/*

 * 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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.nio.channels;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.Reader;

import java.io.Writer;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CharsetEncoder;

import java.nio.charset.UnsupportedCharsetException;

import java.nio.channels.spi.AbstractInterruptibleChannel;

import sun.nio.ch.ChannelInputStream;

import sun.nio.cs.StreamDecoder;

import sun.nio.cs.StreamEncoder;

/**

 * Utility methods for channels and streams.

 *

 * <p> This class defines static methods that support the interoperation of the

 * stream classes of the <tt>{@link java.io}</tt> package with the channel

 * classes of this package.  </p>

 *

 *

 * @author Mark Reinhold

 * @author Mike McCloskey

 * @author JSR-51 Expert Group

 * @since 1.4

 */

public final class Channels {

    private Channels() { }              // No instantiation

    private static void checkNotNull(Object o, String name) {

        if (o == null)

            throw new NullPointerException("\"" + name + "\" is null!");

    }

    /**

     * Write all remaining bytes in buffer to the given channel.

     * If the channel is selectable then it must be configured blocking.

     */

    private static void writeFullyImpl(WritableByteChannel ch, ByteBuffer bb)

        throws IOException

    {

        while (bb.remaining() > 0) {

            int n = ch.write(bb);

            if (n <= 0)

                throw new RuntimeException("no bytes written");

        }

    }

    /**

     * Write all remaining bytes in buffer to the given channel.

     *

     * @throws  IllegalBlockingException

     *          If the channel is selectable and configured non-blocking.

     */

    private static void writeFully(WritableByteChannel ch, ByteBuffer bb)

        throws IOException

    {

        if (ch instanceof SelectableChannel) {

            SelectableChannel sc = (SelectableChannel)ch;

            synchronized (sc.blockingLock()) {

                if (!sc.isBlocking())

                    throw new IllegalBlockingModeException();

                writeFullyImpl(ch, bb);

            }

        } else {

            writeFullyImpl(ch, bb);

        }

    }

    // -- Byte streams from channels --

    /**

     * Constructs a stream that reads bytes from the given channel.

     *

     * <p> The <tt>read</tt> methods of the resulting stream will throw an

     * {@link IllegalBlockingModeException} if invoked while the underlying

     * channel is in non-blocking mode.  The stream will not be buffered, and

     * it will not support the {@link InputStream#mark mark} or {@link

     * InputStream#reset reset} methods.  The stream will be safe for access by

     * multiple concurrent threads.  Closing the stream will in turn cause the

     * channel to be closed.  </p>

     *

     * @param  ch

     *         The channel from which bytes will be read

     *

     * @return  A new input stream

     */

    public static InputStream newInputStream(ReadableByteChannel ch) {

        checkNotNull(ch, "ch");

        return new sun.nio.ch.ChannelInputStream(ch);

    }

    /**

     * Constructs a stream that writes bytes to the given channel.

     *

     * <p> The <tt>write</tt> methods of the resulting stream will throw an

     * {@link IllegalBlockingModeException} if invoked while the underlying

     * channel is in non-blocking mode.  The stream will not be buffered.  The

     * stream will be safe for access by multiple concurrent threads.  Closing

     * the stream will in turn cause the channel to be closed.  </p>

     *

     * @param  ch

     *         The channel to which bytes will be written

     *

     * @return  A new output stream

     */

    public static OutputStream newOutputStream(final WritableByteChannel ch) {

        checkNotNull(ch, "ch");

        return new OutputStream() {

                private ByteBuffer bb = null;

                private byte[] bs = null;       // Invoker's previous array

                private byte[] b1 = null;

                public synchronized void write(int b) throws IOException {

                   if (b1 == null)

                        b1 = new byte[1];

                    b1[0] = (byte)b;

                    this.write(b1);

                }

                public synchronized void write(byte[] bs, int off, int len)

                    throws IOException

                {

                    if ((off < 0) || (off > bs.length) || (len < 0) ||

                        ((off + len) > bs.length) || ((off + len) < 0)) {

                        throw new IndexOutOfBoundsException();

                    } else if (len == 0) {

                        return;

                    }

                    ByteBuffer bb = ((this.bs == bs)

                                     ? this.bb

                                     : ByteBuffer.wrap(bs));

                    bb.limit(Math.min(off + len, bb.capacity()));

                    bb.position(off);

                    this.bb = bb;

                    this.bs = bs;

                    Channels.writeFully(ch, bb);

                }

                public void close() throws IOException {

                    ch.close();

                }

            };

    }

    // -- Channels from streams --

    /**

     * Constructs a channel that reads bytes from the given stream.

