Marshalling a char** in C#

Question

I am interfacing with code that takes a char** (that is, a pointer to a string):

int DoSomething(Whatever* handle, char** error);

Answer 1

For reference, here is code that compiles (but, not tested yet, working on that next tested, works 100%) that does what I need. If anyone can do better, that's what I'm after :D

public static unsafe int DoSomething(IntPtr handle, out string error) {
    byte* buff;

    int ret = DoSomething(handle, &buff);

    if(buff != null) {
        int i = 0;

        //count the number of bytes in the error message
        while (buff[++i] != 0) ;

        //allocate a managed array to store the data
        byte[] tmp = new byte[i];

        //(Marshal only works with IntPtrs)
        IntPtr errPtr = new IntPtr(buff);

        //copy the unmanaged array over
        Marshal.Copy(buff, tmp, 0, i);

        //get the string from the managed array
        error = UTF8Encoding.UTF8.GetString(buff);

        //free the unmanaged array
        //omitted, since it's not important

        //take a shot of whiskey
    } else {
        error = "";
    }

    return ret;
}

Edit: fixed the logic in the while loop, it had an off by one error.