import java.io.InputStream;

public class HGB2312 {

	private byte[] map = new byte[15228];

	private byte[] buffer;
	private int index;

	public HGB2312() throws Exception {
		InputStream is = getClass().getResourceAsStream("/gb2u.dat");
		is.read(map);
		is.close();
	}

	public String gb2utf8(byte[] gb) throws Exception {
		buffer = new byte[gb.length + gb.length / 2 + 3];
		index = 0;
		int c, h, l, ind;
		for (int i = 0; i < gb.length;) {
			if (gb[i] >= 0) {
				fillBuffer(gb[i++]);
			} else {
				h = 256 + gb[i++];
				l = 256 + gb[i++];
				h = h - 0xA0 - 1;
				l = l - 0xA0 - 1;
				if (h < 9) {
					ind = (h * 94 + l) << 1;
					c = (byte2Int(map[ind]) << 8 | byte2Int(map[ind + 1]));
					fillBuffer(c);
				} else if (h >= 9 && h <= 14) {
					fillBuffer(0);
				} else if (h > 14) {
					h -= 6;
					ind = (h * 94 + l) << 1;
					c = (byte2Int(map[ind]) << 8 | byte2Int(map[ind + 1]));
					fillBuffer(c);
				} else {
					fillBuffer(0);
				}
			}
		}
		// ind = index - 2;
		// h = (byte) ((ind >> 8) & 0x7F);
		// l = (byte) (ind & 0xFF);
		// buffer[0] = h;
		// buffer[1] = l;

		return new String(buffer, 0, index, "UTF-8");
	}

	private void fillBuffer(int value) {
		if (value <= 0x0000007F) {
			buffer[index++] = (byte) value;
		} else if (value >= 0x00000080 && value <= 0x000007FF) {
			byte b1 = (byte) (0x60 | (value >> 6));
			byte b2 = (byte) (0x80 | (value & 0x3F));
			buffer[index++] = b1;
			buffer[index++] = b2;
		} else if (value >= 0x00000800 && value <= 0x0000FFFF) {
			byte b1 = (byte) (0xE0 | (value >> 12));
			byte b2 = (byte) (0x80 | ((value >> 6) & 0x3F));
			byte b3 = (byte) (0x80 | (value & 0x3F));
			buffer[index++] = b1;
			buffer[index++] = b2;
			buffer[index++] = b3;
		} else if (value >= 0x00010000 && value <= 0x001FFFFF) {
			byte b1 = (byte) (0x1E | (value >> 18));
			byte b2 = (byte) (0x80 | ((value >> 12) & 0x3F));
			byte b3 = (byte) (0x80 | ((value >> 6) & 0x3F));
			byte b4 = (byte) (0x80 | (value & 0x3F));
			buffer[index++] = b1;
			buffer[index++] = b2;
			buffer[index++] = b3;
			buffer[index++] = b4;
		} else if (value >= 0x00200000 && value <= 0x03FFFFFF) {
			byte b1 = (byte) (0x3E | (value >> 24));
			byte b2 = (byte) (0x80 | ((value >> 18) & 0x3F));
			byte b3 = (byte) (0x80 | ((value >> 12) & 0x3F));
			byte b4 = (byte) (0x80 | ((value >> 6) & 0x3F));
			byte b5 = (byte) (0x80 | (value & 0x3F));
			buffer[index++] = b1;
			buffer[index++] = b2;
			buffer[index++] = b3;
			buffer[index++] = b4;
			buffer[index++] = b5;
		} else if (value >= 0x04000000 && value <= 0x7FFFFFFF) {
			byte b1 = (byte) (0x7E | (value >> 30));
			byte b2 = (byte) (0x80 | ((value >> 24) & 0x3F));
			byte b3 = (byte) (0x80 | ((value >> 18) & 0x3F));
			byte b4 = (byte) (0x80 | ((value >> 12) & 0x3F));
			byte b5 = (byte) (0x80 | ((value >> 6) & 0x3F));
			byte b6 = (byte) (0x80 | (value & 0x3F));
			buffer[index++] = b1;
			buffer[index++] = b2;
			buffer[index++] = b3;
			buffer[index++] = b4;
			buffer[index++] = b5;
			buffer[index++] = b6;
		}
	}

	private int byte2Int(byte b) {
		if (b < 0) {
			return 256 + b;
		} else {
			return b;
		}
	}
}