1/* ******************************************************************
2 bitstream
3 Part of FSE library
4 header file (to include)
5 Copyright (C) 2013-2017, Yann Collet.
6
7 BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
8
9 Redistribution and use in source and binary forms, with or without
10 modification, are permitted provided that the following conditions are
11 met:
12
13 * Redistributions of source code must retain the above copyright
14 notice, this list of conditions and the following disclaimer.
15 * Redistributions in binary form must reproduce the above
16 copyright notice, this list of conditions and the following disclaimer
17 in the documentation and/or other materials provided with the
18 distribution.
19
20 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31
32 You can contact the author at :
33 - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
34****************************************************************** */
35#ifndef BITSTREAM_H_MODULE
36#define BITSTREAM_H_MODULE
37
38#if defined (__cplusplus)
39extern "C" {
40#endif
41
42/*
43* This API consists of small unitary functions, which must be inlined for best performance.
44* Since link-time-optimization is not available for all compilers,
45* these functions are defined into a .h to be included.
46*/
47
48/*-****************************************
49* Dependencies
50******************************************/
51#include "mem.h" /* unaligned access routines */
52#include "error_private.h" /* error codes and messages */
53
54
55/*-*************************************
56* Debug
57***************************************/
58#if defined(BIT_DEBUG) && (BIT_DEBUG>=1)
59# include <assert.h>
60#else
61# ifndef assert
62# define assert(condition) ((void)0)
63# endif
64#endif
65
66
67/*=========================================
68* Target specific
69=========================================*/
70#if defined(__BMI__) && defined(__GNUC__)
71# include <immintrin.h> /* support for bextr (experimental) */
72#endif
73
74#define STREAM_ACCUMULATOR_MIN_32 25
75#define STREAM_ACCUMULATOR_MIN_64 57
76#define STREAM_ACCUMULATOR_MIN ((U32)(MEM_32bits() ? STREAM_ACCUMULATOR_MIN_32 : STREAM_ACCUMULATOR_MIN_64))
77
78
79/*-******************************************
80* bitStream encoding API (write forward)
81********************************************/
82/* bitStream can mix input from multiple sources.
83 * A critical property of these streams is that they encode and decode in **reverse** direction.
84 * So the first bit sequence you add will be the last to be read, like a LIFO stack.
85 */
86typedef struct
87{
88 size_t bitContainer;
89 unsigned bitPos;
90 char* startPtr;
91 char* ptr;
92 char* endPtr;
93} BIT_CStream_t;
94
95MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* dstBuffer, size_t dstCapacity);
96MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits);
97MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC);
98MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC);
99
100/* Start with initCStream, providing the size of buffer to write into.
101* bitStream will never write outside of this buffer.
102* `dstCapacity` must be >= sizeof(bitD->bitContainer), otherwise @return will be an error code.
103*
104* bits are first added to a local register.
105* Local register is size_t, hence 64-bits on 64-bits systems, or 32-bits on 32-bits systems.
106* Writing data into memory is an explicit operation, performed by the flushBits function.
107* Hence keep track how many bits are potentially stored into local register to avoid register overflow.
108* After a flushBits, a maximum of 7 bits might still be stored into local register.
109*
110* Avoid storing elements of more than 24 bits if you want compatibility with 32-bits bitstream readers.
111*
112* Last operation is to close the bitStream.
113* The function returns the final size of CStream in bytes.
114* If data couldn't fit into `dstBuffer`, it will return a 0 ( == not storable)
115*/
116
117
118/*-********************************************
119* bitStream decoding API (read backward)
120**********************************************/
121typedef struct
122{
123 size_t bitContainer;
124 unsigned bitsConsumed;
125 const char* ptr;
126 const char* start;
127 const char* limitPtr;
128} BIT_DStream_t;
129
130typedef enum { BIT_DStream_unfinished = 0,
131 BIT_DStream_endOfBuffer = 1,
132 BIT_DStream_completed = 2,
133 BIT_DStream_overflow = 3 } BIT_DStream_status; /* result of BIT_reloadDStream() */
134 /* 1,2,4,8 would be better for bitmap combinations, but slows down performance a bit ... :( */
135
136MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize);
137MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, unsigned nbBits);
138MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD);
139MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* bitD);
140
141
142/* Start by invoking BIT_initDStream().
143* A chunk of the bitStream is then stored into a local register.
144* Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
145* You can then retrieve bitFields stored into the local register, **in reverse order**.
146* Local register is explicitly reloaded from memory by the BIT_reloadDStream() method.
