BitmapWalker.java

  1. /*
  2.  * Copyright (C) 2012, Google Inc.
  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
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  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
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  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.  */

  44. package org.eclipse.jgit.revwalk;

  46. import java.io.IOException;
  47. import java.util.Arrays;

  49. import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  50. import org.eclipse.jgit.errors.MissingObjectException;
  51. import org.eclipse.jgit.internal.revwalk.AddToBitmapFilter;
  52. import org.eclipse.jgit.internal.revwalk.AddUnseenToBitmapFilter;
  53. import org.eclipse.jgit.lib.AnyObjectId;
  54. import org.eclipse.jgit.lib.BitmapIndex;
  55. import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
  56. import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
  57. import org.eclipse.jgit.lib.NullProgressMonitor;
  58. import org.eclipse.jgit.lib.ObjectId;
  59. import org.eclipse.jgit.lib.ProgressMonitor;
  60. import org.eclipse.jgit.revwalk.filter.ObjectFilter;

  62. /**
  63.  * Helper class to do ObjectWalks with pack index bitmaps.
  64.  *
  65.  * @since 4.10
  66.  */
  67. public final class BitmapWalker {

  69.     private final ObjectWalk walker;

  71.     private final BitmapIndex bitmapIndex;

  73.     private final ProgressMonitor pm;

  75.     private long countOfBitmapIndexMisses;

  77.     /**
  78.      * Create a BitmapWalker.
  79.      *
  80.      * @param walker walker to use when traversing the object graph.
  81.      * @param bitmapIndex index to obtain bitmaps from.
  82.      * @param pm progress monitor to report progress on.
  83.      */
  84.     public BitmapWalker(
  85.             ObjectWalk walker, BitmapIndex bitmapIndex, ProgressMonitor pm) {
  86.         this.walker = walker;
  87.         this.bitmapIndex = bitmapIndex;
  88.         this.pm = (pm == null) ? NullProgressMonitor.INSTANCE : pm;
  89.     }

  91.     /**
  92.      * Return the number of objects that had to be walked because they were not covered by a
  93.      * bitmap.
  94.      *
  95.      * @return the number of objects that had to be walked because they were not covered by a
  96.      *     bitmap.
  97.      */
  98.     public long getCountOfBitmapIndexMisses() {
  99.         return countOfBitmapIndexMisses;
  100.     }

  102.     /**
  103.      * Return, as a bitmap, the objects reachable from the objects in start.
  104.      *
  105.      * @param start
  106.      *            the objects to start the object traversal from.
  107.      * @param seen
  108.      *            the objects to skip if encountered during traversal.
  109.      * @param ignoreMissing
  110.      *            true to ignore missing objects, false otherwise.
  111.      * @return as a bitmap, the objects reachable from the objects in start.
  112.      * @throws org.eclipse.jgit.errors.MissingObjectException
  113.      *             the object supplied is not available from the object
  114.      *             database. This usually indicates the supplied object is
  115.      *             invalid, but the reference was constructed during an earlier
  116.      *             invocation to
  117.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}.
  118.      * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
  119.      *             the object was not parsed yet and it was discovered during
  120.      *             parsing that it is not actually the type of the instance
  121.      *             passed in. This usually indicates the caller used the wrong
  122.      *             type in a
  123.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}
  124.      *             call.
  125.      * @throws java.io.IOException
  126.      *             a pack file or loose object could not be read.
  127.      */
  128.     public BitmapBuilder findObjects(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  129.             boolean ignoreMissing)
  130.             throws MissingObjectException, IncorrectObjectTypeException,
  131.                    IOException {
  132.         if (!ignoreMissing) {
  133.             return findObjectsWalk(start, seen, false);
  134.         }

  136.         try {
  137.             return findObjectsWalk(start, seen, true);
  138.         } catch (MissingObjectException ignore) {
  139.             // An object reachable from one of the "start"s is missing.
  140.             // Walk from the "start"s one at a time so it can be excluded.
  141.         }

