1 /* ****************************************************************** 2 * hist : Histogram functions 3 * part of Finite State Entropy project 4 * Copyright (c) 2013-2020, Yann Collet, Facebook, Inc. 5 * 6 * You can contact the author at : 7 * - FSE 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 /* --- dependencies --- */ 17 #include "../common/mem.h" /* U32, BYTE, etc. */ 18 #include "../common/debug.h" /* assert, DEBUGLOG */ 19 #include "../common/error_private.h" /* ERROR */ 20 #include "hist.h" 21 22 23 /* --- Error management --- */ 24 unsigned HIST_isError(size_t code) { return ERR_isError(code); } 25 26 /*-************************************************************** 27 * Histogram functions 28 ****************************************************************/ 29 unsigned HIST_count_simple(unsigned* count, unsigned* maxSymbolValuePtr, 30 const void* src, size_t srcSize) 31 { 32 const BYTE* ip = (const BYTE*)src; 33 const BYTE* const end = ip + srcSize; 34 unsigned maxSymbolValue = *maxSymbolValuePtr; 35 unsigned largestCount=0; 36 37 ZSTD_memset(count, 0, (maxSymbolValue+1) * sizeof(*count)); 38 if (srcSize==0) { *maxSymbolValuePtr = 0; return 0; } 39 40 while (ip<end) { 41 assert(*ip <= maxSymbolValue); 42 count[*ip++]++; 43 } 44 45 while (!count[maxSymbolValue]) maxSymbolValue--; 46 *maxSymbolValuePtr = maxSymbolValue; 47 48 { U32 s; 49 for (s=0; s<=maxSymbolValue; s++) 50 if (count[s] > largestCount) largestCount = count[s]; 51 } 52 53 return largestCount; 54 } 55 56 typedef enum { trustInput, checkMaxSymbolValue } HIST_checkInput_e; 57 58 /* HIST_count_parallel_wksp() : 59 * store histogram into 4 intermediate tables, recombined at the end. 60 * this design makes better use of OoO cpus, 61 * and is noticeably faster when some values are heavily repeated. 62 * But it needs some additional workspace for intermediate tables. 63 * `workSpace` must be a U32 table of size >= HIST_WKSP_SIZE_U32. 64 * @return : largest histogram frequency, 65 * or an error code (notably when histogram's alphabet is larger than *maxSymbolValuePtr) */ 66 static size_t HIST_count_parallel_wksp( 67 unsigned* count, unsigned* maxSymbolValuePtr, 68 const void* source, size_t sourceSize, 69 HIST_checkInput_e check, 70 U32* const workSpace) 71 { 72 const BYTE* ip = (const BYTE*)source; 73 const BYTE* const iend = ip+sourceSize; 74 size_t const countSize = (*maxSymbolValuePtr + 1) * sizeof(*count); 75 unsigned max=0; 76 U32* const Counting1 = workSpace; 77 U32* const Counting2 = Counting1 + 256; 78 U32* const Counting3 = Counting2 + 256; 79 U32* const Counting4 = Counting3 + 256; 80 81 /* safety checks */ 82 assert(*maxSymbolValuePtr <= 255); 83 if (!sourceSize) { 84 ZSTD_memset(count, 0, countSize); 85 *maxSymbolValuePtr = 0; 86 return 0; 87 } 88 ZSTD_memset(workSpace, 0, 4*256*sizeof(unsigned)); 89 90 /* by stripes of 16 bytes */ 91 { U32 cached = MEM_read32(ip); ip += 4; 92 while (ip < iend-15) { 93 U32 c = cached; cached = MEM_read32(ip); ip += 4; 94 Counting1[(BYTE) c ]++; 95 Counting2[(BYTE)(c>>8) ]++; 96 Counting3[(BYTE)(c>>16)]++; 97 Counting4[ c>>24 ]++; 98 c = cached; cached = MEM_read32(ip); ip += 4; 99 Counting1[(BYTE) c ]++; 100 Counting2[(BYTE)(c>>8) ]++; 101 Counting3[(BYTE)(c>>16)]++; 