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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.lib;
-
- import java.io.BufferedOutputStream;
- 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.channels.FileLock;
- import java.nio.channels.OverlappingFileLockException;
-
- /**
- * 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 {
- static final String SUFFIX = ".lock"; //$NON-NLS-1$
-
- /** Filter to skip over active lock files when listing a directory. */
- static final FilenameFilter FILTER = new FilenameFilter() {
- public boolean accept(File dir, String name) {
- return !name.endsWith(SUFFIX);
- }
- };
-
- private final File ref;
-
- private final File lck;
-
- private FileLock fLck;
-
- private boolean haveLck;
-
- private FileOutputStream os;
-
- private boolean needStatInformation;
-
- private long commitLastModified;
-
- /**
- * Create a new lock for any file.
- *
- * @param f
- * the file that will be locked.
- */
- public LockFile(final File f) {
- ref = f;
- lck = new File(ref.getParentFile(), ref.getName() + SUFFIX);
- }
-
- /**
- * 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 IOException
- * the temporary output file could not be created. The caller
- * does not hold the lock.
- */
- public boolean lock() throws IOException {
- lck.getParentFile().mkdirs();
- if (lck.createNewFile()) {
- haveLck = true;
- try {
- os = new FileOutputStream(lck);
- try {
- fLck = os.getChannel().tryLock();
- if (fLck == null)
- throw new OverlappingFileLockException();
- } catch (OverlappingFileLockException ofle) {
- // We cannot use unlock() here as this file is not
- // held by us, but we thought we created it. We must
- // not delete it, as it belongs to some other process.
- //
- haveLck = false;
- try {
- os.close();
- } catch (IOException ioe) {
- // Fail by returning haveLck = false.
- }
- os = null;
- }
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- }
- }
- 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 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 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 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 {
- final FileInputStream fis = new FileInputStream(ref);
- try {
- final byte[] buf = new byte[2048];
- int r;
- while ((r = fis.read(buf)) >= 0)
- os.write(buf, 0, r);
- } finally {
- fis.close();
- }
- } catch (FileNotFoundException fnfe) {
- // Don't worry about a file that doesn't exist yet, it
- // conceptually has no current content to copy.
- //
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- } catch (RuntimeException ioe) {
- unlock();
- throw ioe;
- } catch (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 IOException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying IO exception to the caller.
- * @throws RuntimeException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying exception to the caller.
- */
- public void write(final ObjectId id) throws IOException {
- requireLock();
- try {
- final BufferedOutputStream b;
- b = new BufferedOutputStream(os, Constants.OBJECT_ID_STRING_LENGTH + 1);
- id.copyTo(b);
- b.write('\n');
- b.flush();
- fLck.release();
- b.close();
- os = null;
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- } catch (RuntimeException ioe) {
- unlock();
- throw ioe;
- } catch (Error ioe) {
- unlock();
- throw ioe;
- }
- }
-
- /**
- * 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 IOException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying IO exception to the caller.
- * @throws RuntimeException
- * the temporary file could not be written. The lock is released
- * before throwing the underlying exception to the caller.
- */
- public void write(final byte[] content) throws IOException {
- requireLock();
- try {
- os.write(content);
- os.flush();
- fLck.release();
- os.close();
- os = null;
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- } catch (RuntimeException ioe) {
- unlock();
- throw ioe;
- } catch (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();
- return new OutputStream() {
- @Override
- public void write(final byte[] b, final int o, final int n)
- throws IOException {
- os.write(b, o, n);
- }
-
- @Override
- public void write(final byte[] b) throws IOException {
- os.write(b);
- }
-
- @Override
- public void write(final int b) throws IOException {
- os.write(b);
- }
-
- @Override
- public void flush() throws IOException {
- os.flush();
- }
-
- @Override
- public void close() throws IOException {
- try {
- os.flush();
- fLck.release();
- os.close();
- os = null;
- } catch (IOException ioe) {
- unlock();
- throw ioe;
- } catch (RuntimeException ioe) {
- unlock();
- throw ioe;
- } catch (Error ioe) {
- unlock();
- throw ioe;
- }
- }
- };
- }
-
- private void requireLock() {
- if (os == null) {
- unlock();
- throw new IllegalStateException("Lock on " + ref + " not held.");
- }
- }
-
- /**
- * Request that {@link #commit()} remember modification time.
- *
- * @param on
- * true if the commit method must remember the modification time.
- */
- public void setNeedStatInformation(final boolean on) {
- needStatInformation = on;
- }
-
- /**
- * Wait until the lock file information differs from the old file.
- * <p>
- * This method tests both the length and 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 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 {
- if (ref.length() == lck.length()) {
- long otime = ref.lastModified();
- long ntime = lck.lastModified();
- while (otime == ntime) {
- Thread.sleep(25 /* milliseconds */);
- lck.setLastModified(System.currentTimeMillis());
- ntime = lck.lastModified();
- }
- }
- }
-
- /**
- * 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 IllegalStateException
- * the lock is not held.
- */
- public boolean commit() {
- if (os != null) {
- unlock();
- throw new IllegalStateException("Lock on " + ref + " not closed.");
- }
-
- saveStatInformation();
- if (lck.renameTo(ref))
- return true;
- if (!ref.exists() || ref.delete())
- if (lck.renameTo(ref))
- return true;
- unlock();
- return false;
- }
-
- private void saveStatInformation() {
- if (needStatInformation)
- commitLastModified = lck.lastModified();
- }
-
- /**
- * 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 commitLastModified;
- }
-
- /**
- * Unlock this file and abort this change.
- * <p>
- * The temporary file (if created) is deleted before returning.
- */
- public void unlock() {
- if (os != null) {
- if (fLck != null) {
- try {
- fLck.release();
- } catch (IOException ioe) {
- // Huh?
- }
- fLck = null;
- }
- try {
- os.close();
- } catch (IOException ioe) {
- // Ignore this
- }
- os = null;
- }
-
- if (haveLck) {
- haveLck = false;
- lck.delete();
- }
- }
-
- @Override
- public String toString() {
- return "LockFile[" + lck + ", haveLck=" + haveLck + "]";
- }
- }
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