1 /*
2 * FSE : Finite State Entropy codec
3 * Public Prototypes declaration
4 * Copyright (C) 2013-2016, Yann Collet.
5 *
6 * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions are
10 * met:
11 *
12 * * Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * * Redistributions in binary form must reproduce the above
15 * copyright notice, this list of conditions and the following disclaimer
16 * in the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 * This program is free software; you can redistribute it and/or modify it under
32 * the terms of the GNU General Public License version 2 as published by the
33 * Free Software Foundation. This program is dual-licensed; you may select
34 * either version 2 of the GNU General Public License ("GPL") or BSD license
35 * ("BSD").
36 *
37 * You can contact the author at :
38 * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
39 */
40 #ifndef FSE_H
41 #define FSE_H
42
43 /*-*****************************************
44 * Dependencies
45 ******************************************/
46 #include <linux/types.h> /* size_t, ptrdiff_t */
47
48 /*-*****************************************
49 * FSE_PUBLIC_API : control library symbols visibility
50 ******************************************/
51 #define FSE_PUBLIC_API
52
53 /*------ Version ------*/
54 #define FSE_VERSION_MAJOR 0
55 #define FSE_VERSION_MINOR 9
56 #define FSE_VERSION_RELEASE 0
57
58 #define FSE_LIB_VERSION FSE_VERSION_MAJOR.FSE_VERSION_MINOR.FSE_VERSION_RELEASE
59 #define FSE_QUOTE(str) #str
60 #define FSE_EXPAND_AND_QUOTE(str) FSE_QUOTE(str)
61 #define FSE_VERSION_STRING FSE_EXPAND_AND_QUOTE(FSE_LIB_VERSION)
62
63 #define FSE_VERSION_NUMBER (FSE_VERSION_MAJOR * 100 * 100 + FSE_VERSION_MINOR * 100 + FSE_VERSION_RELEASE)
64 FSE_PUBLIC_API unsigned FSE_versionNumber(void); /**< library version number; to be used when checking dll version */
65
66 /*-*****************************************
67 * Tool functions
68 ******************************************/
69 FSE_PUBLIC_API size_t FSE_compressBound(size_t size); /* maximum compressed size */
70
71 /* Error Management */
72 FSE_PUBLIC_API unsigned FSE_isError(size_t code); /* tells if a return value is an error code */
73
74 /*-*****************************************
75 * FSE detailed API
76 ******************************************/
77 /*!
78 FSE_compress() does the following:
79 1. count symbol occurrence from source[] into table count[]
80 2. normalize counters so that sum(count[]) == Power_of_2 (2^tableLog)
81 3. save normalized counters to memory buffer using writeNCount()
82 4. build encoding table 'CTable' from normalized counters
83 5. encode the data stream using encoding table 'CTable'
84
85 FSE_decompress() does the following:
86 1. read normalized counters with readNCount()
87 2. build decoding table 'DTable' from normalized counters
88 3. decode the data stream using decoding table 'DTable'
89
90 The following API allows targeting specific sub-functions for advanced tasks.
91 For example, it's possible to compress several blocks using the same 'CTable',
92 or to save and provide normalized distribution using external method.
93 */
94
95 /* *** COMPRESSION *** */
96 /*! FSE_optimalTableLog():
97 dynamically downsize 'tableLog' when conditions are met.
98 It saves CPU time, by using smaller tables, while preserving or even improving compression ratio.
99 @return : recommended tableLog (necessarily <= 'maxTableLog') */
100 FSE_PUBLIC_API unsigned FSE_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue);
101
102 /*! FSE_normalizeCount():
103 normalize counts so that sum(count[]) == Power_of_2 (2^tableLog)
104 'normalizedCounter' is a table of short, of minimum size (maxSymbolValue+1).
