release/src/router/nginx/src/core/ngx_crc.h

   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
  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_ */