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  */
337 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog) (maxSymbolValue + 2 + (1ull << (tableLog - 2)))
338 #define FSE_BUILD_CTABLE_WORKSPACE_SIZE(maxSymbolValue, tableLog) (sizeof(unsigned) * FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog))
339 size_t FSE_buildCTable_wksp(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
340 
341 #define FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) (sizeof(short) * (maxSymbolValue + 1) + (1ULL << maxTableLog) + 8)
342 #define FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) ((FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) + sizeof(unsigned) - 1) / sizeof(unsigned))
343 FSE_PUBLIC_API size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
344 /*< Same as FSE_buildDTable(), using an externally allocated `workspace` produced with `FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxSymbolValue)` */
345 
346 size_t FSE_buildDTable_raw (FSE_DTable* dt, unsigned nbBits);
347 /*< build a fake FSE_DTable, designed to read a flat distribution where each symbol uses nbBits */
348 
349 size_t FSE_buildDTable_rle (FSE_DTable* dt, unsigned char symbolValue);
350 /*< build a fake FSE_DTable, designed to always generate the same symbolValue */
351 
352 #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)
353 #define FSE_DECOMPRESS_WKSP_SIZE(maxTableLog, maxSymbolValue) (FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(unsigned))
354 size_t FSE_decompress_wksp(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize);
355 /*< same as FSE_decompress(), using an externally allocated `workSpace` produced with `FSE_DECOMPRESS_WKSP_SIZE_U32(maxLog, maxSymbolValue)` */
356 
357 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);
358 /*< Same as FSE_decompress_wksp() but with dynamic BMI2 support. Pass 1 if your CPU supports BMI2 or 0 if it doesn't. */
359 
360 typedef enum {
361    FSE_repeat_none,  /*< Cannot use the previous table */
362    FSE_repeat_check, /*< Can use the previous table but it must be checked */
363    FSE_repeat_valid  /*< Can use the previous table and it is assumed to be valid */
364  } FSE_repeat;
365 
366 /* *****************************************
367 *  FSE symbol compression API
368 *******************************************/
369 /*!
370    This API consists of small unitary functions, which highly benefit from being inlined.
371    Hence their body are included in next section.
372 */
373 typedef struct {
374     ptrdiff_t   value;
375     const void* stateTable;
376     const void* symbolTT;
377     unsigned    stateLog;
378 } FSE_CState_t;
379 
380 static void FSE_initCState(FSE_CState_t* CStatePtr, const FSE_CTable* ct);
381 
382 static void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* CStatePtr, unsigned symbol);
383 
384 static void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* CStatePtr);
385 
386 /*<
387 These functions are inner components of FSE_compress_usingCTable().
388 They allow the creation of custom streams, mixing multiple tables and bit sources.
389 
390 A key property to keep in mind is that encoding and decoding are done **in reverse direction**.
391 So the first symbol you will encode is the last you will decode, like a LIFO stack.
392 
393 You will need a few variables to track your CStream. They are :
394 
395 FSE_CTable    ct;         // Provided by FSE_buildCTable()
396 BIT_CStream_t bitStream;  // bitStream tracking structure
397 FSE_CState_t  state;      // State tracking structure (can have several)
398 
399 
400 The first thing to do is to init bitStream and state.
401     size_t errorCode = BIT_initCStream(&bitStream, dstBuffer, maxDstSize);
