org.eclipse.jgit.storage.dfs.ReadableChannel Maven / Gradle / Ivy
/*
* Copyright (C) 2011, Google Inc.
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Distribution License v1.0 which
* accompanies this distribution, is reproduced below, and is
* available at http://www.eclipse.org/org/documents/edl-v10.php
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* - Neither the name of the Eclipse Foundation, Inc. nor the
* names of its contributors may be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.eclipse.jgit.storage.dfs;
import java.io.IOException;
import java.nio.channels.ReadableByteChannel;
/** Readable random access byte channel from a file. */
public interface ReadableChannel extends ReadableByteChannel {
/**
* Get the current position of the channel.
*
* @return r current offset.
* @throws IOException
* the channel's current position cannot be obtained.
*/
public long position() throws IOException;
/**
* Seek the current position of the channel to a new offset.
*
* @param newPosition
* position to move the channel to. The next read will start from
* here. This should be a multiple of the {@link #blockSize()}.
* @throws IOException
* the position cannot be updated. This may be because the
* channel only supports block aligned IO and the current
* position is not block aligned.
*/
public void position(long newPosition) throws IOException;
/**
* Get the total size of the channel.
*
* Prior to reading from a channel the size might not yet be known.
* Implementors may return -1 until after the first read method call. Once a
* read has been completed, the underlying file size should be available.
*
* @return r total size of the channel; -1 if not yet available.
* @throws IOException
* the size cannot be determined.
*/
public long size() throws IOException;
/**
* Get the recommended alignment for reads.
*
* Starting a read at multiples of the blockSize is more efficient than
* starting a read at any other position. If 0 or -1 the channel does not
* have any specific block size recommendation.
*
* Channels should not recommend large block sizes. Sizes up to 1-4 MiB may
* be reasonable, but sizes above that may be horribly inefficient. The
* {@link DfsBlockCache} favors the alignment suggested by the channel
* rather than the configured size under the assumption that reads are very
* expensive and the channel knows what size is best to access it with.
*
* @return recommended alignment size for randomly positioned reads. Does
* not need to be a power of 2.
*/
public int blockSize();
}