIZEHINT_MAX        INT_MAX
1118 
1119 /* internal */
1120 #define ZSTD_HASHLOG3_MAX           17
1121 
1122 
1123 /* ---  Advanced types  --- */
1124 
1125 typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;
1126 
1127 typedef struct {
1128     unsigned int matchPos; /* Match pos in dst */
1129     /* If seqDef.offset > 3, then this is seqDef.offset - 3
1130      * If seqDef.offset < 3, then this is the corresponding repeat offset
1131      * But if seqDef.offset < 3 and litLength == 0, this is the
1132      *   repeat offset before the corresponding repeat offset
1133      * And if seqDef.offset == 3 and litLength == 0, this is the
1134      *   most recent repeat offset - 1
1135      */
1136     unsigned int offset;
1137     unsigned int litLength; /* Literal length */
1138     unsigned int matchLength; /* Match length */
1139     /* 0 when seq not rep and seqDef.offset otherwise
1140      * when litLength == 0 this will be <= 4, otherwise <= 3 like normal
1141      */
1142     unsigned int rep;
1143 } ZSTD_Sequence;
1144 
1145 typedef struct {
1146     unsigned windowLog;       /**< largest match distance : larger == more compression, more memory needed during decompression */
1147     unsigned chainLog;        /**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */
1148     unsigned hashLog;         /**< dispatch table : larger == faster, more memory */
1149     unsigned searchLog;       /**< nb of searches : larger == more compression, slower */
1150     unsigned minMatch;        /**< match length searched : larger == faster decompression, sometimes less compression */
1151     unsigned targetLength;    /**< acceptable match size for optimal parser (only) : larger == more compression, slower */
1152     ZSTD_strategy strategy;   /**< see ZSTD_strategy definition above */
1153 } ZSTD_compressionParameters;
1154 
1155 typedef struct {
1156     int contentSizeFlag; /**< 1: content size will be in frame header (when known) */
1157     int checksumFlag;    /**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */
1158     int noDictIDFlag;    /**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */
1159 } ZSTD_frameParameters;
1160 
1161 typedef struct {
1162     ZSTD_compressionParameters cParams;
1163     ZSTD_frameParameters fParams;
1164 } ZSTD_parameters;
1165 
1166 typedef enum {
1167     ZSTD_dct_auto = 0,       /* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */
1168     ZSTD_dct_rawContent = 1, /* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */
1169     ZSTD_dct_fullDict = 2    /* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */
1170 } ZSTD_dictContentType_e;
1171 
1172 typedef enum {
1173     ZSTD_dlm_byCopy = 0,  /**< Copy dictionary content internally */
1174     ZSTD_dlm_byRef = 1    /**< Reference dictionary content -- the dictionary buffer must outlive its users. */
1175 } ZSTD_dictLoadMethod_e;
1176 
1177 typedef enum {
1178     ZSTD_f_zstd1 = 0,           /* zstd frame format, specified in zstd_compression_format.md (default) */
1179     ZSTD_f_zstd1_magicless = 1  /* Variant of zstd frame format, without initial 4-bytes magic number.
1180                                  * Useful to save 4 bytes per generated frame.
1181                                  * Decoder cannot recognise automatically this format, requiring this instruction. */
1182 } ZSTD_format_e;
1183 
1184 typedef enum {
1185     /* Note: this enum and the behavior it controls are effectively internal
1186      * implementation details of the compressor. They are expected to continue
1187      * to evolve and should be considered only in the context of extremely
1188      * advanced performance tuning.
1189      *
1190      * Zstd currently supports the use of a CDict in three ways:
1191      *
1192      * - The contents of the CDict can be copied into the working context. This
1193      *   means that the compression can search both the dictionary and input
1194      *   while operating on a single set of internal tables. This makes
1195      *   the compression faster per-byte of input. However, the initial copy of
1196      *   the CDict's tables incurs a fixed cost at the beginning of the
1197      *   compression. For small compressions (< 8 KB), that copy can dominate
1198      *   the cost of the compression.
1199      *
1200      * - The CDict's tables can be used in-place. In this model, compression is
1201      *   slower per input byte, because the compressor has to search two sets of
1202      *   tables. However, this model incurs no start-up cost (as long as the
1203      *   working context's tables can be reused). For small inputs, this can be
1204      *   faster than copying the CDict's tables.
1205      *
1206      * - The CDict's tables are not used at all, and instead we use the working
1207      *   context alone to reload the dictionary and use params based on the source
1208      *   size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1209      *   This method is effective when the dictionary sizes are very small relative
1210      *   to the input size, and the input size is fairly large to begin with.
1211      *
1212      * Zstd has a simple internal heuristic that selects which strategy to use
1213      * at the beginning of a compression. However, if experimentation shows that
1214      * Zstd is making poor choices, it is possible to override that choice with
1215      * this enum.