147* A reload guarantee a minimum of ((8*sizeof(bitD->bitContainer))-7) bits when its result is BIT_DStream_unfinished.
148* Otherwise, it can be less than that, so proceed accordingly.
149* Checking if DStream has reached its end can be performed with BIT_endOfDStream().
150*/
151
152
153/*-****************************************
154* unsafe API
155******************************************/
156MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC, size_t value, unsigned nbBits);
157/* faster, but works only if value is "clean", meaning all high bits above nbBits are 0 */
158
159MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC);
160/* unsafe version; does not check buffer overflow */
161
162MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
163/* faster, but works only if nbBits >= 1 */
164
165
166
167/*-**************************************************************
168* Internal functions
169****************************************************************/
170MEM_STATIC unsigned BIT_highbit32 (U32 val)
171{
172 assert(val != 0);
173 {
174# if defined(_MSC_VER) /* Visual */
175 unsigned long r=0;
176 _BitScanReverse ( &r, val );
177 return (unsigned) r;
178# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
179 return 31 - __builtin_clz (val);
180# else /* Software version */
181 static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29,
182 11, 14, 16, 18, 22, 25, 3, 30,
183 8, 12, 20, 28, 15, 17, 24, 7,
184 19, 27, 23, 6, 26, 5, 4, 31 };
185 U32 v = val;
186 v |= v >> 1;
187 v |= v >> 2;
188 v |= v >> 4;
189 v |= v >> 8;
190 v |= v >> 16;
191 return DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27];
192# endif
193 }
194}
195
196/*===== Local Constants =====*/
197static const unsigned BIT_mask[] = {
198 0, 1, 3, 7, 0xF, 0x1F,
199 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF,
200 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF,
201 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF,
202 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF, 0x7FFFFFF, 0xFFFFFFF, 0x1FFFFFFF,
203 0x3FFFFFFF, 0x7FFFFFFF}; /* up to 31 bits */
204#define BIT_MASK_SIZE (sizeof(BIT_mask) / sizeof(BIT_mask[0]))
205
206/*-**************************************************************
207* bitStream encoding
208****************************************************************/
209/*! BIT_initCStream() :
210 * `dstCapacity` must be > sizeof(size_t)
211 * @return : 0 if success,
212 * otherwise an error code (can be tested using ERR_isError()) */
213MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC,
214 void* startPtr, size_t dstCapacity)
215{
216 bitC->bitContainer = 0;
217 bitC->bitPos = 0;
218 bitC->startPtr = (char*)startPtr;
219 bitC->ptr = bitC->startPtr;
220 bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->bitContainer);
221 if (dstCapacity <= sizeof(bitC->bitContainer)) return ERROR(dstSize_tooSmall);
222 return 0;
223}
224
225/*! BIT_addBits() :
226 * can add up to 31 bits into `bitC`.
227 * Note : does not check for register overflow ! */
228MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC,
229 size_t value, unsigned nbBits)
230{
231 MEM_STATIC_ASSERT(BIT_MASK_SIZE == 32);
232 assert(nbBits < BIT_MASK_SIZE);
233 assert(nbBits + bitC->bitPos < sizeof(bitC->bitContainer) * 8);
234 bitC->bitContainer |= (value & BIT_mask[nbBits]) << bitC->bitPos;
235 bitC->bitPos += nbBits;
236}
237
238/*! BIT_addBitsFast() :
239 * works only if `value` is _clean_, meaning all high bits above nbBits are 0 */
240MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC,
241 size_t value, unsigned nbBits)
242{
243 assert((value>>nbBits) == 0);
244 assert(nbBits + bitC->bitPos < sizeof(bitC->bitContainer) * 8);
245 bitC->bitContainer |= value << bitC->bitPos;
246 bitC->bitPos += nbBits;
247}
248
249/*! BIT_flushBitsFast() :
250 * assumption : bitContainer has not overflowed
251 * unsafe version; does not check buffer overflow */
252MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC)
253{
254 size_t const nbBytes = bitC->bitPos >> 3;
255 assert(bitC->bitPos < sizeof(bitC->bitContainer) * 8);
256 MEM_writeLEST(bitC->ptr, bitC->bitContainer);
257 bitC->ptr += nbBytes;
258 assert(bitC->ptr <= bitC->endPtr);
259 bitC->bitPos &= 7;
260 bitC->bitContainer >>= nbBytes*8;
261}
262
263/*! BIT_flushBits() :
264 * assumption : bitContainer has not overflowed
265 * safe version; check for buffer overflow, and prevents it.
