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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

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 * particular file as subject to the "Classpath" exception as provided

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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

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// -- This file was mechanically generated: Do not edit! -- //

package java.nio.charset;

import java.nio.Buffer;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.BufferOverflowException;

import java.nio.BufferUnderflowException;

import java.lang.ref.WeakReference;

import java.nio.charset.CoderMalfunctionError;                  // javadoc

/**

 * An engine that can transform a sequence of bytes in a specific charset into a sequence of

 * sixteen-bit Unicode characters.

 *

 * <a name="steps">

 *

 * <p> The input byte sequence is provided in a byte buffer or a series

 * of such buffers.  The output character sequence is written to a character buffer

 * or a series of such buffers.  A decoder should always be used by making

 * the following sequence of method invocations, hereinafter referred to as a

 * <i>decoding operation</i>:

 *

 * <ol>

 *

 *   <li><p> Reset the decoder via the {@link #reset reset} method, unless it

 *   has not been used before; </p></li>

 *

 *   <li><p> Invoke the {@link #decode decode} method zero or more times, as

 *   long as additional input may be available, passing <tt>false</tt> for the

 *   <tt>endOfInput</tt> argument and filling the input buffer and flushing the

 *   output buffer between invocations; </p></li>

 *

 *   <li><p> Invoke the {@link #decode decode} method one final time, passing

 *   <tt>true</tt> for the <tt>endOfInput</tt> argument; and then </p></li>

 *

 *   <li><p> Invoke the {@link #flush flush} method so that the decoder can

 *   flush any internal state to the output buffer. </p></li>

 *

 * </ol>

 *

 * Each invocation of the {@link #decode decode} method will decode as many

 * bytes as possible from the input buffer, writing the resulting characters

 * to the output buffer.  The {@link #decode decode} method returns when more

 * input is required, when there is not enough room in the output buffer, or

 * when a decoding error has occurred.  In each case a {@link CoderResult}

 * object is returned to describe the reason for termination.  An invoker can

 * examine this object and fill the input buffer, flush the output buffer, or

 * attempt to recover from a decoding error, as appropriate, and try again.

 *

 * <a name="ce">

 *

 * <p> There are two general types of decoding errors.  If the input byte

 * sequence is not legal for this charset then the input is considered <i>malformed</i>.  If

 * the input byte sequence is legal but cannot be mapped to a valid

 * Unicode character then an <i>unmappable character</i> has been encountered.

 *

 * <a name="cae">

 *

 * <p> How a decoding error is handled depends upon the action requested for

 * that type of error, which is described by an instance of the {@link

 * CodingErrorAction} class.  The possible error actions are to {@link

 * CodingErrorAction#IGNORE </code>ignore<code>} the erroneous input, {@link

 * CodingErrorAction#REPORT </code>report<code>} the error to the invoker via

 * the returned {@link CoderResult} object, or {@link CodingErrorAction#REPLACE

 * </code>replace<code>} the erroneous input with the current value of the

 * replacement string.  The replacement

 *

 * has the initial value <tt>"&#92;uFFFD"</tt>;

 *

 * its value may be changed via the {@link #replaceWith(java.lang.String)

 * replaceWith} method.

 *

 * <p> The default action for malformed-input and unmappable-character errors

 * is to {@link CodingErrorAction#REPORT </code>report<code>} them.  The

 * malformed-input error action may be changed via the {@link

 * #onMalformedInput(CodingErrorAction) onMalformedInput} method; the

 * unmappable-character action may be changed via the {@link

 * #onUnmappableCharacter(CodingErrorAction) onUnmappableCharacter} method.

 *

 * <p> This class is designed to handle many of the details of the decoding

 * process, including the implementation of error actions.  A decoder for a

 * specific charset, which is a concrete subclass of this class, need only

 * implement the abstract {@link #decodeLoop decodeLoop} method, which

 * encapsulates the basic decoding loop.  A subclass that maintains internal

 * state should, additionally, override the {@link #implFlush implFlush} and

 * {@link #implReset implReset} methods.