1216      */
1217     ZSTD_dictDefaultAttach = 0, /* Use the default heuristic. */
1218     ZSTD_dictForceAttach   = 1, /* Never copy the dictionary. */
1219     ZSTD_dictForceCopy     = 2, /* Always copy the dictionary. */
1220     ZSTD_dictForceLoad     = 3  /* Always reload the dictionary */
1221 } ZSTD_dictAttachPref_e;
1222 
1223 typedef enum {
1224   ZSTD_lcm_auto = 0,          /**< Automatically determine the compression mode based on the compression level.
1225                                *   Negative compression levels will be uncompressed, and positive compression
1226                                *   levels will be compressed. */
1227   ZSTD_lcm_huffman = 1,       /**< Always attempt Huffman compression. Uncompressed literals will still be
1228                                *   emitted if Huffman compression is not profitable. */
1229   ZSTD_lcm_uncompressed = 2   /**< Always emit uncompressed literals. */
1230 } ZSTD_literalCompressionMode_e;
1231 
1232 
1233 /***************************************
1234 *  Frame size functions
1235 ***************************************/
1236 
1237 /*! ZSTD_findDecompressedSize() :
1238  *  `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1239  *  `srcSize` must be the _exact_ size of this series
1240  *       (i.e. there should be a frame boundary at `src + srcSize`)
1241  *  @return : - decompressed size of all data in all successive frames
1242  *            - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1243  *            - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1244  *
1245  *   note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1246  *            When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1247  *            In which case, it's necessary to use streaming mode to decompress data.
1248  *   note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1249  *   note 3 : decompressed size can be very large (64-bits value),
1250  *            potentially larger than what local system can handle as a single memory segment.
1251  *            In which case, it's necessary to use streaming mode to decompress data.
1252  *   note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1253  *            Always ensure result fits within application's authorized limits.
1254  *            Each application can set its own limits.
1255  *   note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1256  *            read each contained frame header.  This is fast as most of the data is skipped,
1257  *            however it does mean that all frame data must be present and valid. */
1258 ZSTDLIB_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1259 
1260 /*! ZSTD_decompressBound() :
1261  *  `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1262  *  `srcSize` must be the _exact_ size of this series
1263  *       (i.e. there should be a frame boundary at `src + srcSize`)
1264  *  @return : - upper-bound for the decompressed size of all data in all successive frames
1265  *            - if an error occured: ZSTD_CONTENTSIZE_ERROR
1266  *
1267  *  note 1  : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1268  *  note 2  : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1269  *            in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1270  *  note 3  : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1271  *              upper-bound = # blocks * min(128 KB, Window_Size)
1272  */
1273 ZSTDLIB_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1274 
1275 /*! ZSTD_frameHeaderSize() :
1276  *  srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1277  * @return : size of the Frame Header,
1278  *           or an error code (if srcSize is too small) */
1279 ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1280 
1281 /*! ZSTD_getSequences() :
1282  * Extract sequences from the sequence store
1283  * zc can be used to insert custom compression params.
1284  * This function invokes ZSTD_compress2
1285  * @return : number of sequences extracted
1286  */
1287 ZSTDLIB_API size_t ZSTD_getSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs,
1288     size_t outSeqsSize, const void* src, size_t srcSize);
1289 
1290 
1291 /***************************************
1292 *  Memory management
1293 ***************************************/
1294 
1295 /*! ZSTD_estimate*() :
1296  *  These functions make it possible to estimate memory usage
1297  *  of a future {D,C}Ctx, before its creation.
1298  *
1299  *  ZSTD_estimateCCtxSize() will provide a memory budget large enough
1300  *  for any compression level up to selected one.
1301  *  Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
1302  *         does not include space for a window buffer.
1303  *         Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
1304  *  The estimate will assume the input may be arbitrarily large,
1305  *  which is the worst case.
1306  *
1307  *  When srcSize can be bound by a known and rather "small" value,
1308  *  this fact can be used to provide a tighter estimation
1309  *  because the CCtx compression context will need less memory.
1310  *  This tighter estimation can be provided by more advanced functions
1311  *  ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1312  *  and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1313  *  Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1314  *
1315  *  Note 2 : only single-threaded compression is supported.
1316  *  ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1317  */
1318 ZSTDLIB_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
1319 ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1320 ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1321 ZSTDLIB_API size_t ZSTD_estimateDCtxSize(void);
1322 
1323 /*! ZSTD_estimateCStreamSize() :
1324  *  ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1325  *  It will also consider src size to be arbitrarily "large", which is worst case.
1326  *  If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1327  *  ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1328  *  ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
1329  *  Note : CStream size estimation is only correct for single-threaded compression.
1330  *  ZSTD_DStream memory budget depends on window Size.
1331  *  This information can be passed manually, using ZSTD_estimateDStreamSize,
1332  *  or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1333  *  Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1334  *         an internal ?Dict will be created, which additional size is not estimated here.
1335  *         In this case, get total size by adding ZSTD_estimate?DictSize */
1336 ZSTDLIB_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
1337 ZSTDLIB_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1338 ZSTDLIB_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1339 ZSTDLIB_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
1340 ZSTDLIB_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1341 
1342 /*! ZSTD_estimate?DictSize() :
1343  *  ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1344  *  ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1345  *  Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1346  */
1347 ZSTDLIB_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1348 ZSTDLIB_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1349 ZSTDLIB_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1350 
1351 /*! ZSTD_initStatic*() :
1352  *  Initialize an object using a pre-allocated fixed-size buffer.
