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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * 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 org.jboss.netty.handler.stream;

import static org.jboss.netty.buffer.ChannelBuffers.*;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

import org.jboss.netty.channel.FileRegion;

/**
 * A {@link ChunkedInput} that fetches data from a file chunk by chunk.
 * 
 * If your operating system supports
 * zero-copy file transfer
 * such as {@code sendfile()}, you might want to use {@link FileRegion} instead.
 */
public class ChunkedFile implements ChunkedInput {

    private final RandomAccessFile file;
    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 ChunkedFile(File file) throws IOException {
        this(file, 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 #nextChunk()} call
     */
    public ChunkedFile(File file, int chunkSize) throws IOException {
        this(new RandomAccessFile(file, "r"), chunkSize);
    }

    /**
     * Creates a new instance that fetches data from the specified file.
     */
    public ChunkedFile(RandomAccessFile file) throws IOException {
        this(file, 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 #nextChunk()} call
     */
    public ChunkedFile(RandomAccessFile file, int chunkSize) throws IOException {
        this(file, 0, file.length(), 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 #nextChunk()} call
     */
    public ChunkedFile(RandomAccessFile file, long offset, long length, int chunkSize) throws IOException {
        if (file == null) {
            throw new NullPointerException("file");
        }
        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)");
        }

        this.file = file;
        this.offset = startOffset = offset;
        endOffset = offset + length;
        this.chunkSize = chunkSize;

        file.seek(offset);
    }

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

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

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

    public boolean hasNextChunk() throws Exception {
        return offset < endOffset && file.getChannel().isOpen();
    }

    public boolean isEndOfInput() throws Exception {
        return !hasNextChunk();
    }

    public void close() throws Exception {
        file.close();
    }

    public Object nextChunk() throws Exception {
        long offset = this.offset;
        if (offset >= endOffset) {
            return null;
        }

        int chunkSize = (int) Math.min(this.chunkSize, endOffset - offset);
        byte[] chunk = new byte[chunkSize];
        file.readFully(chunk);
        this.offset = offset + chunkSize;
        return wrappedBuffer(chunk);
    }
}