http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
/*
 * 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.buffer;

import io.netty.util.ReferenceCounted;

import java.io.DataInput;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;


An InputStream which reads data from a ByteBuf. 
 A read operation against this stream will occur at the readerIndex of its underlying buffer and the readerIndex will increase during the read operation. Please note that it only reads up to the number of readable bytes determined at the moment of construction. Therefore, updating ByteBuf.writerIndex() will not affect the return value of available(). 
 This stream implements DataInput for your convenience. The endianness of the stream is not always big endian but depends on the endianness of the underlying buffer. 
See Also:
/**
 * An {@link InputStream} which reads data from a {@link ByteBuf}.
 * <p>
 * A read operation against this stream will occur at the {@code readerIndex}
 * of its underlying buffer and the {@code readerIndex} will increase during
 * the read operation.  Please note that it only reads up to the number of
 * readable bytes determined at the moment of construction.  Therefore,
 * updating {@link ByteBuf#writerIndex()} will not affect the return
 * value of {@link #available()}.
 * <p>
 * This stream implements {@link DataInput} for your convenience.
 * The endianness of the stream is not always big endian but depends on
 * the endianness of the underlying buffer.
 *
 * @see ByteBufOutputStream
 */
public class ByteBufInputStream extends InputStream implements DataInput {
    private final ByteBuf buffer;
    private final int startIndex;
    private final int endIndex;
    private boolean closed;
    
To preserve backwards compatibility (which didn't transfer ownership) we support a conditional flag which indicates if buffer should be released when this InputStream is closed. However in future releases ownership should always be transferred and callers of this class should call ReferenceCounted.retain() if necessary. 
/**
     * To preserve backwards compatibility (which didn't transfer ownership) we support a conditional flag which
     * indicates if {@link #buffer} should be released when this {@link InputStream} is closed.
     * However in future releases ownership should always be transferred and callers of this class should call
     * {@link ReferenceCounted#retain()} if necessary.
     */
    private final boolean releaseOnClose;

    
Creates a new stream which reads data from the specified buffer starting at the current readerIndex and ending at the current writerIndex. 
Params:
  • buffer – The buffer which provides the content for this InputStream.
/**
     * Creates a new stream which reads data from the specified {@code buffer}
     * starting at the current {@code readerIndex} and ending at the current
     * {@code writerIndex}.
     * @param buffer The buffer which provides the content for this {@link InputStream}.
     */
    public ByteBufInputStream(ByteBuf buffer) {
        this(buffer, buffer.readableBytes());
    }

    
Creates a new stream which reads data from the specified buffer starting at the current readerIndex and ending at readerIndex + length. 
Params:
  • buffer – The buffer which provides the content for this InputStream.
  • length – The length of the buffer to use for this InputStream.
Throws:
/**
     * Creates a new stream which reads data from the specified {@code buffer}
     * starting at the current {@code readerIndex} and ending at
     * {@code readerIndex + length}.
     * @param buffer The buffer which provides the content for this {@link InputStream}.
     * @param length The length of the buffer to use for this {@link InputStream}.
     * @throws IndexOutOfBoundsException
     *         if {@code readerIndex + length} is greater than
     *            {@code writerIndex}
     */
    public ByteBufInputStream(ByteBuf buffer, int length) {
        this(buffer, length, false);
    }

    
Creates a new stream which reads data from the specified buffer starting at the current readerIndex and ending at the current writerIndex. 
Params:
/**
     * Creates a new stream which reads data from the specified {@code buffer}
     * starting at the current {@code readerIndex} and ending at the current
     * {@code writerIndex}.
     * @param buffer The buffer which provides the content for this {@link InputStream}.
     * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link ByteBuf#release()} will
     *                       be called on {@code buffer}.
     */
    public ByteBufInputStream(ByteBuf buffer, boolean releaseOnClose) {
        this(buffer, buffer.readableBytes(), releaseOnClose);
    }