1353  *  workspace: The memory area to emplace the object into.
1354  *             Provided pointer *must be 8-bytes aligned*.
1355  *             Buffer must outlive object.
1356  *  workspaceSize: Use ZSTD_estimate*Size() to determine
1357  *                 how large workspace must be to support target scenario.
1358  * @return : pointer to object (same address as workspace, just different type),
1359  *           or NULL if error (size too small, incorrect alignment, etc.)
1360  *  Note : zstd will never resize nor malloc() when using a static buffer.
1361  *         If the object requires more memory than available,
1362  *         zstd will just error out (typically ZSTD_error_memory_allocation).
1363  *  Note 2 : there is no corresponding "free" function.
1364  *           Since workspace is allocated externally, it must be freed externally too.
1365  *  Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1366  *           into its associated cParams.
1367  *  Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1368  *                 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1369  *  Limitation 2 : static cctx currently not compatible with multi-threading.
1370  *  Limitation 3 : static dctx is incompatible with legacy support.
1371  */
1372 ZSTDLIB_API ZSTD_CCtx*    ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1373 ZSTDLIB_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize);    /**< same as ZSTD_initStaticCCtx() */
1374 
1375 ZSTDLIB_API ZSTD_DCtx*    ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);
1376 ZSTDLIB_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize);    /**< same as ZSTD_initStaticDCtx() */
1377 
1378 ZSTDLIB_API const ZSTD_CDict* ZSTD_initStaticCDict(
1379                                         void* workspace, size_t workspaceSize,
1380                                         const void* dict, size_t dictSize,
1381                                         ZSTD_dictLoadMethod_e dictLoadMethod,
1382                                         ZSTD_dictContentType_e dictContentType,
1383                                         ZSTD_compressionParameters cParams);
1384 
1385 ZSTDLIB_API const ZSTD_DDict* ZSTD_initStaticDDict(
1386                                         void* workspace, size_t workspaceSize,
1387                                         const void* dict, size_t dictSize,
1388                                         ZSTD_dictLoadMethod_e dictLoadMethod,
1389                                         ZSTD_dictContentType_e dictContentType);
1390 
1391 
1392 /*! Custom memory allocation :
1393  *  These prototypes make it possible to pass your own allocation/free functions.
1394  *  ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1395  *  All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1396  */
1397 typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1398 typedef void  (*ZSTD_freeFunction) (void* opaque, void* address);
1399 typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1400 static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL };  /**< this constant defers to stdlib's functions */
1401 
1402 ZSTDLIB_API ZSTD_CCtx*    ZSTD_createCCtx_advanced(ZSTD_customMem customMem);
1403 ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
1404 ZSTDLIB_API ZSTD_DCtx*    ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
1405 ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
1406 
1407 ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
1408                                                   ZSTD_dictLoadMethod_e dictLoadMethod,
1409                                                   ZSTD_dictContentType_e dictContentType,
1410                                                   ZSTD_compressionParameters cParams,
1411                                                   ZSTD_customMem customMem);
1412 
1413 ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
1414                                                   ZSTD_dictLoadMethod_e dictLoadMethod,
1415                                                   ZSTD_dictContentType_e dictContentType,
1416                                                   ZSTD_customMem customMem);
1417 
1418 
1419 
1420 /***************************************
1421 *  Advanced compression functions
1422 ***************************************/
1423 
1424 /*! ZSTD_createCDict_byReference() :
1425  *  Create a digested dictionary for compression
1426  *  Dictionary content is just referenced, not duplicated.
1427  *  As a consequence, `dictBuffer` **must** outlive CDict,
1428  *  and its content must remain unmodified throughout the lifetime of CDict.
1429  *  note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef */
1430 ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1431 
1432 /*! ZSTD_getCParams() :
1433  * @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1434  * `estimatedSrcSize` value is optional, select 0 if not known */
1435 ZSTDLIB_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1436 
1437 /*! ZSTD_getParams() :
1438  *  same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1439  *  All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 */
1440 ZSTDLIB_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1441 
1442 /*! ZSTD_checkCParams() :
1443  *  Ensure param values remain within authorized range.
1444  * @return 0 on success, or an error code (can be checked with ZSTD_isError()) */
1445 ZSTDLIB_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1446 
1447 /*! ZSTD_adjustCParams() :
1448  *  optimize params for a given `srcSize` and `dictSize`.
1449  * `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1450  * `dictSize` must be `0` when there is no dictionary.
1451  *  cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1452  *  This function never fails (wide contract) */
1453 ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1454 
1455 /*! ZSTD_compress_advanced() :
1456  *  Note : this function is now DEPRECATED.
1457  *         It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1458  *  This prototype will be marked as deprecated and generate compilation warning on reaching v1.5.x */
1459 ZSTDLIB_API size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1460                                           void* dst, size_t dstCapacity,
1461                                     const void* src, size_t srcSize,
1462                                     const void* dict,size_t dictSize,
1463                                           ZSTD_parameters params);
1464 
1465 /*! ZSTD_compress_usingCDict_advanced() :
1466  *  Note : this function is now REDUNDANT.
