1/*
2 * gen_crc32table.c --- Generate CRC32 tables.
3 *
4 * Copyright (C) 2008 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Public
8 * License.
9 * %End-Header%
10 */
11
12#include <stdio.h>
13#include "crc32defs.h"
14#include <inttypes.h>
15
16#define ENTRIES_PER_LINE 4
17
18#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
19#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
20
21static uint32_t crc32table_le[LE_TABLE_SIZE];
22static uint32_t crc32table_be[BE_TABLE_SIZE];
23
24/**
25 * crc32init_le() - allocate and initialize LE table data
26 *
27 * crc is the crc of the byte i; other entries are filled in based on the
28 * fact that crctable[i^j] = crctable[i] ^ crctable[j].
29 *
30 */
31static void crc32init_le(void)
32{
33	unsigned i, j;
34	uint32_t crc = 1;
35
36	crc32table_le[0] = 0;
37
38	for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
39		crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
40		for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
41			crc32table_le[i + j] = crc ^ crc32table_le[j];
42	}
43}
44
45/**
46 * crc32init_be() - allocate and initialize BE table data
47 */
48static void crc32init_be(void)
49{
50	unsigned i, j;
51	uint32_t crc = 0x80000000;
52
53	crc32table_be[0] = 0;
54
55	for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
56		crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
57		for (j = 0; j < i; j++)
58			crc32table_be[i + j] = crc ^ crc32table_be[j];
59	}
60}
61
62static void output_table(uint32_t table[], int len, const char *trans)
63{
64	int i;
65
66	for (i = 0; i < len - 1; i++) {
67		if (i % ENTRIES_PER_LINE == 0)
68			printf("\n");
69		printf("%s(0x%8.8xL), ", trans, table[i]);
70	}
71	printf("%s(0x%8.8xL)\n", trans, table[len - 1]);
72}
73
74#ifdef __GNUC__
75#define ATTR(x) __attribute__(x)
76#else
77#define ATTR(x)
78#endif
79
80int main(int argc ATTR((unused)), char** argv ATTR((unused)))
81{
82	printf("/* this file is generated - do not edit */\n\n");
83
84	printf("#ifdef UNITTEST\n");
85	if (CRC_LE_BITS > 1) {
86		crc32init_le();
87		printf("static const __u32 crc32table_le[] = {");
88		output_table(crc32table_le, LE_TABLE_SIZE, "tole");
89		printf("};\n");
90	}
91	printf("#endif /* UNITTEST */\n");
92
93	if (CRC_BE_BITS > 1) {
94		crc32init_be();
95		printf("static const __u32 crc32table_be[] = {");
96		output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
97		printf("};\n");
98	}
99
100	return 0;
101}
102