zstd/common/entropy_common.c

0001 /* ******************************************************************
0002  * Common functions of New Generation Entropy library
0003  * Copyright (c) Yann Collet, Facebook, Inc.
0004  *
0005  *  You can contact the author at :
0006  *  - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy
0007  *  - Public forum : https://groups.google.com/forum/#!forum/lz4c
0008  *
0009  * This source code is licensed under both the BSD-style license (found in the
0010  * LICENSE file in the root directory of this source tree) and the GPLv2 (found
0011  * in the COPYING file in the root directory of this source tree).
0012  * You may select, at your option, one of the above-listed licenses.
0013 ****************************************************************** */
0014
0015 /* *************************************
0016 *  Dependencies
0017 ***************************************/
0018 #include "mem.h"
0019 #include "error_private.h"       /* ERR_*, ERROR */
0020 #define FSE_STATIC_LINKING_ONLY  /* FSE_MIN_TABLELOG */
0021 #include "fse.h"
0022 #define HUF_STATIC_LINKING_ONLY  /* HUF_TABLELOG_ABSOLUTEMAX */
0023 #include "huf.h"
0024
0025
0026 /*===   Version   ===*/
0027 unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }
0028
0029
0030 /*===   Error Management   ===*/
0031 unsigned FSE_isError(size_t code) { return ERR_isError(code); }
0032 const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }
0033
0034 unsigned HUF_isError(size_t code) { return ERR_isError(code); }
0035 const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }
0036
0037
0038 /*-**************************************************************
0039 *  FSE NCount encoding-decoding
0040 ****************************************************************/
0041 static U32 FSE_ctz(U32 val)
0042 {
0043     assert(val != 0);
0044     {
0045 #   if (__GNUC__ >= 3)   /* GCC Intrinsic */
0046         return __builtin_ctz(val);
0047 #   else   /* Software version */
0048         U32 count = 0;
0049         while ((val & 1) == 0) {
0050             val >>= 1;
0051             ++count;
0052         }
0053         return count;
0054 #   endif
0055     }
0056 }
0057
0058 FORCE_INLINE_TEMPLATE
0059 size_t FSE_readNCount_body(short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
0060                            const void* headerBuffer, size_t hbSize)
0061 {
0062     const BYTE* const istart = (const BYTE*) headerBuffer;
0063     const BYTE* const iend = istart + hbSize;
0064     const BYTE* ip = istart;
0065     int nbBits;
0066     int remaining;
0067     int threshold;
0068     U32 bitStream;
0069     int bitCount;
0070     unsigned charnum = 0;
0071     unsigned const maxSV1 = *maxSVPtr + 1;
0072     int previous0 = 0;
0073
0074     if (hbSize < 8) {
0075         /* This function only works when hbSize >= 8 */
0076         char buffer[8] = {0};
0077         ZSTD_memcpy(buffer, headerBuffer, hbSize);
0078         {   size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
0079                                                     buffer, sizeof(buffer));
0080             if (FSE_isError(countSize)) return countSize;
0081             if (countSize > hbSize) return ERROR(corruption_detected);
0082             return countSize;
0083     }   }
0084     assert(hbSize >= 8);
0085
0086     /* init */
0087     ZSTD_memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0]));   /* all symbols not present in NCount have a frequency of 0 */
0088     bitStream = MEM_readLE32(ip);
0089     nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG;   /* extract tableLog */
0090     if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
0091     bitStream >>= 4;
0092     bitCount = 4;
0093     *tableLogPtr = nbBits;
0094     remaining = (1<<nbBits)+1;
0095     threshold = 1<<nbBits;
0096     nbBits++;
0097
0098     for (;;) {
0099         if (previous0) {
0100             /* Count the number of repeats. Each time the
0101              * 2-bit repeat code is 0b11 there is another
0102              * repeat.
0103              * Avoid UB by setting the high bit to 1.
0104              */
0105             int repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
0106             while (repeats >= 12) {
0107                 charnum += 3 * 12;
0108                 if (LIKELY(ip <= iend-7)) {
0109                     ip += 3;
0110                 } else {
0111                     bitCount -= (int)(8 * (iend - 7 - ip));
0112                     bitCount &= 31;
0113                     ip = iend - 4;
0114                 }
0115                 bitStream = MEM_readLE32(ip) >> bitCount;
0116                 repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
0117             }
0118             charnum += 3 * repeats;
0119             bitStream >>= 2 * repeats;
0120             bitCount += 2 * repeats;
0121
0122             /* Add the final repeat which isn't 0b11. */
0123             assert((bitStream & 3) < 3);
0124             charnum += bitStream & 3;
0125             bitCount += 2;
0126
0127             /* This is an error, but break and return an error
0128              * at the end, because returning out of a loop makes
0129              * it harder for the compiler to optimize.
