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Linux/lib/zstd/common/fse.h

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Differences between /lib/zstd/common/fse.h (Version linux-6.12-rc7) and /lib/zstd/common/fse.h (Version linux-5.10.228)


** Warning: Cannot open xref database.

  1 /* *******************************************      1 
  2  * FSE : Finite State Entropy codec               
  3  * Public Prototypes declaration                  
  4  * Copyright (c) Yann Collet, Facebook, Inc.      
  5  *                                                
  6  * You can contact the author at :                
  7  * - Source repository : https://github.com/Cy    
  8  *                                                
  9  * This source code is licensed under both the    
 10  * LICENSE file in the root directory of this     
 11  * in the COPYING file in the root directory o    
 12  * You may select, at your option, one of the     
 13 **********************************************    
 14                                                   
 15                                                   
 16 #ifndef FSE_H                                     
 17 #define FSE_H                                     
 18                                                   
 19                                                   
 20 /*-*****************************************      
 21 *  Dependencies                                   
 22 ******************************************/       
 23 #include "zstd_deps.h"    /* size_t, ptrdiff_t    
 24                                                   
 25                                                   
 26 /*-*****************************************      
 27 *  FSE_PUBLIC_API : control library symbols vi    
 28 ******************************************/       
 29 #if defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT    
 30 #  define FSE_PUBLIC_API __attribute__ ((visib    
 31 #elif defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPO    
 32 #  define FSE_PUBLIC_API __declspec(dllexport)    
 33 #elif defined(FSE_DLL_IMPORT) && (FSE_DLL_IMPO    
 34 #  define FSE_PUBLIC_API __declspec(dllimport)    
 35 #else                                             
 36 #  define FSE_PUBLIC_API                          
 37 #endif                                            
 38                                                   
 39 /*------   Version   ------*/                     
 40 #define FSE_VERSION_MAJOR    0                    
 41 #define FSE_VERSION_MINOR    9                    
 42 #define FSE_VERSION_RELEASE  0                    
 43                                                   
 44 #define FSE_LIB_VERSION FSE_VERSION_MAJOR.FSE_    
 45 #define FSE_QUOTE(str) #str                       
 46 #define FSE_EXPAND_AND_QUOTE(str) FSE_QUOTE(st    
 47 #define FSE_VERSION_STRING FSE_EXPAND_AND_QUOT    
 48                                                   
 49 #define FSE_VERSION_NUMBER  (FSE_VERSION_MAJOR    
 50 FSE_PUBLIC_API unsigned FSE_versionNumber(void    
 51                                                   
 52                                                   
 53 /*-****************************************       
 54 *  FSE simple functions                           
 55 ******************************************/       
 56 /*! FSE_compress() :                              
 57     Compress content of buffer 'src', of size     
 58     'dst' buffer must be already allocated. Co    
 59     @return : size of compressed data (<= dstC    
 60     Special values : if return == 0, srcData i    
 61                      if return == 1, srcData i    
 62                      if FSE_isError(return), c    
 63 */                                                
 64 FSE_PUBLIC_API size_t FSE_compress(void* dst,     
 65                              const void* src,     
 66                                                   
 67 /*! FSE_decompress():                             
 68     Decompress FSE data from buffer 'cSrc', of    
 69     into already allocated destination buffer     
 70     @return : size of regenerated data (<= max    
 71               or an error code, which can be t    
 72                                                   
 73     ** Important ** : FSE_decompress() does no    
 74     Why ? : making this distinction requires a    
 75     Header management is intentionally delegat    
 76 */                                                
 77 FSE_PUBLIC_API size_t FSE_decompress(void* dst    
 78                                const void* cSr    
 79                                                   
 80                                                   
 81 /*-*****************************************      
 82 *  Tool functions                                 
 83 ******************************************/       
 84 FSE_PUBLIC_API size_t FSE_compressBound(size_t    
 85                                                   
 86 /* Error Management */                            
