| /* |
| * 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 + "]"; |
| } |
| } |