  143.         final BitmapBuilder result = bitmapIndex.newBitmapBuilder();
  144.         for (ObjectId obj : start) {
  145.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  146.             if (bitmap != null) {
  147.                 result.or(bitmap);
  148.             }
  149.         }

  151.         for (ObjectId obj : start) {
  152.             if (result.contains(obj)) {
  153.                 continue;
  154.             }
  155.             try {
  156.                 result.or(findObjectsWalk(Arrays.asList(obj), result, false));
  157.             } catch (MissingObjectException ignore) {
  158.                 // An object reachable from this "start" is missing.
  159.                 //
  160.                 // This can happen when the client specified a "have" line
  161.                 // pointing to an object that is present but unreachable:
  162.                 // "git prune" and "git fsck" only guarantee that the object
  163.                 // database will continue to contain all objects reachable
  164.                 // from a ref and does not guarantee connectivity for other
  165.                 // objects in the object database.
  166.                 //
  167.                 // In this situation, skip the relevant "start" and move on
  168.                 // to the next one.
  169.                 //
  170.                 // TODO(czhen): Make findObjectsWalk resume the walk instead
  171.                 // once RevWalk and ObjectWalk support that.
  172.             }
  173.         }
  174.         return result;
  175.     }

  177.     private BitmapBuilder findObjectsWalk(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  178.             boolean ignoreMissingStart)
  179.             throws MissingObjectException, IncorrectObjectTypeException,
  180.             IOException {
  181.         walker.reset();
  182.         final BitmapBuilder bitmapResult = bitmapIndex.newBitmapBuilder();

  184.         for (ObjectId obj : start) {
  185.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  186.             if (bitmap != null)
  187.                 bitmapResult.or(bitmap);
  188.         }

  190.         boolean marked = false;
  191.         for (ObjectId obj : start) {
  192.             try {
  193.                 if (!bitmapResult.contains(obj)) {
  194.                     walker.markStart(walker.parseAny(obj));
  195.                     marked = true;
  196.                 }
  197.             } catch (MissingObjectException e) {
  198.                 if (ignoreMissingStart)
  199.                     continue;
  200.                 throw e;
  201.             }
  202.         }

  204.         if (marked) {
  205.             if (seen == null) {
  206.                 walker.setRevFilter(new AddToBitmapFilter(bitmapResult));
  207.             } else {
  208.                 walker.setRevFilter(
  209.                         new AddUnseenToBitmapFilter(seen, bitmapResult));
  210.             }
  211.             walker.setObjectFilter(new BitmapObjectFilter(bitmapResult));

  213.             while (walker.next() != null) {
  214.                 // Iterate through all of the commits. The BitmapRevFilter does
  215.                 // the work.
  216.                 //
  217.                 // filter.include returns true for commits that do not have
  218.                 // a bitmap in bitmapIndex and are not reachable from a
  219.                 // bitmap in bitmapIndex encountered earlier in the walk.
  220.                 // Thus the number of commits returned by next() measures how
  221.                 // much history was traversed without being able to make use
  222.                 // of bitmaps.
  223.                 pm.update(1);
  224.                 countOfBitmapIndexMisses++;
  225.             }

  227.             RevObject ro;
  228.             while ((ro = walker.nextObject()) != null) {
  229.                 bitmapResult.addObject(ro, ro.getType());
  230.                 pm.update(1);
  231.             }
  232.         }

  234.         return bitmapResult;
  235.     }

  237.     /**
  238.      * Filter that excludes objects already in the given bitmap.
  239.      */
  240.     static class BitmapObjectFilter extends ObjectFilter {
  241.         private final BitmapBuilder bitmap;

  243.         BitmapObjectFilter(BitmapBuilder bitmap) {
  244.             this.bitmap = bitmap;
  245.         }

  247.         @Override
  248.         public final boolean include(ObjectWalk walker, AnyObjectId objid)
  249.             throws MissingObjectException, IncorrectObjectTypeException,
  250.                    IOException {
  251.             return !bitmap.contains(objid);
  252.         }
  253.     }
  254. }
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