 87 FSE_PUBLIC_API unsigned    FSE_isError(size_t     
 88 FSE_PUBLIC_API const char* FSE_getErrorName(si    
 89                                                   
 90                                                   
 91 /*-*****************************************      
 92 *  FSE advanced functions                         
 93 ******************************************/       
 94 /*! FSE_compress2() :                             
 95     Same as FSE_compress(), but allows the sel    
 96     Both parameters can be defined as '' to me    
 97     @return : size of compressed data             
 98     Special values : if return == 0, srcData i    
 99                      if return == 1, srcData i    
100                      if FSE_isError(return), i    
101 */                                                
102 FSE_PUBLIC_API size_t FSE_compress2 (void* dst    
103                                                   
104                                                   
105 /*-*****************************************      
106 *  FSE detailed API                               
107 ******************************************/       
108 /*!                                               
109 FSE_compress() does the following:                
110 1. count symbol occurrence from source[] into     
111 2. normalize counters so that sum(count[]) ==     
112 3. save normalized counters to memory buffer u    
113 4. build encoding table 'CTable' from normaliz    
114 5. encode the data stream using encoding table    
115                                                   
116 FSE_decompress() does the following:              
117 1. read normalized counters with readNCount()     
118 2. build decoding table 'DTable' from normaliz    
119 3. decode the data stream using decoding table    
120                                                   
121 The following API allows targeting specific su    
122 For example, it's possible to compress several    
123 or to save and provide normalized distribution    
124 */                                                
125                                                   
126 /* *** COMPRESSION *** */                         
127                                                   
128 /*! FSE_optimalTableLog():                        
129     dynamically downsize 'tableLog' when condi    
130     It saves CPU time, by using smaller tables    
131     @return : recommended tableLog (necessaril    
132 FSE_PUBLIC_API unsigned FSE_optimalTableLog(un    
133                                                   
134 /*! FSE_normalizeCount():                         
135     normalize counts so that sum(count[]) == P    
136     'normalizedCounter' is a table of short, o    
137     useLowProbCount is a boolean parameter whi    
138     faster header decoding. When it is set to     
139     smaller. And when it is set to 0, FSE_read    
140     faster. If you are compressing a small amo    
141     is a good default, since header deserializ    
142     Otherwise, useLowProbCount=1 is a good def    
143     @return : tableLog,                           
144               or an errorCode, which can be te    
145 FSE_PUBLIC_API size_t FSE_normalizeCount(short    
146                     const unsigned* count, siz    
147                                                   
148 /*! FSE_NCountWriteBound():                       
149     Provides the maximum possible size of an F    
150     Typically useful for allocation purpose. *    
151 FSE_PUBLIC_API size_t FSE_NCountWriteBound(uns    
152                                                   
153 /*! FSE_writeNCount():                            
154     Compactly save 'normalizedCounter' into 'b    
155     @return : size of the compressed table,       
156               or an errorCode, which can be te    
157 FSE_PUBLIC_API size_t FSE_writeNCount (void* b    
158                                  const short*     
159                                  unsigned maxS    
160                                                   
161 /*! Constructor and Destructor of FSE_CTable.     
162     Note that FSE_CTable size depends on 'tabl    
163 typedef unsigned FSE_CTable;   /* don't alloca    
164 FSE_PUBLIC_API FSE_CTable* FSE_createCTable (u    
165 FSE_PUBLIC_API void        FSE_freeCTable (FSE    
166                                                   
167 /*! FSE_buildCTable():                            
168     Builds `ct`, which must be already allocat    
169     @return : 0, or an errorCode, which can be    
170 FSE_PUBLIC_API size_t FSE_buildCTable(FSE_CTab    
171                                                   
172 /*! FSE_compress_usingCTable():                   
173     Compress `src` using `ct` into `dst` which    
174     @return : size of compressed data (<= `dst    
175               or 0 if compressed data could no    
176               or an errorCode, which can be te    
177 FSE_PUBLIC_API size_t FSE_compress_usingCTable    
178                                                   
179 /*!                                               