 *

 * <p> Instances of this class are not safe for use by multiple concurrent

 * threads.  </p>

 *

 *

 * @author Mark Reinhold

 * @author JSR-51 Expert Group

 * @since 1.4

 *

 * @see ByteBuffer

 * @see CharBuffer

 * @see Charset

 * @see CharsetEncoder

 */

public abstract class CharsetDecoder {

    private final Charset charset;

    private final float averageCharsPerByte;

    private final float maxCharsPerByte;

    private String replacement;

    private CodingErrorAction malformedInputAction

        = CodingErrorAction.REPORT;

    private CodingErrorAction unmappableCharacterAction

        = CodingErrorAction.REPORT;

    // Internal states

    //

    private static final int ST_RESET   = 0;

    private static final int ST_CODING  = 1;

    private static final int ST_END     = 2;

    private static final int ST_FLUSHED = 3;

    private int state = ST_RESET;

    private static String stateNames[]

        = { "RESET", "CODING", "CODING_END", "FLUSHED" };

    /**

     * Initializes a new decoder.  The new decoder will have the given

     * chars-per-byte and replacement values. </p>

     *

     * @param  averageCharsPerByte

     *         A positive float value indicating the expected number of

     *         characters that will be produced for each input byte

     *

     * @param  maxCharsPerByte

     *         A positive float value indicating the maximum number of

     *         characters that will be produced for each input byte

     *

     * @param  replacement

     *         The initial replacement; must not be <tt>null</tt>, must have

     *         non-zero length, must not be longer than maxCharsPerByte,

     *         and must be {@link #isLegalReplacement </code>legal<code>}

     *

     * @throws  IllegalArgumentException

     *          If the preconditions on the parameters do not hold

     */

    private

    CharsetDecoder(Charset cs,

                   float averageCharsPerByte,

                   float maxCharsPerByte,

                   String replacement)

    {

        this.charset = cs;

        if (averageCharsPerByte <= 0.0f)

            throw new IllegalArgumentException("Non-positive "

                                               + "averageCharsPerByte");

        if (maxCharsPerByte <= 0.0f)

            throw new IllegalArgumentException("Non-positive "

                                               + "maxCharsPerByte");

        if (!Charset.atBugLevel("1.4")) {

            if (averageCharsPerByte > maxCharsPerByte)

                throw new IllegalArgumentException("averageCharsPerByte"

                                                   + " exceeds "

                                                   + "maxCharsPerByte");

        }

        this.replacement = replacement;

        this.averageCharsPerByte = averageCharsPerByte;

        this.maxCharsPerByte = maxCharsPerByte;

        replaceWith(replacement);

    }

    /**

     * Initializes a new decoder.  The new decoder will have the given

     * chars-per-byte values and its replacement will be the

     * string <tt>"&#92;uFFFD"</tt>. </p>

     *

     * @param  averageCharsPerByte

     *         A positive float value indicating the expected number of

     *         characters that will be produced for each input byte

     *

     * @param  maxCharsPerByte

     *         A positive float value indicating the maximum number of

     *         characters that will be produced for each input byte

     *

     * @throws  IllegalArgumentException

     *          If the preconditions on the parameters do not hold

     */

    protected CharsetDecoder(Charset cs,

                             float averageCharsPerByte,

                             float maxCharsPerByte)

    {

        this(cs,

             averageCharsPerByte, maxCharsPerByte,

             "\uFFFD");

    }

    /**

     * Returns the charset that created this decoder.  </p>

     *

     * @return  This decoder's charset

     */

    public final Charset charset() {

        return charset;

    }

    /**

     * Returns this decoder's replacement value. </p>

     *

     * @return  This decoder's current replacement,

     *          which is never <tt>null</tt> and is never empty

     */

    public final String replacement() {

        return replacement;

    }

    /**

     * Changes this decoder's replacement value.

