C语言中16进制字符串转为字节流的实现

void HexStrToByte(const char* source, unsigned char* dest, int length)
{
short i;
unsigned char highByte, lowByte;

for (i = 0; i < length; i += 2)
{
highByte = toupper(source[i]);
lowByte = toupper(source[i + 1]);

if (highByte > 0x39)
highByte -= 0x37;
else
highByte -= 0x30;

if (lowByte > 0x39)
lowByte -= 0x37;
else
lowByte -= 0x30;

// dest[i / 2] = (highByte << 4) | lowByte;
dest[(length-2-i)/2] = (highByte << 4) | lowByte;
}
return;
}