402     FSE_initCState(&state, ct);
403 
404 Note that BIT_initCStream() can produce an error code, so its result should be tested, using FSE_isError();
405 You can then encode your input data, byte after byte.
406 FSE_encodeSymbol() outputs a maximum of 'tableLog' bits at a time.
407 Remember decoding will be done in reverse direction.
408     FSE_encodeByte(&bitStream, &state, symbol);
409 
410 At any time, you can also add any bit sequence.
411 Note : maximum allowed nbBits is 25, for compatibility with 32-bits decoders
412     BIT_addBits(&bitStream, bitField, nbBits);
413 
414 The above methods don't commit data to memory, they just store it into local register, for speed.
415 Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
416 Writing data to memory is a manual operation, performed by the flushBits function.
417     BIT_flushBits(&bitStream);
418 
419 Your last FSE encoding operation shall be to flush your last state value(s).
420     FSE_flushState(&bitStream, &state);
421 
422 Finally, you must close the bitStream.
423 The function returns the size of CStream in bytes.
424 If data couldn't fit into dstBuffer, it will return a 0 ( == not compressible)
425 If there is an error, it returns an errorCode (which can be tested using FSE_isError()).
426     size_t size = BIT_closeCStream(&bitStream);
427 */
428 
429 
430 /* *****************************************
431 *  FSE symbol decompression API
432 *******************************************/
433 typedef struct {
434     size_t      state;
435     const void* table;   /* precise table may vary, depending on U16 */
436 } FSE_DState_t;
437 
438 
439 static void     FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt);
440 
441 static unsigned char FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
442 
443 static unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr);
444 
445 /*<
446 Let's now decompose FSE_decompress_usingDTable() into its unitary components.
447 You will decode FSE-encoded symbols from the bitStream,
448 and also any other bitFields you put in, **in reverse order**.
449 
450 You will need a few variables to track your bitStream. They are :
451 
452 BIT_DStream_t DStream;    // Stream context
453 FSE_DState_t  DState;     // State context. Multiple ones are possible
454 FSE_DTable*   DTablePtr;  // Decoding table, provided by FSE_buildDTable()
455 
456 The first thing to do is to init the bitStream.
457     errorCode = BIT_initDStream(&DStream, srcBuffer, srcSize);
458 
459 You should then retrieve your initial state(s)
460 (in reverse flushing order if you have several ones) :
461     errorCode = FSE_initDState(&DState, &DStream, DTablePtr);
462 
463 You can then decode your data, symbol after symbol.
464 For information the maximum number of bits read by FSE_decodeSymbol() is 'tableLog'.
465 Keep in mind that symbols are decoded in reverse order, like a LIFO stack (last in, first out).
466     unsigned char symbol = FSE_decodeSymbol(&DState, &DStream);
467 
468 You can retrieve any bitfield you eventually stored into the bitStream (in reverse order)
469 Note : maximum allowed nbBits is 25, for 32-bits compatibility
470     size_t bitField = BIT_readBits(&DStream, nbBits);
471 
472 All above operations only read from local register (which size depends on size_t).
473 Refueling the register from memory is manually performed by the reload method.
474     endSignal = FSE_reloadDStream(&DStream);
475 
476 BIT_reloadDStream() result tells if there is still some more data to read from DStream.
477 BIT_DStream_unfinished : there is still some data left into the DStream.
478 BIT_DStream_endOfBuffer : Dstream reached end of buffer. Its container may no longer be completely filled.
479 BIT_DStream_completed : Dstream reached its exact end, corresponding in general to decompression completed.
480 BIT_DStream_tooFar : Dstream went too far. Decompression result is corrupted.
481 
482 When reaching end of buffer (BIT_DStream_endOfBuffer), progress slowly, notably if you decode multiple symbols per loop,
483 to properly detect the exact end of stream.
