narya/src/java/com/threerings/io/ByteBufferOutputStream.java

//
// $Id$

package com.threerings.io;

import java.io.OutputStream;

import java.nio.BufferOverflowException;
import java.nio.ByteBuffer;

/**
 * Stores output in an {@link ByteBuffer} that grows automatically to accommodate the data.
 */
public class ByteBufferOutputStream extends OutputStream
{
    /**
     * Creates a new byte buffer output stream.
     */
    public ByteBufferOutputStream ()
    {
        _buffer = ByteBuffer.allocate(INITIAL_BUFFER_SIZE);
    }

    /**
     * Returns a reference to the underlying buffer.
     */
    public ByteBuffer getBuffer ()
    {
        return _buffer;
    }

    /**
     * Flips and returns the buffer.  The returned buffer will have a position of zero and a limit
     * equal to the number of bytes written.  Call {@link #reset} to reset the buffer before
     * writing again.
     */
    public ByteBuffer flip ()
    {
        _buffer.flip();
        return _buffer;
    }

    /**
     * Resets our internal buffer.
     */
    public void reset ()
    {
        _buffer.clear();
    }

    @Override // documentation inherited
    public void write (int b)
    {
        try {
            _buffer.put((byte)b);
        } catch (BufferOverflowException boe) {
            expand(1);
            _buffer.put((byte)b);
        }
    }

    @Override // documentation inherited
    public void write (byte[] b, int off, int len)
    {
        // sanity check the arguments
        if ((off < 0) || (off > b.length) || (len < 0) ||
            ((off + len) > b.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }

        try {
            _buffer.put(b, off, len);
        } catch (BufferOverflowException boe) {
            expand(len);
            _buffer.put(b, off, len);
        }
    }

    /**
     * Expands our buffer to accomodate the specified capacity.
     */
    protected final void expand (int needed)
    {
        int ocapacity = _buffer.capacity();
        int ncapacity = _buffer.position() + needed;
        if (ncapacity > ocapacity) {
            // increase the buffer size in large increments
            ncapacity = Math.max(ocapacity << 1, ncapacity);
            ByteBuffer newbuf = ByteBuffer.allocate(ncapacity);
            newbuf.put((ByteBuffer)_buffer.flip());
            _buffer = newbuf;
        }
    }

    /** The buffer in which we store our frame data. */
    protected ByteBuffer _buffer;

    /** The default initial size of the internal buffer. */
    protected static final int INITIAL_BUFFER_SIZE = 32;
}