     *

     * <p> This method invokes the {@link #implReplaceWith implReplaceWith}

     * method, passing the new replacement, after checking that the new

     * replacement is acceptable.  </p>

     *

     * @param  newReplacement

     *

     *         The new replacement; must not be <tt>null</tt>

     *         and must have non-zero length

     *

     * @return  This decoder

     *

     * @throws  IllegalArgumentException

     *          If the preconditions on the parameter do not hold

     */

    public final CharsetDecoder replaceWith(String newReplacement) {

        if (newReplacement == null)

            throw new IllegalArgumentException("Null replacement");

        int len = newReplacement.length();

        if (len == 0)

            throw new IllegalArgumentException("Empty replacement");

        if (len > maxCharsPerByte)

            throw new IllegalArgumentException("Replacement too long");

        this.replacement = newReplacement;

        implReplaceWith(newReplacement);

        return this;

    }

    /**

     * Reports a change to this decoder's replacement value.

     *

     * <p> The default implementation of this method does nothing.  This method

     * should be overridden by decoders that require notification of changes to

     * the replacement.  </p>

     *

     * @param  newReplacement

     */

    protected void implReplaceWith(String newReplacement) {

    }

    /**

     * Returns this decoder's current action for malformed-input errors.  </p>

     *

     * @return The current malformed-input action, which is never <tt>null</tt>

     */

    public CodingErrorAction malformedInputAction() {

        return malformedInputAction;

    }

    /**

     * Changes this decoder's action for malformed-input errors.  </p>

     *

     * <p> This method invokes the {@link #implOnMalformedInput

     * implOnMalformedInput} method, passing the new action.  </p>

     *

     * @param  newAction  The new action; must not be <tt>null</tt>

     *

     * @return  This decoder

     *

     * @throws IllegalArgumentException

     *         If the precondition on the parameter does not hold

     */

    public final CharsetDecoder onMalformedInput(CodingErrorAction newAction) {

        if (newAction == null)

            throw new IllegalArgumentException("Null action");

        malformedInputAction = newAction;

        implOnMalformedInput(newAction);

        return this;

    }

    /**

     * Reports a change to this decoder's malformed-input action.

     *

     * <p> The default implementation of this method does nothing.  This method

     * should be overridden by decoders that require notification of changes to

     * the malformed-input action.  </p>

     */

    protected void implOnMalformedInput(CodingErrorAction newAction) { }

    /**

     * Returns this decoder's current action for unmappable-character errors.

     * </p>

     *

     * @return The current unmappable-character action, which is never

     *         <tt>null</tt>

     */

    public CodingErrorAction unmappableCharacterAction() {

        return unmappableCharacterAction;

    }

    /**

     * Changes this decoder's action for unmappable-character errors.

     *

     * <p> This method invokes the {@link #implOnUnmappableCharacter

     * implOnUnmappableCharacter} method, passing the new action.  </p>

     *

     * @param  newAction  The new action; must not be <tt>null</tt>

     *

     * @return  This decoder

     *

     * @throws IllegalArgumentException

     *         If the precondition on the parameter does not hold

     */

    public final CharsetDecoder onUnmappableCharacter(CodingErrorAction

                                                      newAction)

    {

        if (newAction == null)

            throw new IllegalArgumentException("Null action");

        unmappableCharacterAction = newAction;

        implOnUnmappableCharacter(newAction);

        return this;

    }

    /**

     * Reports a change to this decoder's unmappable-character action.

     *

     * <p> The default implementation of this method does nothing.  This method

     * should be overridden by decoders that require notification of changes to

     * the unmappable-character action.  </p>

     */

    protected void implOnUnmappableCharacter(CodingErrorAction newAction) { }

    /**

     * Returns the average number of characters that will be produced for each

     * byte of input.  This heuristic value may be used to estimate the size

     * of the output buffer required for a given input sequence. </p>

     *

     * @return  The average number of characters produced

     *          per byte of input

     */

    public final float averageCharsPerByte() {

        return averageCharsPerByte;

    }

    /**

     * Returns the maximum number of characters that will be produced for each

     * byte of input.  This value may be used to compute the worst-case size

     * of the output buffer required for a given input sequence. </p>

     *

     * @return  The maximum number of characters that will be produced per

     *          byte of input

     */

    public final float maxCharsPerByte() {

        return maxCharsPerByte;

    }

    /**

     * Decodes as many bytes as possible from the given input buffer,

     * writing the results to the given output buffer.