105 @return : tableLog,
106 or an errorCode, which can be tested using FSE_isError() */
107 FSE_PUBLIC_API size_t FSE_normalizeCount(short *normalizedCounter, unsigned tableLog, const unsigned *count, size_t srcSize, unsigned maxSymbolValue);
108
109 /*! FSE_NCountWriteBound():
110 Provides the maximum possible size of an FSE normalized table, given 'maxSymbolValue' and 'tableLog'.
111 Typically useful for allocation purpose. */
112 FSE_PUBLIC_API size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog);
113
114 /*! FSE_writeNCount():
115 Compactly save 'normalizedCounter' into 'buffer'.
116 @return : size of the compressed table,
117 or an errorCode, which can be tested using FSE_isError(). */
118 FSE_PUBLIC_API size_t FSE_writeNCount(void *buffer, size_t bufferSize, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
119
120 /*! Constructor and Destructor of FSE_CTable.
121 Note that FSE_CTable size depends on 'tableLog' and 'maxSymbolValue' */
122 typedef unsigned FSE_CTable; /* don't allocate that. It's only meant to be more restrictive than void* */
123
124 /*! FSE_compress_usingCTable():
125 Compress `src` using `ct` into `dst` which must be already allocated.
126 @return : size of compressed data (<= `dstCapacity`),
127 or 0 if compressed data could not fit into `dst`,
128 or an errorCode, which can be tested using FSE_isError() */
129 FSE_PUBLIC_API size_t FSE_compress_usingCTable(void *dst, size_t dstCapacity, const void *src, size_t srcSize, const FSE_CTable *ct);
130
131 /*!
132 Tutorial :
133 ----------
134 The first step is to count all symbols. FSE_count() does this job very fast.
135 Result will be saved into 'count', a table of unsigned int, which must be already allocated, and have 'maxSymbolValuePtr[0]+1' cells.
136 'src' is a table of bytes of size 'srcSize'. All values within 'src' MUST be <= maxSymbolValuePtr[0]
137 maxSymbolValuePtr[0] will be updated, with its real value (necessarily <= original value)
138 FSE_count() will return the number of occurrence of the most frequent symbol.
139 This can be used to know if there is a single symbol within 'src', and to quickly evaluate its compressibility.
140 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
141
142 The next step is to normalize the frequencies.
143 FSE_normalizeCount() will ensure that sum of frequencies is == 2 ^'tableLog'.
144 It also guarantees a minimum of 1 to any Symbol with frequency >= 1.
145 You can use 'tableLog'==0 to mean "use default tableLog value".
146 If you are unsure of which tableLog value to use, you can ask FSE_optimalTableLog(),
147 which will provide the optimal valid tableLog given sourceSize, maxSymbolValue, and a user-defined maximum (0 means "default").
148
149 The result of FSE_normalizeCount() will be saved into a table,
150 called 'normalizedCounter', which is a table of signed short.
151 'normalizedCounter' must be already allocated, and have at least 'maxSymbolValue+1' cells.
152 The return value is tableLog if everything proceeded as expected.
153 It is 0 if there is a single symbol within distribution.
154 If there is an error (ex: invalid tableLog value), the function will return an ErrorCode (which can be tested using FSE_isError()).
155
156 'normalizedCounter' can be saved in a compact manner to a memory area using FSE_writeNCount().
157 'buffer' must be already allocated.
158 For guaranteed success, buffer size must be at least FSE_headerBound().
159 The result of the function is the number of bytes written into 'buffer'.
160 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError(); ex : buffer size too small).
161
162 'normalizedCounter' can then be used to create the compression table 'CTable'.
163 The space required by 'CTable' must be already allocated, using FSE_createCTable().
164 You can then use FSE_buildCTable() to fill 'CTable'.
165 If there is an error, both functions will return an ErrorCode (which can be tested using FSE_isError()).
166
167 'CTable' can then be used to compress 'src', with FSE_compress_usingCTable().
168 Similar to FSE_count(), the convention is that 'src' is assumed to be a table of char of size 'srcSize'
169 The function returns the size of compressed data (without header), necessarily <= `dstCapacity`.
170 If it returns '0', compressed data could not fit into 'dst'.
171 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
172 */
173
174 /* *** DECOMPRESSION *** */
175
176 /*! FSE_readNCount():
177 Read compactly saved 'normalizedCounter' from 'rBuffer'.
178 @return : size read from 'rBuffer',
179 or an errorCode, which can be tested using FSE_isError().
