org.spearce.jgit/src/org/spearce/jgit/lib/PackFile.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.File;
  42 import java.io.IOException;
  43 import java.util.zip.DataFormatException;
  44
  45 import org.spearce.jgit.util.NB;
  46
  47 /**
  48  * A Git version 2 pack file representation. A pack file contains
  49  * Git objects in delta packed format yielding high compression of
  50  * lots of object where some objects are similar.
  51  */
  52 public class PackFile {
  53         private static final byte[] SIGNATURE = { 'P', 'A', 'C', 'K' };
  54
  55         private final WindowedFile pack;
  56
  57         private final PackIndex idx;
  58
  59         /**
  60          * Construct a reader for an existing, pre-indexed packfile.
  61          *
  62          * @param parentRepo
  63          *            Git repository holding this pack file
  64          * @param idxFile
  65          *            path of the <code>.idx</code> file listing the contents.
  66          * @param packFile
  67          *            path of the <code>.pack</code> file holding the data.
  68          * @throws IOException
  69          *             the index file cannot be accessed at this time.
  70          */
  71         public PackFile(final Repository parentRepo, final File idxFile,
  72                         final File packFile) throws IOException {
  73                 pack = new WindowedFile(packFile) {
  74                         @Override
  75                         protected void onOpen() throws IOException {
  76                                 readPackHeader();
  77                         }
  78                 };
  79                 try {
  80                         idx = PackIndex.open(idxFile);
  81                 } catch (IOException ioe) {
  82                         throw ioe;
  83                 }
  84         }
  85
  86         final PackedObjectLoader resolveBase(final WindowCursor curs, final long ofs)
  87                         throws IOException {
  88                 return reader(curs, ofs);
  89         }
  90
  91         /**
  92          * Determine if an object is contained within the pack file.
  93          * <p>
  94          * For performance reasons only the index file is searched; the main pack
  95          * content is ignored entirely.
  96          * </p>
  97          *
  98          * @param id
  99          *            the object to look for. Must not be null.
 100          * @return true if the object is in this pack; false otherwise.
 101          */
 102         public boolean hasObject(final AnyObjectId id) {
 103                 return idx.hasObject(id);
 104         }
 105
 106         /**
 107          * Get an object from this pack.
 108          *
 109          * @param id
 110          *            the object to obtain from the pack. Must not be null.
 111          * @return the object loader for the requested object if it is contained in
 112          *         this pack; null if the object was not found.
 113          * @throws IOException
 114          *             the pack file or the index could not be read.
 115          */
 116         public PackedObjectLoader get(final AnyObjectId id) throws IOException {
 117                 return get(new WindowCursor(), id);
 118         }
 119
 120         /**
 121          * Get an object from this pack.
 122          *
 123          * @param curs
 124          *            temporary working space associated with the calling thread.
 125          * @param id
 126          *            the object to obtain from the pack. Must not be null.
 127          * @return the object loader for the requested object if it is contained in
 128          *         this pack; null if the object was not found.
 129          * @throws IOException
 130          *             the pack file or the index could not be read.
 131          */
 132         public PackedObjectLoader get(final WindowCursor curs, final AnyObjectId id)
 133                         throws IOException {
 134                 final long offset = idx.findOffset(id);
 135                 if (offset == -1)
 136                         return null;
 137                 final PackedObjectLoader objReader = reader(curs, offset);
 138                 objReader.setId(id.toObjectId());
 139                 return objReader;
 140         }
 141
 142         /**
 143          * Close the resources utilized by this repository
 144          */
 145         public void close() {
 146                 UnpackedObjectCache.purge(pack);
 147                 pack.close();
 148         }
 149
 150         final UnpackedObjectCache.Entry readCache(final long position) {
 151                 return UnpackedObjectCache.get(pack, position);
 152         }
 153
 154         final void saveCache(final long position, final byte[] data, final int type) {
 155                 UnpackedObjectCache.store(pack, position, data, type);
 156         }
 157
 158         final byte[] decompress(final long position, final int totalSize,
 159                         final WindowCursor curs) throws DataFormatException, IOException {
 160                 final byte[] dstbuf = new byte[totalSize];
 161                 pack.readCompressed(position, dstbuf, curs);
 162                 return dstbuf;
 163         }
 164
 165         private void readPackHeader() throws IOException {
 166                 final WindowCursor curs = new WindowCursor();
 167                 long position = 0;
 168                 final byte[] sig = new byte[SIGNATURE.length];
 169                 final byte[] intbuf = new byte[4];
 170                 final long vers;
 171
 172                 if (pack.read(position, sig, curs) != SIGNATURE.length)
 173                         throw new IOException("Not a PACK file.");
 174                 for (int k = 0; k < SIGNATURE.length; k++) {
 175                         if (sig[k] != SIGNATURE[k])
 176                                 throw new IOException("Not a PACK file.");
 177                 }
 178                 position += SIGNATURE.length;
 179
 180                 pack.readFully(position, intbuf, curs);
 181                 vers = NB.decodeUInt32(intbuf, 0);
 182                 if (vers != 2 && vers != 3)
 183                         throw new IOException("Unsupported pack version " + vers + ".");
 184                 position += 4;
 185
 186                 pack.readFully(position, intbuf, curs);
 187                 final long objectCnt = NB.decodeUInt32(intbuf, 0);
 188                 if (idx.getObjectCount() != objectCnt)
 189                         throw new IOException("Pack index"
 190                                         + " object count mismatch; expected " + objectCnt
 191                                         + " found " + idx.getObjectCount() + ": "
 192                                         + pack.getName());
 193         }
 194
 195         private PackedObjectLoader reader(final WindowCursor curs,
 196                         final long objOffset)
 197                         throws IOException {
 198                 long pos = objOffset;
 199                 int p = 0;
 200                 final byte[] ib = curs.tempId;
 201                 pack.readFully(pos, ib, curs);
 202                 int c = ib[p++] & 0xff;
 203                 final int typeCode = (c >> 4) & 7;
 204                 long dataSize = c & 15;
 205                 int shift = 4;
 206                 while ((c & 0x80) != 0) {
 207                         c = ib[p++] & 0xff;
 208                         dataSize += (c & 0x7f) << shift;
 209                         shift += 7;
 210                 }
 211                 pos += p;
 212
 213                 switch (typeCode) {
 214                 case Constants.OBJ_COMMIT:
 215                 case Constants.OBJ_TREE:
 216                 case Constants.OBJ_BLOB:
 217                 case Constants.OBJ_TAG:
 218                         return new WholePackedObjectLoader(curs, this, pos, typeCode,
 219                                         (int) dataSize);
 220
 221                 case Constants.OBJ_OFS_DELTA: {
 222                         pack.readFully(pos, ib, curs);
 223                         p = 0;
 224                         c = ib[p++] & 0xff;
 225                         long ofs = c & 127;
 226                         while ((c & 128) != 0) {
 227                                 ofs += 1;
 228                                 c = ib[p++] & 0xff;
 229                                 ofs <<= 7;
 230                                 ofs += (c & 127);
 231                         }
 232                         return new DeltaOfsPackedObjectLoader(curs, this, pos + p,
 233                                         (int) dataSize, objOffset - ofs);
 234                 }
 235                 case Constants.OBJ_REF_DELTA: {
 236                         pack.readFully(pos, ib, curs);
 237                         return new DeltaRefPackedObjectLoader(curs, this, pos + ib.length,
 238                                         (int) dataSize, ObjectId.fromRaw(ib));
 239                 }
 240                 default:
 241                         throw new IOException("Unknown object type " + typeCode + ".");
 242                 }
 243         }
 244 }