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[LE_TABLE_SIZE];
  11 static uint32_t crc32table_be[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;
  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[i + j] = crc ^ crc32table_le[j];
  31         }
  32 }
  33
  34 /**
  35  * crc32init_be() - allocate and initialize BE table data
  36  */
  37 static void crc32init_be(void)
  38 {
  39         unsigned i, j;
  40         uint32_t crc = 0x80000000;
  41
  42         crc32table_be[0] = 0;
  43
  44         for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
  45                 crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
  46                 for (j = 0; j < i; j++)
  47                         crc32table_be[i + j] = crc ^ crc32table_be[j];
  48         }
  49 }
  50
  51 static void output_table(uint32_t table[], int len, char *trans)
  52 {
  53         int i;
  54
  55         for (i = 0; i < len - 1; i++) {
  56                 if (i % ENTRIES_PER_LINE == 0)
  57                         printf("\n");
  58                 printf("%s(0x%8.8xL), ", trans, table[i]);
  59         }
  60         printf("%s(0x%8.8xL)\n", trans, table[len - 1]);
  61 }
  62
  63 int main(int argc, char** argv)
  64 {
  65         printf("/* this file is generated - do not edit */\n\n");
  66
  67         if (CRC_LE_BITS > 1) {
  68                 crc32init_le();
  69                 printf("static const u32 crc32table_le[] = {");
  70                 output_table(crc32table_le, LE_TABLE_SIZE, "tole");
  71                 printf("};\n");
  72         }
  73
  74         if (CRC_BE_BITS > 1) {
  75                 crc32init_be();
  76                 printf("static const u32 crc32table_be[] = {");
  77                 output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
  78                 printf("};\n");
  79         }
  80
  81         return 0;
  82 }