/* * Copyright (C) 2009, Google Inc. * and other copyright owners as documented in the project's IP log. * * This program and the accompanying materials are made available * under the terms of the Eclipse Distribution License v1.0 which * accompanies this distribution, is reproduced below, and is * available at http://www.eclipse.org/org/documents/edl-v10.php * * All rights reserved. * * Redistribution and use in source and binary forms, with or * without modification, are permitted provided that the following * conditions are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * - Neither the name of the Eclipse Foundation, Inc. nor the * names of its contributors may be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package org.eclipse.jgit.lib; import java.io.BufferedReader; import java.io.File; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import java.util.concurrent.atomic.AtomicReference; import org.eclipse.jgit.errors.PackMismatchException; import org.eclipse.jgit.lib.RepositoryCache.FileKey; import org.eclipse.jgit.util.FS; /** * Traditional file system based {@link ObjectDatabase}. *

* This is the classical object database representation for a Git repository, * where objects are stored loose by hashing them into directories by their * {@link ObjectId}, or are stored in compressed containers known as * {@link PackFile}s. */ public class ObjectDirectory extends ObjectDatabase { private static final PackList NO_PACKS = new PackList(-1, -1, new PackFile[0]); private final File objects; private final File infoDirectory; private final File packDirectory; private final File alternatesFile; private final AtomicReference packList; private final File[] alternateObjectDir; /** * Initialize a reference to an on-disk object directory. * * @param dir * the location of the objects directory. * @param alternateObjectDir * a list of alternate object directories */ public ObjectDirectory(final File dir, File[] alternateObjectDir) { objects = dir; this.alternateObjectDir = alternateObjectDir; infoDirectory = new File(objects, "info"); packDirectory = new File(objects, "pack"); alternatesFile = new File(infoDirectory, "alternates"); packList = new AtomicReference(NO_PACKS); } /** * @return the location of the objects directory. */ public final File getDirectory() { return objects; } @Override public boolean exists() { return objects.exists(); } @Override public void create() throws IOException { objects.mkdirs(); infoDirectory.mkdir(); packDirectory.mkdir(); } @Override public void closeSelf() { final PackList packs = packList.get(); packList.set(NO_PACKS); for (final PackFile p : packs.packs) p.close(); } /** * Compute the location of a loose object file. * * @param objectId * identity of the loose object to map to the directory. * @return location of the object, if it were to exist as a loose object. */ public File fileFor(final AnyObjectId objectId) { return fileFor(objectId.name()); } private File fileFor(final String objectName) { final String d = objectName.substring(0, 2); final String f = objectName.substring(2); return new File(new File(objects, d), f); } /** * @return unmodifiable collection of all known pack files local to this * directory. Most recent packs are presented first. Packs most * likely to contain more recent objects appear before packs * containing objects referenced by commits further back in the * history of the repository. */ public Collection getPacks() { final PackFile[] packs = packList.get().packs; return Collections.unmodifiableCollection(Arrays.asList(packs)); } /** * Add a single existing pack to the list of available pack files. * * @param pack * path of the pack file to open. * @param idx * path of the corresponding index file. * @throws IOException * index file could not be opened, read, or is not recognized as * a Git pack file index. */ public void openPack(final File pack, final File idx) throws IOException { final String p = pack.getName(); final String i = idx.getName(); if (p.length() != 50 || !p.startsWith("pack-") || !p.endsWith(".pack")) throw new IOException("Not a valid pack " + pack); if (i.length() != 49 || !i.startsWith("pack-") || !i.endsWith(".idx")) throw new IOException("Not a valid pack " + idx); if (!p.substring(0, 45).equals(i.substring(0, 45))) throw new IOException("Pack " + pack + "does not match index"); insertPack(new PackFile(idx, pack)); } @Override public