1467  *         It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1468  *  This prototype will be marked as deprecated and generate compilation warning in some future version */
1469 ZSTDLIB_API size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1470                                               void* dst, size_t dstCapacity,
1471                                         const void* src, size_t srcSize,
1472                                         const ZSTD_CDict* cdict,
1473                                               ZSTD_frameParameters fParams);
1474 
1475 
1476 /*! ZSTD_CCtx_loadDictionary_byReference() :
1477  *  Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1478  *  It saves some memory, but also requires that `dict` outlives its usage within `cctx` */
1479 ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1480 
1481 /*! ZSTD_CCtx_loadDictionary_advanced() :
1482  *  Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1483  *  how to load the dictionary (by copy ? by reference ?)
1484  *  and how to interpret it (automatic ? force raw mode ? full mode only ?) */
1485 ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1486 
1487 /*! ZSTD_CCtx_refPrefix_advanced() :
1488  *  Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1489  *  how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
1490 ZSTDLIB_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1491 
1492 /* ===   experimental parameters   === */
1493 /* these parameters can be used with ZSTD_setParameter()
1494  * they are not guaranteed to remain supported in the future */
1495 
1496  /* Enables rsyncable mode,
1497   * which makes compressed files more rsync friendly
1498   * by adding periodic synchronization points to the compressed data.
1499   * The target average block size is ZSTD_c_jobSize / 2.
1500   * It's possible to modify the job size to increase or decrease
1501   * the granularity of the synchronization point.
1502   * Once the jobSize is smaller than the window size,
1503   * it will result in compression ratio degradation.
1504   * NOTE 1: rsyncable mode only works when multithreading is enabled.
1505   * NOTE 2: rsyncable performs poorly in combination with long range mode,
1506   * since it will decrease the effectiveness of synchronization points,
1507   * though mileage may vary.
1508   * NOTE 3: Rsyncable mode limits maximum compression speed to ~400 MB/s.
1509   * If the selected compression level is already running significantly slower,
1510   * the overall speed won't be significantly impacted.
1511   */
1512  #define ZSTD_c_rsyncable ZSTD_c_experimentalParam1
1513 
1514 /* Select a compression format.
1515  * The value must be of type ZSTD_format_e.
1516  * See ZSTD_format_e enum definition for details */
1517 #define ZSTD_c_format ZSTD_c_experimentalParam2
1518 
1519 /* Force back-reference distances to remain < windowSize,
1520  * even when referencing into Dictionary content (default:0) */
1521 #define ZSTD_c_forceMaxWindow ZSTD_c_experimentalParam3
1522 
1523 /* Controls whether the contents of a CDict
1524  * are used in place, or copied into the working context.
1525  * Accepts values from the ZSTD_dictAttachPref_e enum.
1526  * See the comments on that enum for an explanation of the feature. */
1527 #define ZSTD_c_forceAttachDict ZSTD_c_experimentalParam4
1528 
1529 /* Controls how the literals are compressed (default is auto).
1530  * The value must be of type ZSTD_literalCompressionMode_e.
1531  * See ZSTD_literalCompressionMode_t enum definition for details.
1532  */
1533 #define ZSTD_c_literalCompressionMode ZSTD_c_experimentalParam5
1534 
1535 /* Tries to fit compressed block size to be around targetCBlockSize.
1536  * No target when targetCBlockSize == 0.
1537  * There is no guarantee on compressed block size (default:0) */
1538 #define ZSTD_c_targetCBlockSize ZSTD_c_experimentalParam6
1539 
1540 /* User's best guess of source size.
1541  * Hint is not valid when srcSizeHint == 0.
1542  * There is no guarantee that hint is close to actual source size,
1543  * but compression ratio may regress significantly if guess considerably underestimates */
1544 #define ZSTD_c_srcSizeHint ZSTD_c_experimentalParam7
1545 
1546 /*! ZSTD_CCtx_getParameter() :
1547  *  Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1548  *  and store it into int* value.
1549  * @return : 0, or an error code (which can be tested with ZSTD_isError()).
1550  */
1551 ZSTDLIB_API size_t ZSTD_CCtx_getParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1552 
1553 
1554 /*! ZSTD_CCtx_params :
1555  *  Quick howto :
1556  *  - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1557  *  - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1558  *                                     an existing ZSTD_CCtx_params structure.
1559  *                                     This is similar to
1560  *                                     ZSTD_CCtx_setParameter().
1561  *  - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1562  *                                    an existing CCtx.
1563  *                                    These parameters will be applied to
1564  *                                    all subsequent frames.
1565  *  - ZSTD_compressStream2() : Do compression using the CCtx.
1566  *  - ZSTD_freeCCtxParams() : Free the memory.
1567  *
1568  *  This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1569  *  for static allocation of CCtx for single-threaded compression.
1570  */
1571 ZSTDLIB_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1572 ZSTDLIB_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params);
1573 
1574 /*! ZSTD_CCtxParams_reset() :
1575  *  Reset params to default values.
1576  */
1577 ZSTDLIB_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1578 
1579 /*! ZSTD_CCtxParams_init() :
1580  *  Initializes the compression parameters of cctxParams according to
1581  *  compression level. All other parameters are reset to their default values.
