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Java example source code file (DefaultFileRegion.java)

This example Java source code file (DefaultFileRegion.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractreferencecounted, defaultfileregion, deprecated, failed, filechannel, fileregion, illegalargumentexception, illegalreferencecountexception, internallogger, ioexception, nullpointerexception, override, randomaccessfile

The DefaultFileRegion.java Java example source code

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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 io.netty.channel;

import io.netty.util.AbstractReferenceCounted;
import io.netty.util.IllegalReferenceCountException;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;

/**
 * Default {@link FileRegion} implementation which transfer data from a {@link FileChannel} or {@link File}.
 *
 * Be aware that the {@link FileChannel} will be automatically closed once {@link #refCnt()} returns
 * {@code 0}.
 */
public class DefaultFileRegion extends AbstractReferenceCounted implements FileRegion {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultFileRegion.class);
    private final File f;
    private final long position;
    private final long count;
    private long transferred;
    private FileChannel file;

    /**
     * Create a new instance
     *
     * @param file      the {@link FileChannel} which should be transfered
     * @param position  the position from which the transfer should start
     * @param count     the number of bytes to transfer
     */
    public DefaultFileRegion(FileChannel file, long position, long count) {
        if (file == null) {
            throw new NullPointerException("file");
        }
        if (position < 0) {
            throw new IllegalArgumentException("position must be >= 0 but was " + position);
        }
        if (count < 0) {
            throw new IllegalArgumentException("count must be >= 0 but was " + count);
        }
        this.file = file;
        this.position = position;
        this.count = count;
        f = null;
    }

    /**
     * Create a new instance using the given {@link File}. The {@link File} will be opened lazily or
     * explicitly via {@link #open()}.
     *
     * @param f         the {@link File} which should be transfered
     * @param position  the position from which the transfer should start
     * @param count     the number of bytes to transfer
     */
    public DefaultFileRegion(File f, long position, long count) {
        if (f == null) {
            throw new NullPointerException("f");
        }
        if (position < 0) {
            throw new IllegalArgumentException("position must be >= 0 but was " + position);
        }
        if (count < 0) {
            throw new IllegalArgumentException("count must be >= 0 but was " + count);
        }
        this.position = position;
        this.count = count;
        this.f = f;
    }

    /**
     * Returns {@code true} if the {@link FileRegion} has a open file-descriptor
     */
    public boolean isOpen() {
        return file != null;
    }

    /**
     * Explicitly open the underlying file-descriptor if not done yet.
     */
    public void open() throws IOException {
        if (!isOpen() && refCnt() > 0) {
            // Only open if this DefaultFileRegion was not released yet.
            file = new RandomAccessFile(f, "r").getChannel();
        }
    }

    @Override
    public long position() {
        return position;
    }

    @Override
    public long count() {
        return count;
    }

    @Deprecated
    @Override
    public long transfered() {
        return transferred;
    }

    @Override
    public long transferred() {
        return transferred;
    }

    @Override
    public long transferTo(WritableByteChannel target, long position) throws IOException {
        long count = this.count - position;
        if (count < 0 || position < 0) {
            throw new IllegalArgumentException(
                    "position out of range: " + position +
                    " (expected: 0 - " + (this.count - 1) + ')');
        }
        if (count == 0) {
            return 0L;
        }
        if (refCnt() == 0) {
            throw new IllegalReferenceCountException(0);
        }
        // Call open to make sure fc is initialized. This is a no-oop if we called it before.
        open();

        long written = file.transferTo(this.position + position, count, target);
        if (written > 0) {
            transferred += written;
        }
        return written;
    }

    @Override
    protected void deallocate() {
        FileChannel file = this.file;

        if (file == null) {
            return;
        }
        this.file = null;

        try {
            file.close();
        } catch (IOException e) {
            if (logger.isWarnEnabled()) {
                logger.warn("Failed to close a file.", e);
            }
        }
    }

    @Override
    public FileRegion retain() {
        super.retain();
        return this;
    }

    @Override
    public FileRegion retain(int increment) {
        super.retain(increment);
        return this;
    }

    @Override
    public FileRegion touch() {
        return this;
    }

    @Override
    public FileRegion touch(Object hint) {
        return this;
    }
}

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