BitmapWalker.java

  1. /*
  2.  * Copyright (C) 2012, Google Inc. and others
  3.  *
  4.  * This program and the accompanying materials are made available under the
  5.  * terms of the Eclipse Distribution License v. 1.0 which is available at
  6.  * https://www.eclipse.org/org/documents/edl-v10.php.
  7.  *
  8.  * SPDX-License-Identifier: BSD-3-Clause
  9.  */

  11. package org.eclipse.jgit.revwalk;

  13. import java.io.IOException;
  14. import java.util.Arrays;

  16. import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  17. import org.eclipse.jgit.errors.MissingObjectException;
  18. import org.eclipse.jgit.internal.revwalk.AddToBitmapFilter;
  19. import org.eclipse.jgit.internal.revwalk.AddToBitmapWithCacheFilter;
  20. import org.eclipse.jgit.internal.revwalk.AddUnseenToBitmapFilter;
  21. import org.eclipse.jgit.lib.AnyObjectId;
  22. import org.eclipse.jgit.lib.BitmapIndex;
  23. import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
  24. import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
  25. import org.eclipse.jgit.lib.NullProgressMonitor;
  26. import org.eclipse.jgit.lib.ObjectId;
  27. import org.eclipse.jgit.lib.ProgressMonitor;
  28. import org.eclipse.jgit.revwalk.filter.ObjectFilter;

  30. /**
  31.  * Helper class to do ObjectWalks with pack index bitmaps.
  32.  *
  33.  * @since 4.10
  34.  */
  35. public final class BitmapWalker {

  37.     private final ObjectWalk walker;

  39.     private final BitmapIndex bitmapIndex;

  41.     private final ProgressMonitor pm;

  43.     private long countOfBitmapIndexMisses;

  45.     // Cached bitmap and commit to save walk time.
  46.     private AnyObjectId prevCommit;

  48.     private Bitmap prevBitmap;

  50.     /**
  51.      * Create a BitmapWalker.
  52.      *
  53.      * @param walker walker to use when traversing the object graph.
  54.      * @param bitmapIndex index to obtain bitmaps from.
  55.      * @param pm progress monitor to report progress on.
  56.      */
  57.     public BitmapWalker(
  58.             ObjectWalk walker, BitmapIndex bitmapIndex, ProgressMonitor pm) {
  59.         this.walker = walker;
  60.         this.bitmapIndex = bitmapIndex;
  61.         this.pm = (pm == null) ? NullProgressMonitor.INSTANCE : pm;
  62.     }

  64.     /**
  65.      * Set the cached commit for the walker.
  66.      *
  67.      * @param prevCommit
  68.      *            the cached commit.
  69.      * @since 5.8
  70.      */
  71.     public void setPrevCommit(AnyObjectId prevCommit) {
  72.         this.prevCommit = prevCommit;
  73.     }

  75.     /**
  76.      * Set the bitmap associated with the cached commit for the walker.
  77.      *
  78.      * @param prevBitmap
  79.      *            the bitmap associated with the cached commit.
  80.      * @since 5.8
  81.      */
  82.     public void setPrevBitmap(Bitmap prevBitmap) {
  83.         this.prevBitmap = prevBitmap;
  84.     }

  86.     /**
  87.      * Return the number of objects that had to be walked because they were not covered by a
  88.      * bitmap.
  89.      *
  90.      * @return the number of objects that had to be walked because they were not covered by a
  91.      *     bitmap.
  92.      */
  93.     public long getCountOfBitmapIndexMisses() {
  94.         return countOfBitmapIndexMisses;
  95.     }

