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Linux/lib/gen_crc32table.c

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

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