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
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  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.revwalk;

  44. import java.io.IOException;
  45. import java.util.Arrays;

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

  58. /**
  59.  * Helper class to do ObjectWalks with pack index bitmaps.
  60.  *
  61.  * @since 4.10
  62.  */
  63. public final class BitmapWalker {

  64.     private final ObjectWalk walker;

  65.     private final BitmapIndex bitmapIndex;

  66.     private final ProgressMonitor pm;

  67.     private long countOfBitmapIndexMisses;

  68.     /**
  69.      * Create a BitmapWalker.
  70.      *
  71.      * @param walker walker to use when traversing the object graph.
  72.      * @param bitmapIndex index to obtain bitmaps from.
  73.      * @param pm progress monitor to report progress on.
  74.      */
  75.     public BitmapWalker(
  76.             ObjectWalk walker, BitmapIndex bitmapIndex, ProgressMonitor pm) {
  77.         this.walker = walker;
  78.         this.bitmapIndex = bitmapIndex;
  79.         this.pm = (pm == null) ? NullProgressMonitor.INSTANCE : pm;
  80.     }

  81.     /**
  82.      * Return the number of objects that had to be walked because they were not covered by a
  83.      * bitmap.
  84.      *
  85.      * @return the number of objects that had to be walked because they were not covered by a
  86.      *     bitmap.
  87.      */
  88.     public long getCountOfBitmapIndexMisses() {
  89.         return countOfBitmapIndexMisses;
  90.     }

  91.     /**
  92.      * Return, as a bitmap, the objects reachable from the objects in start.
  93.      *
  94.      * @param start
  95.      *            the objects to start the object traversal from.
  96.      * @param seen
  97.      *            the objects to skip if encountered during traversal.
  98.      * @param ignoreMissing
  99.      *            true to ignore missing objects, false otherwise.
  100.      * @return as a bitmap, the objects reachable from the objects in start.
  101.      * @throws org.eclipse.jgit.errors.MissingObjectException
  102.      *             the object supplied is not available from the object
  103.      *             database. This usually indicates the supplied object is
  104.      *             invalid, but the reference was constructed during an earlier
  105.      *             invocation to
  106.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}.
  107.      * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
  108.      *             the object was not parsed yet and it was discovered during
  109.      *             parsing that it is not actually the type of the instance
  110.      *             passed in. This usually indicates the caller used the wrong
  111.      *             type in a
  112.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}
  113.      *             call.
  114.      * @throws java.io.IOException
  115.      *             a pack file or loose object could not be read.
  116.      */
  117.     public BitmapBuilder findObjects(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  118.             boolean ignoreMissing)
  119.             throws MissingObjectException, IncorrectObjectTypeException,
  120.                    IOException {
  121.         if (!ignoreMissing) {
  122.             return findObjectsWalk(start, seen, false);
  123.         }

  124.         try {
  125.             return findObjectsWalk(start, seen, true);
  126.         } catch (MissingObjectException ignore) {
  127.             // An object reachable from one of the "start"s is missing.
  128.             // Walk from the "start"s one at a time so it can be excluded.
  129.         }

  130.         final BitmapBuilder result = bitmapIndex.newBitmapBuilder();
  131.         for (ObjectId obj : start) {
  132.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  133.             if (bitmap != null) {
  134.                 result.or(bitmap);
  135.             }
  136.         }

  137.         for (ObjectId obj : start) {
  138.             if (result.contains(obj)) {
  139.                 continue;
  140.             }
  141.             try {
  142.                 result.or(findObjectsWalk(Arrays.asList(obj), result, false));
  143.             } catch (MissingObjectException ignore) {
  144.                 // An object reachable from this "start" is missing.
  145.                 //
  146.                 // This can happen when the client specified a "have" line
  147.                 // pointing to an object that is present but unreachable:
  148.                 // "git prune" and "git fsck" only guarantee that the object
  149.                 // database will continue to contain all objects reachable
  150.                 // from a ref and does not guarantee connectivity for other
  151.                 // objects in the object database.
  152.                 //
  153.                 // In this situation, skip the relevant "start" and move on
  154.                 // to the next one.
  155.                 //
  156.                 // TODO(czhen): Make findObjectsWalk resume the walk instead
  157.                 // once RevWalk and ObjectWalk support that.
  158.             }
  159.         }
  160.         return result;
  161.     }

  162.     private BitmapBuilder findObjectsWalk(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  163.             boolean ignoreMissingStart)
  164.             throws MissingObjectException, IncorrectObjectTypeException,
  165.             IOException {
  166.         walker.reset();
  167.         final BitmapBuilder bitmapResult = bitmapIndex.newBitmapBuilder();

  168.         for (ObjectId obj : start) {
  169.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  170.             if (bitmap != null)
  171.                 bitmapResult.or(bitmap);
  172.         }

  173.         boolean marked = false;
  174.         for (ObjectId obj : start) {
  175.             try {
  176.                 if (!bitmapResult.contains(obj)) {
  177.                     walker.markStart(walker.parseAny(obj));
  178.                     marked = true;
  179.                 }
  180.             } catch (MissingObjectException e) {
  181.                 if (ignoreMissingStart)
  182.                     continue;
  183.                 throw e;
  184.             }
  185.         }

  186.         if (marked) {
  187.             if (seen == null) {
  188.                 walker.setRevFilter(new AddToBitmapFilter(bitmapResult));
  189.             } else {
  190.                 walker.setRevFilter(
  191.                         new AddUnseenToBitmapFilter(seen, bitmapResult));
  192.             }
  193.             walker.setObjectFilter(new BitmapObjectFilter(bitmapResult));

  194.             while (walker.next() != null) {
  195.                 // Iterate through all of the commits. The BitmapRevFilter does
  196.                 // the work.
  197.                 //
  198.                 // filter.include returns true for commits that do not have
  199.                 // a bitmap in bitmapIndex and are not reachable from a
  200.                 // bitmap in bitmapIndex encountered earlier in the walk.
  201.                 // Thus the number of commits returned by next() measures how
  202.                 // much history was traversed without being able to make use
  203.                 // of bitmaps.
  204.                 pm.update(1);
  205.                 countOfBitmapIndexMisses++;
  206.             }

  207.             RevObject ro;
  208.             while ((ro = walker.nextObject()) != null) {
  209.                 bitmapResult.addObject(ro, ro.getType());
  210.                 pm.update(1);
  211.             }
  212.         }

  213.         return bitmapResult;
  214.     }

  215.     /**
  216.      * Filter that excludes objects already in the given bitmap.
  217.      */
  218.     static class BitmapObjectFilter extends ObjectFilter {
  219.         private final BitmapBuilder bitmap;

  220.         BitmapObjectFilter(BitmapBuilder bitmap) {
  221.             this.bitmap = bitmap;
  222.         }

  223.         @Override
  224.         public final boolean include(ObjectWalk walker, AnyObjectId objid)
  225.             throws MissingObjectException, IncorrectObjectTypeException,
  226.                    IOException {
  227.             return !bitmap.contains(objid);
  228.         }
  229.     }
  230. }