1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-only 2 /* ****************************************************************** 3 * Common functions of New Generation Entropy library 4 * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc. 5 * 6 * You can contact the author at : 7 * - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy 8 * - Public forum : https://groups.google.com/forum/#!forum/lz4c 9 * 10 * This source code is licensed under both the BSD-style license (found in the 11 * LICENSE file in the root directory of this source tree) and the GPLv2 (found 12 * in the COPYING file in the root directory of this source tree). 13 * You may select, at your option, one of the above-listed licenses. 14 ****************************************************************** */ 15 16 /* ************************************* 17 * Dependencies 18 ***************************************/ 19 #include "mem.h" 20 #include "error_private.h" /* ERR_*, ERROR */ 21 #define FSE_STATIC_LINKING_ONLY /* FSE_MIN_TABLELOG */ 22 #include "fse.h" 23 #define HUF_STATIC_LINKING_ONLY /* HUF_TABLELOG_ABSOLUTEMAX */ 24 #include "huf.h" 25 26 27 /*=== Version ===*/ 28 unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; } 29 30 31 /*=== Error Management ===*/ 32 unsigned FSE_isError(size_t code) { return ERR_isError(code); } 33 const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); } 34 35 unsigned HUF_isError(size_t code) { return ERR_isError(code); } 36 const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); } 37 38 39 /*-************************************************************** 40 * FSE NCount encoding-decoding 41 ****************************************************************/ 42 size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr, 43 const void* headerBuffer, size_t hbSize) 44 { 45 const BYTE* const istart = (const BYTE*) headerBuffer; 46 const BYTE* const iend = istart + hbSize; 47 const BYTE* ip = istart; 48 int nbBits; 49 int remaining; 50 int threshold; 51 U32 bitStream; 52 int bitCount; 53 unsigned charnum = 0; 54 int previous0 = 0; 55 56 if (hbSize < 4) { 57 /* This function only works when hbSize >= 4 */ 58 char buffer[4]; 59 memset(buffer, 0, sizeof(buffer)); 60 memcpy(buffer, headerBuffer, hbSize); 61 { size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr, 62 buffer, sizeof(buffer)); 63 if (FSE_isError(countSize)) return countSize; 64 if (countSize > hbSize) return ERROR(corruption_detected); 65 return countSize; 66 } } 67 assert(hbSize >= 4); 68 69 /* init */ 70 memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0])); /* all symbols not present in NCount have a frequency of 0 */ 71 bitStream = MEM_readLE32(ip); 72 nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */ 73 if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge); 74 bitStream >>= 4; 75 bitCount = 4; 76 *tableLogPtr = nbBits; 77 remaining = (1<<nbBits)+1; 78 threshold = 1<<nbBits; 79 nbBits++; 80 81 while ((remaining>1) & (charnum<=*maxSVPtr)) { 82 if (previous0) { 83 unsigned n0 = charnum; 84 while ((bitStream & 0xFFFF) == 0xFFFF) { 85 n0 += 24; 86 if (ip < iend-5) { 87 ip += 2; 88 bitStream = MEM_readLE32(ip) >> bitCount; 89 } else { 90 bitStream >>= 16; 91 bitCount += 16; 92 } } 93 while ((bitStream & 3) == 3) { 94 n0 += 3; 95 bitStream >>= 2; 96 bitCount += 2; 97 } 98 n0 += bitStream & 3; 99 bitCount += 2; 100 if (n0 > *maxSVPtr) return ERROR(maxSymbolValue_tooSmall); 101 while (charnum < n0) normalizedCounter[charnum++] = 0; 102 if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) { 103 assert((bitCount >> 3) <= 3); /* For first condition to work */ 104 ip += bitCount>>3; 105 bitCount &= 7; 106 bitStream = MEM_readLE32(ip) >> bitCount; 107 } else { 108 bitStream >>= 2; 109 } } 110 { int const max = (2*threshold-1) - remaining; 111 int count; 112 113 if ((bitStream & (threshold-1)) < (U32)max) { 114 count = bitStream & (threshold-1); 115 bitCount += nbBits-1; 116 } else { 117 count = bitStream & (2*threshold-1); 118 if (count >= threshold) count -= max; 119 bitCount += nbBits; 120 } 121 122 count--; /* extra accuracy */ 123 remaining -= count < 0 ? -count : count; /* -1 means +1 */ 124 normalizedCounter[charnum++] = (short)count; 125 previous0 = !count; 126 while (remaining < threshold) { 127 nbBits--; 128 threshold >>= 1; 129 } 130 131 if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) { 132 ip += bitCount>>3; 133 bitCount &= 7; 134 } else { 135 bitCount -= (int)(8 * (iend - 4 - ip)); 136 ip = iend - 4; 137 } 138 bitStream = MEM_readLE32(ip) >> (bitCount & 31); 139 } } /* while ((remaining>1) & (charnum<=*maxSVPtr)) */ 140 if (remaining != 1) return ERROR(corruption_detected); 141 if (bitCount > 32) return ERROR(corruption_detected); 142 *maxSVPtr = charnum-1; 143 144 ip += (bitCount+7)>>3; 145 return ip-istart; 146 } 147 148 149 /*! HUF_readStats() : 150 Read compact Huffman tree, saved by HUF_writeCTable(). 151 `huffWeight` is destination buffer. 152 `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32. 153 @return : size read from `src` , or an error Code . 154 Note : Needed by HUF_readCTable() and HUF_readDTableX?() . 155 */ 156 size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats, 157 U32* nbSymbolsPtr, U32* tableLogPtr, 158 const void* src, size_t srcSize) 159 { 160 U32 weightTotal; 161 const BYTE* ip = (const BYTE*) src; 162 size_t iSize; 163 size_t oSize; 164 165 if (!srcSize) return ERROR(srcSize_wrong); 166 iSize = ip[0]; 167 /* memset(huffWeight, 0, hwSize); *//* is not necessary, even though some analyzer complain ... */ 168 169 if (iSize >= 128) { /* special header */ 170 oSize = iSize - 127; 171 iSize = ((oSize+1)/2); 172 if (iSize+1 > srcSize) return ERROR(srcSize_wrong); 173 if (oSize >= hwSize) return ERROR(corruption_detected); 174 ip += 1; 175 { U32 n; 176 for (n=0; n<oSize; n+=2) { 177 huffWeight[n] = ip[n/2] >> 4; 178 huffWeight[n+1] = ip[n/2] & 15; 179 } } } 180 else { /* header compressed with FSE (normal case) */ 181 FSE_DTable fseWorkspace[FSE_DTABLE_SIZE_U32(6)]; /* 6 is max possible tableLog for HUF header (maybe even 5, to be tested) */ 182 if (iSize+1 > srcSize) return ERROR(srcSize_wrong); 183 oSize = FSE_decompress_wksp(huffWeight, hwSize-1, ip+1, iSize, fseWorkspace, 6); /* max (hwSize-1) values decoded, as last one is implied */ 184 if (FSE_isError(oSize)) return oSize; 185 } 186 187 /* collect weight stats */ 188 memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32)); 189 weightTotal = 0; 190 { U32 n; for (n=0; n<oSize; n++) { 191 if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected); 192 rankStats[huffWeight[n]]++; 193 weightTotal += (1 << huffWeight[n]) >> 1; 194 } } 195 if (weightTotal == 0) return ERROR(corruption_detected); 196 197 /* get last non-null symbol weight (implied, total must be 2^n) */ 198 { U32 const tableLog = BIT_highbit32(weightTotal) + 1; 199 if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected); 200 *tableLogPtr = tableLog; 201 /* determine last weight */ 202 { U32 const total = 1 << tableLog; 203 U32 const rest = total - weightTotal; 204 U32 const verif = 1 << BIT_highbit32(rest); 205 U32 const lastWeight = BIT_highbit32(rest) + 1; 206 if (verif != rest) return ERROR(corruption_detected); /* last value must be a clean power of 2 */ 207 huffWeight[oSize] = (BYTE)lastWeight; 208 rankStats[lastWeight]++; 209 } } 210 211 /* check tree construction validity */ 212 if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */ 213 214 /* results */ 215 *nbSymbolsPtr = (U32)(oSize+1); 216 return iSize+1; 217 } 218