Back to index...

	/*
	* Copyright (c) 1995, 2005, 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.InputStream;
	import java.io.ByteArrayInputStream;
	import java.io.OutputStream;
	import java.io.ByteArrayOutputStream;
	import java.io.PrintStream;
	import java.io.IOException;
	import java.nio.ByteBuffer;


	/**
	* This class defines the encoding half of character encoders.
	* A character encoder is an algorithim for transforming 8 bit binary
	* data into text (generally 7 bit ASCII or 8 bit ISO-Latin-1 text)
	* for transmition over text channels such as e-mail and network news.
	*
	* The character encoders have been structured around a central theme
	* that, in general, the encoded text has the form:
	*
	* <pre>
	* [Buffer Prefix]
	* [Line Prefix][encoded data atoms][Line Suffix]
	* [Buffer Suffix]
	* </pre>
	*
	* 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 encoder, you must, at a minimum, overide three
	* abstract methods in this class.
	* <DL>
	* <DD>bytesPerAtom which tells the encoder how many bytes to
	* send to encodeAtom
	* <DD>encodeAtom which encodes the bytes sent to it as text.
	* <DD>bytesPerLine which tells the encoder the maximum number of
	* bytes per line.
	* </DL>
	*
	* Several useful encoders have already been written and are
	* referenced in the See Also list below.
	*
	* @author Chuck McManis
	* @see CharacterDecoder;
	* @see UCEncoder
	* @see UUEncoder
	* @see BASE64Encoder
	*/
	public abstract class CharacterEncoder {

	/** Stream that understands "printing" */
	protected PrintStream pStream;

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

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

	/**
	* Encode the prefix for the entire buffer. By default is simply
	* opens the PrintStream for use by the other functions.
	*/
	protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
	pStream = new PrintStream(aStream);
	}

	/**
	* Encode the suffix for the entire buffer.
	*/
	protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
	}

	/**
	* Encode the prefix that starts every output line.
	*/
	protected void encodeLinePrefix(OutputStream aStream, int aLength)
	throws IOException {
	}

	/**
	* Encode the suffix that ends every output line. By default
	* this method just prints a <newline> into the output stream.
	*/
	protected void encodeLineSuffix(OutputStream aStream) throws IOException {
	pStream.println();
	}

	/** Encode one "atom" of information into characters. */
	abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
	int anOffset, int aLength) throws IOException;

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

	/**
	* Encode bytes from the input stream, and write them as text characters
	* to the output stream. This method will run until it exhausts the
	* input stream, but does not print the line suffix for a final
	* line that is shorter than bytesPerLine().
	*/
	public void encode(InputStream inStream, OutputStream outStream)
	throws IOException {
	int j;
	int numBytes;
	byte tmpbuffer[] = new byte[bytesPerLine()];

	encodeBufferPrefix(outStream);

	while (true) {
	numBytes = readFully(inStream, tmpbuffer);
	if (numBytes == 0) {
	break;
	}
	encodeLinePrefix(outStream, numBytes);
	for (j = 0; j < numBytes; j += bytesPerAtom()) {

	if ((j + bytesPerAtom()) <= numBytes) {
	encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
	} else {
	encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
	}
	}
	if (numBytes < bytesPerLine()) {
	break;
	} else {
	encodeLineSuffix(outStream);
	}
	}
	encodeBufferSuffix(outStream);
	}

	/**
	* Encode the buffer in <i>aBuffer</i> and write the encoded
	* result to the OutputStream <i>aStream</i>.
	*/
	public void encode(byte aBuffer[], OutputStream aStream)
	throws IOException {
	ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
	encode(inStream, aStream);
	}

	/**
	* A 'streamless' version of encode that simply takes a buffer of
	* bytes and returns a string containing the encoded buffer.
	*/
	public String encode(byte aBuffer[]) {
	ByteArrayOutputStream outStream = new ByteArrayOutputStream();
	ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
	String retVal = null;
	try {
	encode(inStream, outStream);
	// explicit ascii->unicode conversion
	retVal = outStream.toString("8859_1");
	} catch (Exception IOException) {
	// This should never happen.
	throw new Error("CharacterEncoder.encode internal error");
	}
	return (retVal);
	}