484 After each decoded symbol, check if DStream is fully consumed using this simple test :
485     BIT_reloadDStream(&DStream) >= BIT_DStream_completed
486 
487 When it's done, verify decompression is fully completed, by checking both DStream and the relevant states.
488 Checking if DStream has reached its end is performed by :
489     BIT_endOfDStream(&DStream);
490 Check also the states. There might be some symbols left there, if some high probability ones (>50%) are possible.
491     FSE_endOfDState(&DState);
492 */
493 
494 
495 /* *****************************************
496 *  FSE unsafe API
497 *******************************************/
498 static unsigned char FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
499 /* faster, but works only if nbBits is always >= 1 (otherwise, result will be corrupted) */
500 
501 
502 /* *****************************************
503 *  Implementation of inlined functions
504 *******************************************/
505 typedef struct {
506     int deltaFindState;
507     U32 deltaNbBits;
508 } FSE_symbolCompressionTransform; /* total 8 bytes */
509 
FSE_initCState(FSE_CState_t * statePtr,const FSE_CTable * ct)510 MEM_STATIC void FSE_initCState(FSE_CState_t* statePtr, const FSE_CTable* ct)
511 {
512     const void* ptr = ct;
513     const U16* u16ptr = (const U16*) ptr;
514     const U32 tableLog = MEM_read16(ptr);
515     statePtr->value = (ptrdiff_t)1<<tableLog;
516     statePtr->stateTable = u16ptr+2;
517     statePtr->symbolTT = ct + 1 + (tableLog ? (1<<(tableLog-1)) : 1);
518     statePtr->stateLog = tableLog;
519 }
520 
521 
522 /*! FSE_initCState2() :
523 *   Same as FSE_initCState(), but the first symbol to include (which will be the last to be read)
524 *   uses the smallest state value possible, saving the cost of this symbol */
FSE_initCState2(FSE_CState_t * statePtr,const FSE_CTable * ct,U32 symbol)525 MEM_STATIC void FSE_initCState2(FSE_CState_t* statePtr, const FSE_CTable* ct, U32 symbol)
526 {
527     FSE_initCState(statePtr, ct);
528     {   const FSE_symbolCompressionTransform symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
529         const U16* stateTable = (const U16*)(statePtr->stateTable);
530         U32 nbBitsOut  = (U32)((symbolTT.deltaNbBits + (1<<15)) >> 16);
531         statePtr->value = (nbBitsOut << 16) - symbolTT.deltaNbBits;
532         statePtr->value = stateTable[(statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
533     }
534 }
535 
FSE_encodeSymbol(BIT_CStream_t * bitC,FSE_CState_t * statePtr,unsigned symbol)536 MEM_STATIC void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* statePtr, unsigned symbol)
537 {
538     FSE_symbolCompressionTransform const symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
539     const U16* const stateTable = (const U16*)(statePtr->stateTable);
540     U32 const nbBitsOut  = (U32)((statePtr->value + symbolTT.deltaNbBits) >> 16);
541     BIT_addBits(bitC, statePtr->value, nbBitsOut);
542     statePtr->value = stateTable[ (statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
543 }
544 
FSE_flushCState(BIT_CStream_t * bitC,const FSE_CState_t * statePtr)545 MEM_STATIC void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* statePtr)
546 {
547     BIT_addBits(bitC, statePtr->value, statePtr->stateLog);
548     BIT_flushBits(bitC);
549 }
550 
551 
552 /* FSE_getMaxNbBits() :
553  * Approximate maximum cost of a symbol, in bits.
554  * Fractional get rounded up (i.e : a symbol with a normalized frequency of 3 gives the same result as a frequency of 2)
555  * note 1 : assume symbolValue is valid (<= maxSymbolValue)
556  * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
FSE_getMaxNbBits(const void * symbolTTPtr,U32 symbolValue)557 MEM_STATIC U32 FSE_getMaxNbBits(const void* symbolTTPtr, U32 symbolValue)
558 {
559     const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
560     return (symbolTT[symbolValue].deltaNbBits + ((1<<16)-1)) >> 16;
561 }
562 
563 /* FSE_bitCost() :
564  * Approximate symbol cost, as fractional value, using fixed-point format (accuracyLog fractional bits)
565  * note 1 : assume symbolValue is valid (<= maxSymbolValue)
566  * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
FSE_bitCost(const void * symbolTTPtr,U32 tableLog,U32 symbolValue,U32 accuracyLog)567 MEM_STATIC U32 FSE_bitCost(const void* symbolTTPtr, U32 tableLog, U32 symbolValue, U32 accuracyLog)
568 {
569     const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
570     U32 const minNbBits = symbolTT[symbolValue].deltaNbBits >> 16;
571     U32 const threshold = (minNbBits+1) << 16;
572     assert(tableLog < 16);
573     assert(accuracyLog < 31-tableLog);  /* ensure enough room for renormalization double shift */
574     {   U32 const tableSize = 1 << tableLog;
575         U32 const deltaFromThreshold = threshold - (symbolTT[symbolValue].deltaNbBits + tableSize);
576         U32 const normalizedDeltaFromThreshold = (deltaFromThreshold << accuracyLog) >> tableLog;   /* linear interpolation (very approximate) */