    
Creates a new stream which reads data from the specified buffer starting at the current readerIndex and ending at readerIndex + length. 
Params:
Throws:
/**
     * Creates a new stream which reads data from the specified {@code buffer}
     * starting at the current {@code readerIndex} and ending at
     * {@code readerIndex + length}.
     * @param buffer The buffer which provides the content for this {@link InputStream}.
     * @param length The length of the buffer to use for this {@link InputStream}.
     * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link ByteBuf#release()} will
     *                       be called on {@code buffer}.
     * @throws IndexOutOfBoundsException
     *         if {@code readerIndex + length} is greater than
     *            {@code writerIndex}
     */
    public ByteBufInputStream(ByteBuf buffer, int length, boolean releaseOnClose) {
        if (buffer == null) {
            throw new NullPointerException("buffer");
        }
        if (length < 0) {
            if (releaseOnClose) {
                buffer.release();
            }
            throw new IllegalArgumentException("length: " + length);
        }
        if (length > buffer.readableBytes()) {
            if (releaseOnClose) {
                buffer.release();
            }
            throw new IndexOutOfBoundsException("Too many bytes to be read - Needs "
                    + length + ", maximum is " + buffer.readableBytes());
        }

        this.releaseOnClose = releaseOnClose;
        this.buffer = buffer;
        startIndex = buffer.readerIndex();
        endIndex = startIndex + length;
        buffer.markReaderIndex();
    }

    
Returns the number of read bytes by this stream so far.

/**
     * Returns the number of read bytes by this stream so far.
     */
    public int readBytes() {
        return buffer.readerIndex() - startIndex;
    }

    @Override
    public void close() throws IOException {
        try {
            super.close();
        } finally {
            // The Closable interface says "If the stream is already closed then invoking this method has no effect."
            if (releaseOnClose && !closed) {
                closed = true;
                buffer.release();
            }
        }
    }

    @Override
    public int available() throws IOException {
        return endIndex - buffer.readerIndex();
    }

    @Override
    public void mark(int readlimit) {
        buffer.markReaderIndex();
    }

    @Override
    public boolean markSupported() {
        return true;
    }

    @Override
    public int read() throws IOException {
        if (!buffer.isReadable()) {
            return -1;
        }
        return buffer.readByte() & 0xff;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int available = available();
        if (available == 0) {
            return -1;
        }

        len = Math.min(available, len);
        buffer.readBytes(b, off, len);
        return len;
    }

    @Override
    public void reset() throws IOException {
        buffer.resetReaderIndex();
    }

    @Override
    public long skip(long n) throws IOException {
        if (n > Integer.MAX_VALUE) {
            return skipBytes(Integer.MAX_VALUE);
        } else {
            return skipBytes((int) n);
        }
    }

    @Override
    public boolean readBoolean() throws IOException {
        checkAvailable(1);
        return read() != 0;
    }

    @Override
    public byte readByte() throws IOException {
        if (!buffer.isReadable()) {
            throw new EOFException();
        }
        return buffer.readByte();
    }

    @Override
    public char readChar() throws IOException {
        return (char) readShort();
    }

    @Override
    public double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    @Override
    public float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    @Override
    public void readFully(byte[] b) throws IOException {
        readFully(b, 0, b.length);
    }

    @Override
    public void readFully(byte[] b, int off, int len) throws IOException {
        checkAvailable(len);
        buffer.readBytes(b, off, len);
    }

    @Override
    public int readInt() throws IOException {
        checkAvailable(4);
        return buffer.readInt();
    }

    private final StringBuilder lineBuf = new StringBuilder();

    @Override
    public String readLine() throws IOException {
        lineBuf.setLength(0);

        loop: while (true) {
            if (!buffer.isReadable()) {
                return lineBuf.length() > 0 ? lineBuf.toString() : null;
            }

            int c = buffer.readUnsignedByte();
            switch (c) {
                case '\n':
                    break loop;

                case '\r':
                    if (buffer.isReadable() && (char) buffer.getUnsignedByte(buffer.readerIndex()) == '\n') {
                        buffer.skipBytes(1);
                    }
                    break loop;

                default:
                    lineBuf.append((char) c);
            }
        }

        return lineBuf.toString();
    }

    @Override
    public long readLong() throws IOException {
        checkAvailable(8);
        return buffer.readLong();
    }

    @Override
    public short readShort() throws IOException {
        checkAvailable(2);
        return buffer.readShort();
    }

    @Override
    public String readUTF() throws IOException {
        return DataInputStream.readUTF(this);
    }

    @Override
    public int readUnsignedByte() throws IOException {
        return readByte() & 0xff;
    }

    @Override
    public int readUnsignedShort() throws IOException {
        return readShort() & 0xffff;
    }

    @Override
    public int skipBytes(int n) throws IOException {
        int nBytes = Math.min(available(), n);
        buffer.skipBytes(nBytes);
        return nBytes;
    }

    private void checkAvailable(int fieldSize) throws IOException {
        if (fieldSize < 0) {
            throw new IndexOutOfBoundsException("fieldSize cannot be a negative number");
        }
        if (fieldSize > available()) {
            throw new EOFException("fieldSize is too long! Length is " + fieldSize
                    + ", but maximum is " + available());
        }
    }
}