180 maxSymbolValuePtr[0] and tableLogPtr[0] will also be updated with their respective values */
181 FSE_PUBLIC_API size_t FSE_readNCount(short *normalizedCounter, unsigned *maxSymbolValuePtr, unsigned *tableLogPtr, const void *rBuffer, size_t rBuffSize);
182
183 /*! Constructor and Destructor of FSE_DTable.
184 Note that its size depends on 'tableLog' */
185 typedef unsigned FSE_DTable; /* don't allocate that. It's just a way to be more restrictive than void* */
186
187 /*! FSE_buildDTable():
188 Builds 'dt', which must be already allocated, using FSE_createDTable().
189 return : 0, or an errorCode, which can be tested using FSE_isError() */
190 FSE_PUBLIC_API size_t FSE_buildDTable_wksp(FSE_DTable *dt, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void *workspace, size_t workspaceSize);
191
192 /*! FSE_decompress_usingDTable():
193 Decompress compressed source `cSrc` of size `cSrcSize` using `dt`
194 into `dst` which must be already allocated.
195 @return : size of regenerated data (necessarily <= `dstCapacity`),
196 or an errorCode, which can be tested using FSE_isError() */
197 FSE_PUBLIC_API size_t FSE_decompress_usingDTable(void *dst, size_t dstCapacity, const void *cSrc, size_t cSrcSize, const FSE_DTable *dt);
198
199 /*!
200 Tutorial :
201 ----------
202 (Note : these functions only decompress FSE-compressed blocks.
203 If block is uncompressed, use memcpy() instead
204 If block is a single repeated byte, use memset() instead )
205
206 The first step is to obtain the normalized frequencies of symbols.
207 This can be performed by FSE_readNCount() if it was saved using FSE_writeNCount().
208 'normalizedCounter' must be already allocated, and have at least 'maxSymbolValuePtr[0]+1' cells of signed short.
209 In practice, that means it's necessary to know 'maxSymbolValue' beforehand,
210 or size the table to handle worst case situations (typically 256).
211 FSE_readNCount() will provide 'tableLog' and 'maxSymbolValue'.
212 The result of FSE_readNCount() is the number of bytes read from 'rBuffer'.
213 Note that 'rBufferSize' must be at least 4 bytes, even if useful information is less than that.
214 If there is an error, the function will return an error code, which can be tested using FSE_isError().
215
216 The next step is to build the decompression tables 'FSE_DTable' from 'normalizedCounter'.
217 This is performed by the function FSE_buildDTable().
218 The space required by 'FSE_DTable' must be already allocated using FSE_createDTable().
219 If there is an error, the function will return an error code, which can be tested using FSE_isError().
220
221 `FSE_DTable` can then be used to decompress `cSrc`, with FSE_decompress_usingDTable().
222 `cSrcSize` must be strictly correct, otherwise decompression will fail.
223 FSE_decompress_usingDTable() result will tell how many bytes were regenerated (<=`dstCapacity`).
224 If there is an error, the function will return an error code, which can be tested using FSE_isError(). (ex: dst buffer too small)
225 */
226
227 /* *** Dependency *** */
228 #include "bitstream.h"
229
230 /* *****************************************
231 * Static allocation
232 *******************************************/
233 /* FSE buffer bounds */
234 #define FSE_NCOUNTBOUND 512
235 #define FSE_BLOCKBOUND(size) (size + (size >> 7))
236 #define FSE_COMPRESSBOUND(size) (FSE_NCOUNTBOUND + FSE_BLOCKBOUND(size)) /* Macro version, useful for static allocation */
237
238 /* It is possible to statically allocate FSE CTable/DTable as a table of FSE_CTable/FSE_DTable using below macros */
239 #define FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) (1 + (1 << (maxTableLog - 1)) + ((maxSymbolValue + 1) * 2))
240 #define FSE_DTABLE_SIZE_U32(maxTableLog) (1 + (1 << maxTableLog))
241
242 /* *****************************************
243 * FSE advanced API
244 *******************************************/
245 /* FSE_count_wksp() :
246 * Same as FSE_count(), but using an externally provided scratch buffer.