577         U32 const bitMultiplier = 1 << accuracyLog;
578         assert(symbolTT[symbolValue].deltaNbBits + tableSize <= threshold);
579         assert(normalizedDeltaFromThreshold <= bitMultiplier);
580         return (minNbBits+1)*bitMultiplier - normalizedDeltaFromThreshold;
581     }
582 }
583 
584 
585 /* ======    Decompression    ====== */
586 
587 typedef struct {
588     U16 tableLog;
589     U16 fastMode;
590 } FSE_DTableHeader;   /* sizeof U32 */
591 
592 typedef struct
593 {
594     unsigned short newState;
595     unsigned char  symbol;
596     unsigned char  nbBits;
597 } FSE_decode_t;   /* size == U32 */
598 
FSE_initDState(FSE_DState_t * DStatePtr,BIT_DStream_t * bitD,const FSE_DTable * dt)599 MEM_STATIC void FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt)
600 {
601     const void* ptr = dt;
602     const FSE_DTableHeader* const DTableH = (const FSE_DTableHeader*)ptr;
603     DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
604     BIT_reloadDStream(bitD);
605     DStatePtr->table = dt + 1;
606 }
607 
FSE_peekSymbol(const FSE_DState_t * DStatePtr)608 MEM_STATIC BYTE FSE_peekSymbol(const FSE_DState_t* DStatePtr)
609 {
610     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
611     return DInfo.symbol;
612 }
613 
FSE_updateState(FSE_DState_t * DStatePtr,BIT_DStream_t * bitD)614 MEM_STATIC void FSE_updateState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
615 {
616     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
617     U32 const nbBits = DInfo.nbBits;
618     size_t const lowBits = BIT_readBits(bitD, nbBits);
619     DStatePtr->state = DInfo.newState + lowBits;
620 }
621 
FSE_decodeSymbol(FSE_DState_t * DStatePtr,BIT_DStream_t * bitD)622 MEM_STATIC BYTE FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
623 {
624     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
625     U32 const nbBits = DInfo.nbBits;
626     BYTE const symbol = DInfo.symbol;
627     size_t const lowBits = BIT_readBits(bitD, nbBits);
628 
629     DStatePtr->state = DInfo.newState + lowBits;
630     return symbol;
631 }
632 
633 /*! FSE_decodeSymbolFast() :
634     unsafe, only works if no symbol has a probability > 50% */
FSE_decodeSymbolFast(FSE_DState_t * DStatePtr,BIT_DStream_t * bitD)635 MEM_STATIC BYTE FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
636 {
637     FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
638     U32 const nbBits = DInfo.nbBits;
639     BYTE const symbol = DInfo.symbol;
640     size_t const lowBits = BIT_readBitsFast(bitD, nbBits);
641 
642     DStatePtr->state = DInfo.newState + lowBits;
643     return symbol;
644 }
645 
FSE_endOfDState(const FSE_DState_t * DStatePtr)646 MEM_STATIC unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr)
647 {
648     return DStatePtr->state == 0;
649 }
650 
651 
652 
653 #ifndef FSE_COMMONDEFS_ONLY
654 
655 /* **************************************************************
656 *  Tuning parameters
657 ****************************************************************/
658 /*!MEMORY_USAGE :
659 *  Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
660 *  Increasing memory usage improves compression ratio
661 *  Reduced memory usage can improve speed, due to cache effect
662 *  Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */
663 #ifndef FSE_MAX_MEMORY_USAGE
664 #  define FSE_MAX_MEMORY_USAGE 14
665 #endif
666 #ifndef FSE_DEFAULT_MEMORY_USAGE
667 #  define FSE_DEFAULT_MEMORY_USAGE 13
668 #endif
669 #if (FSE_DEFAULT_MEMORY_USAGE > FSE_MAX_MEMORY_USAGE)
670 #  error "FSE_DEFAULT_MEMORY_USAGE must be <= FSE_MAX_MEMORY_USAGE"
671 #endif
672 
673 /*!FSE_MAX_SYMBOL_VALUE :
674 *  Maximum symbol value authorized.
675 *  Required for proper stack allocation */
676 #ifndef FSE_MAX_SYMBOL_VALUE
677 #  define FSE_MAX_SYMBOL_VALUE 255
678 #endif
679 
680 /* **************************************************************
681 *  template functions type & suffix
682 ****************************************************************/
683 #define FSE_FUNCTION_TYPE BYTE
684 #define FSE_FUNCTION_EXTENSION
685 #define FSE_DECODE_TYPE FSE_decode_t
686 
687 
688 #endif   /* !FSE_COMMONDEFS_ONLY */
689 
690 
691 /* ***************************************************************
692 *  Constants
693 *****************************************************************/
694 #define FSE_MAX_TABLELOG  (FSE_MAX_MEMORY_USAGE-2)
695 #define FSE_MAX_TABLESIZE (1U<<FSE_MAX_TABLELOG)
696 #define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESIZE-1)
697 #define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMORY_USAGE-2)
698 #define FSE_MIN_TABLELOG 5
699 
700 #define FSE_TABLELOG_ABSOLUTE_MAX 15
701 #if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX
702 #  error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX is not supported"
703 #endif
704 
705 #define FSE_TABLESTEP(tableSize) (((tableSize)>>1) + ((tableSize)>>3) + 3)
706 
707 
708 #endif /* FSE_STATIC_LINKING_ONLY */
709 
710 
711