http://www.eclipse.org/jgit//org.eclipse.jgit: Repository access and algorithms (Eclipse JGit Project)
  • Eclipse Distribution License (New BSD License)
  • Andrey Loskutov
  • Christian Halstrick
  • Dave Borowitz
  • David Pursehouse
  • Gunnar Wagenknecht
  • Jonathan Nieder
  • Jonathan Tan
  • Matthias Sohn
  • Sasa Zivkov
  • Terry Parker
  • Thomas Wolf 
/*
 * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
 * 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.internal.storage.file;

import java.io.IOException;
import java.util.zip.DataFormatException;
import java.util.zip.Inflater;

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


A window of data currently stored within a cache.


All bytes in the window can be assumed to be "immediately available", that is
they are very likely already in memory, unless the operating system's memory
is very low and has paged part of this process out to disk. Therefore copying
bytes from a window is very inexpensive.



/**
 * A window of data currently stored within a cache.
 * <p>
 * All bytes in the window can be assumed to be "immediately available", that is
 * they are very likely already in memory, unless the operating system's memory
 * is very low and has paged part of this process out to disk. Therefore copying
 * bytes from a window is very inexpensive.
 * </p>
 */
abstract class ByteWindow {
	protected final PackFile pack;

	protected final long start;

	protected final long end;

	
Constructor for ByteWindow.

Params:
  • p –  a PackFile.
  • s – 
           where the byte window starts in the pack file
  • n – 
           size of the byte window
/**
	 * Constructor for ByteWindow.
	 *
	 * @param p
	 *            a {@link org.eclipse.jgit.internal.storage.file.PackFile}.
	 * @param s
	 *            where the byte window starts in the pack file
	 * @param n
	 *            size of the byte window
	 */
	protected ByteWindow(PackFile p, long s, int n) {
		pack = p;
		start = s;
		end = start + n;
	}

	final int size() {
		return (int) (end - start);
	}

	final boolean contains(PackFile neededFile, long neededPos) {
		return pack == neededFile && start <= neededPos && neededPos < end;
	}

	
Copy bytes from the window to a caller supplied buffer.

Params:
  • pos – 
           offset within the file to start copying from.
  • dstbuf – 
           destination buffer to copy into.
  • dstoff – 
           offset within dstbuf to start copying into.
  • cnt – 
           number of bytes to copy. This value may exceed the number of
           bytes remaining in the window starting at offset
           pos.
Returns:number of bytes actually copied; this may be less than
        cnt if cnt exceeded the number of
        bytes available.
/**
	 * Copy bytes from the window to a caller supplied buffer.
	 *
	 * @param pos
	 *            offset within the file to start copying from.
	 * @param dstbuf
	 *            destination buffer to copy into.
	 * @param dstoff
	 *            offset within <code>dstbuf</code> to start copying into.
	 * @param cnt
	 *            number of bytes to copy. This value may exceed the number of
	 *            bytes remaining in the window starting at offset
	 *            <code>pos</code>.
	 * @return number of bytes actually copied; this may be less than
	 *         <code>cnt</code> if <code>cnt</code> exceeded the number of
	 *         bytes available.
	 */
	final int copy(long pos, byte[] dstbuf, int dstoff, int cnt) {
		return copy((int) (pos - start), dstbuf, dstoff, cnt);
	}

	
Copy bytes from the window to a caller supplied buffer.

Params:
  • pos – 
           offset within the window to start copying from.
  • dstbuf – 
           destination buffer to copy into.
  • dstoff – 
           offset within dstbuf to start copying into.
  • cnt – 
           number of bytes to copy. This value may exceed the number of
           bytes remaining in the window starting at offset
           pos.
Returns:number of bytes actually copied; this may be less than
        cnt if cnt exceeded the number of
        bytes available.
/**
	 * Copy bytes from the window to a caller supplied buffer.
	 *
	 * @param pos
	 *            offset within the window to start copying from.
	 * @param dstbuf
	 *            destination buffer to copy into.
	 * @param dstoff
	 *            offset within <code>dstbuf</code> to start copying into.
	 * @param cnt
	 *            number of bytes to copy. This value may exceed the number of
	 *            bytes remaining in the window starting at offset
	 *            <code>pos</code>.
	 * @return number of bytes actually copied; this may be less than
	 *         <code>cnt</code> if <code>cnt</code> exceeded the number of
	 *         bytes available.
	 */
	protected abstract int copy(int pos, byte[] dstbuf, int dstoff, int cnt);

	abstract void write(PackOutputStream out, long pos, int cnt)
			throws IOException;

	final int setInput(long pos, Inflater inf) throws DataFormatException {
		return setInput((int) (pos - start), inf);
	}

	
Set the input

Params:
  • pos – 
           position
  • inf –  an Inflater object.
Throws:
Returns:size of the byte window
/**
	 * Set the input
	 *
	 * @param pos
	 *            position
	 * @param inf
	 *            an {@link java.util.zip.Inflater} object.
	 * @return size of the byte window
	 * @throws java.util.zip.DataFormatException
	 *             if any.
	 */
	protected abstract int setInput(int pos, Inflater inf)
			throws DataFormatException;
}