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	/*
	* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* 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
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.misc;

	import java.io.OutputStream;
	import java.io.ByteArrayOutputStream;
	import java.io.InputStream;
	import java.io.PushbackInputStream;
	import java.io.ByteArrayInputStream;
	import java.io.IOException;
	import java.nio.ByteBuffer;

	/**
	* This class defines the decoding half of character encoders.
	* A character decoder is an algorithim for transforming 8 bit
	* binary data that has been encoded into text by a character
	* encoder, back into original binary form.
	*
	* The character encoders, in general, have been structured
	* around a central theme that binary data can be encoded into
	* text that has the form:
	*
	* <pre>
	* [Buffer Prefix]
	* [Line Prefix][encoded data atoms][Line Suffix]
	* [Buffer Suffix]
	* </pre>
	*
	* Of course in the simplest encoding schemes, the buffer has no
	* distinct prefix of suffix, however all have some fixed relationship
	* between the text in an 'atom' and the binary data itself.
	*
	* In the CharacterEncoder and CharacterDecoder classes, one complete
	* chunk of data is referred to as a <i>buffer</i>. Encoded buffers
	* are all text, and decoded buffers (sometimes just referred to as
	* buffers) are binary octets.
	*
	* To create a custom decoder, you must, at a minimum, overide three
	* abstract methods in this class.
	* <DL>
	* <DD>bytesPerAtom which tells the decoder how many bytes to
	* expect from decodeAtom
	* <DD>decodeAtom which decodes the bytes sent to it as text.
	* <DD>bytesPerLine which tells the encoder the maximum number of
	* bytes per line.
	* </DL>
	*
	* In general, the character decoders return error in the form of a
	* CEFormatException. The syntax of the detail string is
	* <pre>
	* DecoderClassName: Error message.
	* </pre>
	*
	* Several useful decoders have already been written and are
	* referenced in the See Also list below.
	*
	* @author Chuck McManis
	* @see CEFormatException
	* @see CharacterEncoder
	* @see UCDecoder
	* @see UUDecoder
	* @see BASE64Decoder
	*/

	public abstract class CharacterDecoder {

	/** Return the number of bytes per atom of decoding */
	abstract protected int bytesPerAtom();

	/** Return the maximum number of bytes that can be encoded per line */
	abstract protected int bytesPerLine();

	/** decode the beginning of the buffer, by default this is a NOP. */
	protected void decodeBufferPrefix(PushbackInputStream aStream, OutputStream bStream) throws IOException { }

	/** decode the buffer suffix, again by default it is a NOP. */
	protected void decodeBufferSuffix(PushbackInputStream aStream, OutputStream bStream) throws IOException { }

	/**
	* This method should return, if it knows, the number of bytes
	* that will be decoded. Many formats such as uuencoding provide
	* this information. By default we return the maximum bytes that
	* could have been encoded on the line.
	*/
	protected int decodeLinePrefix(PushbackInputStream aStream, OutputStream bStream) throws IOException {
	return (bytesPerLine());
	}

	/**
	* This method post processes the line, if there are error detection
	* or correction codes in a line, they are generally processed by
	* this method. The simplest version of this method looks for the
	* (newline) character.
	*/
	protected void decodeLineSuffix(PushbackInputStream aStream, OutputStream bStream) throws IOException { }

	/**
	* This method does an actual decode. It takes the decoded bytes and
	* writes them to the OutputStream. The integer <i>l</i> tells the
	* method how many bytes are required. This is always <= bytesPerAtom().
	*/
	protected void decodeAtom(PushbackInputStream aStream, OutputStream bStream, int l) throws IOException {
	throw new CEStreamExhausted();
	}

	/**
	* This method works around the bizarre semantics of BufferedInputStream's
	* read method.
	*/
	protected int readFully(InputStream in, byte buffer[], int offset, int len)
	throws java.io.IOException {
	for (int i = 0; i < len; i++) {
	int q = in.read();
	if (q == -1)
	return ((i == 0) ? -1 : i);
	buffer[i+offset] = (byte)q;
	}
	return len;
	}

	/**
	* Decode the text from the InputStream and write the decoded
	* octets to the OutputStream. This method runs until the stream
	* is exhausted.
	* @exception CEFormatException An error has occurred while decoding
	* @exception CEStreamExhausted The input stream is unexpectedly out of data
	*/
	public void decodeBuffer(InputStream aStream, OutputStream bStream) throws IOException {
	int i;
	int totalBytes = 0;

	PushbackInputStream ps = new PushbackInputStream (aStream);
	decodeBufferPrefix(ps, bStream);
	while (true) {
	int length;

	try {
	length = decodeLinePrefix(ps, bStream);
	for (i = 0; (i+bytesPerAtom()) < length; i += bytesPerAtom()) {
	decodeAtom(ps, bStream, bytesPerAtom());
	totalBytes += bytesPerAtom();
	}
	if ((i + bytesPerAtom()) == length) {
	decodeAtom(ps, bStream, bytesPerAtom());
	totalBytes += bytesPerAtom();
	} else {
	decodeAtom(ps, bStream, length - i);
	totalBytes += (length - i);
	}
	decodeLineSuffix(ps, bStream);
	} catch (CEStreamExhausted e) {
	break;
	}
	}
	decodeBufferSuffix(ps, bStream);
	}

	/**
	* Alternate decode interface that takes a String containing the encoded
	* buffer and returns a byte array containing the data.
	* @exception CEFormatException An error has occurred while decoding
	*/
	public byte decodeBuffer(String inputString)[] throws IOException {
	byte inputBuffer[] = new byte[inputString.length()];
	ByteArrayInputStream inStream;
	ByteArrayOutputStream outStream;

	inputString.getBytes(0, inputString.length(), inputBuffer, 0);
	inStream = new ByteArrayInputStream(inputBuffer);
	outStream = new ByteArrayOutputStream();
	decodeBuffer(inStream, outStream);
	return (outStream.toByteArray());
	}

	/**
	* Decode the contents of the inputstream into a buffer.
	*/
	public byte decodeBuffer(InputStream in)[] throws IOException {
	ByteArrayOutputStream outStream = new ByteArrayOutputStream();
	decodeBuffer(in, outStream);
	return (outStream.toByteArray());
	}

	/**
	* Decode the contents of the String into a ByteBuffer.
	*/
	public ByteBuffer decodeBufferToByteBuffer(String inputString)
	throws IOException {
	return ByteBuffer.wrap(decodeBuffer(inputString));
	}

	/**
	* Decode the contents of the inputStream into a ByteBuffer.
	*/
	public ByteBuffer decodeBufferToByteBuffer(InputStream in)
	throws IOException {
	return ByteBuffer.wrap(decodeBuffer(in));
	}
	}

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