Question

I have been trying to carry out a conversion from CString that contains Hex string to a Byte array and have been

unsuccessful so far. I have looked on forums and none of them seem to help so far. Is there a function with just a few

lines of code to do this conversion?

My code:

BYTE abyData[8];    // BYTE = unsigned char

CString sByte = "0E00000000000400";

Expecting:

abyData[0] = 0x0E;
abyData[6] = 0x04; // etc.

Answer 1

You can simply gobble up two characters at a time:

unsigned int value(char c)
{
    if (c >= '0' && c <= '9') { return c - '0'; }
    if (c >= 'A' && c <= 'F') { return c - 'A' + 10; }
    if (c >= 'a' && c <= 'f') { return c - 'a' + 10; }

    return -1; // Error!
}

for (unsigned int i = 0; i != 8; ++i)
{
    abyData[i] = value(sByte[2 * i]) * 16 + value(sByte[2 * i + 1]);
}

Of course 8 should be the size of your array, and you should ensure that the string is precisely twice as long. A checking version of this would make sure that each character is a valid hex digit and signal some type of error if that isn’t the case.