180 Tutorial :                                        
181 ----------                                        
182 The first step is to count all symbols. FSE_co    
183 Result will be saved into 'count', a table of     
184 'src' is a table of bytes of size 'srcSize'. A    
185 maxSymbolValuePtr[0] will be updated, with its    
186 FSE_count() will return the number of occurren    
187 This can be used to know if there is a single     
188 If there is an error, the function will return    
189                                                   
190 The next step is to normalize the frequencies.    
191 FSE_normalizeCount() will ensure that sum of f    
192 It also guarantees a minimum of 1 to any Symbo    
193 You can use 'tableLog'==0 to mean "use default    
194 If you are unsure of which tableLog value to u    
195 which will provide the optimal valid tableLog     
196                                                   
197 The result of FSE_normalizeCount() will be sav    
198 called 'normalizedCounter', which is a table o    
199 'normalizedCounter' must be already allocated,    
200 The return value is tableLog if everything pro    
201 It is 0 if there is a single symbol within dis    
202 If there is an error (ex: invalid tableLog val    
203                                                   
204 'normalizedCounter' can be saved in a compact     
205 'buffer' must be already allocated.               
206 For guaranteed success, buffer size must be at    
207 The result of the function is the number of by    
208 If there is an error, the function will return    
209                                                   
210 'normalizedCounter' can then be used to create    
211 The space required by 'CTable' must be already    
212 You can then use FSE_buildCTable() to fill 'CT    
213 If there is an error, both functions will retu    
214                                                   
215 'CTable' can then be used to compress 'src', w    
216 Similar to FSE_count(), the convention is that    
217 The function returns the size of compressed da    
218 If it returns '', compressed data could not fi    
219 If there is an error, the function will return    
220 */                                                
221                                                   
222                                                   
223 /* *** DECOMPRESSION *** */                       
224                                                   
225 /*! FSE_readNCount():                             
226     Read compactly saved 'normalizedCounter' f    
227     @return : size read from 'rBuffer',           
228               or an errorCode, which can be te    
229               maxSymbolValuePtr[0] and tableLo    
230 FSE_PUBLIC_API size_t FSE_readNCount (short* n    
231                            unsigned* maxSymbol    
232                            const void* rBuffer    
233                                                   
234 /*! FSE_readNCount_bmi2():                        
235  * Same as FSE_readNCount() but pass bmi2=1 wh    
236  */                                               
237 FSE_PUBLIC_API size_t FSE_readNCount_bmi2(shor    
238                            unsigned* maxSymbol    
239                            const void* rBuffer    
240                                                   
241 /*! Constructor and Destructor of FSE_DTable.     
