PackFileSnapshot.java

  1. /*
  2.  * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com>
  3.  * and other copyright owners as documented in the project's IP log.
  4.  *
  5.  * This program and the accompanying materials are made available
  6.  * under the terms of the Eclipse Distribution License v1.0 which
  7.  * accompanies this distribution, is reproduced below, and is
  8.  * available at http://www.eclipse.org/org/documents/edl-v10.php
  9.  *
  10.  * All rights reserved.
  11.  *
  12.  * Redistribution and use in source and binary forms, with or
  13.  * without modification, are permitted provided that the following
  14.  * conditions are met:
  15.  *
  16.  * - Redistributions of source code must retain the above copyright
  17.  *   notice, this list of conditions and the following disclaimer.
  18.  *
  19.  * - Redistributions in binary form must reproduce the above
  20.  *   copyright notice, this list of conditions and the following
  21.  *   disclaimer in the documentation and/or other materials provided
  22.  *   with the distribution.
  23.  *
  24.  * - Neither the name of the Eclipse Foundation, Inc. nor the
  25.  *   names of its contributors may be used to endorse or promote
  26.  *   products derived from this software without specific prior
  27.  *   written permission.
  28.  *
  29.  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  30.  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  31.  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  32.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  33.  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  34.  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  35.  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  36.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  37.  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  38.  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  39.  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  40.  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  41.  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  42.  */
  43. package org.eclipse.jgit.internal.storage.file;

  44. import java.io.File;
  45. import java.io.IOException;
  46. import java.io.RandomAccessFile;

  47. import org.eclipse.jgit.lib.AnyObjectId;
  48. import org.eclipse.jgit.lib.ObjectId;

  49. class PackFileSnapshot extends FileSnapshot {

  50.     private static final ObjectId MISSING_CHECKSUM = ObjectId.zeroId();

  51.     /**
  52.      * Record a snapshot for a specific packfile path.
  53.      * <p>
  54.      * This method should be invoked before the packfile is accessed.
  55.      *
  56.      * @param path
  57.      *            the path to later remember. The path's current status
  58.      *            information is saved.
  59.      * @return the snapshot.
  60.      */
  61.     public static PackFileSnapshot save(File path) {
  62.         return new PackFileSnapshot(path);
  63.     }

  64.     private AnyObjectId checksum = MISSING_CHECKSUM;

  65.     private boolean wasChecksumChanged;


  66.     PackFileSnapshot(File packFile) {
  67.         super(packFile);
  68.     }

  69.     void setChecksum(AnyObjectId checksum) {
  70.         this.checksum = checksum;
  71.     }

  72.     /** {@inheritDoc} */
  73.     @Override
  74.     public boolean isModified(File packFile) {
  75.         if (!super.isModified(packFile)) {
  76.             return false;
  77.         }
  78.         if (wasSizeChanged() || wasFileKeyChanged()
  79.                 || !wasLastModifiedRacilyClean()) {
  80.             return true;
  81.         }
  82.         return isChecksumChanged(packFile);
  83.     }

  84.     boolean isChecksumChanged(File packFile) {
  85.         return wasChecksumChanged = checksum != MISSING_CHECKSUM
  86.                 && !checksum.equals(readChecksum(packFile));
  87.     }

  88.     private AnyObjectId readChecksum(File packFile) {
  89.         try (RandomAccessFile fd = new RandomAccessFile(packFile, "r")) { //$NON-NLS-1$
  90.             fd.seek(fd.length() - 20);
  91.             final byte[] buf = new byte[20];
  92.             fd.readFully(buf, 0, 20);
  93.             return ObjectId.fromRaw(buf);
  94.         } catch (IOException e) {
  95.             return MISSING_CHECKSUM;
  96.         }
  97.     }

  98.     boolean wasChecksumChanged() {
  99.         return wasChecksumChanged;
  100.     }

  101.     @SuppressWarnings("nls")
  102.     @Override
  103.     public String toString() {
  104.         return "PackFileSnapshot [checksum=" + checksum + ", "
  105.                 + super.toString() + "]";
  106.     }

  107. }