格雷码和二进制码的转换

/*
* This function converts an unsigned binary
* number to reflected binary Gray code.
*
* The operator >> is shift right. The operator ^ is exclusive or.
*/
unsigned int binaryToGray(unsigned int num)
{
return num ^ (num >> 1);
}

/*
* This function converts a reflected binary
* Gray code number to a binary number.
* Each Gray code bit is exclusive-ored with all
* more significant bits.
*/
unsigned int grayToBinary(unsigned int num)
{
unsigned int mask;
for (mask = num >> 1; mask != 0; mask = mask >> 1)
{
num = num ^ mask;
}
return num;
}

/*
* A more efficient version, for Gray codes of 32 or fewer bits.
*/
unsigned int grayToBinary32(unsigned int num)
{
num = num ^ (num >> 16);
num = num ^ (num >> 8);
num = num ^ (num >> 4);
num = num ^ (num >> 2);
num = num ^ (num >> 1);
return num;
}