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

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  *

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

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

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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]);

     }

 }