1582  */
1583 ZSTDLIB_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1584 
1585 /*! ZSTD_CCtxParams_init_advanced() :
1586  *  Initializes the compression and frame parameters of cctxParams according to
1587  *  params. All other parameters are reset to their default values.
1588  */
1589 ZSTDLIB_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1590 
1591 /*! ZSTD_CCtxParams_setParameter() :
1592  *  Similar to ZSTD_CCtx_setParameter.
1593  *  Set one compression parameter, selected by enum ZSTD_cParameter.
1594  *  Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams().
1595  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1596  */
1597 ZSTDLIB_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1598 
1599 /*! ZSTD_CCtxParams_getParameter() :
1600  * Similar to ZSTD_CCtx_getParameter.
1601  * Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1602  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
1603  */
1604 ZSTDLIB_API size_t ZSTD_CCtxParams_getParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1605 
1606 /*! ZSTD_CCtx_setParametersUsingCCtxParams() :
1607  *  Apply a set of ZSTD_CCtx_params to the compression context.
1608  *  This can be done even after compression is started,
1609  *    if nbWorkers==0, this will have no impact until a new compression is started.
1610  *    if nbWorkers>=1, new parameters will be picked up at next job,
1611  *       with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1612  */
1613 ZSTDLIB_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1614         ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1615 
1616 /*! ZSTD_compressStream2_simpleArgs() :
1617  *  Same as ZSTD_compressStream2(),
1618  *  but using only integral types as arguments.
1619  *  This variant might be helpful for binders from dynamic languages
1620  *  which have troubles handling structures containing memory pointers.
1621  */
1622 ZSTDLIB_API size_t ZSTD_compressStream2_simpleArgs (
1623                             ZSTD_CCtx* cctx,
1624                             void* dst, size_t dstCapacity, size_t* dstPos,
1625                       const void* src, size_t srcSize, size_t* srcPos,
1626                             ZSTD_EndDirective endOp);
1627 
1628 
1629 /***************************************
1630 *  Advanced decompression functions
1631 ***************************************/
1632 
1633 /*! ZSTD_isFrame() :
1634  *  Tells if the content of `buffer` starts with a valid Frame Identifier.
1635  *  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1636  *  Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1637  *  Note 3 : Skippable Frame Identifiers are considered valid. */
1638 ZSTDLIB_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
1639 
1640 /*! ZSTD_createDDict_byReference() :
1641  *  Create a digested dictionary, ready to start decompression operation without startup delay.
1642  *  Dictionary content is referenced, and therefore stays in dictBuffer.
1643  *  It is important that dictBuffer outlives DDict,
1644  *  it must remain read accessible throughout the lifetime of DDict */
1645 ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1646 
1647 /*! ZSTD_DCtx_loadDictionary_byReference() :
1648  *  Same as ZSTD_DCtx_loadDictionary(),
1649  *  but references `dict` content instead of copying it into `dctx`.
1650  *  This saves memory if `dict` remains around.,
1651  *  However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. */
1652 ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1653 
1654 /*! ZSTD_DCtx_loadDictionary_advanced() :
1655  *  Same as ZSTD_DCtx_loadDictionary(),
1656  *  but gives direct control over
1657  *  how to load the dictionary (by copy ? by reference ?)
1658  *  and how to interpret it (automatic ? force raw mode ? full mode only ?). */
1659 ZSTDLIB_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1660 
1661 /*! ZSTD_DCtx_refPrefix_advanced() :
1662  *  Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1663  *  how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) */
1664 ZSTDLIB_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1665 
1666 /*! ZSTD_DCtx_setMaxWindowSize() :
1667  *  Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1668  *  This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1669  *  This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1670  *  By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1671  * @return : 0, or an error code (which can be tested using ZSTD_isError()).
1672  */
1673 ZSTDLIB_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1674 
1675 /* ZSTD_d_format
1676  * experimental parameter,
1677  * allowing selection between ZSTD_format_e input compression formats
1678  */
1679 #define ZSTD_d_format ZSTD_d_experimentalParam1
1680 /* ZSTD_d_stableOutBuffer
1681  * Experimental parameter.
1682  * Default is 0 == disabled. Set to 1 to enable.
1683  *
1684  * Tells the decompressor that the ZSTD_outBuffer will ALWAYS be the same
1685  * between calls, except for the modifications that zstd makes to pos (the
1686  * caller must not modify pos). This is checked by the decompressor, and
1687  * decompression will fail if it ever changes. Therefore the ZSTD_outBuffer
1688  * MUST be large enough to fit the entire decompressed frame. This will be
1689  * checked when the frame content size is known. The data in the ZSTD_outBuffer
1690  * in the range [dst, dst + pos) MUST not be modified during decompression
1691  * or you will get data corruption.
1692  *
1693  * When this flags is enabled zstd won't allocate an output buffer, because
1694  * it can write directly to the ZSTD_outBuffer, but it will still allocate
1695  * an input buffer large enough to fit any compressed block. This will also
1696  * avoid the memcpy() from the internal output buffer to the ZSTD_outBuffer.
1697  * If you need to avoid the input buffer allocation use the buffer-less
1698  * streaming API.
