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package com.firefly.utils.lang;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * Utf8 Appendable abstract base class
 *
 * This abstract class wraps a standard {@link java.lang.Appendable} and
 * provides methods to append UTF-8 encoded bytes, that are converted into
 * characters.
 *
 * This class is stateful and up to 4 calls to {@link #append(byte)} may be
 * needed before state a character is appended to the string buffer.
 *
 * The UTF-8 decoding is done by this class and no additional buffers or Readers
 * are used. The UTF-8 code was inspired by
 * http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
 *
 * License information for Bjoern Hoehrmann's code:
 *
 * Copyright (c) 2008-2009 Bjoern Hoehrmann <[email protected]>
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 **/
public abstract class Utf8Appendable {
	public static final char REPLACEMENT = '\ufffd';
	public static final byte[] REPLACEMENT_UTF8 = new byte[] { (byte) 0xEF, (byte) 0xBF, (byte) 0xBD };
	private static final int UTF8_ACCEPT = 0;
	private static final int UTF8_REJECT = 12;

	protected final Appendable appendable;
	protected int _state = UTF8_ACCEPT;
	private static final byte[] BYTE_TABLE =
    {
        // The first part of the table maps bytes to character classes that
        // to reduce the size of the transition table and create bitmasks.
         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
         1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,  9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
         7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,  7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
         8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
        10,3,3,3,3,3,3,3,3,3,3,3,3,4,3,3, 11,6,6,6,5,8,8,8,8,8,8,8,8,8,8,8
    };

    private static final byte[] TRANS_TABLE =
    {
        // The second part is a transition table that maps a combination
        // of a state of the automaton and a character class to a state.
         0,12,24,36,60,96,84,12,12,12,48,72, 12,12,12,12,12,12,12,12,12,12,12,12,
        12, 0,12,12,12,12,12, 0,12, 0,12,12, 12,24,12,12,12,12,12,24,12,24,12,12,
        12,12,12,12,12,12,12,24,12,12,12,12, 12,24,12,12,12,12,12,12,12,24,12,12,
        12,12,12,12,12,12,12,36,12,36,12,12, 12,36,12,12,12,12,12,36,12,36,12,12,
        12,36,12,12,12,12,12,12,12,12,12,12
    };
	private int codep;

	public Utf8Appendable(Appendable appendable) {
		this.appendable = appendable;
	}

	public abstract int length();

	protected void reset() {
		_state = UTF8_ACCEPT;
	}

	private void checkCharAppend() throws IOException {
		if (_state != UTF8_ACCEPT) {
			appendable.append(REPLACEMENT);
			int state = _state;
			_state = UTF8_ACCEPT;
			throw new NotUtf8Exception("char appended in state " + state);
		}
	}

	public void append(char c) {
		try {
			checkCharAppend();
			appendable.append(c);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void append(String s) {
		try {
			checkCharAppend();
			appendable.append(s);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void append(String s, int offset, int length) {
		try {
			checkCharAppend();
			appendable.append(s, offset, offset + length);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void append(byte b) {
		try {
			appendByte(b);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void append(ByteBuffer buf) {
		try {
			while (buf.remaining() > 0) {
				appendByte(buf.get());
			}
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void append(byte[] b, int offset, int length) {
		try {
			int end = offset + length;
			for (int i = offset; i < end; i++)
				appendByte(b[i]);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	public boolean append(byte[] b, int offset, int length, int maxChars) {
		try {
			int end = offset + length;
			for (int i = offset; i < end; i++) {
				if (length() > maxChars)
					return false;
				appendByte(b[i]);
			}
			return true;
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	protected void appendByte(byte b) throws IOException {

		if (b > 0 && _state == UTF8_ACCEPT) {
			appendable.append((char) (b & 0xFF));
		} else {
			int i = b & 0xFF;
			int type = BYTE_TABLE[i];
			codep = _state == UTF8_ACCEPT ? (0xFF >> type) & i : (i & 0x3F) | (codep << 6);
			int next = TRANS_TABLE[_state + type];

			switch (next) {
			case UTF8_ACCEPT:
				_state = next;
				if (codep < Character.MIN_HIGH_SURROGATE) {
					appendable.append((char) codep);
				} else {
					for (char c : Character.toChars(codep))
						appendable.append(c);
				}
				break;

			case UTF8_REJECT:
				String reason = "byte " + TypeUtils.toHexString(b) + " in state " + (_state / 12);
				codep = 0;
				_state = UTF8_ACCEPT;
				appendable.append(REPLACEMENT);
				throw new NotUtf8Exception(reason);

			default:
				_state = next;

			}
		}
	}

	public boolean isUtf8SequenceComplete() {
		return _state == UTF8_ACCEPT;
	}

	@SuppressWarnings("serial")
	public static class NotUtf8Exception extends IllegalArgumentException {
		public NotUtf8Exception(String reason) {
			super("Not valid UTF8! " + reason);
		}
	}

	protected void checkState() {
		if (!isUtf8SequenceComplete()) {
			codep = 0;
			_state = UTF8_ACCEPT;
			try {
				appendable.append(REPLACEMENT);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
			throw new NotUtf8Exception("incomplete UTF8 sequence");
		}
	}

	public String toReplacedString() {
		if (!isUtf8SequenceComplete()) {
			codep = 0;
			_state = UTF8_ACCEPT;
			try {
				appendable.append(REPLACEMENT);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		return appendable.toString();
	}
}




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