org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java

   1 /*
   2  * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
   3  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
   4  *
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or
   8  * without modification, are permitted provided that the following
   9  * conditions are met:
  10  *
  11  * - Redistributions of source code must retain the above copyright
  12  *   notice, this list of conditions and the following disclaimer.
  13  *
  14  * - Redistributions in binary form must reproduce the above
  15  *   copyright notice, this list of conditions and the following
  16  *   disclaimer in the documentation and/or other materials provided
  17  *   with the distribution.
  18  *
  19  * - Neither the name of the Git Development Community nor the
  20  *   names of its contributors may be used to endorse or promote
  21  *   products derived from this software without specific prior
  22  *   written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  25  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  26  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  29  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  30  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  32  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  33  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  34  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  36  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 package org.spearce.jgit.lib;
  40
  41 import java.io.IOException;
  42 import java.io.InputStream;
  43
  44 import org.spearce.jgit.errors.CorruptObjectException;
  45 import org.spearce.jgit.util.NB;
  46
  47 class PackIndexV1 extends PackIndex {
  48         private static final int IDX_HDR_LEN = 256 * 4;
  49
  50         private byte[][] idxdata;
  51
  52         private long objectCnt;
  53
  54         PackIndexV1(final InputStream fd, final byte[] hdr)
  55                         throws CorruptObjectException, IOException {
  56                 final byte[] fanoutTable = new byte[IDX_HDR_LEN];
  57                 System.arraycopy(hdr, 0, fanoutTable, 0, hdr.length);
  58                 NB.readFully(fd, fanoutTable, hdr.length, IDX_HDR_LEN - hdr.length);
  59
  60                 final long[] idxHeader = new long[256]; // really unsigned 32-bit...
  61                 for (int k = 0; k < idxHeader.length; k++)
  62                         idxHeader[k] = NB.decodeUInt32(fanoutTable, k * 4);
  63                 idxdata = new byte[idxHeader.length][];
  64                 for (int k = 0; k < idxHeader.length; k++) {
  65                         int n;
  66                         if (k == 0) {
  67                                 n = (int)(idxHeader[k]);
  68                         } else {
  69                                 n = (int)(idxHeader[k]-idxHeader[k-1]);
  70                         }
  71                         if (n > 0) {
  72                                 idxdata[k] = new byte[n * (Constants.OBJECT_ID_LENGTH + 4)];
  73                                 NB.readFully(fd, idxdata[k], 0, idxdata[k].length);
  74                         }
  75                 }
  76                 objectCnt = idxHeader[255];
  77         }
  78
  79         long getObjectCount() {
  80                 return objectCnt;
  81         }
  82
  83         long findOffset(final AnyObjectId objId) {
  84                 final int levelOne = objId.getFirstByte();
  85                 byte[] data = idxdata[levelOne];
  86                 if (data == null)
  87                         return -1;
  88                 int high = data.length / (4 + Constants.OBJECT_ID_LENGTH);
  89                 int low = 0;
  90                 do {
  91                         final int mid = (low + high) / 2;
  92                         final int pos = ((4 + Constants.OBJECT_ID_LENGTH) * mid) + 4;
  93                         final int cmp = objId.compareTo(data, pos);
  94                         if (cmp < 0)
  95                                 high = mid;
  96                         else if (cmp == 0) {
  97                                 int b0 = data[pos-4] & 0xff;
  98                                 int b1 = data[pos-3] & 0xff;
  99                                 int b2 = data[pos-2] & 0xff;
 100                                 int b3 = data[pos-1] & 0xff;
 101                                 return (((long)b0) << 24) | ( b1 << 16 ) | ( b2 << 8 ) | (b3);
 102                         } else
 103                                 low = mid + 1;
 104                 } while (low < high);
 105                 return -1;
 106         }
 107 }