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- /*
- * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
- * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
- * 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.internal.storage.file;
-
- import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
-
- import java.io.File;
- import java.io.FileInputStream;
- import java.io.FileNotFoundException;
- import java.io.FileOutputStream;
- import java.io.FilenameFilter;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.nio.ByteBuffer;
- import java.nio.channels.Channels;
- import java.nio.channels.FileChannel;
- import java.nio.file.StandardCopyOption;
- import java.text.MessageFormat;
-
- import org.eclipse.jgit.internal.JGitText;
- import org.eclipse.jgit.lib.Constants;
- import org.eclipse.jgit.lib.ObjectId;
- import org.eclipse.jgit.util.FS;
- import org.eclipse.jgit.util.FS.LockToken;
- import org.eclipse.jgit.util.FileUtils;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
-
- /**
- * Git style file locking and replacement.
- * <p>
- * To modify a ref file Git tries to use an atomic update approach: we write the
- * new data into a brand new file, then rename it in place over the old name.
- * This way we can just delete the temporary file if anything goes wrong, and
- * nothing has been damaged. To coordinate access from multiple processes at
- * once Git tries to atomically create the new temporary file under a well-known
- * name.
- */
- public class LockFile {
- private final static Logger LOG = LoggerFactory.getLogger(LockFile.class);
-
- /**
- * Unlock the given file.
- * <p>
- * This method can be used for recovering from a thrown
- * {@link org.eclipse.jgit.errors.LockFailedException} . This method does
- * not validate that the lock is or is not currently held before attempting
- * to unlock it.
- *
- * @param file
- * a {@link java.io.File} object.
- * @return true if unlocked, false if unlocking failed
- */
- public static boolean unlock(File file) {
- final File lockFile = getLockFile(file);
- final int flags = FileUtils.RETRY | FileUtils.SKIP_MISSING;
- try {
- FileUtils.delete(lockFile, flags);
- } catch (IOException ignored) {
- // Ignore and return whether lock file still exists
- }
- return !lockFile.exists();
- }
-
- /**
- * Get the lock file corresponding to the given file.
- *
- * @param file
- * @return lock file
- */
- static File getLockFile(File file) {
- return new File(file.getParentFile(),
- file.getName() + LOCK_SUFFIX);
- }
-
- /** Filter to skip over active lock files when listing a directory. */
- static final FilenameFilter FILTER = new FilenameFilter() {
- @Override
- public boolean accept(File dir, String name) {
- return !name.endsWith(LOCK_SUFFIX);
- }
- };
-
- private final File ref;
-
- private final File lck;
-
- private boolean haveLck;
-
- FileOutputStream os;
-
- private boolean needSnapshot;
-
- boolean fsync;
-
- private FileSnapshot commitSnapshot;
-
- private LockToken token;
-
- /**
- * Create a new lock for any file.
- *
- * @param f
- * the file that will be locked.
- */
- public LockFile(File f) {
- ref = f;
- lck = getLockFile(ref);
- }
-
- /**
- * Try to establish the lock.
- *
- * @return true if the lock is now held by the caller; false if it is held
- * by someone else.
- * @throws java.io.IOException
- * the temporary output file could not be created. The caller
- * does not hold the lock.
- */
- public boolean lock() throws IOException {
- FileUtils.mkdirs(lck.getParentFile(), true);
- token = FS.DETECTED.createNewFileAtomic(lck);
- if (token.isCreated()) {
- haveLck = true;
- try {
- os = new FileOutputStream(lck);
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- }
- } else {
- closeToken();
- }
- return haveLck;
- }
-
- /**
- * Try to establish the lock for appending.
- *
- * @return true if the lock is now held by the caller; false if it is held
- * by someone else.
- * @throws java.io.IOException
- * the temporary output file could not be created. The caller
- * does not hold the lock.
- */
- public boolean lockForAppend() throws IOException {
- if (!lock())
- return false;
- copyCurrentContent();
- return true;
- }
-
- /**
- * Copy the current file content into the temporary file.
- * <p>
- * This method saves the current file content by inserting it into the
- * temporary file, so that the caller can safely append rather than replace
- * the primary file.