String toString() { return "ObjectDirectory[" + getDirectory() + "]"; } @Override protected boolean hasObject1(final AnyObjectId objectId) { for (final PackFile p : packList.get().packs) { try { if (p.hasObject(objectId)) { return true; } } catch (IOException e) { // The hasObject call should have only touched the index, // so any failure here indicates the index is unreadable // by this process, and the pack is likewise not readable. // removePack(p); continue; } } return false; } @Override protected ObjectLoader openObject1(final WindowCursor curs, final AnyObjectId objectId) throws IOException { PackList pList = packList.get(); SEARCH: for (;;) { for (final PackFile p : pList.packs) { try { final PackedObjectLoader ldr = p.get(curs, objectId); if (ldr != null) { ldr.materialize(curs); return ldr; } } catch (PackMismatchException e) { // Pack was modified; refresh the entire pack list. // pList = scanPacks(pList); continue SEARCH; } catch (IOException e) { // Assume the pack is corrupted. // removePack(p); } } return null; } } @Override void openObjectInAllPacks1(final Collection out, final WindowCursor curs, final AnyObjectId objectId) throws IOException { PackList pList = packList.get(); SEARCH: for (;;) { for (final PackFile p : pList.packs) { try { final PackedObjectLoader ldr = p.get(curs, objectId); if (ldr != null) { out.add(ldr); } } catch (PackMismatchException e) { // Pack was modified; refresh the entire pack list. // pList = scanPacks(pList); continue SEARCH; } catch (IOException e) { // Assume the pack is corrupted. // removePack(p); } } break SEARCH; } } @Override protected boolean hasObject2(final String objectName) { return fileFor(objectName).exists(); } @Override protected ObjectLoader openObject2(final WindowCursor curs, final String objectName, final AnyObjectId objectId) throws IOException { try { return new UnpackedObjectLoader(fileFor(objectName), objectId); } catch (FileNotFoundException noFile) { return null; } } @Override protected boolean tryAgain1() { final PackList old = packList.get(); if (old.tryAgain(packDirectory.lastModified())) return old != scanPacks(old); return false; } private void insertPack(final PackFile pf) { PackList o, n; do { o = packList.get(); final PackFile[] oldList = o.packs; final PackFile[] newList = new PackFile[1 + oldList.length]; newList[0] = pf; System.arraycopy(oldList, 0, newList, 1, oldList.length); n = new PackList(o.lastRead, o.lastModified, newList); } while (!packList.compareAndSet(o, n)); } private void removePack(final PackFile deadPack) { PackList o, n; do { o = packList.get(); final PackFile[] oldList = o.packs; final int j = indexOf(oldList, deadPack); if (j < 0) break; final PackFile[] newList = new PackFile[oldList.length - 1]; System.arraycopy(oldList, 0, newList, 0, j); System.arraycopy(oldList, j + 1, newList, j, newList.length - j); n = new PackList(o.lastRead, o.lastModified, newList); } while (!packList.compareAndSet(o, n)); deadPack.close(); } private static int indexOf(final PackFile[] list, final PackFile pack) { for (int i = 0; i < list.length; i++) { if (list[i] == pack) return i; } return -1; } private PackList scanPacks(final PackList original) { synchronized (packList) { PackList o, n; do { o = packList.get(); if (o != original) { // Another thread did the scan for us, while we // were blocked on the monitor above. // return o; } n = scanPacksImpl(o); if (n == o) return n; } while (!packList.compareAndSet(o, n)); return n; } } private PackList scanPacksImpl(final PackList old) { final Map forReuse = reuseMap(old); final long lastRead = System.currentTimeMillis(); final long lastModified = packDirectory.lastModified(); final Set names = listPackDirectory(); final List list = new ArrayList(names.size() >> 2); boolean foundNew = false; for (final String indexName : names) { // Must match "pack-[0-9a-f]{40}.idx" to be an index. // if (indexName.length() != 49 || !indexName.endsWith(".idx")) continue; final String base = indexName.substring(0, indexName.length() - 4); final String packName = base + ".pack"; if (!names.contains(packName)) { // Sometimes C Git's HTTP fetch transport leaves a // .idx file behind and does not download the .pack. // We have to skip over such useless indexes. // continue; } final PackFile oldPack = forReuse.remove(packName); if (oldPack != null) { list.add(oldPack); continue; } final File packFile = new