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 #define LE_TABLE_SIZE (1 << CRC_LE_BITS)
   8 #define BE_TABLE_SIZE (1 << CRC_BE_BITS)
   9
  10 static uint32_t crc32table_le[4][LE_TABLE_SIZE];
  11 static uint32_t crc32table_be[4][BE_TABLE_SIZE];
  12
  13 /**
  14  * crc32init_le() - allocate and initialize LE table data
  15  *
  16  * crc is the crc of the byte i; other entries are filled in based on the
  17  * fact that crctable[i^j] = crctable[i] ^ crctable[j].
  18  *
  19  */
  20 static void crc32init_le(void)
  21 {
  22         unsigned i, j;
  23         uint32_t crc = 1;
  24
  25         crc32table_le[0][0] = 0;
  26
  27         for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
  28                 crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
  29                 for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
  30                         crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
  31         }
  32         for (i = 0; i < LE_TABLE_SIZE; i++) {
  33                 crc = crc32table_le[0][i];
  34                 for (j = 1; j < 4; j++) {
  35                         crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
  36                         crc32table_le[j][i] = crc;
  37                 }
  38         }
  39 }
  40
  41 /**
  42  * crc32init_be() - allocate and initialize BE table data
  43  */
  44 static void crc32init_be(void)
  45 {
  46         unsigned i, j;
  47         uint32_t crc = 0x80000000;
  48
  49         crc32table_be[0][0] = 0;
  50
  51         for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
  52                 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
  53                 for (j = 0; j < i; j++)
  54                         crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
  55         }
  56         for (i = 0; i < BE_TABLE_SIZE; i++) {
  57                 crc = crc32table_be[0][i];
  58                 for (j = 1; j < 4; j++) {
  59                         crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
  60                         crc32table_be[j][i] = crc;
  61                 }
  62         }
  63 }
  64
  65 static void output_table(uint32_t table[4][256], int len, char *trans)
  66 {
  67         int i, j;
  68
  69         for (j = 0 ; j < 4; j++) {
  70                 printf("{");
  71                 for (i = 0; i < len - 1; i++) {
  72                         if (i % ENTRIES_PER_LINE == 0)
  73                                 printf("\n");
  74                         printf("%s(0x%8.8xL), ", trans, table[j][i]);
  75                 }
  76                 printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
  77         }
  78 }
  79
  80 int main(int argc, char** argv)
  81 {
  82         printf("/* this file is generated - do not edit */\n\n");
  83
  84         if (CRC_LE_BITS > 1) {
  85                 crc32init_le();
  86                 printf("static const u32 crc32table_le[4][256] = {");
  87                 output_table(crc32table_le, LE_TABLE_SIZE, "tole");
  88                 printf("};\n");
  89         }
  90
  91         if (CRC_BE_BITS > 1) {
  92                 crc32init_be();
  93                 printf("static const u32 crc32table_be[4][256] = {");
  94                 output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
  95                 printf("};\n");
  96         }
  97
  98         return 0;
  99 }