266 * note : does not signal buffer overflow.
267 * overflow will be revealed later on using BIT_closeCStream() */
268MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC)
269{
270 size_t const nbBytes = bitC->bitPos >> 3;
271 assert(bitC->bitPos < sizeof(bitC->bitContainer) * 8);
272 MEM_writeLEST(bitC->ptr, bitC->bitContainer);
273 bitC->ptr += nbBytes;
274 if (bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;
275 bitC->bitPos &= 7;
276 bitC->bitContainer >>= nbBytes*8;
277}
278
279/*! BIT_closeCStream() :
280 * @return : size of CStream, in bytes,
281 * or 0 if it could not fit into dstBuffer */
282MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC)
283{
284 BIT_addBitsFast(bitC, 1, 1); /* endMark */
285 BIT_flushBits(bitC);
286 if (bitC->ptr >= bitC->endPtr) return 0; /* overflow detected */
287 return (bitC->ptr - bitC->startPtr) + (bitC->bitPos > 0);
288}
289
290
291/*-********************************************************
292* bitStream decoding
293**********************************************************/
294/*! BIT_initDStream() :
295 * Initialize a BIT_DStream_t.
296 * `bitD` : a pointer to an already allocated BIT_DStream_t structure.
297 * `srcSize` must be the *exact* size of the bitStream, in bytes.
298 * @return : size of stream (== srcSize), or an errorCode if a problem is detected
299 */
300MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize)
301{
302 if (srcSize < 1) { memset(bitD, 0, sizeof(*bitD)); return ERROR(srcSize_wrong); }
303
304 bitD->start = (const char*)srcBuffer;
305 bitD->limitPtr = bitD->start + sizeof(bitD->bitContainer);
306
307 if (srcSize >= sizeof(bitD->bitContainer)) { /* normal case */
308 bitD->ptr = (const char*)srcBuffer + srcSize - sizeof(bitD->bitContainer);
309 bitD->bitContainer = MEM_readLEST(bitD->ptr);
310 { BYTE const lastByte = ((const BYTE*)srcBuffer)[srcSize-1];
311 bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0; /* ensures bitsConsumed is always set */
312 if (lastByte == 0) return ERROR(GENERIC); /* endMark not present */ }
313 } else {
314 bitD->ptr = bitD->start;
315 bitD->bitContainer = *(const BYTE*)(bitD->start);
316 switch(srcSize)
317 {
318 case 7: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[6]) << (sizeof(bitD->bitContainer)*8 - 16);
319 /* fall-through */
320
321 case 6: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[5]) << (sizeof(bitD->bitContainer)*8 - 24);
322 /* fall-through */
323
324 case 5: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[4]) << (sizeof(bitD->bitContainer)*8 - 32);
325 /* fall-through */
326
327 case 4: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[3]) << 24;
328 /* fall-through */
329
330 case 3: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[2]) << 16;
331 /* fall-through */
332
333 case 2: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[1]) << 8;
334 /* fall-through */
335
336 default: break;
337 }
338 { BYTE const lastByte = ((const BYTE*)srcBuffer)[srcSize-1];
339 bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0;
340 if (lastByte == 0) return ERROR(corruption_detected); /* endMark not present */
341 }
342 bitD->bitsConsumed += (U32)(sizeof(bitD->bitContainer) - srcSize)*8;
343 }
344
345 return srcSize;
346}
347
348MEM_STATIC size_t BIT_getUpperBits(size_t bitContainer, U32 const start)
349{
350 return bitContainer >> start;
351}
352
353MEM_STATIC size_t BIT_getMiddleBits(size_t bitContainer, U32 const start, U32 const nbBits)
354{
355#if defined(__BMI__) && defined(__GNUC__) && __GNUC__*1000+__GNUC_MINOR__ >= 4008 /* experimental */
356# if defined(__x86_64__)
357 if (sizeof(bitContainer)==8)
358 return _bextr_u64(bitContainer, start, nbBits);
359 else
360# endif
361 return _bextr_u32(bitContainer, start, nbBits);
362#else
363 assert(nbBits < BIT_MASK_SIZE);
364 return (bitContainer >> start) & BIT_mask[nbBits];
365#endif
366}
367
368MEM_STATIC size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits)
369{
370 assert(nbBits < BIT_MASK_SIZE);
371 return bitContainer & BIT_mask[nbBits];
372}
373
374/*! BIT_lookBits() :
375 * Provides next n bits from local register.