     *

     * <p> The buffers are read from, and written to, starting at their current

     * positions.  At most {@link Buffer#remaining in.remaining()} bytes

     * will be read and at most {@link Buffer#remaining out.remaining()}

     * characters will be written.  The buffers' positions will be advanced to

     * reflect the bytes read and the characters written, but their marks and

     * limits will not be modified.

     *

     * <p> In addition to reading bytes from the input buffer and writing

     * characters to the output buffer, this method returns a {@link CoderResult}

     * object to describe its reason for termination:

     *

     * <ul>

     *

     *   <li><p> {@link CoderResult#UNDERFLOW} indicates that as much of the

     *   input buffer as possible has been decoded.  If there is no further

     *   input then the invoker can proceed to the next step of the

     *   <a href="#steps">decoding operation</a>.  Otherwise this method

     *   should be invoked again with further input.  </p></li>

     *

     *   <li><p> {@link CoderResult#OVERFLOW} indicates that there is

     *   insufficient space in the output buffer to decode any more bytes.

     *   This method should be invoked again with an output buffer that has

     *   more {@linkplain Buffer#remaining remaining} characters. This is

     *   typically done by draining any decoded characters from the output

     *   buffer.  </p></li>

     *

     *   <li><p> A {@link CoderResult#malformedForLength

     *   </code>malformed-input<code>} result indicates that a malformed-input

     *   error has been detected.  The malformed bytes begin at the input

     *   buffer's (possibly incremented) position; the number of malformed

     *   bytes may be determined by invoking the result object's {@link

     *   CoderResult#length() length} method.  This case applies only if the

     *   {@link #onMalformedInput </code>malformed action<code>} of this decoder

     *   is {@link CodingErrorAction#REPORT}; otherwise the malformed input

     *   will be ignored or replaced, as requested.  </p></li>

     *

     *   <li><p> An {@link CoderResult#unmappableForLength

     *   </code>unmappable-character<code>} result indicates that an

     *   unmappable-character error has been detected.  The bytes that

     *   decode the unmappable character begin at the input buffer's (possibly

     *   incremented) position; the number of such bytes may be determined

     *   by invoking the result object's {@link CoderResult#length() length}

     *   method.  This case applies only if the {@link #onUnmappableCharacter

     *   </code>unmappable action<code>} of this decoder is {@link

     *   CodingErrorAction#REPORT}; otherwise the unmappable character will be

     *   ignored or replaced, as requested.  </p></li>

     *

     * </ul>

     *

     * In any case, if this method is to be reinvoked in the same decoding

     * operation then care should be taken to preserve any bytes remaining

     * in the input buffer so that they are available to the next invocation.

     *

     * <p> The <tt>endOfInput</tt> parameter advises this method as to whether

     * the invoker can provide further input beyond that contained in the given

     * input buffer.  If there is a possibility of providing additional input

     * then the invoker should pass <tt>false</tt> for this parameter; if there

     * is no possibility of providing further input then the invoker should

     * pass <tt>true</tt>.  It is not erroneous, and in fact it is quite

     * common, to pass <tt>false</tt> in one invocation and later discover that

     * no further input was actually available.  It is critical, however, that

     * the final invocation of this method in a sequence of invocations always

     * pass <tt>true</tt> so that any remaining undecoded input will be treated

     * as being malformed.

