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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.InputStream;
import java.io.PushbackInputStream;

/**
 * A {@link ChunkedInput} that fetches data from an {@link InputStream} chunk by
 * chunk.
 * 
 * Please note that the {@link InputStream} instance that feeds data into
 * {@link ChunkedStream} must implement {@link InputStream#available()} as
 * accurately as possible, rather than using the default implementation.
 * Otherwise, {@link ChunkedStream} will generate many too small chunks or
 * block unnecessarily often.
 */
public class ChunkedStream implements ChunkedInput {

    static final int DEFAULT_CHUNK_SIZE = 8192;

    private final PushbackInputStream in;
    private final int chunkSize;
    private long offset;

    /**
     * Creates a new instance that fetches data from the specified stream.
     */
    public ChunkedStream(InputStream in) {
        this(in, DEFAULT_CHUNK_SIZE);
    }

    /**
     * Creates a new instance that fetches data from the specified stream.
     *
     * @param chunkSize the number of bytes to fetch on each
     *                  {@link #nextChunk()} call
     */
    public ChunkedStream(InputStream in, int chunkSize) {
        if (in == null) {
            throw new NullPointerException("in");
        }
        if (chunkSize <= 0) {
            throw new IllegalArgumentException(
                    "chunkSize: " + chunkSize +
                    " (expected: a positive integer)");
        }

        if (in instanceof PushbackInputStream) {
            this.in = (PushbackInputStream) in;
        } else {
            this.in = new PushbackInputStream(in);
        }
        this.chunkSize = chunkSize;
    }

    /**
     * Returns the number of transferred bytes.
     */
    public long getTransferredBytes() {
        return offset;
    }

    public boolean hasNextChunk() throws Exception {
        int b = in.read();
        if (b < 0) {
            return false;
        } else {
            in.unread(b);
            return true;
        }
    }

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

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

    public Object nextChunk() throws Exception {
        if (!hasNextChunk()) {
            return null;
        }

        final int availableBytes = in.available();
        final int chunkSize;
        if (availableBytes <= 0) {
            chunkSize = this.chunkSize;
        } else {
            chunkSize = Math.min(this.chunkSize, in.available());
        }
        final byte[] chunk = new byte[chunkSize];
        int readBytes = 0;
        for (;;) {
            int localReadBytes = in.read(chunk, readBytes, chunkSize - readBytes);
            if (localReadBytes < 0) {
                break;
            }
            readBytes += localReadBytes;
            offset += localReadBytes;

            if (readBytes == chunkSize) {
                break;
            }
        }

        return wrappedBuffer(chunk, 0, readBytes);
    }
}