     *

     * <p> The resulting channel will not be buffered; it will simply redirect

     * its I/O operations to the given stream.  Closing the channel will in

     * turn cause the stream to be closed.  </p>

     *

     * @param  in

     *         The stream from which bytes are to be read

     *

     * @return  A new readable byte channel

     */

    public static ReadableByteChannel newChannel(final InputStream in) {

        checkNotNull(in, "in");

        if (in instanceof FileInputStream &&

            FileInputStream.class.equals(in.getClass())) {

            return ((FileInputStream)in).getChannel();

        }

        return new ReadableByteChannelImpl(in);

    }

    private static class ReadableByteChannelImpl

        extends AbstractInterruptibleChannel    // Not really interruptible

        implements ReadableByteChannel

    {

        InputStream in;

        private static final int TRANSFER_SIZE = 8192;

        private byte buf[] = new byte[0];

        private boolean open = true;

        private Object readLock = new Object();

        ReadableByteChannelImpl(InputStream in) {

            this.in = in;

        }

        public int read(ByteBuffer dst) throws IOException {

            int len = dst.remaining();

            int totalRead = 0;

            int bytesRead = 0;

            synchronized (readLock) {

                while (totalRead < len) {

                    int bytesToRead = Math.min((len - totalRead),

                                               TRANSFER_SIZE);

                    if (buf.length < bytesToRead)

                        buf = new byte[bytesToRead];

                    if ((totalRead > 0) && !(in.available() > 0))

                        break; // block at most once

                    try {

                        begin();

                        bytesRead = in.read(buf, 0, bytesToRead);

                    } finally {

                        end(bytesRead > 0);

                    }

                    if (bytesRead < 0)

                        break;

                    else

                        totalRead += bytesRead;

                    dst.put(buf, 0, bytesRead);

                }

                if ((bytesRead < 0) && (totalRead == 0))

                    return -1;

                return totalRead;

            }

        }

        protected void implCloseChannel() throws IOException {

            in.close();

            open = false;

        }

    }

    /**

     * Constructs a channel that writes bytes to the given stream.

     *

     * <p> The resulting channel will not be buffered; it will simply redirect

     * its I/O operations to the given stream.  Closing the channel will in

     * turn cause the stream to be closed.  </p>

     *

     * @param  out

     *         The stream to which bytes are to be written

     *

     * @return  A new writable byte channel

     */

    public static WritableByteChannel newChannel(final OutputStream out) {

        checkNotNull(out, "out");

        if (out instanceof FileOutputStream &&

            FileOutputStream.class.equals(out.getClass())) {

                return ((FileOutputStream)out).getChannel();

        }

        return new WritableByteChannelImpl(out);

    }

    private static class WritableByteChannelImpl

        extends AbstractInterruptibleChannel    // Not really interruptible

        implements WritableByteChannel

    {

        OutputStream out;

        private static final int TRANSFER_SIZE = 8192;

        private byte buf[] = new byte[0];

        private boolean open = true;

        private Object writeLock = new Object();

        WritableByteChannelImpl(OutputStream out) {

            this.out = out;

        }

        public int write(ByteBuffer src) throws IOException {

            int len = src.remaining();

            int totalWritten = 0;

            synchronized (writeLock) {

                while (totalWritten < len) {

                    int bytesToWrite = Math.min((len - totalWritten),

                                                TRANSFER_SIZE);

                    if (buf.length < bytesToWrite)

                        buf = new byte[bytesToWrite];

                    src.get(buf, 0, bytesToWrite);

                    try {

                        begin();

                        out.write(buf, 0, bytesToWrite);

                    } finally {

                        end(bytesToWrite > 0);

                    }

                    totalWritten += bytesToWrite;

                }

                return totalWritten;

            }

        }

        protected void implCloseChannel() throws IOException {

            out.close();

            open = false;

        }

    }

    // -- Character streams from channels --

    /**

     * Constructs a reader that decodes bytes from the given channel using the

     * given decoder.

     *

     * <p> The resulting stream will contain an internal input buffer of at

     * least <tt>minBufferCap</tt> bytes.  The stream's <tt>read</tt> methods

     * will, as needed, fill the buffer by reading bytes from the underlying

     * channel; if the channel is in non-blocking mode when bytes are to be

     * read then an {@link IllegalBlockingModeException} will be thrown.  The

     * resulting stream will not otherwise be buffered, and it will not support

     * the {@link Reader#mark mark} or {@link Reader#reset reset} methods.

     * Closing the stream will in turn cause the channel to be closed.  </p>

     *

     * @param  ch

     *         The channel from which bytes will be read

     *

     * @param  dec

     *         The charset decoder to be used

     *

     * @param  minBufferCap

     *         The minimum capacity of the internal byte buffer,

     *         or <tt>-1</tt> if an implementation-dependent

     *         default capacity is to be used

     *

     * @return  A new reader

     */

    public static Reader newReader(ReadableByteChannel ch,

                                   CharsetDecoder dec,

                                   int minBufferCap)

    {

        checkNotNull(ch, "ch");

        return StreamDecoder.forDecoder(ch, dec.reset(), minBufferCap);

    }

    /**

     * Constructs a reader that decodes bytes from the given channel according