/* * Copyright (C) 2009 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.android.internal.util; import java.io.File; import java.io.IOException; /** * @deprecated Use {@code AtomicFile} instead. It would * be nice to update all existing uses of this to switch to AtomicFile, but since * their on-file semantics are slightly different that would run the risk of losing * data if at the point of the platform upgrade to the new code it would need to * roll back to the backup file. This can be solved... but is it worth it and * all of the testing needed to make sure it is correct? */ @Deprecated public class JournaledFile { File mReal; File mTemp; boolean mWriting; public JournaledFile(File real, File temp) { mReal = real; mTemp = temp; } /** Returns the file for you to read. * @more * Prefers the real file. If it doesn't exist, uses the temp one, and then copies * it to the real one. If there is both a real file and a temp one, assumes that the * temp one isn't fully written and deletes it. */ public File chooseForRead() { File result; if (mReal.exists()) { result = mReal; if (mTemp.exists()) { mTemp.delete(); } } else if (mTemp.exists()) { result = mTemp; mTemp.renameTo(mReal); } else { return mReal; } return result; } /** * Returns a file for you to write. * @more * If a write is already happening, throws. In other words, you must provide your * own locking. *

* Call {@link #commit} to commit the changes, or {@link #rollback} to forget the changes. */ public File chooseForWrite() { if (mWriting) { throw new IllegalStateException("uncommitted write already in progress"); } if (!mReal.exists()) { // If the real one doesn't exist, it's either because this is the first time // or because something went wrong while copying them. In this case, we can't // trust anything that's in temp. In order to have the chooseForRead code not // use the temporary one until it's fully written, create an empty file // for real, which will we'll shortly delete. try { mReal.createNewFile(); } catch (IOException e) { // Ignore } } if (mTemp.exists()) { mTemp.delete(); } mWriting = true; return mTemp; } /** * Commit changes. */ public void commit() { if (!mWriting) { throw new IllegalStateException("no file to commit"); } mWriting = false; mTemp.renameTo(mReal); } /** * Roll back changes. */ public void rollback() { if (!mWriting) { throw new IllegalStateException("no file to roll back"); } mWriting = false; mTemp.delete(); } }