lib/zstd/common/fse.h

   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/Cyan4973/FiniteStateEntropy
   8  *
   9  * This source code is licensed under both the BSD-style license (found in the
  10  * LICENSE file in the root directory of this source tree) and the GPLv2 (found
  11  * in the COPYING file in the root directory of this source tree).
  12  * You may select, at your option, one of the above-listed licenses.
  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 visibility
  28 ******************************************/
  29 #if defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1) && defined(__GNUC__) && (__GNUC__ >= 4)
  30 #  define FSE_PUBLIC_API __attribute__ ((visibility ("default")))
  31 #elif defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1)   /* Visual expected */
  32 #  define FSE_PUBLIC_API __declspec(dllexport)
  33 #elif defined(FSE_DLL_IMPORT) && (FSE_DLL_IMPORT==1)
  34 #  define FSE_PUBLIC_API __declspec(dllimport) /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
  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_VERSION_MINOR.FSE_VERSION_RELEASE
  45 #define FSE_QUOTE(str) #str
  46 #define FSE_EXPAND_AND_QUOTE(str) FSE_QUOTE(str)
  47 #define FSE_VERSION_STRING FSE_EXPAND_AND_QUOTE(FSE_LIB_VERSION)
  48
  49 #define FSE_VERSION_NUMBER  (FSE_VERSION_MAJOR *100*100 + FSE_VERSION_MINOR *100 + FSE_VERSION_RELEASE)
  50 FSE_PUBLIC_API unsigned FSE_versionNumber(void);   /*< library version number; to be used when checking dll version */
  51
  52
  53 /*-****************************************
  54 *  FSE simple functions
  55 ******************************************/
  56 /*! FSE_compress() :
  57     Compress content of buffer 'src', of size 'srcSize', into destination buffer 'dst'.
  58     'dst' buffer must be already allocated. Compression runs faster is dstCapacity >= FSE_compressBound(srcSize).
  59     @return : size of compressed data (<= dstCapacity).
  60     Special values : if return == 0, srcData is not compressible => Nothing is stored within dst !!!
  61                      if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression instead.
  62                      if FSE_isError(return), compression failed (more details using FSE_getErrorName())
  63 */
  64 FSE_PUBLIC_API size_t FSE_compress(void* dst, size_t dstCapacity,
  65                              const void* src, size_t srcSize);
  66
  67 /*! FSE_decompress():
  68     Decompress FSE data from buffer 'cSrc', of size 'cSrcSize',
  69     into already allocated destination buffer 'dst', of size 'dstCapacity'.
  70     @return : size of regenerated data (<= maxDstSize),
  71               or an error code, which can be tested using FSE_isError() .
  72
  73     ** Important ** : FSE_decompress() does not decompress non-compressible nor RLE data !!!
  74     Why ? : making this distinction requires a header.
  75     Header management is intentionally delegated to the user layer, which can better manage special cases.
  76 */
  77 FSE_PUBLIC_API size_t FSE_decompress(void* dst,  size_t dstCapacity,
  78                                const void* cSrc, size_t cSrcSize);
  79
  80
  81 /*-*****************************************
  82 *  Tool functions
  83 ******************************************/
  84 FSE_PUBLIC_API size_t FSE_compressBound(size_t size);       /* maximum compressed size */
  85
  86 /* Error Management */
  87 FSE_PUBLIC_API unsigned    FSE_isError(size_t code);        /* tells if a return value is an error code */
  88 FSE_PUBLIC_API const char* FSE_getErrorName(size_t code);   /* provides error code string (useful for debugging) */
  89
  90
  91 /*-*****************************************
  92 *  FSE advanced functions
  93 ******************************************/
  94 /*! FSE_compress2() :
  95     Same as FSE_compress(), but allows the selection of 'maxSymbolValue' and 'tableLog'
  96     Both parameters can be defined as '0' to mean : use default value
  97     @return : size of compressed data
  98     Special values : if return == 0, srcData is not compressible => Nothing is stored within cSrc !!!
  99                      if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression.
