STM32 CRC32与对应的软件CRC32

//STM32硬件CRC32 byte数据计算,将数据移到最高位,低位补上FF
u32 stm32_crc32_byte(u8 *pBuff, u32 len)
{
	u32 i;
	u8 buff[4];
	u32 *p32 = (u32 *)buff;
	
	CRC->CR = 1;	//复位CRC寄存器
	buff[0] = buff[1] = buff[2] = buff[3] = 0XFF;
	for(i = 0;i < len;i ++)
	{
		buff[3] = pBuff[i];
		CRC->DR = *p32;
	}
	return CRC->DR;
}

//STM32硬件CRC32 u32数据计算
u32 stm32_crc32(u32 *pBuff, u32 len)
{
	u32 i;

	CRC->CR = 1;	//复位CRC寄存器
	for(i = 0;i < len;i ++)
	{
		CRC->DR = pBuff[i];
	}
	return CRC->DR;
}

//软件CRC32 u32数据计算
u32 crc32(u32 *ptr, u32 len)
{
    u32	xbit;
    u32	data;
    u32	CRC32 = 0xFFFFFFFF;
	u32 bits;
	const u32 dwPolynomial = 0x04c11db7;
	u32	i;
	
    for(i = 0;i < len;i ++)
	{
        xbit = 1 << 31;
        data = ptr[i];
        for (bits = 0; bits < 32; bits++) 
		{
            if (CRC32 & 0x80000000) {
                CRC32 <<= 1;
                CRC32 ^= dwPolynomial;
            }
            else
                CRC32 <<= 1;
            if (data & xbit)
                CRC32 ^= dwPolynomial;

            xbit >>= 1;
        }
    }
    return CRC32;
}

//软件CRC32 byte数据计算,将数据移到最高位,低位补上FF
u32 crc32_byte(u8 *ptr, u32 len)
{
    u32	xbit;
    u32	data;
    u32	CRC32 = 0xFFFFFFFF;		//初值
	u32 bits;
	u32	i;
	u8 buff[4];
	u32 *p32 = (u32 *)buff;
	const u32 dwPolynomial = 0x04c11db7;
	
	buff[0] = buff[1] = buff[2] = buff[3] = 0XFF;
    for(i = 0;i < len;i ++)
	{
        xbit = 1 << 31;
		
		buff[3] = ptr[i];
        data = *p32;
        for(bits = 0; bits < 32; bits++) 
		{
            if (CRC32 & 0x80000000) {
                CRC32 <<= 1;
                CRC32 ^= dwPolynomial;
            }
            else
                CRC32 <<= 1;
            if (data & xbit)
                CRC32 ^= dwPolynomial;

            xbit >>= 1;
        }
    }
    return CRC32;
}