lib/gen_crc32table.c

   1 #include <stdio.h>
   2 #include "crc32defs.h"
   3 #include <inttypes.h>
   4
   5 #define ENTRIES_PER_LINE 4
   6
   7 #if CRC_LE_BITS <= 8
   8 #define LE_TABLE_SIZE (1 << CRC_LE_BITS)
   9 #else
  10 #define LE_TABLE_SIZE 256
  11 #endif
  12
  13 #if CRC_BE_BITS <= 8
  14 #define BE_TABLE_SIZE (1 << CRC_BE_BITS)
  15 #else
  16 #define BE_TABLE_SIZE 256
  17 #endif
  18
  19 static uint32_t crc32table_le[8][256];
  20 static uint32_t crc32table_be[8][256];
  21
  22 /**
  23  * crc32init_le() - allocate and initialize LE table data
  24  *
  25  * crc is the crc of the byte i; other entries are filled in based on the
  26  * fact that crctable[i^j] = crctable[i] ^ crctable[j].
  27  *
  28  */
  29 static void crc32init_le(void)
  30 {
  31         unsigned i, j;
  32         uint32_t crc = 1;
  33
  34         crc32table_le[0][0] = 0;
  35
  36         for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
  37                 crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
  38                 for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
  39                         crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
  40         }
  41         for (i = 0; i < LE_TABLE_SIZE; i++) {
  42                 crc = crc32table_le[0][i];
  43                 for (j = 1; j < 8; j++) {
  44                         crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
  45                         crc32table_le[j][i] = crc;
  46                 }
  47         }
  48 }
  49
  50 /**
  51  * crc32init_be() - allocate and initialize BE table data
  52  */
  53 static void crc32init_be(void)
  54 {
  55         unsigned i, j;
  56         uint32_t crc = 0x80000000;
  57
  58         crc32table_be[0][0] = 0;
  59
  60         for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
  61                 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
  62                 for (j = 0; j < i; j++)
  63                         crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
  64         }
  65         for (i = 0; i < BE_TABLE_SIZE; i++) {
  66                 crc = crc32table_be[0][i];
  67                 for (j = 1; j < 8; j++) {
  68                         crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
  69                         crc32table_be[j][i] = crc;
  70                 }
  71         }
  72 }
  73
  74 static void output_table(uint32_t table[8][256], int len, char trans)
  75 {
  76         int i, j;
  77
  78         for (j = 0 ; j < 8; j++) {
  79                 printf("static const u32 t%d_%ce[] = {", j, trans);
  80                 for (i = 0; i < len - 1; i++) {
  81                         if ((i % ENTRIES_PER_LINE) == 0)
  82                                 printf("\n");
  83                         printf("to%ce(0x%8.8xL),", trans, table[j][i]);
  84                         if ((i % ENTRIES_PER_LINE) != (ENTRIES_PER_LINE - 1))
  85                                 printf(" ");
  86                 }
  87                 printf("to%ce(0x%8.8xL)};\n\n", trans, table[j][len - 1]);
  88
  89                 if (trans == 'l') {
  90                         if ((j+1)*8 >= CRC_LE_BITS)
  91                                 break;
  92                 } else {
  93                         if ((j+1)*8 >= CRC_BE_BITS)
  94                                 break;
  95                 }
  96         }
  97 }
  98
  99 int main(int argc, char** argv)
 100 {
 101         printf("/*\n");
 102         printf(" * crc32table.h - CRC32 tables\n");
 103         printf(" *    this file is generated - do not edit\n");
 104         printf(" *      # gen_crc32table > crc32table.h\n");
 105         printf(" *    with\n");
 106         printf(" *      CRC_LE_BITS = %d\n", CRC_LE_BITS);
 107         printf(" *      CRC_BE_BITS = %d\n", CRC_BE_BITS);
 108         printf(" */\n");
 109         printf("\n");
 110
 111         if (CRC_LE_BITS > 1) {
 112                 crc32init_le();
 113                 output_table(crc32table_le, LE_TABLE_SIZE, 'l');
 114         }
 115
 116         if (CRC_BE_BITS > 1) {
 117                 crc32init_be();
 118                 output_table(crc32table_be, BE_TABLE_SIZE, 'b');
 119         }
 120
 121         return 0;
 122 }