 100                      if FSE_isError(return), it's an error code.
 101 */
 102 FSE_PUBLIC_API size_t FSE_compress2 (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned tableLog);
 103
 104
 105 /*-*****************************************
 106 *  FSE detailed API
 107 ******************************************/
 108 /*!
 109 FSE_compress() does the following:
 110 1. count symbol occurrence from source[] into table count[] (see hist.h)
 111 2. normalize counters so that sum(count[]) == Power_of_2 (2^tableLog)
 112 3. save normalized counters to memory buffer using writeNCount()
 113 4. build encoding table 'CTable' from normalized counters
 114 5. encode the data stream using encoding table 'CTable'
 115
 116 FSE_decompress() does the following:
 117 1. read normalized counters with readNCount()
 118 2. build decoding table 'DTable' from normalized counters
 119 3. decode the data stream using decoding table 'DTable'
 120
 121 The following API allows targeting specific sub-functions for advanced tasks.
 122 For example, it's possible to compress several blocks using the same 'CTable',
 123 or to save and provide normalized distribution using external method.
 124 */
 125
 126 /* *** COMPRESSION *** */
 127
 128 /*! FSE_optimalTableLog():
 129     dynamically downsize 'tableLog' when conditions are met.
 130     It saves CPU time, by using smaller tables, while preserving or even improving compression ratio.
 131     @return : recommended tableLog (necessarily <= 'maxTableLog') */
 132 FSE_PUBLIC_API unsigned FSE_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue);
 133
 134 /*! FSE_normalizeCount():
 135     normalize counts so that sum(count[]) == Power_of_2 (2^tableLog)
 136     'normalizedCounter' is a table of short, of minimum size (maxSymbolValue+1).
 137     useLowProbCount is a boolean parameter which trades off compressed size for
 138     faster header decoding. When it is set to 1, the compressed data will be slightly
 139     smaller. And when it is set to 0, FSE_readNCount() and FSE_buildDTable() will be
 140     faster. If you are compressing a small amount of data (< 2 KB) then useLowProbCount=0
 141     is a good default, since header deserialization makes a big speed difference.
 142     Otherwise, useLowProbCount=1 is a good default, since the speed difference is small.
 143     @return : tableLog,
 144               or an errorCode, which can be tested using FSE_isError() */
 145 FSE_PUBLIC_API size_t FSE_normalizeCount(short* normalizedCounter, unsigned tableLog,
 146                     const unsigned* count, size_t srcSize, unsigned maxSymbolValue, unsigned useLowProbCount);
 147
 148 /*! FSE_NCountWriteBound():
 149     Provides the maximum possible size of an FSE normalized table, given 'maxSymbolValue' and 'tableLog'.
 150     Typically useful for allocation purpose. */
 151 FSE_PUBLIC_API size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog);
 152
 153 /*! FSE_writeNCount():
 154     Compactly save 'normalizedCounter' into 'buffer'.
 155     @return : size of the compressed table,
 156               or an errorCode, which can be tested using FSE_isError(). */
 157 FSE_PUBLIC_API size_t FSE_writeNCount (void* buffer, size_t bufferSize,
 158                                  const short* normalizedCounter,
 159                                  unsigned maxSymbolValue, unsigned tableLog);
 160
 161 /*! Constructor and Destructor of FSE_CTable.
 162     Note that FSE_CTable size depends on 'tableLog' and 'maxSymbolValue' */
 163 typedef unsigned FSE_CTable;   /* don't allocate that. It's only meant to be more restrictive than void* */
 164 FSE_PUBLIC_API FSE_CTable* FSE_createCTable (unsigned maxSymbolValue, unsigned tableLog);
 165 FSE_PUBLIC_API void        FSE_freeCTable (FSE_CTable* ct);
 166
 167 /*! FSE_buildCTable():
 168     Builds `ct`, which must be already allocated, using FSE_createCTable().
 169     @return : 0, or an errorCode, which can be tested using FSE_isError() */
 170 FSE_PUBLIC_API size_t FSE_buildCTable(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
 171
 172 /*! FSE_compress_usingCTable():
 173     Compress `src` using `ct` into `dst` which must be already allocated.
 174     @return : size of compressed data (<= `dstCapacity`),
 175               or 0 if compressed data could not fit into `dst`,
 176               or an errorCode, which can be tested using FSE_isError() */
 177 FSE_PUBLIC_API size_t FSE_compress_usingCTable (void* dst, size_t dstCapacity, const void* src, size_t srcSize, const FSE_CTable* ct);
 178
 179 /*!