242     Note that its size depends on 'tableLog' *    
243 typedef unsigned FSE_DTable;   /* don't alloca    
244 FSE_PUBLIC_API FSE_DTable* FSE_createDTable(un    
245 FSE_PUBLIC_API void        FSE_freeDTable(FSE_    
246                                                   
247 /*! FSE_buildDTable():                            
248     Builds 'dt', which must be already allocat    
249     return : 0, or an errorCode, which can be     
250 FSE_PUBLIC_API size_t FSE_buildDTable (FSE_DTa    
251                                                   
252 /*! FSE_decompress_usingDTable():                 
253     Decompress compressed source `cSrc` of siz    
254     into `dst` which must be already allocated    
255     @return : size of regenerated data (necess    
256               or an errorCode, which can be te    
257 FSE_PUBLIC_API size_t FSE_decompress_usingDTab    
258                                                   
259 /*!                                               
260 Tutorial :                                        
261 ----------                                        
262 (Note : these functions only decompress FSE-co    
263  If block is uncompressed, use memcpy() instea    
264  If block is a single repeated byte, use memse    
265                                                   
266 The first step is to obtain the normalized fre    
267 This can be performed by FSE_readNCount() if i    
268 'normalizedCounter' must be already allocated,    
269 In practice, that means it's necessary to know    
270 or size the table to handle worst case situati    
271 FSE_readNCount() will provide 'tableLog' and '    
272 The result of FSE_readNCount() is the number o    
273 Note that 'rBufferSize' must be at least 4 byt    
274 If there is an error, the function will return    
275                                                   
276 The next step is to build the decompression ta    
277 This is performed by the function FSE_buildDTa    
278 The space required by 'FSE_DTable' must be alr    
279 If there is an error, the function will return    
280                                                   
281 `FSE_DTable` can then be used to decompress `c    
282 `cSrcSize` must be strictly correct, otherwise    
283 FSE_decompress_usingDTable() result will tell     
284 If there is an error, the function will return    
285 */                                                
286                                                   
287 #endif  /* FSE_H */                               
288                                                   
289 #if !defined(FSE_H_FSE_STATIC_LINKING_ONLY)       
290 #define FSE_H_FSE_STATIC_LINKING_ONLY             
291                                                   
292 /* *** Dependency *** */                          
293 #include "bitstream.h"                            
294                                                   
295                                                   
296 /* *****************************************      
297 *  Static allocation                              
298 *******************************************/      
299 /* FSE buffer bounds */                           
300 #define FSE_NCOUNTBOUND 512                       
301 #define FSE_BLOCKBOUND(size) ((size) + ((size)    
302 #define FSE_COMPRESSBOUND(size) (FSE_NCOUNTBOU    
303                                                   
304 /* It is possible to statically allocate FSE C    
305 #define FSE_CTABLE_SIZE_U32(maxTableLog, maxSy    
306 #define FSE_DTABLE_SIZE_U32(maxTableLog)          
307                                                   
308 /* or use the size to malloc() space directly.    
309 #define FSE_CTABLE_SIZE(maxTableLog, maxSymbol    
310 #define FSE_DTABLE_SIZE(maxTableLog)              
311                                                   