247 * `workSpace` size must be table of >= `1024` unsigned
248 */
249 size_t FSE_count_wksp(unsigned *count, unsigned *maxSymbolValuePtr, const void *source, size_t sourceSize, unsigned *workSpace);
250
251 /* FSE_countFast_wksp() :
252 * Same as FSE_countFast(), but using an externally provided scratch buffer.
253 * `workSpace` must be a table of minimum `1024` unsigned
254 */
255 size_t FSE_countFast_wksp(unsigned *count, unsigned *maxSymbolValuePtr, const void *src, size_t srcSize, unsigned *workSpace);
256
257 /*! FSE_count_simple
258 * Same as FSE_countFast(), but does not use any additional memory (not even on stack).
259 * This function is unsafe, and will segfault if any value within `src` is `> *maxSymbolValuePtr` (presuming it's also the size of `count`).
260 */
261 size_t FSE_count_simple(unsigned *count, unsigned *maxSymbolValuePtr, const void *src, size_t srcSize);
262
263 unsigned FSE_optimalTableLog_internal(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, unsigned minus);
264 /**< same as FSE_optimalTableLog(), which used `minus==2` */
265
266 size_t FSE_buildCTable_raw(FSE_CTable *ct, unsigned nbBits);
267 /**< build a fake FSE_CTable, designed for a flat distribution, where each symbol uses nbBits */
268
269 size_t FSE_buildCTable_rle(FSE_CTable *ct, unsigned char symbolValue);
270 /**< build a fake FSE_CTable, designed to compress always the same symbolValue */
271
272 /* FSE_buildCTable_wksp() :
273 * Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).
274 * `wkspSize` must be >= `(1<<tableLog)`.
275 */
276 size_t FSE_buildCTable_wksp(FSE_CTable *ct, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void *workSpace, size_t wkspSize);
277
278 size_t FSE_buildDTable_raw(FSE_DTable *dt, unsigned nbBits);
279 /**< build a fake FSE_DTable, designed to read a flat distribution where each symbol uses nbBits */
280
281 size_t FSE_buildDTable_rle(FSE_DTable *dt, unsigned char symbolValue);
282 /**< build a fake FSE_DTable, designed to always generate the same symbolValue */
283
284 size_t FSE_decompress_wksp(void *dst, size_t dstCapacity, const void *cSrc, size_t cSrcSize, unsigned maxLog, void *workspace, size_t workspaceSize);
285 /**< same as FSE_decompress(), using an externally allocated `workSpace` produced with `FSE_DTABLE_SIZE_U32(maxLog)` */
286
287 /* *****************************************
288 * FSE symbol compression API
289 *******************************************/
290 /*!
291 This API consists of small unitary functions, which highly benefit from being inlined.
292 Hence their body are included in next section.
293 */
294 typedef struct {
295 ptrdiff_t value;
296 const void *stateTable;
297 const void *symbolTT;
298 unsigned stateLog;
299 } FSE_CState_t;
300
301 static void FSE_initCState(FSE_CState_t *CStatePtr, const FSE_CTable *ct);
302
303 static void FSE_encodeSymbol(BIT_CStream_t *bitC, FSE_CState_t *CStatePtr, unsigned symbol);
304
305 static void FSE_flushCState(BIT_CStream_t *bitC, const FSE_CState_t *CStatePtr);
