On Tuesday, 11 October 2016 at 07:30:26 UTC, Matthias Bentrup
wrote:
A branch-free version:
void popFront4(ref char[] s) @trusted pure nothrow {
immutable c = s[0];
uint char_length = 1 + (c >= 192) + (c >= 240) + (c >= 248);
s = s.ptr[char_length .. s.length];
}
Theoretically the char_length could be computed with three sub
and addc instructions, but no compiler is smart enough to
detect that.
You still need to special case c < 128
as well as the follow chars.
also smaller c's are more common the bigger ones making the
branching version faster on average.
