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Linux/lib/gen_crc32table.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 #include <stdio.h>
  3 #include "../include/linux/crc32poly.h"
  4 #include "../include/generated/autoconf.h"
  5 #include "crc32defs.h"
  6 #include <inttypes.h>
  7 
  8 #define ENTRIES_PER_LINE 4
  9 
 10 #if CRC_LE_BITS > 8
 11 # define LE_TABLE_ROWS (CRC_LE_BITS/8)
 12 # define LE_TABLE_SIZE 256
 13 #else
 14 # define LE_TABLE_ROWS 1
 15 # define LE_TABLE_SIZE (1 << CRC_LE_BITS)
 16 #endif
 17 
 18 #if CRC_BE_BITS > 8
 19 # define BE_TABLE_ROWS (CRC_BE_BITS/8)
 20 # define BE_TABLE_SIZE 256
 21 #else
 22 # define BE_TABLE_ROWS 1
 23 # define BE_TABLE_SIZE (1 << CRC_BE_BITS)
 24 #endif
 25 
 26 static uint32_t crc32table_le[LE_TABLE_ROWS][256];
 27 static uint32_t crc32table_be[BE_TABLE_ROWS][256];
 28 static uint32_t crc32ctable_le[LE_TABLE_ROWS][256];
 29 
 30 /**
 31  * crc32init_le() - allocate and initialize LE table data
 32  *
 33  * crc is the crc of the byte i; other entries are filled in based on the
 34  * fact that crctable[i^j] = crctable[i] ^ crctable[j].
 35  *
 36  */
 37 static void crc32init_le_generic(const uint32_t polynomial,
 38                                  uint32_t (*tab)[256])
 39 {
 40         unsigned i, j;
 41         uint32_t crc = 1;
 42 
 43         tab[0][0] = 0;
 44 
 45         for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
 46                 crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
 47                 for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
 48                         tab[0][i + j] = crc ^ tab[0][j];
 49         }
 50         for (i = 0; i < LE_TABLE_SIZE; i++) {
 51                 crc = tab[0][i];
 52                 for (j = 1; j < LE_TABLE_ROWS; j++) {
 53                         crc = tab[0][crc & 0xff] ^ (crc >> 8);
 54                         tab[j][i] = crc;
 55                 }
 56         }
 57 }
 58 
 59 static void crc32init_le(void)
 60 {
 61         crc32init_le_generic(CRC32_POLY_LE, crc32table_le);
 62 }
 63 
 64 static void crc32cinit_le(void)
 65 {
 66         crc32init_le_generic(CRC32C_POLY_LE, crc32ctable_le);
 67 }
 68 
 69 /**
 70  * crc32init_be() - allocate and initialize BE table data
 71  */
 72 static void crc32init_be(void)
 73 {
 74         unsigned i, j;
 75         uint32_t crc = 0x80000000;
 76 
 77         crc32table_be[0][0] = 0;
 78 
 79         for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
 80                 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRC32_POLY_BE : 0);
 81                 for (j = 0; j < i; j++)
 82                         crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
 83         }
 84         for (i = 0; i < BE_TABLE_SIZE; i++) {
 85                 crc = crc32table_be[0][i];
 86                 for (j = 1; j < BE_TABLE_ROWS; j++) {
 87                         crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
 88                         crc32table_be[j][i] = crc;
 89                 }
 90         }
 91 }
 92 
 93 static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
 94 {
 95         int i, j;
 96 
 97         for (j = 0 ; j < rows; j++) {
 98                 printf("{");
 99                 for (i = 0; i < len - 1; i++) {
100                         if (i % ENTRIES_PER_LINE == 0)
101                                 printf("\n");
102                         printf("%s(0x%8.8xL), ", trans, table[j][i]);
103                 }
104                 printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
105         }
106 }
107 
108 int main(int argc, char** argv)
109 {
110         printf("/* this file is generated - do not edit */\n\n");
111 
112         if (CRC_LE_BITS > 1) {
113                 crc32init_le();
114                 printf("static const u32 ____cacheline_aligned "
115                        "crc32table_le[%d][%d] = {",
116                        LE_TABLE_ROWS, LE_TABLE_SIZE);
117                 output_table(crc32table_le, LE_TABLE_ROWS,
118                              LE_TABLE_SIZE, "tole");
119                 printf("};\n");
120         }
121 
122         if (CRC_BE_BITS > 1) {
123                 crc32init_be();
124                 printf("static const u32 ____cacheline_aligned "
125                        "crc32table_be[%d][%d] = {",
126                        BE_TABLE_ROWS, BE_TABLE_SIZE);
127                 output_table(crc32table_be, LE_TABLE_ROWS,
128                              BE_TABLE_SIZE, "tobe");
129                 printf("};\n");
130         }
131         if (CRC_LE_BITS > 1) {
132                 crc32cinit_le();
133                 printf("static const u32 ____cacheline_aligned "
134                        "crc32ctable_le[%d][%d] = {",
135                        LE_TABLE_ROWS, LE_TABLE_SIZE);
136                 output_table(crc32ctable_le, LE_TABLE_ROWS,
137                              LE_TABLE_SIZE, "tole");
138                 printf("};\n");
139         }
140 
141         return 0;
142 }
143 

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