 180 Tutorial :
 181 ----------
 182 The first step is to count all symbols. FSE_count() does this job very fast.
 183 Result will be saved into 'count', a table of unsigned int, which must be already allocated, and have 'maxSymbolValuePtr[0]+1' cells.
 184 'src' is a table of bytes of size 'srcSize'. All values within 'src' MUST be <= maxSymbolValuePtr[0]
 185 maxSymbolValuePtr[0] will be updated, with its real value (necessarily <= original value)
 186 FSE_count() will return the number of occurrence of the most frequent symbol.
 187 This can be used to know if there is a single symbol within 'src', and to quickly evaluate its compressibility.
 188 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
 189
 190 The next step is to normalize the frequencies.
 191 FSE_normalizeCount() will ensure that sum of frequencies is == 2 ^'tableLog'.
 192 It also guarantees a minimum of 1 to any Symbol with frequency >= 1.
 193 You can use 'tableLog'==0 to mean "use default tableLog value".
 194 If you are unsure of which tableLog value to use, you can ask FSE_optimalTableLog(),
 195 which will provide the optimal valid tableLog given sourceSize, maxSymbolValue, and a user-defined maximum (0 means "default").
 196
 197 The result of FSE_normalizeCount() will be saved into a table,
 198 called 'normalizedCounter', which is a table of signed short.
 199 'normalizedCounter' must be already allocated, and have at least 'maxSymbolValue+1' cells.
 200 The return value is tableLog if everything proceeded as expected.
 201 It is 0 if there is a single symbol within distribution.
 202 If there is an error (ex: invalid tableLog value), the function will return an ErrorCode (which can be tested using FSE_isError()).
 203
 204 'normalizedCounter' can be saved in a compact manner to a memory area using FSE_writeNCount().
 205 'buffer' must be already allocated.
 206 For guaranteed success, buffer size must be at least FSE_headerBound().
 207 The result of the function is the number of bytes written into 'buffer'.
 208 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError(); ex : buffer size too small).
 209
 210 'normalizedCounter' can then be used to create the compression table 'CTable'.
 211 The space required by 'CTable' must be already allocated, using FSE_createCTable().
 212 You can then use FSE_buildCTable() to fill 'CTable'.
 213 If there is an error, both functions will return an ErrorCode (which can be tested using FSE_isError()).
 214
 215 'CTable' can then be used to compress 'src', with FSE_compress_usingCTable().
 216 Similar to FSE_count(), the convention is that 'src' is assumed to be a table of char of size 'srcSize'
 217 The function returns the size of compressed data (without header), necessarily <= `dstCapacity`.
 218 If it returns '0', compressed data could not fit into 'dst'.
 219 If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
 220 */
 221
 222
 223 /* *** DECOMPRESSION *** */
 224
 225 /*! FSE_readNCount():
 226     Read compactly saved 'normalizedCounter' from 'rBuffer'.
 227     @return : size read from 'rBuffer',
 228               or an errorCode, which can be tested using FSE_isError().
 229               maxSymbolValuePtr[0] and tableLogPtr[0] will also be updated with their respective values */
 230 FSE_PUBLIC_API size_t FSE_readNCount (short* normalizedCounter,
 231                            unsigned* maxSymbolValuePtr, unsigned* tableLogPtr,
 232                            const void* rBuffer, size_t rBuffSize);
 233
 234 /*! FSE_readNCount_bmi2():
 235  * Same as FSE_readNCount() but pass bmi2=1 when your CPU supports BMI2 and 0 otherwise.