312                                                   
313 /* *****************************************      
314  *  FSE advanced API                              
315  ***************************************** */     
316                                                   
317 unsigned FSE_optimalTableLog_internal(unsigned    
318 /*< same as FSE_optimalTableLog(), which used     
319                                                   
320 /* FSE_compress_wksp() :                          
321  * Same as FSE_compress2(), but using an exter    
322  * FSE_COMPRESS_WKSP_SIZE_U32() provides the m    
323  */                                               
324 #define FSE_COMPRESS_WKSP_SIZE_U32(maxTableLog    
325 size_t FSE_compress_wksp (void* dst, size_t ds    
326                                                   
327 size_t FSE_buildCTable_raw (FSE_CTable* ct, un    
328 /*< build a fake FSE_CTable, designed for a fl    
329                                                   
330 size_t FSE_buildCTable_rle (FSE_CTable* ct, un    
331 /*< build a fake FSE_CTable, designed to compr    
332                                                   
333 /* FSE_buildCTable_wksp() :                       
334  * Same as FSE_buildCTable(), but using an ext    
335  * `wkspSize` must be >= `FSE_BUILD_CTABLE_WOR    
336  * See FSE_buildCTable_wksp() for breakdown of    
337  */                                               
338 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(ma    
339 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE(maxSym    
340 size_t FSE_buildCTable_wksp(FSE_CTable* ct, co    
341                                                   
342 #define FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog    
343 #define FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTabl    
344 FSE_PUBLIC_API size_t FSE_buildDTable_wksp(FSE    
345 /*< Same as FSE_buildDTable(), using an extern    
346                                                   
347 size_t FSE_buildDTable_raw (FSE_DTable* dt, un    
348 /*< build a fake FSE_DTable, designed to read     
349                                                   
350 size_t FSE_buildDTable_rle (FSE_DTable* dt, un    
351 /*< build a fake FSE_DTable, designed to alway    
352                                                   
353 #define FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableL    
354 #define FSE_DECOMPRESS_WKSP_SIZE(maxTableLog,     
355 size_t FSE_decompress_wksp(void* dst, size_t d    
356 /*< same as FSE_decompress(), using an externa    
357                                                   
358 size_t FSE_decompress_wksp_bmi2(void* dst, siz    
359 /*< Same as FSE_decompress_wksp() but with dyn    
360                                                   
361 typedef enum {                                    
362    FSE_repeat_none,  /*< Cannot use the previo    
363    FSE_repeat_check, /*< Can use the previous     
364    FSE_repeat_valid  /*< Can use the previous     
365  } FSE_repeat;                                    
366                                                   
367 /* *****************************************      
368 *  FSE symbol compression API                     
369 *******************************************/      
370 /*!                                               
371    This API consists of small unitary function    
372    Hence their body are included in next secti    
373 */                                                
374 typedef struct {                                  
375     ptrdiff_t   value;                            
376     const void* stateTable;                       
377     const void* symbolTT;                         
378     unsigned    stateLog;                         
379 } FSE_CState_t;                                   
