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package utf16
REPLACEMENT_CHAR :: '\ufffd';
MAX_RUNE :: '\U0010ffff';
_surr1 :: 0xd800;
_surr2 :: 0xdc00;
_surr3 :: 0xe000;
_surr_self :: 0x10000;
is_surrogate :: proc(r: rune) -> bool {
return _surr1 <= r && r < _surr3;
}
decode_surrogate_pair :: proc(r1, r2: rune) -> rune {
if _surr1 <= r1 && r1 < _surr2 && _surr2 <= r2 && r2 < _surr3 {
return (r1-_surr1)<<10 | (r2 - _surr2) + _surr_self;
}
return REPLACEMENT_CHAR;
}
encode_surrogate_pair :: proc(c: rune) -> (r1, r2: rune) {
r := c;
if r < _surr_self || r > MAX_RUNE {
return REPLACEMENT_CHAR, REPLACEMENT_CHAR;
}
r -= _surr_self;
return _surr1 + (r>>10)&0x3ff, _surr2 + r&0x3ff;
}
encode :: proc(d: []u16, s: []rune) -> int {
n, m := 0, len(d);
loop: for r in s {
switch r {
case 0..<_surr1, _surr3 ..< _surr_self:
if m+1 < n { break loop; }
d[n] = u16(r);
n += 1;
case _surr_self ..= MAX_RUNE:
if m+2 < n { break loop; }
r1, r2 := encode_surrogate_pair(r);
d[n] = u16(r1);
d[n+1] = u16(r2);
n += 2;
case:
if m+1 < n { break loop; }
d[n] = u16(REPLACEMENT_CHAR);
n += 1;
}
}
return n;
}
encode_string :: proc(d: []u16, s: string) -> int {
n, m := 0, len(d);
loop: for r in s {
switch r {
case 0..<_surr1, _surr3 ..< _surr_self:
if m+1 < n { break loop; }
d[n] = u16(r);
n += 1;
case _surr_self ..= MAX_RUNE:
if m+2 < n { break loop; }
r1, r2 := encode_surrogate_pair(r);
d[n] = u16(r1);
d[n+1] = u16(r2);
n += 2;
case:
if m+1 < n { break loop; }
d[n] = u16(REPLACEMENT_CHAR);
n += 1;
}
}
return n;
}
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