     *

     * <p> This method works by invoking the {@link #decodeLoop decodeLoop}

     * method, interpreting its results, handling error conditions, and

     * reinvoking it as necessary.  </p>

     *

     *

     * @param  in

     *         The input byte buffer

     *

     * @param  out

     *         The output character buffer

     *

     * @param  endOfInput

     *         <tt>true</tt> if, and only if, the invoker can provide no

     *         additional input bytes beyond those in the given buffer

     *

     * @return  A coder-result object describing the reason for termination

     *

     * @throws  IllegalStateException

     *          If a decoding operation is already in progress and the previous

     *          step was an invocation neither of the {@link #reset reset}

     *          method, nor of this method with a value of <tt>false</tt> for

     *          the <tt>endOfInput</tt> parameter, nor of this method with a

     *          value of <tt>true</tt> for the <tt>endOfInput</tt> parameter

     *          but a return value indicating an incomplete decoding operation

     *

     * @throws  CoderMalfunctionError

     *          If an invocation of the decodeLoop method threw

     *          an unexpected exception

     */

    public final CoderResult decode(ByteBuffer in, CharBuffer out,

                                    boolean endOfInput)

    {

        int newState = endOfInput ? ST_END : ST_CODING;

        if ((state != ST_RESET) && (state != ST_CODING)

            && !(endOfInput && (state == ST_END)))

            throwIllegalStateException(state, newState);

        state = newState;

        for (;;) {

            CoderResult cr;

            try {

                cr = decodeLoop(in, out);

            } catch (BufferUnderflowException x) {

                throw new CoderMalfunctionError(x);

            } catch (BufferOverflowException x) {

                throw new CoderMalfunctionError(x);

            }

            if (cr.isOverflow())

                return cr;

            if (cr.isUnderflow()) {

                if (endOfInput && in.hasRemaining()) {

                    cr = CoderResult.malformedForLength(in.remaining());

                    // Fall through to malformed-input case

                } else {

                    return cr;

                }

            }

            CodingErrorAction action = null;

            if (cr.isMalformed())

                action = malformedInputAction;

            else if (cr.isUnmappable())

                action = unmappableCharacterAction;

            else

                assert false : cr.toString();

            if (action == CodingErrorAction.REPORT)

                return cr;

            if (action == CodingErrorAction.REPLACE) {

                if (out.remaining() < replacement.length())

                    return CoderResult.OVERFLOW;

                out.put(replacement);

            }

            if ((action == CodingErrorAction.IGNORE)

                || (action == CodingErrorAction.REPLACE)) {

                // Skip erroneous input either way

                in.position(in.position() + cr.length());

                continue;

            }

            assert false;

        }

    }

    /**

     * Flushes this decoder.

     *

     * <p> Some decoders maintain internal state and may need to write some

     * final characters to the output buffer once the overall input sequence has

     * been read.

     *

     * <p> Any additional output is written to the output buffer beginning at

     * its current position.  At most {@link Buffer#remaining out.remaining()}

     * characters will be written.  The buffer's position will be advanced

     * appropriately, but its mark and limit will not be modified.

     *

     * <p> If this method completes successfully then it returns {@link

     * CoderResult#UNDERFLOW}.  If there is insufficient room in the output

     * buffer then it returns {@link CoderResult#OVERFLOW}.  If this happens

     * then this method must be invoked again, with an output buffer that has

     * more room, in order to complete the current <a href="#steps">decoding

     * operation</a>.

     *

     * <p> If this decoder has already been flushed then invoking this method

     * has no effect.

     *

     * <p> This method invokes the {@link #implFlush implFlush} method to

     * perform the actual flushing operation.  </p>

     *

     * @param  out

     *         The output character buffer

     *

     * @return  A coder-result object, either {@link CoderResult#UNDERFLOW} or

     *          {@link CoderResult#OVERFLOW}

     *

     * @throws  IllegalStateException

     *          If the previous step of the current decoding operation was an

     *          invocation neither of the {@link #flush flush} method nor of

     *          the three-argument {@link

     *          #decode(ByteBuffer,CharBuffer,boolean) decode} method

     *          with a value of <tt>true</tt> for the <tt>endOfInput</tt>

     *          parameter

     */

    public final CoderResult flush(CharBuffer out) {

        if (state == ST_END) {

            CoderResult cr = implFlush(out);

            if (cr.isUnderflow())

                state = ST_FLUSHED;

            return cr;

        }

        if (state != ST_FLUSHED)

            throwIllegalStateException(state, ST_FLUSHED);

        return CoderResult.UNDERFLOW; // Already flushed

    }

    /**

     * Flushes this decoder.

