//  crc32.c
//  WeChat Embedded
//
//  Created by harlliu on 14-03-03.
//  Copyright 2014 Tencent. All rights reserved.
//


#include "prf_defs.h"
#if (WX_AIRSYNC_CFG)

#include <stdio.h>
#include "wechar_crc.h"

#define DO1(buf) crc = crc_table(((int)crc ^ (*buf++)) & 0xff) ^ (crc >> 8);
#define DO2(buf)  DO1(buf); DO1(buf);
#define DO4(buf)  DO2(buf); DO2(buf);
#define DO8(buf)  DO4(buf); DO4(buf);


static uint32_t crc_table(uint32_t index)
{
	uint32_t c = index;
	uint32_t poly = 0xedb88320L;
	int k;

	for (k = 0; k < 8; k++)
		c = c & 1 ? poly ^ (c >> 1) : c >> 1;

	return c;
}

uint32_t crc32(uint32_t crc, const uint8_t *buf, int len)
{
    if (buf == NULL) return 0L;

    crc = crc ^ 0xffffffffL;
    while (len >= 8)
    {
      DO8(buf);
      len -= 8;
    }
    if (len) do {
      DO1(buf);
    } while (--len);
    return crc ^ 0xffffffffL;
}


#endif	///WX_AIRSYNC_CFG