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Java example source code file (ChunkedNioFile.java)

This example Java source code file (ChunkedNioFile.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

bytebuf, chunkedinput, chunkedniofile, deprecated, exception, filechannel, illegalargumentexception, ioexception, nullpointerexception, override

The ChunkedNioFile.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.handler.stream;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.FileRegion;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

/**
 * A {@link ChunkedInput} that fetches data from a file chunk by chunk using
 * NIO {@link FileChannel}.
 * <p>
 * If your operating system supports
 * <a href="http://en.wikipedia.org/wiki/Zero-copy">zero-copy file transfer
 * such as {@code sendfile()}, you might want to use {@link FileRegion} instead.
 */
public class ChunkedNioFile implements ChunkedInput<ByteBuf> {

    private final FileChannel in;
    private final long startOffset;
    private final long endOffset;
    private final int chunkSize;
    private long offset;

    /**
     * Creates a new instance that fetches data from the specified file.
     */
    public ChunkedNioFile(File in) throws IOException {
        this(new FileInputStream(in).getChannel());
    }

    /**
     * Creates a new instance that fetches data from the specified file.
     *
     * @param chunkSize the number of bytes to fetch on each
     *                  {@link #readChunk(ChannelHandlerContext)} call
     */
    public ChunkedNioFile(File in, int chunkSize) throws IOException {
        this(new FileInputStream(in).getChannel(), chunkSize);
    }

    /**
     * Creates a new instance that fetches data from the specified file.
     */
    public ChunkedNioFile(FileChannel in) throws IOException {
        this(in, ChunkedStream.DEFAULT_CHUNK_SIZE);
    }

    /**
     * Creates a new instance that fetches data from the specified file.
     *
     * @param chunkSize the number of bytes to fetch on each
     *                  {@link #readChunk(ChannelHandlerContext)} call
     */
    public ChunkedNioFile(FileChannel in, int chunkSize) throws IOException {
        this(in, 0, in.size(), chunkSize);
    }

    /**
     * Creates a new instance that fetches data from the specified file.
     *
     * @param offset the offset of the file where the transfer begins
     * @param length the number of bytes to transfer
     * @param chunkSize the number of bytes to fetch on each
     *                  {@link #readChunk(ChannelHandlerContext)} call
     */
    public ChunkedNioFile(FileChannel in, long offset, long length, int chunkSize)
            throws IOException {
        if (in == null) {
            throw new NullPointerException("in");
        }
        if (offset < 0) {
            throw new IllegalArgumentException(
                    "offset: " + offset + " (expected: 0 or greater)");
        }
        if (length < 0) {
            throw new IllegalArgumentException(
                    "length: " + length + " (expected: 0 or greater)");
        }
        if (chunkSize <= 0) {
            throw new IllegalArgumentException(
                    "chunkSize: " + chunkSize +
                    " (expected: a positive integer)");
        }

        if (offset != 0) {
            in.position(offset);
        }
        this.in = in;
        this.chunkSize = chunkSize;
        this.offset = startOffset = offset;
        endOffset = offset + length;
    }

    /**
     * Returns the offset in the file where the transfer began.
     */
    public long startOffset() {
        return startOffset;
    }

    /**
     * Returns the offset in the file where the transfer will end.
     */
    public long endOffset() {
        return endOffset;
    }

    /**
     * Returns the offset in the file where the transfer is happening currently.
     */
    public long currentOffset() {
        return offset;
    }

    @Override
    public boolean isEndOfInput() throws Exception {
        return !(offset < endOffset && in.isOpen());
    }

    @Override
    public void close() throws Exception {
        in.close();
    }

    @Deprecated
    @Override
    public ByteBuf readChunk(ChannelHandlerContext ctx) throws Exception {
        return readChunk(ctx.alloc());
    }

    @Override
    public ByteBuf readChunk(ByteBufAllocator allocator) throws Exception {
        long offset = this.offset;
        if (offset >= endOffset) {
            return null;
        }

        int chunkSize = (int) Math.min(this.chunkSize, endOffset - offset);
        ByteBuf buffer = allocator.buffer(chunkSize);
        boolean release = true;
        try {
            int readBytes = 0;
            for (;;) {
                int localReadBytes = buffer.writeBytes(in, chunkSize - readBytes);
                if (localReadBytes < 0) {
                    break;
                }
                readBytes += localReadBytes;
                if (readBytes == chunkSize) {
                    break;
                }
            }
            this.offset += readBytes;
            release = false;
            return buffer;
        } finally {
            if (release) {
                buffer.release();
            }
        }
    }

    @Override
    public long length() {
        return endOffset - startOffset;
    }

    @Override
    public long progress() {
        return offset - startOffset;
    }
}

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