1699  *
1700  * NOTE: So long as the ZSTD_outBuffer always points to valid memory, using
1701  * this flag is ALWAYS memory safe, and will never access out-of-bounds
1702  * memory. However, decompression WILL fail if you violate the preconditions.
1703  *
1704  * WARNING: The data in the ZSTD_outBuffer in the range [dst, dst + pos) MUST
1705  * not be modified during decompression or you will get data corruption. This
1706  * is because zstd needs to reference data in the ZSTD_outBuffer to regenerate
1707  * matches. Normally zstd maintains its own buffer for this purpose, but passing
1708  * this flag tells zstd to use the user provided buffer.
1709  */
1710 #define ZSTD_d_stableOutBuffer ZSTD_d_experimentalParam2
1711 
1712 /*! ZSTD_DCtx_setFormat() :
1713  *  Instruct the decoder context about what kind of data to decode next.
1714  *  This instruction is mandatory to decode data without a fully-formed header,
1715  *  such ZSTD_f_zstd1_magicless for example.
1716  * @return : 0, or an error code (which can be tested using ZSTD_isError()). */
1717 ZSTDLIB_API size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1718 
1719 /*! ZSTD_decompressStream_simpleArgs() :
1720  *  Same as ZSTD_decompressStream(),
1721  *  but using only integral types as arguments.
1722  *  This can be helpful for binders from dynamic languages
1723  *  which have troubles handling structures containing memory pointers.
1724  */
1725 ZSTDLIB_API size_t ZSTD_decompressStream_simpleArgs (
1726                             ZSTD_DCtx* dctx,
1727                             void* dst, size_t dstCapacity, size_t* dstPos,
1728                       const void* src, size_t srcSize, size_t* srcPos);
1729 
1730 
1731 /********************************************************************
1732 *  Advanced streaming functions
1733 *  Warning : most of these functions are now redundant with the Advanced API.
1734 *  Once Advanced API reaches "stable" status,
1735 *  redundant functions will be deprecated, and then at some point removed.
1736 ********************************************************************/
1737 
1738 /*=====   Advanced Streaming compression functions  =====*/
1739 /**! ZSTD_initCStream_srcSize() :
1740  * This function is deprecated, and equivalent to:
1741  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1742  *     ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
1743  *     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1744  *     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1745  *
1746  * pledgedSrcSize must be correct. If it is not known at init time, use
1747  * ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
1748  * "0" also disables frame content size field. It may be enabled in the future.
1749  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1750  */
1751 ZSTDLIB_API size_t
1752 ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
1753                          int compressionLevel,
1754                          unsigned long long pledgedSrcSize);
1755 
1756 /**! ZSTD_initCStream_usingDict() :
1757  * This function is deprecated, and is equivalent to:
1758  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1759  *     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1760  *     ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1761  *
1762  * Creates of an internal CDict (incompatible with static CCtx), except if
1763  * dict == NULL or dictSize < 8, in which case no dict is used.
1764  * Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
1765  * it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
1766  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1767  */
1768 ZSTDLIB_API size_t
1769 ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
1770                      const void* dict, size_t dictSize,
1771                            int compressionLevel);
1772 
1773 /**! ZSTD_initCStream_advanced() :
1774  * This function is deprecated, and is approximately equivalent to:
1775  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1776  *     // Pseudocode: Set each zstd parameter and leave the rest as-is.
1777  *     for ((param, value) : params) {
1778  *         ZSTD_CCtx_setParameter(zcs, param, value);
1779  *     }
1780  *     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1781  *     ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1782  *
1783  * dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
1784  * pledgedSrcSize must be correct.
1785  * If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
1786  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1787  */
1788 ZSTDLIB_API size_t
1789 ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
1790                     const void* dict, size_t dictSize,
1791                           ZSTD_parameters params,
1792                           unsigned long long pledgedSrcSize);
1793 
1794 /**! ZSTD_initCStream_usingCDict() :
1795  * This function is deprecated, and equivalent to:
1796  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1797  *     ZSTD_CCtx_refCDict(zcs, cdict);
1798  *
1799  * note : cdict will just be referenced, and must outlive compression session
1800  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1801  */
1802 ZSTDLIB_API size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
1803 
1804 /**! ZSTD_initCStream_usingCDict_advanced() :
1805  *   This function is DEPRECATED, and is approximately equivalent to:
1806  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1807  *     // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
1808  *     for ((fParam, value) : fParams) {
1809  *         ZSTD_CCtx_setParameter(zcs, fParam, value);
1810  *     }
1811  *     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1812  *     ZSTD_CCtx_refCDict(zcs, cdict);
1813  *
1814  * same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
1815  * pledgedSrcSize must be correct. If srcSize is not known at init time, use
1816  * value ZSTD_CONTENTSIZE_UNKNOWN.
1817  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1818  */
1819 ZSTDLIB_API size_t
1820 ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
1821                                const ZSTD_CDict* cdict,
1822                                      ZSTD_frameParameters fParams,
1823                                      unsigned long long pledgedSrcSize);
1824 
1825 /*! ZSTD_resetCStream() :
1826  * This function is deprecated, and is equivalent to:
1827  *     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1828  *     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1829  *
1830  *  start a new frame, using same parameters from previous frame.
