Root/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

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