380                                                   
381 static void FSE_initCState(FSE_CState_t* CStat    
382                                                   
383 static void FSE_encodeSymbol(BIT_CStream_t* bi    
384                                                   
385 static void FSE_flushCState(BIT_CStream_t* bit    
386                                                   
387 /*<                                               
388 These functions are inner components of FSE_co    
389 They allow the creation of custom streams, mix    
390                                                   
391 A key property to keep in mind is that encodin    
392 So the first symbol you will encode is the las    
393                                                   
394 You will need a few variables to track your CS    
395                                                   
396 FSE_CTable    ct;         // Provided by FSE_b    
397 BIT_CStream_t bitStream;  // bitStream trackin    
398 FSE_CState_t  state;      // State tracking st    
399                                                   
400                                                   
401 The first thing to do is to init bitStream and    
402     size_t errorCode = BIT_initCStream(&bitStr    
403     FSE_initCState(&state, ct);                   
404                                                   
405 Note that BIT_initCStream() can produce an err    
406 You can then encode your input data, byte afte    
407 FSE_encodeSymbol() outputs a maximum of 'table    
408 Remember decoding will be done in reverse dire    
409     FSE_encodeByte(&bitStream, &state, symbol)    
410                                                   
411 At any time, you can also add any bit sequence    
412 Note : maximum allowed nbBits is 25, for compa    
413     BIT_addBits(&bitStream, bitField, nbBits);    
414                                                   
415 The above methods don't commit data to memory,    
416 Local register size is 64-bits on 64-bits syst    
417 Writing data to memory is a manual operation,     
418     BIT_flushBits(&bitStream);                    
419                                                   
420 Your last FSE encoding operation shall be to f    
421     FSE_flushState(&bitStream, &state);           
422                                                   
423 Finally, you must close the bitStream.            
424 The function returns the size of CStream in by    
425 If data couldn't fit into dstBuffer, it will r    
426 If there is an error, it returns an errorCode     
427     size_t size = BIT_closeCStream(&bitStream)    
428 */                                                
429                                                   
430                                                   
431 /* *****************************************      
432 *  FSE symbol decompression API                   
433 *******************************************/      
434 typedef struct {                                  
435     size_t      state;                            
436     const void* table;   /* precise table may     
437 } FSE_DState_t;                                   
438                                                   
439                                                   
440 static void     FSE_initDState(FSE_DState_t* D    
441                                                   
442 static unsigned char FSE_decodeSymbol(FSE_DSta    
443                                                   
444 static unsigned FSE_endOfDState(const FSE_DSta    
445                                                   
446 /*<                                               
447 Let's now decompose FSE_decompress_usingDTable    
448 You will decode FSE-encoded symbols from the b    
449 and also any other bitFields you put in, **in     
450                                                   
451 You will need a few variables to track your bi    
452                                                   
453 BIT_DStream_t DStream;    // Stream context       
454 FSE_DState_t  DState;     // State context. Mu    
455 FSE_DTable*   DTablePtr;  // Decoding table, p    
456                                                   
457 The first thing to do is to init the bitStream    
458     errorCode = BIT_initDStream(&DStream, srcB    
459                                                   
460 You should then retrieve your initial state(s)    
461 (in reverse flushing order if you have several    
462     errorCode = FSE_initDState(&DState, &DStre    
463                                                   
464 You can then decode your data, symbol after sy    
465 For information the maximum number of bits rea    
466 Keep in mind that symbols are decoded in rever    
467     unsigned char symbol = FSE_decodeSymbol(&D    
468                                                   
469 You can retrieve any bitfield you eventually s    
470 Note : maximum allowed nbBits is 25, for 32-bi    
471     size_t bitField = BIT_readBits(&DStream, n    
472                                                   
473 All above operations only read from local regi    
474 Refueling the register from memory is manually    
475     endSignal = FSE_reloadDStream(&DStream);      
476                                                   
477 BIT_reloadDStream() result tells if there is s    
478 BIT_DStream_unfinished : there is still some d    
479 BIT_DStream_endOfBuffer : Dstream reached end     
480 BIT_DStream_completed : Dstream reached its ex    
481 BIT_DStream_tooFar : Dstream went too far. Dec    
482                                                   
483 When reaching end of buffer (BIT_DStream_endOf    
484 to properly detect the exact end of stream.       
485 After each decoded symbol, check if DStream is    
486     BIT_reloadDStream(&DStream) >= BIT_DStream    
487                                                   
488 When it's done, verify decompression is fully     
489 Checking if DStream has reached its end is per    
490     BIT_endOfDStream(&DStream);                   
491 Check also the states. There might be some sym    
492     FSE_endOfDState(&DState);                     
493 */                                                
494                                                   
495                                                   
496 /* *****************************************      
497 *  FSE unsafe API                                 
498 *******************************************/      
499 static unsigned char FSE_decodeSymbolFast(FSE_    
500 /* faster, but works only if nbBits is always     
501                                                   
502                                                   
503 /* *****************************************      
504 *  Implementation of inlined functions            
505 *******************************************/      
506 typedef struct {                                  
507     int deltaFindState;                           
508     U32 deltaNbBits;                              
509 } FSE_symbolCompressionTransform; /* total 8 b    
510                                                   
511 MEM_STATIC void FSE_initCState(FSE_CState_t* s    
512 {                                                 
513     const void* ptr = ct;                         
514     const U16* u16ptr = (const U16*) ptr;         
515     const U32 tableLog = MEM_read16(ptr);         
516     statePtr->value = (ptrdiff_t)1<<tableLog;     
517     statePtr->stateTable = u16ptr+2;              
518     statePtr->symbolTT = ct + 1 + (tableLog ?     