 236  */
 237 FSE_PUBLIC_API size_t FSE_readNCount_bmi2(short* normalizedCounter,
 238                            unsigned* maxSymbolValuePtr, unsigned* tableLogPtr,
 239                            const void* rBuffer, size_t rBuffSize, int bmi2);
 240
 241 /*! Constructor and Destructor of FSE_DTable.
 242     Note that its size depends on 'tableLog' */
 243 typedef unsigned FSE_DTable;   /* don't allocate that. It's just a way to be more restrictive than void* */
 244 FSE_PUBLIC_API FSE_DTable* FSE_createDTable(unsigned tableLog);
 245 FSE_PUBLIC_API void        FSE_freeDTable(FSE_DTable* dt);
 246
 247 /*! FSE_buildDTable():
 248     Builds 'dt', which must be already allocated, using FSE_createDTable().
 249     return : 0, or an errorCode, which can be tested using FSE_isError() */
 250 FSE_PUBLIC_API size_t FSE_buildDTable (FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
 251
 252 /*! FSE_decompress_usingDTable():
 253     Decompress compressed source `cSrc` of size `cSrcSize` using `dt`
 254     into `dst` which must be already allocated.
 255     @return : size of regenerated data (necessarily <= `dstCapacity`),
 256               or an errorCode, which can be tested using FSE_isError() */
 257 FSE_PUBLIC_API size_t FSE_decompress_usingDTable(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, const FSE_DTable* dt);
 258
 259 /*!
 260 Tutorial :
 261 ----------
 262 (Note : these functions only decompress FSE-compressed blocks.
 263  If block is uncompressed, use memcpy() instead
 264  If block is a single repeated byte, use memset() instead )
 265
 266 The first step is to obtain the normalized frequencies of symbols.
 267 This can be performed by FSE_readNCount() if it was saved using FSE_writeNCount().
 268 'normalizedCounter' must be already allocated, and have at least 'maxSymbolValuePtr[0]+1' cells of signed short.
 269 In practice, that means it's necessary to know 'maxSymbolValue' beforehand,
 270 or size the table to handle worst case situations (typically 256).
 271 FSE_readNCount() will provide 'tableLog' and 'maxSymbolValue'.
 272 The result of FSE_readNCount() is the number of bytes read from 'rBuffer'.
 273 Note that 'rBufferSize' must be at least 4 bytes, even if useful information is less than that.
 274 If there is an error, the function will return an error code, which can be tested using FSE_isError().
 275
 276 The next step is to build the decompression tables 'FSE_DTable' from 'normalizedCounter'.
 277 This is performed by the function FSE_buildDTable().
 278 The space required by 'FSE_DTable' must be already allocated using FSE_createDTable().
 279 If there is an error, the function will return an error code, which can be tested using FSE_isError().
 280
 281 `FSE_DTable` can then be used to decompress `cSrc`, with FSE_decompress_usingDTable().
 282 `cSrcSize` must be strictly correct, otherwise decompression will fail.
 283 FSE_decompress_usingDTable() result will tell how many bytes were regenerated (<=`dstCapacity`).
 284 If there is an error, the function will return an error code, which can be tested using FSE_isError(). (ex: dst buffer too small)
 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)>>7) + 4 /* fse states */ + sizeof(size_t) /* bitContainer */)
 302 #define FSE_COMPRESSBOUND(size) (FSE_NCOUNTBOUND + FSE_BLOCKBOUND(size))   /* Macro version, useful for static allocation */
 303
 304 /* It is possible to statically allocate FSE CTable/DTable as a table of FSE_CTable/FSE_DTable using below macros */
 305 #define FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue)   (1 + (1<<((maxTableLog)-1)) + (((maxSymbolValue)+1)*2))
 306 #define FSE_DTABLE_SIZE_U32(maxTableLog)                   (1 + (1<<(maxTableLog)))
 307
 308 /* or use the size to malloc() space directly. Pay attention to alignment restrictions though */
 309 #define FSE_CTABLE_SIZE(maxTableLog, maxSymbolValue)   (FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(FSE_CTable))
 310 #define FSE_DTABLE_SIZE(maxTableLog)                   (FSE_DTABLE_SIZE_U32(maxTableLog) * sizeof(FSE_DTable))
 311
 312
 313 /* *****************************************
 314  *  FSE advanced API
 315  ***************************************** */
 316
 317 unsigned FSE_optimalTableLog_internal(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, unsigned minus);
 318 /*< same as FSE_optimalTableLog(), which used `minus==2` */
 319
 320 /* FSE_compress_wksp() :
 321  * Same as FSE_compress2(), but using an externally allocated scratch buffer (`workSpace`).
