xref: /f-stack/app/nginx-1.16.1/src/core/ngx_crc.h (revision 3da8d17d) 
1 
2 /*
3  * Copyright (C) Igor Sysoev
4  * Copyright (C) Nginx, Inc.
5  */
6 
7 
8 #ifndef _NGX_CRC_H_INCLUDED_
9 #define _NGX_CRC_H_INCLUDED_
10 
11 
12 #include <ngx_config.h>
13 #include <ngx_core.h>
14 
15 
16 /* 32-bit crc16 */
17 
18 static ngx_inline uint32_t
ngx_crc(u_char * data,size_t len)19 ngx_crc(u_char *data, size_t len)
20 {
21     uint32_t  sum;
22 
23     for (sum = 0; len; len--) {
24 
25         /*
26          * gcc 2.95.2 x86 and icc 7.1.006 compile
27          * that operator into the single "rol" opcode,
28          * msvc 6.0sp2 compiles it into four opcodes.
29          */
30         sum = sum >> 1 | sum << 31;
31 
32         sum += *data++;
33     }
34 
35     return sum;
36 }
37 
38 
39 #endif /* _NGX_CRC_H_INCLUDED_ */
40