- * <p>
- * This method does nothing if the current file does not exist, or exists
- * but is empty.
- *
- * @throws java.io.IOException
- * the temporary file could not be written, or a read error
- * occurred while reading from the current file. The lock is
- * released before throwing the underlying IO exception to the
- * caller.
- * @throws java.lang.RuntimeException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying exception to the caller.
- */
- public void copyCurrentContent() throws IOException {
- requireLock();
- try {
- try (FileInputStream fis = new FileInputStream(ref)) {
- if (fsync) {
- FileChannel in = fis.getChannel();
- long pos = 0;
- long cnt = in.size();
- while (0 < cnt) {
- long r = os.getChannel().transferFrom(in, pos, cnt);
- pos += r;
- cnt -= r;
- }
- } else {
- final byte[] buf = new byte[2048];
- int r;
- while ((r = fis.read(buf)) >= 0)
- os.write(buf, 0, r);
- }
- }
- } catch (FileNotFoundException fnfe) {
- if (ref.exists()) {
- unlock();
- throw fnfe;
- }
- // Don't worry about a file that doesn't exist yet, it
- // conceptually has no current content to copy.
- //
- } catch (IOException | RuntimeException | Error ioe) {
- unlock();
- throw ioe;
- }
- }
-
- /**
- * Write an ObjectId and LF to the temporary file.
- *
- * @param id
- * the id to store in the file. The id will be written in hex,
- * followed by a sole LF.
- * @throws java.io.IOException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying IO exception to the caller.
- * @throws java.lang.RuntimeException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying exception to the caller.
- */
- public void write(ObjectId id) throws IOException {
- byte[] buf = new byte[Constants.OBJECT_ID_STRING_LENGTH + 1];
- id.copyTo(buf, 0);
- buf[Constants.OBJECT_ID_STRING_LENGTH] = '\n';
- write(buf);
- }
-
- /**
- * Write arbitrary data to the temporary file.
- *
- * @param content
- * the bytes to store in the temporary file. No additional bytes
- * are added, so if the file must end with an LF it must appear
- * at the end of the byte array.
- * @throws java.io.IOException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying IO exception to the caller.
- * @throws java.lang.RuntimeException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying exception to the caller.
- */
- public void write(byte[] content) throws IOException {
- requireLock();
- try {
- if (fsync) {
- FileChannel fc = os.getChannel();
- ByteBuffer buf = ByteBuffer.wrap(content);
- while (0 < buf.remaining())
- fc.write(buf);
- fc.force(true);
- } else {
- os.write(content);
- }
- os.close();
- os = null;
- } catch (IOException | RuntimeException | Error ioe) {
- unlock();
- throw ioe;
- }
- }
-
- /**
- * Obtain the direct output stream for this lock.
- * <p>
- * The stream may only be accessed once, and only after {@link #lock()} has
- * been successfully invoked and returned true. Callers must close the
- * stream prior to calling {@link #commit()} to commit the change.
- *
- * @return a stream to write to the new file. The stream is unbuffered.
- */
- public OutputStream getOutputStream() {
- requireLock();
-
- final OutputStream out;
- if (fsync)
- out = Channels.newOutputStream(os.getChannel());
- else
- out = os;
-
- return new OutputStream() {
- @Override
- public void write(byte[] b, int o, int n)
- throws IOException {
- out.write(b, o, n);
- }
-
- @Override
- public void write(byte[] b) throws IOException {
- out.write(b);
- }
-
- @Override
- public void write(int b) throws IOException {
- out.write(b);
- }
-
- @Override
- public void close() throws IOException {
- try {
- if (fsync)
- os.getChannel().force(true);
- out.close();
- os = null;
- } catch (IOException | RuntimeException | Error ioe) {
- unlock();
- throw ioe;
- }
- }
- };
- }
-
- void requireLock() {
- if (os == null) {
- unlock();
- throw new IllegalStateException(MessageFormat.format(JGitText.get().lockOnNotHeld, ref));
- }
- }
-
- /**
- * Request that {@link #commit()} remember modification time.