1831  *  This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
1832  *  Note that zcs must be init at least once before using ZSTD_resetCStream().
1833  *  If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1834  *  If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1835  *  For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1836  *  but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1837  * @return : 0, or an error code (which can be tested using ZSTD_isError())
1838  *  Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1839  */
1840 ZSTDLIB_API size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1841 
1842 
1843 typedef struct {
1844     unsigned long long ingested;   /* nb input bytes read and buffered */
1845     unsigned long long consumed;   /* nb input bytes actually compressed */
1846     unsigned long long produced;   /* nb of compressed bytes generated and buffered */
1847     unsigned long long flushed;    /* nb of compressed bytes flushed : not provided; can be tracked from caller side */
1848     unsigned currentJobID;         /* MT only : latest started job nb */
1849     unsigned nbActiveWorkers;      /* MT only : nb of workers actively compressing at probe time */
1850 } ZSTD_frameProgression;
1851 
1852 /* ZSTD_getFrameProgression() :
1853  * tells how much data has been ingested (read from input)
1854  * consumed (input actually compressed) and produced (output) for current frame.
1855  * Note : (ingested - consumed) is amount of input data buffered internally, not yet compressed.
1856  * Aggregates progression inside active worker threads.
1857  */
1858 ZSTDLIB_API ZSTD_frameProgression ZSTD_getFrameProgression(const ZSTD_CCtx* cctx);
1859 
1860 /*! ZSTD_toFlushNow() :
1861  *  Tell how many bytes are ready to be flushed immediately.
1862  *  Useful for multithreading scenarios (nbWorkers >= 1).
1863  *  Probe the oldest active job, defined as oldest job not yet entirely flushed,
1864  *  and check its output buffer.
1865  * @return : amount of data stored in oldest job and ready to be flushed immediately.
1866  *  if @return == 0, it means either :
1867  *  + there is no active job (could be checked with ZSTD_frameProgression()), or
1868  *  + oldest job is still actively compressing data,
1869  *    but everything it has produced has also been flushed so far,
1870  *    therefore flush speed is limited by production speed of oldest job
1871  *    irrespective of the speed of concurrent (and newer) jobs.
1872  */
1873 ZSTDLIB_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1874 
1875 
1876 /*=====   Advanced Streaming decompression functions  =====*/
1877 /**
1878  * This function is deprecated, and is equivalent to:
1879  *
1880  *     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1881  *     ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
1882  *
1883  * note: no dictionary will be used if dict == NULL or dictSize < 8
1884  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1885  */
1886 ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
1887 
1888 /**
1889  * This function is deprecated, and is equivalent to:
1890  *
1891  *     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1892  *     ZSTD_DCtx_refDDict(zds, ddict);
1893  *
1894  * note : ddict is referenced, it must outlive decompression session
1895  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1896  */
1897 ZSTDLIB_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
1898 
1899 /**
1900  * This function is deprecated, and is equivalent to:
1901  *
1902  *     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1903  *
1904  * re-use decompression parameters from previous init; saves dictionary loading
1905  * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1906  */
1907 ZSTDLIB_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
1908 
1909 
1910 /*********************************************************************
1911 *  Buffer-less and synchronous inner streaming functions
1912 *
1913 *  This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
1914 *  But it's also a complex one, with several restrictions, documented below.
1915 *  Prefer normal streaming API for an easier experience.
1916 ********************************************************************* */
1917 
1918 /**
1919   Buffer-less streaming compression (synchronous mode)
1920 
1921   A ZSTD_CCtx object is required to track streaming operations.
1922   Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
1923   ZSTD_CCtx object can be re-used multiple times within successive compression operations.
1924 
1925   Start by initializing a context.
1926   Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
1927   or ZSTD_compressBegin_advanced(), for finer parameter control.
1928   It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
1929 
1930   Then, consume your input using ZSTD_compressContinue().
1931   There are some important considerations to keep in mind when using this advanced function :
1932   - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
1933   - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
1934   - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
1935     Worst case evaluation is provided by ZSTD_compressBound().
1936     ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
1937   - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
1938     It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
1939   - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
1940     In which case, it will "discard" the relevant memory section from its history.
1941 
1942   Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
1943   It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
1944   Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
1945 
1946   `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
1947 */
1948 
1949 /*=====   Buffer-less streaming compression functions  =====*/
1950 ZSTDLIB_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
1951 ZSTDLIB_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
1952 ZSTDLIB_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 */
1953 ZSTDLIB_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); /**< note: fails if cdict==NULL */
1954 ZSTDLIB_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 */
1955 ZSTDLIB_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 */
1956 
1957 ZSTDLIB_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1958 ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1959 
1960 
1961 /*-
1962   Buffer-less streaming decompression (synchronous mode)
1963 
1964   A ZSTD_DCtx object is required to track streaming operations.
1965   Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
1966   A ZSTD_DCtx object can be re-used multiple times.
1967 
1968   First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
1969   Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
1970   Data fragment must be large enough to ensure successful decoding.
1971  `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
1972   @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
1973            >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
1974            errorCode, which can be tested using ZSTD_isError().
