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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.common.channel;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.OutputStream;

import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.SshException;
import org.apache.sshd.common.util.Buffer;
import org.slf4j.Logger;

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

public class ChannelOutputStream extends OutputStream {

    private final AbstractChannel channel;
    private final Window remoteWindow;
    private final Logger log;
    private final byte cmd;
    private final byte[] b = new byte[1];
    private Buffer buffer;
    private boolean closed;
    private int bufferLength;
    private int lastSize;
    private boolean noDelay = false;

    public ChannelOutputStream(AbstractChannel channel, Window remoteWindow, Logger log, byte cmd) {
        this.channel = channel;
        this.remoteWindow = remoteWindow;
        this.log = log;
        this.cmd = cmd;
        newBuffer(0);
    }

    public void setNoDelay(boolean noDelay) {
        this.noDelay = noDelay;
    }

    public boolean isNoDelay() {
        return noDelay;
    }

    public synchronized void write(int w) throws IOException {
        b[0] = (byte) w;
        write(b, 0, 1);
    }

    public synchronized void write(byte[] buf, int s, int l) throws IOException {
        if (closed) {
            throw new SshException("Already closed");
        }
        while (l > 0) {
            // The maximum amount we should admit without flushing again
            // is enough to make up one full packet within our allowed
            // window size.  We give ourselves a credit equal to the last
            // packet we sent to allow the producer to race ahead and fill
            // out the next packet before we block and wait for space to
            // become available again.
            //
            int _l = Math.min(l, Math.min(remoteWindow.getSize() + lastSize, remoteWindow.getPacketSize()) - bufferLength);
            if (_l <= 0) {
                if (bufferLength > 0) {
                    flush();
                } else {
                    try {
                        remoteWindow.waitForSpace();
                    } catch (WindowClosedException e) {
                        closed = true;
                        throw e;
                    } catch (InterruptedException e) {
                        throw (IOException)new InterruptedIOException().initCause(e);
                    }
                }
                continue;
            }
            buffer.putRawBytes(buf, s, _l);
            bufferLength += _l;
            s += _l;
            l -= _l;
        }
        if (noDelay) {
            flush();
        }
    }

    @Override
    public synchronized void flush() throws IOException {
        if (closed) {
            throw new SshException("Already closed");
        }
        try {
            while (bufferLength > 0) {
                Buffer buf = buffer;
                int total = bufferLength;
                int length = Math.min(Math.min(remoteWindow.waitForSpace(), total), remoteWindow.getPacketSize());
                int pos = buf.wpos();
                buf.wpos(cmd == SshConstants.SSH_MSG_CHANNEL_EXTENDED_DATA ? 14 : 10);
                buf.putInt(length);
                buf.wpos(buf.wpos() + length);
                if (total == length) {
                    newBuffer(length);
                } else {
                    int leftover = total - length;
                    newBuffer(Math.max(leftover, length));
                    buffer.putRawBytes(buf.array(), pos - leftover, leftover);
                    bufferLength = leftover;
                }
                lastSize = length;
                remoteWindow.waitAndConsume(length);
                log.debug("Send {} on channel {}", cmd == SshConstants.SSH_MSG_CHANNEL_DATA ? "SSH_MSG_CHANNEL_DATA" : "SSH_MSG_CHANNEL_EXTENDED_DATA", channel.getId());
                channel.writePacket(buf);
            }
        } catch (WindowClosedException e) {
            closed = true;
            throw e;
        } catch (SshException e) {
            throw e;
        } catch (Exception e) {
            throw new SshException(e);
        }
    }

    @Override
    public synchronized void close() throws IOException {
        flush();
        closed = true;
    }

    private void newBuffer(int size) {
        buffer = channel.getSession().createBuffer(cmd, size <= 0 ? 0 : 12 + size);
        buffer.putInt(channel.getRecipient());
        if (cmd == SshConstants.SSH_MSG_CHANNEL_EXTENDED_DATA) {
            buffer.putInt(1);
        }
        buffer.putInt(0);
        bufferLength = 0;
    }

}