0130              */
0131             if (charnum >= maxSV1) break;
0132
0133             /* We don't need to set the normalized count to 0
0134              * because we already memset the whole buffer to 0.
0135              */
0136
0137             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
0138                 assert((bitCount >> 3) <= 3); /* For first condition to work */
0139                 ip += bitCount>>3;
0140                 bitCount &= 7;
0141             } else {
0142                 bitCount -= (int)(8 * (iend - 4 - ip));
0143                 bitCount &= 31;
0144                 ip = iend - 4;
0145             }
0146             bitStream = MEM_readLE32(ip) >> bitCount;
0147         }
0148         {
0149             int const max = (2*threshold-1) - remaining;
0150             int count;
0151
0152             if ((bitStream & (threshold-1)) < (U32)max) {
0153                 count = bitStream & (threshold-1);
0154                 bitCount += nbBits-1;
0155             } else {
0156                 count = bitStream & (2*threshold-1);
0157                 if (count >= threshold) count -= max;
0158                 bitCount += nbBits;
0159             }
0160
0161             count--;   /* extra accuracy */
0162             /* When it matters (small blocks), this is a
0163              * predictable branch, because we don't use -1.
0164              */
0165             if (count >= 0) {
0166                 remaining -= count;
0167             } else {
0168                 assert(count == -1);
0169                 remaining += count;
0170             }
0171             normalizedCounter[charnum++] = (short)count;
0172             previous0 = !count;
0173
0174             assert(threshold > 1);
0175             if (remaining < threshold) {
0176                 /* This branch can be folded into the
0177                  * threshold update condition because we
0178                  * know that threshold > 1.
0179                  */
0180                 if (remaining <= 1) break;
0181                 nbBits = BIT_highbit32(remaining) + 1;
0182                 threshold = 1 << (nbBits - 1);
0183             }
0184             if (charnum >= maxSV1) break;
0185
0186             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
0187                 ip += bitCount>>3;
0188                 bitCount &= 7;
0189             } else {
0190                 bitCount -= (int)(8 * (iend - 4 - ip));
0191                 bitCount &= 31;
0192                 ip = iend - 4;
0193             }
0194             bitStream = MEM_readLE32(ip) >> bitCount;
0195     }   }
0196     if (remaining != 1) return ERROR(corruption_detected);
0197     /* Only possible when there are too many zeros. */
0198     if (charnum > maxSV1) return ERROR(maxSymbolValue_tooSmall);
0199     if (bitCount > 32) return ERROR(corruption_detected);
0200     *maxSVPtr = charnum-1;
0201
0202     ip += (bitCount+7)>>3;
0203     return ip-istart;
0204 }
0205
0206 /* Avoids the FORCE_INLINE of the _body() function. */
0207 static size_t FSE_readNCount_body_default(
0208         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
0209         const void* headerBuffer, size_t hbSize)
0210 {
0211     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
0212 }
0213
0214 #if DYNAMIC_BMI2
0215 TARGET_ATTRIBUTE("bmi2") static size_t FSE_readNCount_body_bmi2(
0216         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
0217         const void* headerBuffer, size_t hbSize)
0218 {
0219     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
0220 }
0221 #endif
0222
0223 size_t FSE_readNCount_bmi2(
0224         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
0225         const void* headerBuffer, size_t hbSize, int bmi2)
0226 {
0227 #if DYNAMIC_BMI2
0228     if (bmi2) {
0229         return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
0230     }
0231 #endif
0232     (void)bmi2;
0233     return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
0234 }
0235
0236 size_t FSE_readNCount(
0237         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
0238         const void* headerBuffer, size_t hbSize)
0239 {
0240     return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);
0241 }
0242
0243
0244 /*! HUF_readStats() :
0245     Read compact Huffman tree, saved by HUF_writeCTable().
0246     `huffWeight` is destination buffer.
0247     `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
0248     @return : size read from `src` , or an error Code .
