_grapheme_category

pub func _grapheme_category(scalar: Int) -> Int {
	if scalar == 13 { return _GC_CR }
	if scalar == 10 { return _GC_LF }
	if scalar < 32 { return _GC_CONTROL }
	if scalar < 127 { return _GC_OTHER }
	let table: String = _gcb_table()
	let entry_count: Int = table.byte_count / 4
	// The last entry whose start <= scalar.
	let lo: Int = 0
	let hi: Int = entry_count - 1
	loop lo < hi {
		let mid: Int = (lo + hi + 1) / 2
		let mid_start: Int = _entry_value(storage: table.storage, index: mid) / 32
		if scalar < mid_start {
			hi = mid - 1
		} else {
			lo = mid
		}
	}
	let v: Int = _entry_value(storage: table.storage, index: lo)
	v - (v / 32) * 32
}