- * <p>
- * This is an alias for {@code setNeedSnapshot(true)}.
- *
- * @param on
- * true if the commit method must remember the modification time.
- */
- public void setNeedStatInformation(boolean on) {
- setNeedSnapshot(on);
- }
-
- /**
- * Request that {@link #commit()} remember the
- * {@link org.eclipse.jgit.internal.storage.file.FileSnapshot}.
- *
- * @param on
- * true if the commit method must remember the FileSnapshot.
- */
- public void setNeedSnapshot(boolean on) {
- needSnapshot = on;
- }
-
- /**
- * Request that {@link #commit()} force dirty data to the drive.
- *
- * @param on
- * true if dirty data should be forced to the drive.
- */
- public void setFSync(boolean on) {
- fsync = on;
- }
-
- /**
- * Wait until the lock file information differs from the old file.
- * <p>
- * This method tests the last modification date. If both are the same, this
- * method sleeps until it can force the new lock file's modification date to
- * be later than the target file.
- *
- * @throws java.lang.InterruptedException
- * the thread was interrupted before the last modified date of
- * the lock file was different from the last modified date of
- * the target file.
- */
- public void waitForStatChange() throws InterruptedException {
- FileSnapshot o = FileSnapshot.save(ref);
- FileSnapshot n = FileSnapshot.save(lck);
- while (o.equals(n)) {
- Thread.sleep(25 /* milliseconds */);
- lck.setLastModified(System.currentTimeMillis());
- n = FileSnapshot.save(lck);
- }
- }
-
- /**
- * Commit this change and release the lock.
- * <p>
- * If this method fails (returns false) the lock is still released.
- *
- * @return true if the commit was successful and the file contains the new
- * data; false if the commit failed and the file remains with the
- * old data.
- * @throws java.lang.IllegalStateException
- * the lock is not held.
- */
- public boolean commit() {
- if (os != null) {
- unlock();
- throw new IllegalStateException(MessageFormat.format(JGitText.get().lockOnNotClosed, ref));
- }
-
- saveStatInformation();
- try {
- FileUtils.rename(lck, ref, StandardCopyOption.ATOMIC_MOVE);
- haveLck = false;
- closeToken();
- return true;
- } catch (IOException e) {
- unlock();
- return false;
- }
- }
-
- private void closeToken() {
- if (token != null) {
- token.close();
- token = null;
- }
- }
-
- private void saveStatInformation() {
- if (needSnapshot)
- commitSnapshot = FileSnapshot.save(lck);
- }
-
- /**
- * Get the modification time of the output file when it was committed.
- *
- * @return modification time of the lock file right before we committed it.
- */
- public long getCommitLastModified() {
- return commitSnapshot.lastModified();
- }
-
- /**
- * Get the {@link FileSnapshot} just before commit.
- *
- * @return get the {@link FileSnapshot} just before commit.
- */
- public FileSnapshot getCommitSnapshot() {
- return commitSnapshot;
- }
-
- /**
- * Update the commit snapshot {@link #getCommitSnapshot()} before commit.
- * <p>
- * This may be necessary if you need time stamp before commit occurs, e.g
- * while writing the index.
- */
- public void createCommitSnapshot() {
- saveStatInformation();
- }
-
- /**
- * Unlock this file and abort this change.
- * <p>
- * The temporary file (if created) is deleted before returning.
- */
- public void unlock() {
- if (os != null) {
- try {
- os.close();
- } catch (IOException e) {
- LOG.error(MessageFormat
- .format(JGitText.get().unlockLockFileFailed, lck), e);
- }
- os = null;
- }
-
- if (haveLck) {
- haveLck = false;
- try {
- FileUtils.delete(lck, FileUtils.RETRY);
- } catch (IOException e) {
- LOG.error(MessageFormat
- .format(JGitText.get().unlockLockFileFailed, lck), e);
- } finally {
- closeToken();
- }
- }
- }
-
- /** {@inheritDoc} */
- @SuppressWarnings("nls")
- @Override
- public String toString() {
- return "LockFile[" + lck + ", haveLck=" + haveLck + "]";
- }
- }
|