  97.     /**
  98.      * Return, as a bitmap, the objects reachable from the objects in start.
  99.      *
  100.      * @param start
  101.      *            the objects to start the object traversal from.
  102.      * @param seen
  103.      *            the objects to skip if encountered during traversal.
  104.      * @param ignoreMissing
  105.      *            true to ignore missing objects, false otherwise.
  106.      * @return as a bitmap, the objects reachable from the objects in start.
  107.      * @throws org.eclipse.jgit.errors.MissingObjectException
  108.      *             the object supplied is not available from the object
  109.      *             database. This usually indicates the supplied object is
  110.      *             invalid, but the reference was constructed during an earlier
  111.      *             invocation to
  112.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}.
  113.      * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
  114.      *             the object was not parsed yet and it was discovered during
  115.      *             parsing that it is not actually the type of the instance
  116.      *             passed in. This usually indicates the caller used the wrong
  117.      *             type in a
  118.      *             {@link org.eclipse.jgit.revwalk.RevWalk#lookupAny(AnyObjectId, int)}
  119.      *             call.
  120.      * @throws java.io.IOException
  121.      *             a pack file or loose object could not be read.
  122.      */
  123.     public BitmapBuilder findObjects(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  124.             boolean ignoreMissing)
  125.             throws MissingObjectException, IncorrectObjectTypeException,
  126.                    IOException {
  127.         if (!ignoreMissing) {
  128.             return findObjectsWalk(start, seen, false);
  129.         }

  131.         try {
  132.             return findObjectsWalk(start, seen, true);
  133.         } catch (MissingObjectException ignore) {
  134.             // An object reachable from one of the "start"s is missing.
  135.             // Walk from the "start"s one at a time so it can be excluded.
  136.         }

  138.         final BitmapBuilder result = bitmapIndex.newBitmapBuilder();
  139.         for (ObjectId obj : start) {
  140.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  141.             if (bitmap != null) {
  142.                 result.or(bitmap);
  143.             }
  144.         }

  146.         for (ObjectId obj : start) {
  147.             if (result.contains(obj)) {
  148.                 continue;
  149.             }
  150.             try {
  151.                 result.or(findObjectsWalk(Arrays.asList(obj), result, false));
  152.             } catch (MissingObjectException ignore) {
  153.                 // An object reachable from this "start" is missing.
  154.                 //
  155.                 // This can happen when the client specified a "have" line
  156.                 // pointing to an object that is present but unreachable:
  157.                 // "git prune" and "git fsck" only guarantee that the object
  158.                 // database will continue to contain all objects reachable
  159.                 // from a ref and does not guarantee connectivity for other
  160.                 // objects in the object database.
  161.                 //
  162.                 // In this situation, skip the relevant "start" and move on
  163.                 // to the next one.
  164.                 //
  165.                 // TODO(czhen): Make findObjectsWalk resume the walk instead
  166.                 // once RevWalk and ObjectWalk support that.
  167.             }
  168.         }
  169.         return result;
  170.     }

  172.     private BitmapBuilder findObjectsWalk(Iterable<? extends ObjectId> start, BitmapBuilder seen,
  173.             boolean ignoreMissingStart)
  174.             throws MissingObjectException, IncorrectObjectTypeException,
  175.             IOException {
  176.         walker.reset();
  177.         final BitmapBuilder bitmapResult = bitmapIndex.newBitmapBuilder();

  179.         for (ObjectId obj : start) {
  180.             Bitmap bitmap = bitmapIndex.getBitmap(obj);
  181.             if (bitmap != null)
  182.                 bitmapResult.or(bitmap);
  183.         }

  185.         boolean marked = false;
  186.         for (ObjectId obj : start) {
  187.             try {
  188.                 if (!bitmapResult.contains(obj)) {
  189.                     walker.markStart(walker.parseAny(obj));
  190.                     marked = true;
  191.                 }
  192.             } catch (MissingObjectException e) {
  193.                 if (ignoreMissingStart)
  194.                     continue;
  195.                 throw e;
  196.             }
  197.         }

  199.         if (marked) {
  200.             if (prevCommit != null) {
  201.                 walker.setRevFilter(new AddToBitmapWithCacheFilter(prevCommit,
  202.                         prevBitmap, bitmapResult));
  203.             } else if (seen == null) {
  204.                 walker.setRevFilter(new AddToBitmapFilter(bitmapResult));
  205.             } else {
  206.                 walker.setRevFilter(
  207.                         new AddUnseenToBitmapFilter(seen, bitmapResult));
  208.             }
  209.             walker.setObjectFilter(new BitmapObjectFilter(bitmapResult));

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

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

  232.         return bitmapResult;
  233.     }

  235.     /**
  236.      * Filter that excludes objects already in the given bitmap.
  237.      */
  238.     static class BitmapObjectFilter extends ObjectFilter {
  239.         private final BitmapBuilder bitmap;

  241.         BitmapObjectFilter(BitmapBuilder bitmap) {
  242.             this.bitmap = bitmap;
  243.         }

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