nginx/src/core/ngx_crc.h

/*
 * Copyright (C) 2002-2004 Igor Sysoev
 */


#ifndef _NGX_CRC_H_INCLUDED_
#define _NGX_CRC_H_INCLUDED_


/* 32-bit crc16 */

ngx_inline static uint32_t ngx_crc(char *data, size_t len)
{
    uint32_t  sum;

    for (sum = 0; len; len--) {

        /*
         * gcc 2.95.2 x86 and icc 7.1.006 compile that operator
         *                                into the single "rol" opcode.
         * msvc 6.0sp2 compiles it into four opcodes.
         */
        sum = sum >> 1 | sum << 31;

        sum += *data++;
    }

    return sum;
}


#endif /* _NGX_CRC_H_INCLUDED_ */