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Utility classes for Jetty

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// ========================================================================
// Copyright (c) 2006-2009 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
// You may elect to redistribute this code under either of these licenses.
// ========================================================================

package org.eclipse.jetty.util;

/* ------------------------------------------------------------ */
/**
 * UTF-8 StringBuffer.
 *
 * This class wraps a standard {@link java.lang.StringBuffer} 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/
 */
public class Utf8StringBuffer extends Utf8Appendable
{
    final StringBuffer _buffer;

    public Utf8StringBuffer()
    {
        super(new StringBuffer());
        _buffer = (StringBuffer)_appendable;
    }

    public Utf8StringBuffer(int capacity)
    {
        super(new StringBuffer(capacity));
        _buffer = (StringBuffer)_appendable;
    }

    @Override
    public int length()
    {
        return _buffer.length();
    }

    @Override
    public void reset()
    {
        super.reset();
        _buffer.setLength(0);
    }

    public StringBuffer getStringBuffer()
    {
        checkState();
        return _buffer;
    }

    @Override
    public String toString()
    {
        checkState();
        return _buffer.toString();
    }

    private void checkState()
    {
        if (!isUtf8SequenceComplete())
            throw new IllegalArgumentException("Tried to read incomplete UTF8 decoded String");
    }
}