519     statePtr->stateLog = tableLog;                
520 }                                                 
521                                                   
522                                                   
523 /*! FSE_initCState2() :                           
524 *   Same as FSE_initCState(), but the first sy    
525 *   uses the smallest state value possible, sa    
526 MEM_STATIC void FSE_initCState2(FSE_CState_t*     
527 {                                                 
528     FSE_initCState(statePtr, ct);                 
529     {   const FSE_symbolCompressionTransform s    
530         const U16* stateTable = (const U16*)(s    
531         U32 nbBitsOut  = (U32)((symbolTT.delta    
532         statePtr->value = (nbBitsOut << 16) -     
533         statePtr->value = stateTable[(statePtr    
534     }                                             
535 }                                                 
536                                                   
537 MEM_STATIC void FSE_encodeSymbol(BIT_CStream_t    
538 {                                                 
539     FSE_symbolCompressionTransform const symbo    
540     const U16* const stateTable = (const U16*)    
541     U32 const nbBitsOut  = (U32)((statePtr->va    
542     BIT_addBits(bitC, statePtr->value, nbBitsO    
543     statePtr->value = stateTable[ (statePtr->v    
544 }                                                 
545                                                   
546 MEM_STATIC void FSE_flushCState(BIT_CStream_t*    
547 {                                                 
548     BIT_addBits(bitC, statePtr->value, statePt    
549     BIT_flushBits(bitC);                          
550 }                                                 
551                                                   
552                                                   
553 /* FSE_getMaxNbBits() :                           
554  * Approximate maximum cost of a symbol, in bi    
555  * Fractional get rounded up (i.e : a symbol w    
556  * note 1 : assume symbolValue is valid (<= ma    
557  * note 2 : if freq[symbolValue]==0, @return a    
558 MEM_STATIC U32 FSE_getMaxNbBits(const void* sy    
559 {                                                 
560     const FSE_symbolCompressionTransform* symb    
561     return (symbolTT[symbolValue].deltaNbBits     
562 }                                                 
563                                                   
564 /* FSE_bitCost() :                                
565  * Approximate symbol cost, as fractional valu    
566  * note 1 : assume symbolValue is valid (<= ma    
567  * note 2 : if freq[symbolValue]==0, @return a    
568 MEM_STATIC U32 FSE_bitCost(const void* symbolT    
569 {                                                 
570     const FSE_symbolCompressionTransform* symb    
571     U32 const minNbBits = symbolTT[symbolValue    
572     U32 const threshold = (minNbBits+1) << 16;    
573     assert(tableLog < 16);                        
574     assert(accuracyLog < 31-tableLog);  /* ens    
575     {   U32 const tableSize = 1 << tableLog;      
576         U32 const deltaFromThreshold = thresho    
577         U32 const normalizedDeltaFromThreshold    
578         U32 const bitMultiplier = 1 << accurac    
579         assert(symbolTT[symbolValue].deltaNbBi    
580         assert(normalizedDeltaFromThreshold <=    
581         return (minNbBits+1)*bitMultiplier - n    
582     }                                             
583 }                                                 
584                                                   
585                                                   
586 /* ======    Decompression    ====== */           
587                                                   
588 typedef struct {                                  
589     U16 tableLog;                                 
590     U16 fastMode;                                 
591 } FSE_DTableHeader;   /* sizeof U32 */            
592                                                   
593 typedef struct                                    
594 {                                                 
595     unsigned short newState;                      
596     unsigned char  symbol;                        
597     unsigned char  nbBits;                        
598 } FSE_decode_t;   /* size == U32 */               
599                                                   
600 MEM_STATIC void FSE_initDState(FSE_DState_t* D    
601 {                                                 
602     const void* ptr = dt;                         
603     const FSE_DTableHeader* const DTableH = (c    
604     DStatePtr->state = BIT_readBits(bitD, DTab    
605     BIT_reloadDStream(bitD);                      
606     DStatePtr->table = dt + 1;                    
607 }                                                 
608                                                   
609 MEM_STATIC BYTE FSE_peekSymbol(const FSE_DStat    
610 {                                                 
611     FSE_decode_t const DInfo = ((const FSE_dec    
612     return DInfo.symbol;                          
613 }                                                 
614                                                   
615 MEM_STATIC void FSE_updateState(FSE_DState_t*     
616 {                                                 