102 Counting4[ c>>24 ]++; 103 c = cached; cached = MEM_read32(ip); ip += 4; 104 Counting1[(BYTE) c ]++; 105 Counting2[(BYTE)(c>>8) ]++; 106 Counting3[(BYTE)(c>>16)]++; 107 Counting4[ c>>24 ]++; 108 c = cached; cached = MEM_read32(ip); ip += 4; 109 Counting1[(BYTE) c ]++; 110 Counting2[(BYTE)(c>>8) ]++; 111 Counting3[(BYTE)(c>>16)]++; 112 Counting4[ c>>24 ]++; 113 } 114 ip-=4; 115 } 116 117 /* finish last symbols */ 118 while (ip<iend) Counting1[*ip++]++; 119 120 { U32 s; 121 for (s=0; s<256; s++) { 122 Counting1[s] += Counting2[s] + Counting3[s] + Counting4[s]; 123 if (Counting1[s] > max) max = Counting1[s]; 124 } } 125 126 { unsigned maxSymbolValue = 255; 127 while (!Counting1[maxSymbolValue]) maxSymbolValue--; 128 if (check && maxSymbolValue > *maxSymbolValuePtr) return ERROR(maxSymbolValue_tooSmall); 129 *maxSymbolValuePtr = maxSymbolValue; 130 ZSTD_memmove(count, Counting1, countSize); /* in case count & Counting1 are overlapping */ 131 } 132 return (size_t)max; 133 } 134 135 /* HIST_countFast_wksp() : 136 * Same as HIST_countFast(), but using an externally provided scratch buffer. 137 * `workSpace` is a writable buffer which must be 4-bytes aligned, 138 * `workSpaceSize` must be >= HIST_WKSP_SIZE 139 */ 140 size_t HIST_countFast_wksp(unsigned* count, unsigned* maxSymbolValuePtr, 141 const void* source, size_t sourceSize, 142 void* workSpace, size_t workSpaceSize) 143 { 144 if (sourceSize < 1500) /* heuristic threshold */ 145 return HIST_count_simple(count, maxSymbolValuePtr, source, sourceSize); 146 if ((size_t)workSpace & 3) return ERROR(GENERIC); /* must be aligned on 4-bytes boundaries */ 147 if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall); 148 return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, trustInput, (U32*)workSpace); 149 } 150 151 /* HIST_count_wksp() : 152 * Same as HIST_count(), but using an externally provided scratch buffer. 153 * `workSpace` size must be table of >= HIST_WKSP_SIZE_U32 unsigned */ 154 size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr, 155 const void* source, size_t sourceSize, 156 void* workSpace, size_t workSpaceSize) 157 { 158 if ((size_t)workSpace & 3) return ERROR(GENERIC); /* must be aligned on 4-bytes boundaries */ 159 if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall); 160 if (*maxSymbolValuePtr < 255) 161 return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, checkMaxSymbolValue, (U32*)workSpace); 162 *maxSymbolValuePtr = 255; 163 return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, workSpace, workSpaceSize); 164 } 165 166 #ifndef ZSTD_NO_UNUSED_FUNCTIONS 167 /* fast variant (unsafe : won't check if src contains values beyond count[] limit) */ 168 size_t HIST_countFast(unsigned* count, unsigned* maxSymbolValuePtr, 169 const void* source, size_t sourceSize) 170 { 171 unsigned tmpCounters[HIST_WKSP_SIZE_U32]; 172 return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, tmpCounters, sizeof(tmpCounters)); 173 } 174 175 size_t HIST_count(unsigned* count, unsigned* maxSymbolValuePtr, 176 const void* src, size_t srcSize) 177 { 178 unsigned tmpCounters[HIST_WKSP_SIZE_U32]; 179 return HIST_count_wksp(count, maxSymbolValuePtr, src, srcSize, tmpCounters, sizeof(tmpCounters)); 180 } 181 #endif 182