utf16.d

size_t bytesToUTF16Count(size_t bytes)
{
	if (bytes > text.length)
		bytes = text.length;

	size_t offset;
	size_t index;
	while (index < bytes)
	{
		switch (text.ptr[index] & 0b1111_0000)
		{
		case 0b1110_0000:
			// assume valid encoding (no wrong surrogates)
			offset++;
			index += 3;
			break;
		case 0b1111_0000:
			offset += 2;
			index += 4;
			break;
		case 0b1100_0000:
		case 0b1101_0000:
			offset++;
			index += 2;
			break;
		default:
			offset++;
			index++;
			break;
		}
	}
	return offset;
}