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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.sshd.client.channel;

import java.io.IOException;
import java.io.InputStream;

import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.channel.ChannelOutputStream;
import org.apache.sshd.common.channel.ChannelPipedInputStream;
import org.apache.sshd.common.channel.ChannelPipedOutputStream;
import org.apache.sshd.common.channel.ChannelAsyncInputStream;
import org.apache.sshd.common.channel.ChannelAsyncOutputStream;
import org.apache.sshd.common.future.CloseFuture;

/**
 * TODO Add javadoc
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */

public class ChannelSession extends AbstractClientChannel {

    private Thread streamPumper;

    public ChannelSession() {
        super("session");
    }

    @Override
    protected void doOpen() throws IOException {
        if (streaming == Streaming.Async) {
            asyncIn = new ChannelAsyncOutputStream(this, SshConstants.SSH_MSG_CHANNEL_DATA) {
                @Override
                protected CloseFuture doCloseGracefully() {
                    try {
                        sendEof();
                    } catch (IOException e) {
                        session.exceptionCaught(e);
                    }
                    return super.doCloseGracefully();
                }
            };
            asyncOut = new ChannelAsyncInputStream(this);
            asyncErr = new ChannelAsyncInputStream(this);
        } else {
            invertedIn = new ChannelOutputStream(this, remoteWindow, log, SshConstants.SSH_MSG_CHANNEL_DATA);
            if (out == null) {
                ChannelPipedInputStream pis = new ChannelPipedInputStream(localWindow);
                ChannelPipedOutputStream pos = new ChannelPipedOutputStream(pis);
                out = pos;
                invertedOut = pis;
            }
            if (err == null) {
                ChannelPipedInputStream pis = new ChannelPipedInputStream(localWindow);
                ChannelPipedOutputStream pos = new ChannelPipedOutputStream(pis);
                err = pos;
                invertedErr = pis;
            }
            if (in != null) {
                streamPumper = new Thread("ClientInputStreamPump") {
                    @Override
                    public void run() {
                        pumpInputStream();
                    }
                };
                // Interrupt does not really work and the thread will only exit when
                // the call to read() will return.  So ensure this thread is a daemon
                // to avoid blocking the whole app
                streamPumper.setDaemon(true);
                streamPumper.start();
            }
        }
    }

    @Override
    protected void doCloseImmediately() {
        if (streamPumper != null) {
            streamPumper.interrupt();
            streamPumper = null;
        }
        super.doCloseImmediately();
    }

    protected void pumpInputStream() {
        try {
            byte[] buffer = new byte[remoteWindow.getPacketSize()];
            while (!closeFuture.isClosed()) {
                int len = securedRead(in, buffer, 0, buffer.length);
                if (len > 0) {
                    invertedIn.write(buffer, 0, len);
                    invertedIn.flush();
                } else {
                    sendEof();
                    break;
                }
            }
        } catch (Exception e) {
            if (!isClosing()) {
                log.info("Caught exception", e);
                close(false);
            }
        }
    }

    //
    // On some platforms, a call to System.in.read(new byte[65536], 0,32768) always throws an IOException.
    // So we need to protect against that and chunk the call into smaller calls.
    // This problem was found on Windows, JDK 1.6.0_03-b05.
    //
    protected int securedRead(InputStream in, byte[] buf, int off, int len) throws IOException {
        int n = 0;
        for (;;) {
            int nread = in.read(buf, off + n, Math.min(1024, len - n));
            if (nread <= 0) {
                return (n == 0) ? nread : n;
            }
            n += nread;
            if (n >= len) {
                return n;
            }
            // if not closed but no bytes available, return
            if (in.available() <= 0) {
                return n;
            }
        }
    }

}