File(packDirectory, packName); final File idxFile = new File(packDirectory, indexName); list.add(new PackFile(idxFile, packFile)); foundNew = true; } // If we did not discover any new files, the modification time was not // changed, and we did not remove any files, then the set of files is // the same as the set we were given. Instead of building a new object // return the same collection. // if (!foundNew && lastModified == old.lastModified && forReuse.isEmpty()) return old.updateLastRead(lastRead); for (final PackFile p : forReuse.values()) { p.close(); } if (list.isEmpty()) return new PackList(lastRead, lastModified, NO_PACKS.packs); final PackFile[] r = list.toArray(new PackFile[list.size()]); Arrays.sort(r, PackFile.SORT); return new PackList(lastRead, lastModified, r); } private static Map reuseMap(final PackList old) { final Map forReuse = new HashMap(); for (final PackFile p : old.packs) { if (p.invalid()) { // The pack instance is corrupted, and cannot be safely used // again. Do not include it in our reuse map. // p.close(); continue; } final PackFile prior = forReuse.put(p.getPackFile().getName(), p); if (prior != null) { // This should never occur. It should be impossible for us // to have two pack files with the same name, as all of them // came out of the same directory. If it does, we promised to // close any PackFiles we did not reuse, so close the one we // just evicted out of the reuse map. // prior.close(); } } return forReuse; } private Set listPackDirectory() { final String[] nameList = packDirectory.list(); if (nameList == null) return Collections.emptySet(); final Set nameSet = new HashSet(nameList.length << 1); for (final String name : nameList) { if (name.startsWith("pack-")) nameSet.add(name); } return nameSet; } @Override protected ObjectDatabase[] loadAlternates() throws IOException { final List l = new ArrayList(4); if (alternateObjectDir != null) { for (File d : alternateObjectDir) { l.add(openAlternate(d)); } } else { final BufferedReader br = open(alternatesFile); try { String line; while ((line = br.readLine()) != null) { l.add(openAlternate(line)); } } finally { br.close(); } } if (l.isEmpty()) { return NO_ALTERNATES; } return l.toArray(new ObjectDatabase[l.size()]); } private static BufferedReader open(final File f) throws FileNotFoundException { return new BufferedReader(new FileReader(f)); } private ObjectDatabase openAlternate(final String location) throws IOException { final File objdir = FS.resolve(objects, location); return openAlternate(objdir); } private ObjectDatabase openAlternate(File objdir) throws IOException { final File parent = objdir.getParentFile(); if (FileKey.isGitRepository(parent)) { final Repository db = RepositoryCache.open(FileKey.exact(parent)); return new AlternateRepositoryDatabase(db); } return new ObjectDirectory(objdir, null); } private static final class PackList { /** Last wall-clock time the directory was read. */ volatile long lastRead; /** Last modification time of {@link ObjectDirectory#packDirectory}. */ final long lastModified; /** All known packs, sorted by {@link PackFile#SORT}. */ final PackFile[] packs; private boolean cannotBeRacilyClean; PackList(final long lastRead, final long lastModified, final PackFile[] packs) { this.lastRead = lastRead; this.lastModified = lastModified; this.packs = packs; this.cannotBeRacilyClean = notRacyClean(lastRead); } private boolean notRacyClean(final long read) { return read - lastModified > 2 * 60 * 1000L; } PackList updateLastRead(final long now) { if (notRacyClean(now)) cannotBeRacilyClean = true; lastRead = now; return this; } boolean tryAgain(final long currLastModified) { // Any difference indicates the directory was modified. // if (lastModified != currLastModified) return true; // We have already determined the last read was far enough // after the last modification that any new modifications // are certain to change the last modified time. // if (cannotBeRacilyClean) return false; if (notRacyClean(lastRead)) { // Our last read should have marked cannotBeRacilyClean, // but this thread may not have seen the change. The read // of the volatile field lastRead should have fixed that. // return false; } // We last read this directory too close to its last observed // modification time. We may have missed a modification. Scan // the directory again, to ensure we still see the same state. // return true; } } }