BasePackBitmapIndex.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.
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  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.
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  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
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  29.  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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  40.  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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  43. package org.eclipse.jgit.internal.storage.file;

  44. import org.eclipse.jgit.lib.AnyObjectId;
  45. import org.eclipse.jgit.lib.ObjectIdOwnerMap;

  46. import com.googlecode.javaewah.EWAHCompressedBitmap;

  47. /**
  48.  * Base implementation of the PackBitmapIndex.
  49.  */
  50. abstract class BasePackBitmapIndex extends PackBitmapIndex {
  51.     private final ObjectIdOwnerMap<StoredBitmap> bitmaps;

  52.     BasePackBitmapIndex(ObjectIdOwnerMap<StoredBitmap> bitmaps) {
  53.         this.bitmaps = bitmaps;
  54.     }

  55.     /** {@inheritDoc} */
  56.     @Override
  57.     public EWAHCompressedBitmap getBitmap(AnyObjectId objectId) {
  58.         StoredBitmap sb = bitmaps.get(objectId);
  59.         return sb != null ? sb.getBitmap() : null;
  60.     }

  61.     ObjectIdOwnerMap<StoredBitmap> getBitmaps() {
  62.         return bitmaps;
  63.     }

  64.     /**
  65.      * Data representation of the bitmap entry restored from a pack index. The
  66.      * commit of the bitmap is the map key.
  67.      */
  68.     static final class StoredBitmap extends ObjectIdOwnerMap.Entry {
  69.         private volatile Object bitmapContainer;
  70.         private final int flags;

  71.         StoredBitmap(AnyObjectId objectId, EWAHCompressedBitmap bitmap,
  72.                 StoredBitmap xorBitmap, int flags) {
  73.             super(objectId);
  74.             this.bitmapContainer = xorBitmap == null
  75.                     ? bitmap
  76.                     : new XorCompressedBitmap(bitmap, xorBitmap);
  77.             this.flags = flags;
  78.         }

  79.         /**
  80.          * Computes and returns the full bitmap.
  81.          *
  82.          * @return the full bitmap
  83.          */
  84.         EWAHCompressedBitmap getBitmap() {
  85.             // Fast path to immediately return the expanded result.
  86.             Object r = bitmapContainer;
  87.             if (r instanceof EWAHCompressedBitmap)
  88.                 return (EWAHCompressedBitmap) r;

  89.             // Expand the bitmap and cache the result.
  90.             XorCompressedBitmap xb = (XorCompressedBitmap) r;
  91.             EWAHCompressedBitmap out = xb.bitmap;
  92.             for (;;) {
  93.                 r = xb.xorBitmap.bitmapContainer;
  94.                 if (r instanceof EWAHCompressedBitmap) {
  95.                     out = out.xor((EWAHCompressedBitmap) r);
  96.                     out.trim();
  97.                     bitmapContainer = out;
  98.                     return out;
  99.                 }
  100.                 xb = (XorCompressedBitmap) r;
  101.                 out = out.xor(xb.bitmap);
  102.             }
  103.         }

  104.         /** @return the flags associated with the bitmap */
  105.         int getFlags() {
  106.             return flags;
  107.         }
  108.     }

  109.     private static final class XorCompressedBitmap {
  110.         final EWAHCompressedBitmap bitmap;
  111.         final StoredBitmap xorBitmap;

  112.         XorCompressedBitmap(EWAHCompressedBitmap b, StoredBitmap xb) {
  113.             bitmap = b;
  114.             xorBitmap = xb;
  115.         }
  116.     }
  117. }