 322  * FSE_COMPRESS_WKSP_SIZE_U32() provides the minimum size required for `workSpace` as a table of FSE_CTable.
 323  */
 324 #define FSE_COMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue)   ( FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) + ((maxTableLog > 12) ? (1 << (maxTableLog - 2)) : 1024) )
 325 size_t FSE_compress_wksp (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
 326
 327 size_t FSE_buildCTable_raw (FSE_CTable* ct, unsigned nbBits);
 328 /*< build a fake FSE_CTable, designed for a flat distribution, where each symbol uses nbBits */
 329
 330 size_t FSE_buildCTable_rle (FSE_CTable* ct, unsigned char symbolValue);
 331 /*< build a fake FSE_CTable, designed to compress always the same symbolValue */
 332
 333 /* FSE_buildCTable_wksp() :
 334  * Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).
 335  * `wkspSize` must be >= `FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog)` of `unsigned`.
 336  * See FSE_buildCTable_wksp() for breakdown of workspace usage.
 337  */
 338 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog) (((maxSymbolValue + 2) + (1ull << (tableLog)))/2 + sizeof(U64)/sizeof(U32) /* additional 8 bytes for potential table overwrite */)
 339 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE(maxSymbolValue, tableLog) (sizeof(unsigned) * FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog))
 340 size_t FSE_buildCTable_wksp(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
 341
 342 #define FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) (sizeof(short) * (maxSymbolValue + 1) + (1ULL << maxTableLog) + 8)
 343 #define FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) ((FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) + sizeof(unsigned) - 1) / sizeof(unsigned))
 344 FSE_PUBLIC_API size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
 345 /*< Same as FSE_buildDTable(), using an externally allocated `workspace` produced with `FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxSymbolValue)` */
 346
 347 size_t FSE_buildDTable_raw (FSE_DTable* dt, unsigned nbBits);
 348 /*< build a fake FSE_DTable, designed to read a flat distribution where each symbol uses nbBits */
 349
 350 size_t FSE_buildDTable_rle (FSE_DTable* dt, unsigned char symbolValue);
 351 /*< build a fake FSE_DTable, designed to always generate the same symbolValue */
 352
 353 #define FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) (FSE_DTABLE_SIZE_U32(maxTableLog) + FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) + (FSE_MAX_SYMBOL_VALUE + 1) / 2 + 1)
 354 #define FSE_DECOMPRESS_WKSP_SIZE(maxTableLog, maxSymbolValue) (FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(unsigned))
 355 size_t FSE_decompress_wksp(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize);
 356 /*< same as FSE_decompress(), using an externally allocated `workSpace` produced with `FSE_DECOMPRESS_WKSP_SIZE_U32(maxLog, maxSymbolValue)` */
 357
 358 size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2);
 359 /*< Same as FSE_decompress_wksp() but with dynamic BMI2 support. Pass 1 if your CPU supports BMI2 or 0 if it doesn't. */
 360
 361 typedef enum {
 362    FSE_repeat_none,  /*< Cannot use the previous table */
 363    FSE_repeat_check, /*< Can use the previous table but it must be checked */
 364    FSE_repeat_valid  /*< Can use the previous table and it is assumed to be valid */
 365  } FSE_repeat;
 366
 367 /* *****************************************
 368 *  FSE symbol compression API
 369 *******************************************/
 370 /*!
