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/*
 * JBoss, Home of Professional Open Source
 * Copyright 2009, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jboss.xnio.channels;

import java.nio.channels.ScatteringByteChannel;
import java.nio.ByteBuffer;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

/**
 * A blocking wrapper for a {@code StreamSourceChannel}.  Read operations will block until some data may be transferred.
 * Once any amount of data is read, the operation will return.  If a read timeout is specified, then the read methods
 * will return a 0 if the timeout has elapsed without any data transfer.
 */
public class BlockingReadableByteChannel implements ScatteringByteChannel {
    private final StreamSourceChannel delegate;
    private volatile long readTimeout;

    /**
     * Construct a new instance.
     *
     * @param delegate the channel to forward I/O operations to
     */
    public BlockingReadableByteChannel(final StreamSourceChannel delegate) {
        this.delegate = delegate;
    }

    /**
     * Construct a new instance.
     *
     * @param delegate the channel to forward I/O operations to
     * @param readTimeout the read timeout
     * @param readTimeoutUnit the read timeout unit
     */
    public BlockingReadableByteChannel(final StreamSourceChannel delegate, final long readTimeout, final TimeUnit readTimeoutUnit) {
        if (readTimeout < 0L) {
            throw new IllegalArgumentException("Negative read timeout");
        }
        this.delegate = delegate;
        final long calcTimeout = readTimeoutUnit.toMillis(readTimeout);
        this.readTimeout = readTimeout == 0L ? 0L : calcTimeout < 1L ? 1L : calcTimeout;
    }

    /**
     * Set the read timeout.
     *
     * @param readTimeout the read timeout
     * @param readTimeoutUnit the read timeout unit
     */
    public void setReadTimeout(long readTimeout, TimeUnit readTimeoutUnit) {
        if (readTimeout < 0L) {
            throw new IllegalArgumentException("Negative read timeout");
        }
        final long calcTimeout = readTimeoutUnit.toMillis(readTimeout);
        this.readTimeout = readTimeout == 0L ? 0L : calcTimeout < 1L ? 1L : calcTimeout;
    }

    /**
     * Perform a blocking, scattering read operation.
     *
     * @param dsts the destination buffers
     * @param offset the offset into the destination buffer array
     * @param length the number of buffers to read into
     * @return the number of bytes actually read (will be greater than zero)
     * @throws IOException if an I/O error occurs
     */
    public long read(final ByteBuffer[] dsts, final int offset, final int length) throws IOException {
        final StreamSourceChannel delegate = this.delegate;
        long res;
        final long readTimeout = this.readTimeout;
        if (readTimeout == 0L) {
            while ((res = delegate.read(dsts, offset, length)) == 0L) {
                delegate.awaitReadable();
            }
        } else {
            long now = System.currentTimeMillis();
            final long deadline = now + readTimeout;
            while ((res = delegate.read(dsts, offset, length)) == 0L) {
                if (now >= deadline) {
                    throw new ReadTimeoutException("Read timed out");
                }
                delegate.awaitReadable(deadline - now, TimeUnit.MILLISECONDS);
            }
        }
        return res;
    }

    /**
     * Perform a blocking, scattering read operation.
     *
     * @param dsts the destination buffers
     * @return the number of bytes actually read (will be greater than zero)
     * @throws IOException if an I/O error occurs
     */
    public long read(final ByteBuffer[] dsts) throws IOException {
        return read(dsts, 0, dsts.length);
    }

    /**
     * Perform a blocking read operation.
     *
     * @param dst the destination buffer
     * @return the number of bytes actually read (will be greater than zero)
     * @throws IOException if an I/O error occurs
     */
    public int read(final ByteBuffer dst) throws IOException {
        final StreamSourceChannel delegate = this.delegate;
        int res;
        final long readTimeout = this.readTimeout;
        if (readTimeout == 0L) {
            while ((res = delegate.read(dst)) == 0L) {
                delegate.awaitReadable();
            }
        } else {
            long now = System.currentTimeMillis();
            final long deadline = now + readTimeout;
            while ((res = delegate.read(dst)) == 0L) {
                if (now >= deadline) {
                    throw new ReadTimeoutException("Read timed out");
                }
                delegate.awaitReadable(deadline - now, TimeUnit.MILLISECONDS);
            }
        }
        return res;
    }

    /** {@inheritDoc} */
    public boolean isOpen() {
        return delegate.isOpen();
    }

    /** {@inheritDoc} */
    public void close() throws IOException {
        delegate.close();
    }
}