/// diff compares a and b.
void Diff(string aname, string bname, slice <byte> a, slice <byte> b)
{
var buf = new GoBuffer(); // holding long error message
// compare lengths
if (a.Length != b.Length)
{
buf.WriteString($"\nlength changed: len({aname}) = {a.Length},"
+ " len({bname}) = {b.Length}");
}
// compare contents
var line = 1;
var offs = 1;
for (var i = 0; i < a.Length && i < b.Length; i++)
{
var ch = a[i];
if (ch != b[i])
{
buf.WriteString(string.Format("\n{0}:{1}:{2}: {3}", aname, line, i - offs + 1,
LineAt(a, offs)));
buf.WriteString(string.Format("\n{0}:{1}:{2}: {3}", bname, line, i - offs + 1,
LineAt(b, offs)));
buf.WriteString("\n\n");
break;
}
if (ch == '\n')
{
line++;
offs = i + 1;
}
}
if (buf.Len() > 0)
{
throw new IOException(buf.ToString());
}
}