306
307 /**<
308 These functions are inner components of FSE_compress_usingCTable().
309 They allow the creation of custom streams, mixing multiple tables and bit sources.
310
311 A key property to keep in mind is that encoding and decoding are done **in reverse direction**.
312 So the first symbol you will encode is the last you will decode, like a LIFO stack.
313
314 You will need a few variables to track your CStream. They are :
315
316 FSE_CTable ct; // Provided by FSE_buildCTable()
317 BIT_CStream_t bitStream; // bitStream tracking structure
318 FSE_CState_t state; // State tracking structure (can have several)
319
320
321 The first thing to do is to init bitStream and state.
322 size_t errorCode = BIT_initCStream(&bitStream, dstBuffer, maxDstSize);
323 FSE_initCState(&state, ct);
324
325 Note that BIT_initCStream() can produce an error code, so its result should be tested, using FSE_isError();
326 You can then encode your input data, byte after byte.
327 FSE_encodeSymbol() outputs a maximum of 'tableLog' bits at a time.
328 Remember decoding will be done in reverse direction.
329 FSE_encodeByte(&bitStream, &state, symbol);
330
331 At any time, you can also add any bit sequence.
332 Note : maximum allowed nbBits is 25, for compatibility with 32-bits decoders
333 BIT_addBits(&bitStream, bitField, nbBits);
334
335 The above methods don't commit data to memory, they just store it into local register, for speed.
336 Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
337 Writing data to memory is a manual operation, performed by the flushBits function.
338 BIT_flushBits(&bitStream);
339
340 Your last FSE encoding operation shall be to flush your last state value(s).
341 FSE_flushState(&bitStream, &state);
342
343 Finally, you must close the bitStream.
344 The function returns the size of CStream in bytes.
345 If data couldn't fit into dstBuffer, it will return a 0 ( == not compressible)
346 If there is an error, it returns an errorCode (which can be tested using FSE_isError()).
347 size_t size = BIT_closeCStream(&bitStream);
348 */
349
350 /* *****************************************
351 * FSE symbol decompression API
352 *******************************************/
353 typedef struct {
354 size_t state;
355 const void *table; /* precise table may vary, depending on U16 */
356 } FSE_DState_t;
357
358 static void FSE_initDState(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD, const FSE_DTable *dt);
359
360 static unsigned char FSE_decodeSymbol(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD);
361
362 static unsigned FSE_endOfDState(const FSE_DState_t *DStatePtr);
363
364 /**<
365 Let's now decompose FSE_decompress_usingDTable() into its unitary components.
366 You will decode FSE-encoded symbols from the bitStream,
367 and also any other bitFields you put in, **in reverse order**.
368
369 You will need a few variables to track your bitStream. They are :
370
371 BIT_DStream_t DStream; // Stream context
372 FSE_DState_t DState; // State context. Multiple ones are possible
373 FSE_DTable* DTablePtr; // Decoding table, provided by FSE_buildDTable()
374
375 The first thing to do is to init the bitStream.
376 errorCode = BIT_initDStream(&DStream, srcBuffer, srcSize);
377
378 You should then retrieve your initial state(s)
379 (in reverse flushing order if you have several ones) :
380 errorCode = FSE_initDState(&DState, &DStream, DTablePtr);
381
382 You can then decode your data, symbol after symbol.
383 For information the maximum number of bits read by FSE_decodeSymbol() is 'tableLog'.
384 Keep in mind that symbols are decoded in reverse order, like a LIFO stack (last in, first out).
385 unsigned char symbol = FSE_decodeSymbol(&DState, &DStream);
386
387 You can retrieve any bitfield you eventually stored into the bitStream (in reverse order)
388 Note : maximum allowed nbBits is 25, for 32-bits compatibility
389 size_t bitField = BIT_readBits(&DStream, nbBits);
390
391 All above operations only read from local register (which size depends on size_t).
392 Refueling the register from memory is manually performed by the reload method.
393 endSignal = FSE_reloadDStream(&DStream);
394
395 BIT_reloadDStream() result tells if there is still some more data to read from DStream.
396 BIT_DStream_unfinished : there is still some data left into the DStream.
397 BIT_DStream_endOfBuffer : Dstream reached end of buffer. Its container may no longer be completely filled.
398 BIT_DStream_completed : Dstream reached its exact end, corresponding in general to decompression completed.
399 BIT_DStream_tooFar : Dstream went too far. Decompression result is corrupted.
400
401 When reaching end of buffer (BIT_DStream_endOfBuffer), progress slowly, notably if you decode multiple symbols per loop,
402 to properly detect the exact end of stream.