617     FSE_decode_t const DInfo = ((const FSE_dec    
618     U32 const nbBits = DInfo.nbBits;              
619     size_t const lowBits = BIT_readBits(bitD,     
620     DStatePtr->state = DInfo.newState + lowBit    
621 }                                                 
622                                                   
623 MEM_STATIC BYTE FSE_decodeSymbol(FSE_DState_t*    
624 {                                                 
625     FSE_decode_t const DInfo = ((const FSE_dec    
626     U32 const nbBits = DInfo.nbBits;              
627     BYTE const symbol = DInfo.symbol;             
628     size_t const lowBits = BIT_readBits(bitD,     
629                                                   
630     DStatePtr->state = DInfo.newState + lowBit    
631     return symbol;                                
632 }                                                 
633                                                   
634 /*! FSE_decodeSymbolFast() :                      
635     unsafe, only works if no symbol has a prob    
636 MEM_STATIC BYTE FSE_decodeSymbolFast(FSE_DStat    
637 {                                                 
638     FSE_decode_t const DInfo = ((const FSE_dec    
639     U32 const nbBits = DInfo.nbBits;              
640     BYTE const symbol = DInfo.symbol;             
641     size_t const lowBits = BIT_readBitsFast(bi    
642                                                   
643     DStatePtr->state = DInfo.newState + lowBit    
644     return symbol;                                
645 }                                                 
646                                                   
647 MEM_STATIC unsigned FSE_endOfDState(const FSE_    
648 {                                                 
649     return DStatePtr->state == 0;                 
650 }                                                 
651                                                   
652                                                   
653                                                   
654 #ifndef FSE_COMMONDEFS_ONLY                       
655                                                   
656 /* *******************************************    
657 *  Tuning parameters                              
658 **********************************************    
659 /*!MEMORY_USAGE :                                 
660 *  Memory usage formula : N->2^N Bytes (exampl    
661 *  Increasing memory usage improves compressio    
662 *  Reduced memory usage can improve speed, due    
663 *  Recommended max value is 14, for 16KB, whic    
664 #ifndef FSE_MAX_MEMORY_USAGE                      
665 #  define FSE_MAX_MEMORY_USAGE 14                 
666 #endif                                            
667 #ifndef FSE_DEFAULT_MEMORY_USAGE                  
668 #  define FSE_DEFAULT_MEMORY_USAGE 13             
669 #endif                                            
670 #if (FSE_DEFAULT_MEMORY_USAGE > FSE_MAX_MEMORY    
671 #  error "FSE_DEFAULT_MEMORY_USAGE must be <=     
672 #endif                                            
673                                                   
674 /*!FSE_MAX_SYMBOL_VALUE :                         
675 *  Maximum symbol value authorized.               
676 *  Required for proper stack allocation */        
677 #ifndef FSE_MAX_SYMBOL_VALUE                      
678 #  define FSE_MAX_SYMBOL_VALUE 255                
679 #endif                                            
680                                                   
681 /* *******************************************    
682 *  template functions type & suffix               
683 **********************************************    
684 #define FSE_FUNCTION_TYPE BYTE                    
685 #define FSE_FUNCTION_EXTENSION                    
686 #define FSE_DECODE_TYPE FSE_decode_t              
687                                                   
688                                                   
689 #endif   /* !FSE_COMMONDEFS_ONLY */               
690                                                   
691                                                   
692 /* *******************************************    
693 *  Constants                                      
694 **********************************************    
695 #define FSE_MAX_TABLELOG  (FSE_MAX_MEMORY_USAG    
696 #define FSE_MAX_TABLESIZE (1U<<FSE_MAX_TABLELO    
697 #define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESI    
698 #define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMO    
699 #define FSE_MIN_TABLELOG 5                        
700                                                   
701 #define FSE_TABLELOG_ABSOLUTE_MAX 15              
702 #if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_M    
703 #  error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSO    
704 #endif                                            
705                                                   
706 #define FSE_TABLESTEP(tableSize) (((tableSize)    
707                                                   
708                                                   
709 #endif /* FSE_STATIC_LINKING_ONLY */              
710                                                   
711                                                   
712                                                   

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