1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <stdint.h>
18 #include <nanohub/crc.h>
19
20 /* this implements crc32 as crc.h defines it. It is not a normal CRC by any measure, so be careful with it */
21
22 static const uint32_t crctab[] =
23 {
24 0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
25 0x130476DC ,0x17C56B6B ,0x1A864DB2 ,0x1E475005,
26 0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
27 0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD
28 };
29
crcOneWord(uint32_t crc,uint32_t data,int cnt)30 static uint32_t crcOneWord(uint32_t crc, uint32_t data, int cnt)
31 {
32 int i;
33
34 crc = crc ^ data;
35 for (i = 0; i < cnt; i++)
36 crc = (crc << 4) ^ crctab[crc >> 28];
37
38 return crc;
39 }
40
soft_crc32(const void * buf,size_t size,uint32_t crc)41 uint32_t soft_crc32(const void *buf, size_t size, uint32_t crc)
42 {
43 const uint32_t *data32 = (const uint32_t *)buf;
44 const uint8_t *data8;
45 uint32_t word;
46 size_t i;
47
48 // word by word crc32
49 for (i = 0; i < size / 4; i++)
50 crc = crcOneWord(crc, *data32++, 8);
51
52 data8 = (const uint8_t*)data32;
53
54 // zero pad last word if required
55 if (size & 0x3) {
56 for (i *= 4, word = 0; i < size; i++)
57 word |= (*data8++) << ((i & 0x3) * 8);
58 crc = crcOneWord(crc, word, 8);
59 }
60
61 return crc;
62 }
63