403 After each decoded symbol, check if DStream is fully consumed using this simple test :
404 BIT_reloadDStream(&DStream) >= BIT_DStream_completed
405
406 When it's done, verify decompression is fully completed, by checking both DStream and the relevant states.
407 Checking if DStream has reached its end is performed by :
408 BIT_endOfDStream(&DStream);
409 Check also the states. There might be some symbols left there, if some high probability ones (>50%) are possible.
410 FSE_endOfDState(&DState);
411 */
412
413 /* *****************************************
414 * FSE unsafe API
415 *******************************************/
416 static unsigned char FSE_decodeSymbolFast(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD);
417 /* faster, but works only if nbBits is always >= 1 (otherwise, result will be corrupted) */
418
419 /* *****************************************
420 * Implementation of inlined functions
421 *******************************************/
422 typedef struct {
423 int deltaFindState;
424 U32 deltaNbBits;
425 } FSE_symbolCompressionTransform; /* total 8 bytes */
426
427 ZSTD_STATIC void FSE_initCState(FSE_CState_t *statePtr, const FSE_CTable *ct)
428 {
429 const void *ptr = ct;
430 const U16 *u16ptr = (const U16 *)ptr;
431 const U32 tableLog = ZSTD_read16(ptr);
432 statePtr->value = (ptrdiff_t)1 << tableLog;
433 statePtr->stateTable = u16ptr + 2;
434 statePtr->symbolTT = ((const U32 *)ct + 1 + (tableLog ? (1 << (tableLog - 1)) : 1));
435 statePtr->stateLog = tableLog;
436 }
437
438 /*! FSE_initCState2() :
439 * Same as FSE_initCState(), but the first symbol to include (which will be the last to be read)
440 * uses the smallest state value possible, saving the cost of this symbol */
441 ZSTD_STATIC void FSE_initCState2(FSE_CState_t *statePtr, const FSE_CTable *ct, U32 symbol)
442 {
443 FSE_initCState(statePtr, ct);
444 {
445 const FSE_symbolCompressionTransform symbolTT = ((const FSE_symbolCompressionTransform *)(statePtr->symbolTT))[symbol];
446 const U16 *stateTable = (const U16 *)(statePtr->stateTable);
447 U32 nbBitsOut = (U32)((symbolTT.deltaNbBits + (1 << 15)) >> 16);
448 statePtr->value = (nbBitsOut << 16) - symbolTT.deltaNbBits;
449 statePtr->value = stateTable[(statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
450 }
451 }
452
453 ZSTD_STATIC void FSE_encodeSymbol(BIT_CStream_t *bitC, FSE_CState_t *statePtr, U32 symbol)
454 {
455 const FSE_symbolCompressionTransform symbolTT = ((const FSE_symbolCompressionTransform *)(statePtr->symbolTT))[symbol];
456 const U16 *const stateTable = (const U16 *)(statePtr->stateTable);
457 U32 nbBitsOut = (U32)((statePtr->value + symbolTT.deltaNbBits) >> 16);
458 BIT_addBits(bitC, statePtr->value, nbBitsOut);
459 statePtr->value = stateTable[(statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
460 }
461
462 ZSTD_STATIC void FSE_flushCState(BIT_CStream_t *bitC, const FSE_CState_t *statePtr)
463 {
464 BIT_addBits(bitC, statePtr->value, statePtr->stateLog);
465 BIT_flushBits(bitC);
466 }
467
468 /* ====== Decompression ====== */
469
470 typedef struct {
471 U16 tableLog;
472 U16 fastMode;
473 } FSE_DTableHeader; /* sizeof U32 */
474
475 typedef struct {
476 unsigned short newState;
477 unsigned char symbol;
478 unsigned char nbBits;
479 } FSE_decode_t; /* size == U32 */
480
481 ZSTD_STATIC void FSE_initDState(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD, const FSE_DTable *dt)
482 {
483 const void *ptr = dt;
484 const FSE_DTableHeader *const DTableH = (const FSE_DTableHeader *)ptr;
