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[4][LE_TABLE_SIZE];
  11static 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 */
  20static 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 */
  44static 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
  65static 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
  80int 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}
 100