     *

     * <p> The default implementation of this method does nothing, and always

     * returns {@link CoderResult#UNDERFLOW}.  This method should be overridden

     * by decoders that may need to write final characters to the output buffer

     * once the entire input sequence has been read. </p>

     *

     * @param  out

     *         The output character buffer

     *

     * @return  A coder-result object, either {@link CoderResult#UNDERFLOW} or

     *          {@link CoderResult#OVERFLOW}

     */

    protected CoderResult implFlush(CharBuffer out) {

        return CoderResult.UNDERFLOW;

    }

    /**

     * Resets this decoder, clearing any internal state.

     *

     * <p> This method resets charset-independent state and also invokes the

     * {@link #implReset() implReset} method in order to perform any

     * charset-specific reset actions.  </p>

     *

     * @return  This decoder

     *

     */

    public final CharsetDecoder reset() {

        implReset();

        state = ST_RESET;

        return this;

    }

    /**

     * Resets this decoder, clearing any charset-specific internal state.

     *

     * <p> The default implementation of this method does nothing.  This method

     * should be overridden by decoders that maintain internal state.  </p>

     */

    protected void implReset() { }

    /**

     * Decodes one or more bytes into one or more characters.

     *

     * <p> This method encapsulates the basic decoding loop, decoding as many

     * bytes as possible until it either runs out of input, runs out of room

     * in the output buffer, or encounters a decoding error.  This method is

     * invoked by the {@link #decode decode} method, which handles result

     * interpretation and error recovery.

     *

     * <p> The buffers are read from, and written to, starting at their current

     * positions.  At most {@link Buffer#remaining in.remaining()} bytes

     * will be read, and at most {@link Buffer#remaining out.remaining()}

     * characters will be written.  The buffers' positions will be advanced to

     * reflect the bytes read and the characters written, but their marks and

     * limits will not be modified.

     *

     * <p> This method returns a {@link CoderResult} object to describe its

     * reason for termination, in the same manner as the {@link #decode decode}

     * method.  Most implementations of this method will handle decoding errors

     * by returning an appropriate result object for interpretation by the

     * {@link #decode decode} method.  An optimized implementation may instead

     * examine the relevant error action and implement that action itself.

     *

     * <p> An implementation of this method may perform arbitrary lookahead by

     * returning {@link CoderResult#UNDERFLOW} until it receives sufficient

     * input.  </p>

     *

     * @param  in

     *         The input byte buffer

     *

     * @param  out

     *         The output character buffer

     *

     * @return  A coder-result object describing the reason for termination

     */

    protected abstract CoderResult decodeLoop(ByteBuffer in,

                                              CharBuffer out);

    /**

     * Convenience method that decodes the remaining content of a single input

     * byte buffer into a newly-allocated character buffer.

     *

     * <p> This method implements an entire <a href="#steps">decoding

     * operation</a>; that is, it resets this decoder, then it decodes the

     * bytes in the given byte buffer, and finally it flushes this

     * decoder.  This method should therefore not be invoked if a decoding

     * operation is already in progress.  </p>

     *

     * @param  in

     *         The input byte buffer

     *

     * @return A newly-allocated character buffer containing the result of the

     *         decoding operation.  The buffer's position will be zero and its

     *         limit will follow the last character written.

