/*

 * 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

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 */

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         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

     */

    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("ISO-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);

    }

}