 371    This API consists of small unitary functions, which highly benefit from being inlined.
 372    Hence their body are included in next section.
 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* CStatePtr, const FSE_CTable* ct);
 382
 383 static void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* CStatePtr, unsigned symbol);
 384
 385 static void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* CStatePtr);
 386
 387 /*<
 388 These functions are inner components of FSE_compress_usingCTable().
 389 They allow the creation of custom streams, mixing multiple tables and bit sources.
 390
 391 A key property to keep in mind is that encoding and decoding are done **in reverse direction**.
 392 So the first symbol you will encode is the last you will decode, like a LIFO stack.
 393
 394 You will need a few variables to track your CStream. They are :
 395
 396 FSE_CTable    ct;         // Provided by FSE_buildCTable()
 397 BIT_CStream_t bitStream;  // bitStream tracking structure
 398 FSE_CState_t  state;      // State tracking structure (can have several)
 399
 400
 401 The first thing to do is to init bitStream and state.
 402     size_t errorCode = BIT_initCStream(&bitStream, dstBuffer, maxDstSize);
 403     FSE_initCState(&state, ct);
 404
 405 Note that BIT_initCStream() can produce an error code, so its result should be tested, using FSE_isError();
 406 You can then encode your input data, byte after byte.
 407 FSE_encodeSymbol() outputs a maximum of 'tableLog' bits at a time.
 408 Remember decoding will be done in reverse direction.
 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 compatibility with 32-bits decoders
 413     BIT_addBits(&bitStream, bitField, nbBits);
 414
 415 The above methods don't commit data to memory, they just store it into local register, for speed.
 416 Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
 417 Writing data to memory is a manual operation, performed by the flushBits function.
 418     BIT_flushBits(&bitStream);
 419
 420 Your last FSE encoding operation shall be to flush your last state value(s).
 421     FSE_flushState(&bitStream, &state);
 422
 423 Finally, you must close the bitStream.
 424 The function returns the size of CStream in bytes.
 425 If data couldn't fit into dstBuffer, it will return a 0 ( == not compressible)
 426 If there is an error, it returns an errorCode (which can be tested using FSE_isError()).
 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 vary, depending on U16 */
 437 } FSE_DState_t;
 438
 439
 440 static void     FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt);
 441
 442 static unsigned char FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
 443
 444 static unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr);
 445
 446 /*<
 447 Let's now decompose FSE_decompress_usingDTable() into its unitary components.
 448 You will decode FSE-encoded symbols from the bitStream,
 449 and also any other bitFields you put in, **in reverse order**.
 450
 451 You will need a few variables to track your bitStream. They are :
 452
 453 BIT_DStream_t DStream;    // Stream context
 454 FSE_DState_t  DState;     // State context. Multiple ones are possible
 455 FSE_DTable*   DTablePtr;  // Decoding table, provided by FSE_buildDTable()
 456
 457 The first thing to do is to init the bitStream.
 458     errorCode = BIT_initDStream(&DStream, srcBuffer, srcSize);
 459
 460 You should then retrieve your initial state(s)
 461 (in reverse flushing order if you have several ones) :
 462     errorCode = FSE_initDState(&DState, &DStream, DTablePtr);
 463
 464 You can then decode your data, symbol after symbol.
 465 For information the maximum number of bits read by FSE_decodeSymbol() is 'tableLog'.
 466 Keep in mind that symbols are decoded in reverse order, like a LIFO stack (last in, first out).
 467     unsigned char symbol = FSE_decodeSymbol(&DState, &DStream);
 468
 469 You can retrieve any bitfield you eventually stored into the bitStream (in reverse order)
 470 Note : maximum allowed nbBits is 25, for 32-bits compatibility
 471     size_t bitField = BIT_readBits(&DStream, nbBits);
 472
 473 All above operations only read from local register (which size depends on size_t).
 474 Refueling the register from memory is manually performed by the reload method.
 475     endSignal = FSE_reloadDStream(&DStream);
 476
 477 BIT_reloadDStream() result tells if there is still some more data to read from DStream.
 478 BIT_DStream_unfinished : there is still some data left into the DStream.
 479 BIT_DStream_endOfBuffer : Dstream reached end of buffer. Its container may no longer be completely filled.
 480 BIT_DStream_completed : Dstream reached its exact end, corresponding in general to decompression completed.
 481 BIT_DStream_tooFar : Dstream went too far. Decompression result is corrupted.
 482
 483 When reaching end of buffer (BIT_DStream_endOfBuffer), progress slowly, notably if you decode multiple symbols per loop,
 484 to properly detect the exact end of stream.