     *

     * @throws  IllegalStateException

     *          If a decoding operation is already in progress

     *

     * @throws  MalformedInputException

     *          If the byte sequence starting at the input buffer's current

     *          position is not legal for this charset and the current malformed-input action

     *          is {@link CodingErrorAction#REPORT}

     *

     * @throws  UnmappableCharacterException

     *          If the byte sequence starting at the input buffer's current

     *          position cannot be mapped to an equivalent character sequence and

     *          the current unmappable-character action is {@link

     *          CodingErrorAction#REPORT}

     */

    public final CharBuffer decode(ByteBuffer in)

        throws CharacterCodingException

    {

        int n = (int)(in.remaining() * averageCharsPerByte());

        CharBuffer out = CharBuffer.allocate(n);

        if ((n == 0) && (in.remaining() == 0))

            return out;

        reset();

        for (;;) {

            CoderResult cr = in.hasRemaining() ?

                decode(in, out, true) : CoderResult.UNDERFLOW;

            if (cr.isUnderflow())

                cr = flush(out);

            if (cr.isUnderflow())

                break;

            if (cr.isOverflow()) {

                n = 2*n + 1;    // Ensure progress; n might be 0!

                CharBuffer o = CharBuffer.allocate(n);

                out.flip();

                o.put(out);

                out = o;

                continue;

            }

            cr.throwException();

        }

        out.flip();

        return out;

    }

    /**

     * Tells whether or not this decoder implements an auto-detecting charset.

     *

     * <p> The default implementation of this method always returns

     * <tt>false</tt>; it should be overridden by auto-detecting decoders to

     * return <tt>true</tt>.  </p>

     *

     * @return  <tt>true</tt> if, and only if, this decoder implements an

     *          auto-detecting charset

     */

    public boolean isAutoDetecting() {

        return false;

    }

    /**

     * Tells whether or not this decoder has yet detected a

     * charset&nbsp;&nbsp;<i>(optional operation)</i>.

     *

     * <p> If this decoder implements an auto-detecting charset then at a

     * single point during a decoding operation this method may start returning

     * <tt>true</tt> to indicate that a specific charset has been detected in

     * the input byte sequence.  Once this occurs, the {@link #detectedCharset

     * detectedCharset} method may be invoked to retrieve the detected charset.

     *

     * <p> That this method returns <tt>false</tt> does not imply that no bytes

     * have yet been decoded.  Some auto-detecting decoders are capable of

     * decoding some, or even all, of an input byte sequence without fixing on

     * a particular charset.

     *

     * <p> The default implementation of this method always throws an {@link

     * UnsupportedOperationException}; it should be overridden by

     * auto-detecting decoders to return <tt>true</tt> once the input charset

     * has been determined.  </p>

     *

     * @return  <tt>true</tt> if, and only if, this decoder has detected a

     *          specific charset

     *

     * @throws  UnsupportedOperationException

     *          If this decoder does not implement an auto-detecting charset

     */

    public boolean isCharsetDetected() {

        throw new UnsupportedOperationException();

    }

    /**

     * Retrieves the charset that was detected by this

     * decoder&nbsp;&nbsp;<i>(optional operation)</i>.

     *

     * <p> If this decoder implements an auto-detecting charset then this

     * method returns the actual charset once it has been detected.  After that

     * point, this method returns the same value for the duration of the

     * current decoding operation.  If not enough input bytes have yet been

     * read to determine the actual charset then this method throws an {@link

     * IllegalStateException}.

     *

     * <p> The default implementation of this method always throws an {@link

     * UnsupportedOperationException}; it should be overridden by

     * auto-detecting decoders to return the appropriate value.  </p>

     *

     * @return  The charset detected by this auto-detecting decoder,

     *          or <tt>null</tt> if the charset has not yet been determined

     *

     * @throws  IllegalStateException

     *          If insufficient bytes have been read to determine a charset

     *

     * @throws  UnsupportedOperationException

     *          If this decoder does not implement an auto-detecting charset

     */

    public Charset detectedCharset() {

        throw new UnsupportedOperationException();

    }

    private void throwIllegalStateException(int from, int to) {

        throw new IllegalStateException("Current state = " + stateNames[from]

                                        + ", new state = " + stateNames[to]);

    }

}