xref: /linux/lib/gen_crc32table.c (revision fed3819bac88835b54c68a15ba41d95151ebaf12)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <stdio.h>
3 #include "../include/linux/crc32poly.h"
4 #include "../include/generated/autoconf.h"
5 #include <inttypes.h>
6 
7 static uint32_t crc32table_le[256];
8 static uint32_t crc32table_be[256];
9 static uint32_t crc32ctable_le[256];
10 
11 /**
12  * crc32init_le() - allocate and initialize LE table data
13  *
14  * crc is the crc of the byte i; other entries are filled in based on the
15  * fact that crctable[i^j] = crctable[i] ^ crctable[j].
16  *
17  */
18 static void crc32init_le_generic(const uint32_t polynomial, uint32_t tab[256])
19 {
20 	unsigned i, j;
21 	uint32_t crc = 1;
22 
23 	tab[0] = 0;
24 
25 	for (i = 128; i; i >>= 1) {
26 		crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
27 		for (j = 0; j < 256; j += 2 * i)
28 			tab[i + j] = crc ^ tab[j];
29 	}
30 }
31 
32 static void crc32init_le(void)
33 {
34 	crc32init_le_generic(CRC32_POLY_LE, crc32table_le);
35 }
36 
37 static void crc32cinit_le(void)
38 {
39 	crc32init_le_generic(CRC32C_POLY_LE, crc32ctable_le);
40 }
41 
42 /**
43  * crc32init_be() - allocate and initialize BE table data
44  */
45 static void crc32init_be(void)
46 {
47 	unsigned i, j;
48 	uint32_t crc = 0x80000000;
49 
50 	crc32table_be[0] = 0;
51 
52 	for (i = 1; i < 256; i <<= 1) {
53 		crc = (crc << 1) ^ ((crc & 0x80000000) ? CRC32_POLY_BE : 0);
54 		for (j = 0; j < i; j++)
55 			crc32table_be[i + j] = crc ^ crc32table_be[j];
56 	}
57 }
58 
59 static void output_table(const uint32_t table[256])
60 {
61 	int i;
62 
63 	for (i = 0; i < 256; i += 4) {
64 		printf("\t0x%08x, 0x%08x, 0x%08x, 0x%08x,\n",
65 		       table[i], table[i + 1], table[i + 2], table[i + 3]);
66 	}
67 }
68 
69 int main(int argc, char** argv)
70 {
71 	printf("/* this file is generated - do not edit */\n\n");
72 
73 	crc32init_le();
74 	printf("static const u32 ____cacheline_aligned crc32table_le[256] = {\n");
75 	output_table(crc32table_le);
76 	printf("};\n");
77 
78 	crc32init_be();
79 	printf("static const u32 ____cacheline_aligned crc32table_be[256] = {\n");
80 	output_table(crc32table_be);
81 	printf("};\n");
82 
83 	crc32cinit_le();
84 	printf("static const u32 ____cacheline_aligned crc32ctable_le[256] = {\n");
85 	output_table(crc32ctable_le);
86 	printf("};\n");
87 
88 	return 0;
89 }
90