nrf51822连接微信---crc32计算

<span style="font-family: Arial, Helvetica, sans-serif;">#ifndef __CRC32_H__</span>

#define __CRC32_H__

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

    uint32_t crc32(uint32_t crc, const uint8_t *buf, int len);

#ifdef __cplusplus
}
#endif


#endif                                                                                                                                                    

<pre name="code" class="cpp">#include <stdio.h>
#include "crc32.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;
}