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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.
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 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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package org.scijava.io.nio;

import java.nio.ByteBuffer;
import java.util.function.Function;

import org.scijava.io.ByteBank;

/**
 * A {@link ByteBank} backed by a {@link ByteBuffer}. Self-growing up to a
 * maximal capacity of {@link Integer#MAX_VALUE}
 *
 * @author Gabriel Einsdorf
 */
public class ByteBufferByteBank implements ByteBank {

	private static final int DEFAULT_CAPACITY = 10_000;

	private ByteBuffer buffer;

	private int size;

	private Function provider;

	public ByteBufferByteBank() {
		provider = ByteBuffer::allocate;
		buffer = provider.apply(DEFAULT_CAPACITY);
	}

	public ByteBufferByteBank(final Function provider) {
		this.provider = provider;
		buffer = provider.apply(DEFAULT_CAPACITY);
	}

	public ByteBufferByteBank(final Function provider,
		final int initialCapacity)
	{
		this.provider = provider;
		buffer = provider.apply(initialCapacity);
	}

	public ByteBufferByteBank(final int initialCapacity) {
		provider = ByteBuffer::allocate;
		buffer = provider.apply(initialCapacity);
	}

	@Override
	public long getMaxBufferSize() {
		return Integer.MAX_VALUE;
	}

	@Override
	public void setBytes(final long startpos, final byte[] bytes,
		final int offset, final int length)
	{
		// ensure we have space
		checkWritePos(startpos, startpos + length);
		final int neededCapacity = size + length;
		ensureCapacity(neededCapacity);

		// copy the data
		buffer.position((int) startpos);
		buffer.put(bytes, offset, length);

		// update the maxpos
		updateSize(startpos + length);
	}

	@Override
	public void setByte(final long pos, final byte b) {
		checkWritePos(pos, pos);
		if (pos == buffer.capacity()) {
			ensureCapacity((int) pos + 1);
		}
		buffer.put((int) pos, b);
		updateSize(pos + 1);
	}

	@Override
	public void clear() {
		buffer.clear();
		size = 0;
	}

	@Override
	public byte getByte(final long pos) {
		checkReadPos(pos, pos);
		// the buffer might contain bytes with negative value
		// we need to flip the sign to positive to satisfy the contract of this
		// method
		return buffer.get((int) pos);
	}

	@Override
	public int getBytes(final long startPos, final byte[] b, final int offset,
		final int length)
	{
		checkReadPos(startPos, startPos + length);
		// ensure we don't try to read data which is not in the buffer
		final int readLength = (int) Math.min(size() - startPos, length);
		buffer.position((int) startPos);
		buffer.get(b, offset, readLength);

		return readLength;
	}

	@Override
	public long size() {
		return size;
	}

	@Override
	public boolean isReadOnly() {
		// NB: Some ByteBuffers are read-only. But there is no API to check it.
		// Therefore, we make a "best effort" guess based on known read-only types.
		// Since these read-only types are not public, we compare class names rather
		// than checking for type equality or using instanceof.
		final String className = buffer.getClass().getName();
		return className.equals("java.nio.HeapByteBufferR") ||
			className.equals("java.nio.DirectByteBufferR");
	}

	// -- Helper methods --

	private void ensureCapacity(final int minCapacity) {
		final int oldCapacity = buffer.capacity();
		if (minCapacity <= oldCapacity) return; // no need to grow

		// grow the array by up to 50% (plus a small constant)
		final int growth = Math.min(oldCapacity / 2 + 16, Integer.MAX_VALUE);
		final int newCapacity;
		if (growth > Integer.MAX_VALUE - oldCapacity) {
			// growth would push array over the maximum array size
			newCapacity = Integer.MAX_VALUE;
		}
		else newCapacity = oldCapacity + growth;
		// ensure the array grows by at least the requested minimum capacity
		final int newLength = Math.max(minCapacity, newCapacity);

		// copy the data into a new array
		buffer.position(0);
		final ByteBuffer newBuffer = ByteBuffer.allocate(newLength);
		newBuffer.order(buffer.order());
		newBuffer.put(buffer);
		buffer = newBuffer;
	}

	private void updateSize(final long newSize) {
		size = (int) (newSize > size ? newSize : size);
	}

}