376 * local register is not modified.
377 * On 32-bits, maxNbBits==24.
378 * On 64-bits, maxNbBits==56.
379 * @return : value extracted */
380MEM_STATIC size_t BIT_lookBits(const BIT_DStream_t* bitD, U32 nbBits)
381{
382#if defined(__BMI__) && defined(__GNUC__) /* experimental; fails if bitD->bitsConsumed + nbBits > sizeof(bitD->bitContainer)*8 */
383 return BIT_getMiddleBits(bitD->bitContainer, (sizeof(bitD->bitContainer)*8) - bitD->bitsConsumed - nbBits, nbBits);
384#else
385 U32 const regMask = sizeof(bitD->bitContainer)*8 - 1;
386 return ((bitD->bitContainer << (bitD->bitsConsumed & regMask)) >> 1) >> ((regMask-nbBits) & regMask);
387#endif
388}
389
390/*! BIT_lookBitsFast() :
391 * unsafe version; only works if nbBits >= 1 */
392MEM_STATIC size_t BIT_lookBitsFast(const BIT_DStream_t* bitD, U32 nbBits)
393{
394 U32 const regMask = sizeof(bitD->bitContainer)*8 - 1;
395 assert(nbBits >= 1);
396 return (bitD->bitContainer << (bitD->bitsConsumed & regMask)) >> (((regMask+1)-nbBits) & regMask);
397}
398
399MEM_STATIC void BIT_skipBits(BIT_DStream_t* bitD, U32 nbBits)
400{
401 bitD->bitsConsumed += nbBits;
402}
403
404/*! BIT_readBits() :
405 * Read (consume) next n bits from local register and update.
406 * Pay attention to not read more than nbBits contained into local register.
407 * @return : extracted value. */
408MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits)
409{
410 size_t const value = BIT_lookBits(bitD, nbBits);
411 BIT_skipBits(bitD, nbBits);
412 return value;
413}
414
415/*! BIT_readBitsFast() :
416 * unsafe version; only works only if nbBits >= 1 */
417MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, U32 nbBits)
418{
419 size_t const value = BIT_lookBitsFast(bitD, nbBits);
420 assert(nbBits >= 1);
421 BIT_skipBits(bitD, nbBits);
422 return value;
423}
424
425/*! BIT_reloadDStream() :
426 * Refill `bitD` from buffer previously set in BIT_initDStream() .
427 * This function is safe, it guarantees it will not read beyond src buffer.
428 * @return : status of `BIT_DStream_t` internal register.
429 * when status == BIT_DStream_unfinished, internal register is filled with at least 25 or 57 bits */
430MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD)
431{
432 if (bitD->bitsConsumed > (sizeof(bitD->bitContainer)*8)) /* overflow detected, like end of stream */
433 return BIT_DStream_overflow;
434
435 if (bitD->ptr >= bitD->limitPtr) {
436 bitD->ptr -= bitD->bitsConsumed >> 3;
437 bitD->bitsConsumed &= 7;
438 bitD->bitContainer = MEM_readLEST(bitD->ptr);
439 return BIT_DStream_unfinished;
440 }
441 if (bitD->ptr == bitD->start) {
442 if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return BIT_DStream_endOfBuffer;
443 return BIT_DStream_completed;
444 }
445 /* start < ptr < limitPtr */
446 { U32 nbBytes = bitD->bitsConsumed >> 3;
447 BIT_DStream_status result = BIT_DStream_unfinished;
448 if (bitD->ptr - nbBytes < bitD->start) {
449 nbBytes = (U32)(bitD->ptr - bitD->start); /* ptr > start */
450 result = BIT_DStream_endOfBuffer;
451 }
452 bitD->ptr -= nbBytes;
453 bitD->bitsConsumed -= nbBytes*8;
454 bitD->bitContainer = MEM_readLEST(bitD->ptr); /* reminder : srcSize > sizeof(bitD->bitContainer), otherwise bitD->ptr == bitD->start */
455 return result;
456 }
457}
458
459/*! BIT_endOfDStream() :
460 * @return : 1 if DStream has _exactly_ reached its end (all bits consumed).
461 */
462MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* DStream)
463{
464 return ((DStream->ptr == DStream->start) && (DStream->bitsConsumed == sizeof(DStream->bitContainer)*8));
465}
466
467#if defined (__cplusplus)
468}
469#endif
470
471#endif /* BITSTREAM_H_MODULE */
472