 485 After each decoded symbol, check if DStream is fully consumed using this simple test :
 486     BIT_reloadDStream(&DStream) >= BIT_DStream_completed
 487
 488 When it's done, verify decompression is fully completed, by checking both DStream and the relevant states.
 489 Checking if DStream has reached its end is performed by :
 490     BIT_endOfDStream(&DStream);
 491 Check also the states. There might be some symbols left there, if some high probability ones (>50%) are possible.
 492     FSE_endOfDState(&DState);
 493 */
 494
 495
 496 /* *****************************************
 497 *  FSE unsafe API
 498 *******************************************/
 499 static unsigned char FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
 500 /* faster, but works only if nbBits is always >= 1 (otherwise, result will be corrupted) */
 501
 502
 503 /* *****************************************
 504 *  Implementation of inlined functions
 505 *******************************************/
 506 typedef struct {
 507     int deltaFindState;
 508     U32 deltaNbBits;
 509 } FSE_symbolCompressionTransform; /* total 8 bytes */
 510
 511 MEM_STATIC void FSE_initCState(FSE_CState_t* statePtr, const FSE_CTable* ct)
 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 ? (1<<(tableLog-1)) : 1);
 519     statePtr->stateLog = tableLog;
 520 }
 521
 522
 523 /*! FSE_initCState2() :
 524 *   Same as FSE_initCState(), but the first symbol to include (which will be the last to be read)
 525 *   uses the smallest state value possible, saving the cost of this symbol */
 526 MEM_STATIC void FSE_initCState2(FSE_CState_t* statePtr, const FSE_CTable* ct, U32 symbol)
 527 {
 528     FSE_initCState(statePtr, ct);
 529     {   const FSE_symbolCompressionTransform symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
 530         const U16* stateTable = (const U16*)(statePtr->stateTable);
 531         U32 nbBitsOut  = (U32)((symbolTT.deltaNbBits + (1<<15)) >> 16);
 532         statePtr->value = (nbBitsOut << 16) - symbolTT.deltaNbBits;
 533         statePtr->value = stateTable[(statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
 534     }
 535 }
 536
 537 MEM_STATIC void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* statePtr, unsigned symbol)
 538 {
 539     FSE_symbolCompressionTransform const symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
 540     const U16* const stateTable = (const U16*)(statePtr->stateTable);
 541     U32 const nbBitsOut  = (U32)((statePtr->value + symbolTT.deltaNbBits) >> 16);
 542     BIT_addBits(bitC, statePtr->value, nbBitsOut);
 543     statePtr->value = stateTable[ (statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
 544 }
 545
 546 MEM_STATIC void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* statePtr)
 547 {
 548     BIT_addBits(bitC, statePtr->value, statePtr->stateLog);
 549     BIT_flushBits(bitC);
 550 }
 551
 552
 553 /* FSE_getMaxNbBits() :
 554  * Approximate maximum cost of a symbol, in bits.
