LXR linux/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
  10static uint32_t crc32table_le[LE_TABLE_SIZE];
  11static 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 */
  20static 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 */
  37static 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
  51static 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
  63int 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}
  83