static bool ReadHex(StringStream &in, dword &hex, int n) {
	hex = 0;
	while (n--) {
		if (in.IsEof())
			return false;
		int c = in.Get();
		if (!IsXDigit(c))
			return false;
		hex = (hex << 4) + ctoi(c);
	}
	return true;
}

static String GetUtfSmall(StringStream &in) {
	String result;
	dword hex = 0;
	if (ReadHex(in, hex, 4)) {
		if (hex >= 0xD800 && hex < 0xDBFF) {
			int c = in.Get();
			int next = in.Get();
			if (c == '\\' && next == 'u') {
				dword hex2;
				if (ReadHex(in, hex2, 4) && hex2 >= 0xDC00 && hex2 <= 0xDFFF) {
					result.Cat(ToUtf8(((hex & 0x3ff) << 10) | (hex2 & 0x3ff) + 0x10000));
				}
			}
		} else {
			if (hex > 0 && hex < 0xDC00) {
				result.Cat(ToUtf8(hex));
			}
		}
	}
	return result;
}

static String GetUtfCapital(StringStream &in) {
	String result;
	dword hex = 0;
	if (ReadHex(in, hex, 8) && hex > 0 && hex < 0x10ffff) {
		result.Cat(ToUtf8(hex));
	}
	return result;
}

static String DecodeEscapedUtf(const String &s) {
	StringStream ss(s);
	String result;

	while (!ss.IsEof()) {
		int c = ss.Get();
		if (c == '\\') {
			int next = ss.Get();
			int64 pos = ss.GetPos();
			String utf;
			switch (next) {
			case 'u':
				utf = GetUtfSmall(ss);
				break;
			case 'U':
				utf = GetUtfCapital(ss);
				break;
			default:
				break;
			}
			if (utf.GetCount() > 0) {
				result.Cat(utf);
			} else {
				ss.Seek(pos);
				result.Cat(c);
				result.Cat(next);
			}
		} else {
			result.Cat(c);
		}
	}
	return result;
}