485 DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
486 BIT_reloadDStream(bitD);
487 DStatePtr->table = dt + 1;
488 }
489
490 ZSTD_STATIC BYTE FSE_peekSymbol(const FSE_DState_t *DStatePtr)
491 {
492 FSE_decode_t const DInfo = ((const FSE_decode_t *)(DStatePtr->table))[DStatePtr->state];
493 return DInfo.symbol;
494 }
495
496 ZSTD_STATIC void FSE_updateState(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD)
497 {
498 FSE_decode_t const DInfo = ((const FSE_decode_t *)(DStatePtr->table))[DStatePtr->state];
499 U32 const nbBits = DInfo.nbBits;
500 size_t const lowBits = BIT_readBits(bitD, nbBits);
501 DStatePtr->state = DInfo.newState + lowBits;
502 }
503
504 ZSTD_STATIC BYTE FSE_decodeSymbol(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD)
505 {
506 FSE_decode_t const DInfo = ((const FSE_decode_t *)(DStatePtr->table))[DStatePtr->state];
507 U32 const nbBits = DInfo.nbBits;
508 BYTE const symbol = DInfo.symbol;
509 size_t const lowBits = BIT_readBits(bitD, nbBits);
510
511 DStatePtr->state = DInfo.newState + lowBits;
512 return symbol;
513 }
514
515 /*! FSE_decodeSymbolFast() :
516 unsafe, only works if no symbol has a probability > 50% */
517 ZSTD_STATIC BYTE FSE_decodeSymbolFast(FSE_DState_t *DStatePtr, BIT_DStream_t *bitD)
518 {
519 FSE_decode_t const DInfo = ((const FSE_decode_t *)(DStatePtr->table))[DStatePtr->state];
520 U32 const nbBits = DInfo.nbBits;
521 BYTE const symbol = DInfo.symbol;
522 size_t const lowBits = BIT_readBitsFast(bitD, nbBits);
523
524 DStatePtr->state = DInfo.newState + lowBits;
525 return symbol;
526 }
527
528 ZSTD_STATIC unsigned FSE_endOfDState(const FSE_DState_t *DStatePtr) { return DStatePtr->state == 0; }
529
530 /* **************************************************************
531 * Tuning parameters
532 ****************************************************************/
533 /*!MEMORY_USAGE :
534 * Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
535 * Increasing memory usage improves compression ratio
536 * Reduced memory usage can improve speed, due to cache effect
537 * Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */
538 #ifndef FSE_MAX_MEMORY_USAGE
539 #define FSE_MAX_MEMORY_USAGE 14
540 #endif
541 #ifndef FSE_DEFAULT_MEMORY_USAGE
542 #define FSE_DEFAULT_MEMORY_USAGE 13
543 #endif
544
545 /*!FSE_MAX_SYMBOL_VALUE :
546 * Maximum symbol value authorized.
547 * Required for proper stack allocation */
548 #ifndef FSE_MAX_SYMBOL_VALUE
549 #define FSE_MAX_SYMBOL_VALUE 255
550 #endif
551
552 /* **************************************************************
553 * template functions type & suffix
554 ****************************************************************/
555 #define FSE_FUNCTION_TYPE BYTE
556 #define FSE_FUNCTION_EXTENSION
557 #define FSE_DECODE_TYPE FSE_decode_t
558
559 /* ***************************************************************
560 * Constants
561 *****************************************************************/
562 #define FSE_MAX_TABLELOG (FSE_MAX_MEMORY_USAGE - 2)
563 #define FSE_MAX_TABLESIZE (1U << FSE_MAX_TABLELOG)
564 #define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESIZE - 1)
565 #define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMORY_USAGE - 2)
566 #define FSE_MIN_TABLELOG 5
567
568 #define FSE_TABLELOG_ABSOLUTE_MAX 15
569 #if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX
570 #error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX is not supported"
571 #endif
572
573 #define FSE_TABLESTEP(tableSize) ((tableSize >> 1) + (tableSize >> 3) + 3)
574
575 #endif /* FSE_H */