0249     Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
0250 */
0251 size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
0252                      U32* nbSymbolsPtr, U32* tableLogPtr,
0253                      const void* src, size_t srcSize)
0254 {
0255     U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];
0256     return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* bmi2 */ 0);
0257 }
0258
0259 FORCE_INLINE_TEMPLATE size_t
0260 HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
0261                    U32* nbSymbolsPtr, U32* tableLogPtr,
0262                    const void* src, size_t srcSize,
0263                    void* workSpace, size_t wkspSize,
0264                    int bmi2)
0265 {
0266     U32 weightTotal;
0267     const BYTE* ip = (const BYTE*) src;
0268     size_t iSize;
0269     size_t oSize;
0270
0271     if (!srcSize) return ERROR(srcSize_wrong);
0272     iSize = ip[0];
0273     /* ZSTD_memset(huffWeight, 0, hwSize);   *//* is not necessary, even though some analyzer complain ... */
0274
0275     if (iSize >= 128) {  /* special header */
0276         oSize = iSize - 127;
0277         iSize = ((oSize+1)/2);
0278         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
0279         if (oSize >= hwSize) return ERROR(corruption_detected);
0280         ip += 1;
0281         {   U32 n;
0282             for (n=0; n<oSize; n+=2) {
0283                 huffWeight[n]   = ip[n/2] >> 4;
0284                 huffWeight[n+1] = ip[n/2] & 15;
0285     }   }   }
0286     else  {   /* header compressed with FSE (normal case) */
0287         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
0288         /* max (hwSize-1) values decoded, as last one is implied */
0289         oSize = FSE_decompress_wksp_bmi2(huffWeight, hwSize-1, ip+1, iSize, 6, workSpace, wkspSize, bmi2);
0290         if (FSE_isError(oSize)) return oSize;
0291     }
0292
0293     /* collect weight stats */
0294     ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
0295     weightTotal = 0;
0296     {   U32 n; for (n=0; n<oSize; n++) {
0297             if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
0298             rankStats[huffWeight[n]]++;
0299             weightTotal += (1 << huffWeight[n]) >> 1;
0300     }   }
0301     if (weightTotal == 0) return ERROR(corruption_detected);
0302
0303     /* get last non-null symbol weight (implied, total must be 2^n) */
0304     {   U32 const tableLog = BIT_highbit32(weightTotal) + 1;
0305         if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
0306         *tableLogPtr = tableLog;
0307         /* determine last weight */
0308         {   U32 const total = 1 << tableLog;
0309             U32 const rest = total - weightTotal;
0310             U32 const verif = 1 << BIT_highbit32(rest);
0311             U32 const lastWeight = BIT_highbit32(rest) + 1;
0312             if (verif != rest) return ERROR(corruption_detected);    /* last value must be a clean power of 2 */
0313             huffWeight[oSize] = (BYTE)lastWeight;
0314             rankStats[lastWeight]++;
0315     }   }
0316
0317     /* check tree construction validity */
0318     if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected);   /* by construction : at least 2 elts of rank 1, must be even */
0319
0320     /* results */
0321     *nbSymbolsPtr = (U32)(oSize+1);
0322     return iSize+1;
0323 }
0324
0325 /* Avoids the FORCE_INLINE of the _body() function. */
0326 static size_t HUF_readStats_body_default(BYTE* huffWeight, size_t hwSize, U32* rankStats,
0327                      U32* nbSymbolsPtr, U32* tableLogPtr,
0328                      const void* src, size_t srcSize,
0329                      void* workSpace, size_t wkspSize)
0330 {
0331     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);
0332 }
0333
0334 #if DYNAMIC_BMI2
0335 static TARGET_ATTRIBUTE("bmi2") size_t HUF_readStats_body_bmi2(BYTE* huffWeight, size_t hwSize, U32* rankStats,
0336                      U32* nbSymbolsPtr, U32* tableLogPtr,
0337                      const void* src, size_t srcSize,
0338                      void* workSpace, size_t wkspSize)
0339 {
0340     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);
0341 }
0342 #endif
0343
0344 size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats,
0345                      U32* nbSymbolsPtr, U32* tableLogPtr,
0346                      const void* src, size_t srcSize,
0347                      void* workSpace, size_t wkspSize,
0348                      int bmi2)
0349 {
0350 #if DYNAMIC_BMI2
0351     if (bmi2) {
0352         return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
0353     }
0354 #endif
0355     (void)bmi2;
0356     return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
0357 }