1975 
1976   It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
1977   such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
1978   Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
1979   As a consequence, check that values remain within valid application range.
1980   For example, do not allocate memory blindly, check that `windowSize` is within expectation.
1981   Each application can set its own limits, depending on local restrictions.
1982   For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
1983 
1984   ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
1985   ZSTD_decompressContinue() is very sensitive to contiguity,
1986   if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
1987   or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
1988   There are multiple ways to guarantee this condition.
1989 
1990   The most memory efficient way is to use a round buffer of sufficient size.
1991   Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
1992   which can @return an error code if required value is too large for current system (in 32-bits mode).
1993   In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
1994   up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
1995   which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
1996   At which point, decoding can resume from the beginning of the buffer.
1997   Note that already decoded data stored in the buffer should be flushed before being overwritten.
1998 
1999   There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
2000 
2001   Finally, if you control the compression process, you can also ignore all buffer size rules,
2002   as long as the encoder and decoder progress in "lock-step",
2003   aka use exactly the same buffer sizes, break contiguity at the same place, etc.
2004 
2005   Once buffers are setup, start decompression, with ZSTD_decompressBegin().
2006   If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
2007 
2008   Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
2009   ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
2010   ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
2011 
2012  @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
2013   It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
2014   It can also be an error code, which can be tested with ZSTD_isError().
2015 
2016   A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
2017   Context can then be reset to start a new decompression.
2018 
2019   Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
2020   This information is not required to properly decode a frame.
2021 
2022   == Special case : skippable frames ==
2023 
2024   Skippable frames allow integration of user-defined data into a flow of concatenated frames.
2025   Skippable frames will be ignored (skipped) by decompressor.
2026   The format of skippable frames is as follows :
2027   a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
2028   b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
2029   c) Frame Content - any content (User Data) of length equal to Frame Size
2030   For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
2031   For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
2032 */
2033 
2034 /*=====   Buffer-less streaming decompression functions  =====*/
2035 typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
2036 typedef struct {
2037     unsigned long long frameContentSize; /* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */
2038     unsigned long long windowSize;       /* can be very large, up to <= frameContentSize */
2039     unsigned blockSizeMax;
2040     ZSTD_frameType_e frameType;          /* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */
2041     unsigned headerSize;
2042     unsigned dictID;
2043     unsigned checksumFlag;
2044 } ZSTD_frameHeader;
2045 
2046 /*! ZSTD_getFrameHeader() :
2047  *  decode Frame Header, or requires larger `srcSize`.
2048  * @return : 0, `zfhPtr` is correctly filled,
2049  *          >0, `srcSize` is too small, value is wanted `srcSize` amount,
2050  *           or an error code, which can be tested using ZSTD_isError() */
2051 ZSTDLIB_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize);   /**< doesn't consume input */
2052 /*! ZSTD_getFrameHeader_advanced() :
2053  *  same as ZSTD_getFrameHeader(),
2054  *  with added capability to select a format (like ZSTD_f_zstd1_magicless) */
2055 ZSTDLIB_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
2056 ZSTDLIB_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 */
2057 
2058 ZSTDLIB_API size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
2059 ZSTDLIB_API size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
2060 ZSTDLIB_API size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
2061 
2062 ZSTDLIB_API size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
2063 ZSTDLIB_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2064 
2065 /* misc */
2066 ZSTDLIB_API void   ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
2067 typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
2068 ZSTDLIB_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
2069 
2070 
2071 
2072 
2073 /* ============================ */
2074 /**       Block level API       */
2075 /* ============================ */
2076 
2077 /*!
2078     Block functions produce and decode raw zstd blocks, without frame metadata.
2079     Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
2080     But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
2081 
2082     A few rules to respect :
2083     - Compressing and decompressing require a context structure
2084       + Use ZSTD_createCCtx() and ZSTD_createDCtx()
2085     - It is necessary to init context before starting
2086       + compression : any ZSTD_compressBegin*() variant, including with dictionary
2087       + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
2088       + copyCCtx() and copyDCtx() can be used too
2089     - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
2090       + If input is larger than a block size, it's necessary to split input data into multiple blocks
2091       + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
2092         Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
2093     - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
2094       ===> In which case, nothing is produced into `dst` !
2095       + User __must__ test for such outcome and deal directly with uncompressed data
2096       + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
2097         Doing so would mess up with statistics history, leading to potential data corruption.
2098       + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
2099       + In case of multiple successive blocks, should some of them be uncompressed,
2100         decoder must be informed of their existence in order to follow proper history.
2101         Use ZSTD_insertBlock() for such a case.
2102 */
2103 
2104 /*=====   Raw zstd block functions  =====*/
2105 ZSTDLIB_API size_t ZSTD_getBlockSize   (const ZSTD_CCtx* cctx);
2106 ZSTDLIB_API size_t ZSTD_compressBlock  (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2107 ZSTDLIB_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
2108 ZSTDLIB_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. */
2109 
2110 
2111 #endif   /* ZSTD_H_ZSTD_STATIC_LINKING_ONLY */
2112 
2113 #if defined (__cplusplus)
2114 }
2115 #endif
2116