On Tuesday, 11 October 2016 at 03:58:59 UTC, Andrei Alexandrescu
wrote:
On 10/10/16 11:00 PM, Stefan Koch wrote:
On Tuesday, 11 October 2016 at 02:48:22 UTC, Andrei
Alexandrescu wrote:
That looks good. I'm just worried about the jump forward -
ideally the
case c < 127 would simply entail a quick return. I tried a
fix, but it
didn't do what I wanted in ldc. We shouldn't assert(0) if
wrong - just
skip one byte. Also, are we right to not worry about 5- and
6-byte
sequences? The docs keep on threatening with it, and then
immediately
mention those are not valid.
[ ... ]
Andrei
If you want to skip a byte it's easy to do as well.
void popFront3(ref char[] s) @trusted pure nothrow {
immutable c = s[0];
uint char_length = 1;
if (c < 127)
{
Lend :
s = s.ptr[char_length .. s.length];
} else {
if ((c & b01100_0000) == 0b1000_0000)
{
//just skip one in case this is not the beginning of a
code-point
char
goto Lend;
}
if (c < 192)
{
char_length = 2;
goto Lend;
}
if (c < 240)
{
char_length = 3;
goto Lend;
}
if (c < 248)
{
char_length = 4;
goto Lend;
}
}
}
Affirmative. That's identical to the code in "[ ... ]" :o).
Generated code still does a jmp forward though. -- Andrei
It was not identical.
((c & b01100_0000) == 0b1000_0000))
Can be true in all of the 3 following cases.
If we do not do a jmp to return here, we cannot guarantee that we
will not skip over the next valid char.
Thereby corrupting already corrupt strings even more.
For best performance we need to leave the gotos in there.
