nginx/src/core/ngx_crc.h

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