DfsOutputStream.java

/*
 * Copyright (C) 2011, 2012 Google Inc. and others. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.internal.storage.dfs;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;

import org.eclipse.jgit.internal.storage.pack.PackExt;

/**
 * Output stream to create a file on the DFS.
 *
 * @see DfsObjDatabase#writeFile(DfsPackDescription, PackExt)
 */
public abstract class DfsOutputStream extends OutputStream {
    /**
     * Get the recommended alignment for writing.
     * <p>
     * Starting a write at multiples of the blockSize is more efficient than
     * starting a write at any other position. If 0 or -1 the channel does not
     * have any specific block size recommendation.
     * <p>
     * Channels should not recommend large block sizes. Sizes up to 1-4 MiB may
     * be reasonable, but sizes above that may be horribly inefficient.
     *
     * @return recommended alignment size for randomly positioned reads. Does
     *         not need to be a power of 2.
     */
    public int blockSize() {
        return 0;
    }

    /** {@inheritDoc} */
    @Override
    public void write(int b) throws IOException {
        write(new byte[] { (byte) b });
    }

    /** {@inheritDoc} */
    @Override
    public abstract void write(byte[] buf, int off, int len) throws IOException;

    /**
     * Read back a portion of already written data.
     * <p>
     * The writing position of the output stream is not affected by a read.
     *
     * @param position
     *            offset to read from.
     * @param buf
     *            buffer to populate. Up to {@code buf.remaining()} bytes will
     *            be read from {@code position}.
     * @return number of bytes actually read.
     * @throws java.io.IOException
     *             reading is not supported, or the read cannot be performed due
     *             to DFS errors.
     */
    public abstract int read(long position, ByteBuffer buf) throws IOException;
}