LXR linux/lib/gen_crc32table.c

   1#include <stdio.h>
   2#include "../include/generated/autoconf.h"
   3#include "crc32defs.h"
   4#include <inttypes.h>
   5
   6#define ENTRIES_PER_LINE 4
   7
   8#if CRC_LE_BITS > 8
   9# define LE_TABLE_ROWS (CRC_LE_BITS/8)
  10# define LE_TABLE_SIZE 256
  11#else
  12# define LE_TABLE_ROWS 1
  13# define LE_TABLE_SIZE (1 << CRC_LE_BITS)
  14#endif
  15
  16#if CRC_BE_BITS > 8
  17# define BE_TABLE_ROWS (CRC_BE_BITS/8)
  18# define BE_TABLE_SIZE 256
  19#else
  20# define BE_TABLE_ROWS 1
  21# define BE_TABLE_SIZE (1 << CRC_BE_BITS)
  22#endif
  23
  24static uint32_t crc32table_le[LE_TABLE_ROWS][256];
  25static uint32_t crc32table_be[BE_TABLE_ROWS][256];
  26static uint32_t crc32ctable_le[LE_TABLE_ROWS][256];
  27
  28/**
  29 * crc32init_le() - allocate and initialize LE table data
  30 *
  31 * crc is the crc of the byte i; other entries are filled in based on the
  32 * fact that crctable[i^j] = crctable[i] ^ crctable[j].
  33 *
  34 */
  35static void crc32init_le_generic(const uint32_t polynomial,
  36                                 uint32_t (*tab)[256])
  37{
  38        unsigned i, j;
  39        uint32_t crc = 1;
  40
  41        tab[0][0] = 0;
  42
  43        for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
  44                crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
  45                for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
  46                        tab[0][i + j] = crc ^ tab[0][j];
  47        }
  48        for (i = 0; i < LE_TABLE_SIZE; i++) {
  49                crc = tab[0][i];
  50                for (j = 1; j < LE_TABLE_ROWS; j++) {
  51                        crc = tab[0][crc & 0xff] ^ (crc >> 8);
  52                        tab[j][i] = crc;
  53                }
  54        }
  55}
  56
  57static void crc32init_le(void)
  58{
  59        crc32init_le_generic(CRCPOLY_LE, crc32table_le);
  60}
  61
  62static void crc32cinit_le(void)
  63{
  64        crc32init_le_generic(CRC32C_POLY_LE, crc32ctable_le);
  65}
  66
  67/**
  68 * crc32init_be() - allocate and initialize BE table data
  69 */
  70static void crc32init_be(void)
  71{
  72        unsigned i, j;
  73        uint32_t crc = 0x80000000;
  74
  75        crc32table_be[0][0] = 0;
  76
  77        for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
  78                crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
  79                for (j = 0; j < i; j++)
  80                        crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
  81        }
  82        for (i = 0; i < BE_TABLE_SIZE; i++) {
  83                crc = crc32table_be[0][i];
  84                for (j = 1; j < BE_TABLE_ROWS; j++) {
  85                        crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
  86                        crc32table_be[j][i] = crc;
  87                }
  88        }
  89}
  90
  91static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
  92{
  93        int i, j;
  94
  95        for (j = 0 ; j < rows; j++) {
  96                printf("{");
  97                for (i = 0; i < len - 1; i++) {
  98                        if (i % ENTRIES_PER_LINE == 0)
  99                                printf("\n");
 100                        printf("%s(0x%8.8xL), ", trans, table[j][i]);
 101                }
 102                printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
 103        }
 104}
 105
 106int main(int argc, char** argv)
 107{
 108        printf("/* this file is generated - do not edit */\n\n");
 109
 110        if (CRC_LE_BITS > 1) {
 111                crc32init_le();
 112                printf("static u32 __cacheline_aligned "
 113                       "crc32table_le[%d][%d] = {",
 114                       LE_TABLE_ROWS, LE_TABLE_SIZE);
 115                output_table(crc32table_le, LE_TABLE_ROWS,
 116                             LE_TABLE_SIZE, "tole");
 117                printf("};\n");
 118        }
 119
 120        if (CRC_BE_BITS > 1) {
 121                crc32init_be();
 122                printf("static u32 __cacheline_aligned "
 123                       "crc32table_be[%d][%d] = {",
 124                       BE_TABLE_ROWS, BE_TABLE_SIZE);
 125                output_table(crc32table_be, LE_TABLE_ROWS,
 126                             BE_TABLE_SIZE, "tobe");
 127                printf("};\n");
 128        }
 129        if (CRC_LE_BITS > 1) {
 130                crc32cinit_le();
 131                printf("static u32 __cacheline_aligned "
 132                       "crc32ctable_le[%d][%d] = {",
 133                       LE_TABLE_ROWS, LE_TABLE_SIZE);
 134                output_table(crc32ctable_le, LE_TABLE_ROWS,
 135                             LE_TABLE_SIZE, "tole");
 136                printf("};\n");
 137        }
 138
 139        return 0;
 140}
 141