 555  * Fractional get rounded up (i.e : a symbol with a normalized frequency of 3 gives the same result as a frequency of 2)
 556  * note 1 : assume symbolValue is valid (<= maxSymbolValue)
 557  * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
 558 MEM_STATIC U32 FSE_getMaxNbBits(const void* symbolTTPtr, U32 symbolValue)
 559 {
 560     const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
 561     return (symbolTT[symbolValue].deltaNbBits + ((1<<16)-1)) >> 16;
 562 }
 563
 564 /* FSE_bitCost() :
 565  * Approximate symbol cost, as fractional value, using fixed-point format (accuracyLog fractional bits)
 566  * note 1 : assume symbolValue is valid (<= maxSymbolValue)
 567  * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
 568 MEM_STATIC U32 FSE_bitCost(const void* symbolTTPtr, U32 tableLog, U32 symbolValue, U32 accuracyLog)
 569 {
 570     const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
 571     U32 const minNbBits = symbolTT[symbolValue].deltaNbBits >> 16;
 572     U32 const threshold = (minNbBits+1) << 16;
 573     assert(tableLog < 16);
 574     assert(accuracyLog < 31-tableLog);  /* ensure enough room for renormalization double shift */
 575     {   U32 const tableSize = 1 << tableLog;
 576         U32 const deltaFromThreshold = threshold - (symbolTT[symbolValue].deltaNbBits + tableSize);
 577         U32 const normalizedDeltaFromThreshold = (deltaFromThreshold << accuracyLog) >> tableLog;   /* linear interpolation (very approximate) */
 578         U32 const bitMultiplier = 1 << accuracyLog;
 579         assert(symbolTT[symbolValue].deltaNbBits + tableSize <= threshold);
 580         assert(normalizedDeltaFromThreshold <= bitMultiplier);
 581         return (minNbBits+1)*bitMultiplier - normalizedDeltaFromThreshold;
 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* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt)
 601 {
 602     const void* ptr = dt;
 603     const FSE_DTableHeader* const DTableH = (const FSE_DTableHeader*)ptr;
 604     DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
 605     BIT_reloadDStream(bitD);
 606     DStatePtr->table = dt + 1;
 607 }
 608
 609 MEM_STATIC BYTE FSE_peekSymbol(const FSE_DState_t* DStatePtr)
 610 {
 611     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
 612     return DInfo.symbol;
 613 }
 614
 615 MEM_STATIC void FSE_updateState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
 616 {
 617     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
 618     U32 const nbBits = DInfo.nbBits;
 619     size_t const lowBits = BIT_readBits(bitD, nbBits);
 620     DStatePtr->state = DInfo.newState + lowBits;
 621 }
 622
 623 MEM_STATIC BYTE FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
 624 {
 625     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
 626     U32 const nbBits = DInfo.nbBits;
 627     BYTE const symbol = DInfo.symbol;
 628     size_t const lowBits = BIT_readBits(bitD, nbBits);
 629
 630     DStatePtr->state = DInfo.newState + lowBits;
 631     return symbol;
 632 }
 633
 634 /*! FSE_decodeSymbolFast() :
 635     unsafe, only works if no symbol has a probability > 50% */
 636 MEM_STATIC BYTE FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
 637 {
 638     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
 639     U32 const nbBits = DInfo.nbBits;
 640     BYTE const symbol = DInfo.symbol;
 641     size_t const lowBits = BIT_readBitsFast(bitD, nbBits);
 642
 643     DStatePtr->state = DInfo.newState + lowBits;
 644     return symbol;
 645 }
 646
 647 MEM_STATIC unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr)
 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 (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
 661 *  Increasing memory usage improves compression ratio
 662 *  Reduced memory usage can improve speed, due to cache effect
 663 *  Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */
 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_USAGE)
 671 #  error "FSE_DEFAULT_MEMORY_USAGE must be <= FSE_MAX_MEMORY_USAGE"
 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_USAGE-2)
 696 #define FSE_MAX_TABLESIZE (1U<<FSE_MAX_TABLELOG)
 697 #define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESIZE-1)
 698 #define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMORY_USAGE-2)
 699 #define FSE_MIN_TABLELOG 5
 700
 701 #define FSE_TABLELOG_ABSOLUTE_MAX 15
 702 #if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX
 703 #  error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX is not supported"
 704 #endif
 705
 706 #define FSE_TABLESTEP(tableSize) (((tableSize)>>1) + ((tableSize)>>3) + 3)
 707
 708
 709 #endif /* FSE_STATIC_LINKING_ONLY */
 710
 711