	/**
	* Return a byte array from the remaining bytes in this ByteBuffer.
	* <P>
	* The ByteBuffer's position will be advanced to ByteBuffer's limit.
	* <P>
	* To avoid an extra copy, the implementation will attempt to return the
	* byte array backing the ByteBuffer. If this is not possible, a
	* new byte array will be created.
	*/
	private byte [] getBytes(ByteBuffer bb) {
	/*
	* This should never return a BufferOverflowException, as we're
	* careful to allocate just the right amount.
	*/
	byte [] buf = null;

	/*
	* If it has a usable backing byte buffer, use it. Use only
	* if the array exactly represents the current ByteBuffer.
	*/
	if (bb.hasArray()) {
	byte [] tmp = bb.array();
	if ((tmp.length == bb.capacity()) &&
	(tmp.length == bb.remaining())) {
	buf = tmp;
	bb.position(bb.limit());
	}
	}

	if (buf == null) {
	/*
	* This class doesn't have a concept of encode(buf, len, off),
	* so if we have a partial buffer, we must reallocate
	* space.
	*/
	buf = new byte[bb.remaining()];

	/*
	* position() automatically updated
	*/
	bb.get(buf);
	}

	return buf;
	}

	/**
	* Encode the <i>aBuffer</i> ByteBuffer and write the encoded
	* result to the OutputStream <i>aStream</i>.
	* <P>
	* The ByteBuffer's position will be advanced to ByteBuffer's limit.
	*/
	public void encode(ByteBuffer aBuffer, OutputStream aStream)
	throws IOException {
	byte [] buf = getBytes(aBuffer);
	encode(buf, aStream);
	}

	/**
	* A 'streamless' version of encode that simply takes a ByteBuffer
	* and returns a string containing the encoded buffer.
	* <P>
	* The ByteBuffer's position will be advanced to ByteBuffer's limit.
	*/
	public String encode(ByteBuffer aBuffer) {
	byte [] buf = getBytes(aBuffer);
	return encode(buf);
	}

	/**
	* Encode bytes from the input stream, and write them as text characters
	* to the output stream. This method will run until it exhausts the
	* input stream. It differs from encode in that it will add the
	* line at the end of a final line that is shorter than bytesPerLine().
	*/
	public void encodeBuffer(InputStream inStream, OutputStream outStream)
	throws IOException {
	int j;
	int numBytes;
	byte tmpbuffer[] = new byte[bytesPerLine()];

	encodeBufferPrefix(outStream);

	while (true) {
	numBytes = readFully(inStream, tmpbuffer);
	if (numBytes == 0) {
	break;
	}
	encodeLinePrefix(outStream, numBytes);
	for (j = 0; j < numBytes; j += bytesPerAtom()) {
	if ((j + bytesPerAtom()) <= numBytes) {
	encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
	} else {
	encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
	}
	}
	encodeLineSuffix(outStream);
	if (numBytes < bytesPerLine()) {
	break;
	}
	}
	encodeBufferSuffix(outStream);
	}

	/**
	* Encode the buffer in <i>aBuffer</i> and write the encoded
	* result to the OutputStream <i>aStream</i>.
	*/
	public void encodeBuffer(byte aBuffer[], OutputStream aStream)
	throws IOException {
	ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
	encodeBuffer(inStream, aStream);
	}

	/**
	* A 'streamless' version of encode that simply takes a buffer of
	* bytes and returns a string containing the encoded buffer.
	*/
	public String encodeBuffer(byte aBuffer[]) {
	ByteArrayOutputStream outStream = new ByteArrayOutputStream();
	ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
	try {
	encodeBuffer(inStream, outStream);
	} catch (Exception IOException) {
	// This should never happen.
	throw new Error("CharacterEncoder.encodeBuffer internal error");
	}
	return (outStream.toString());
	}

	/**
	* Encode the <i>aBuffer</i> ByteBuffer and write the encoded
	* result to the OutputStream <i>aStream</i>.
	* <P>
	* The ByteBuffer's position will be advanced to ByteBuffer's limit.
	*/
	public void encodeBuffer(ByteBuffer aBuffer, OutputStream aStream)
	throws IOException {
	byte [] buf = getBytes(aBuffer);
	encodeBuffer(buf, aStream);
	}

	/**
	* A 'streamless' version of encode that simply takes a ByteBuffer
	* and returns a string containing the encoded buffer.
	* <P>
	* The ByteBuffer's position will be advanced to ByteBuffer's limit.
	*/
	public String encodeBuffer(ByteBuffer aBuffer) {
	byte [] buf = getBytes(aBuffer);
	return encodeBuffer(buf);
	}

	}

Back to index...