charsetdecoder.java

JAVA基本类源代码,大家可以学习学习!

    /**
     * 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 are no bytes
     *   remaining and the invoker has no further input then the decoding
     *   operation is complete.  Otherwise there is insufficient input for the
     *   operation to proceed, so this method should be invoked again with
     *   further input.  </p></li>
     *
     *   <li><p> {@link CoderResult#OVERFLOW} indicates that the output buffer
     *   is full.  This method should be invoked again with a non-full 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> 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 #reset reset} 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)
	    throwIllegalStateException(state, ST_FLUSHED);
	state = ST_FLUSHED;
	return implFlush(out);
    }