| /* |
| * 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 android.annotation.UnsupportedAppUsage; |
| import android.os.Build; |
| 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; |
| |
| @UnsupportedAppUsage |
| 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. |
| */ |
| @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) |
| 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. |
| * <p> |
| * Call {@link #commit} to commit the changes, or {@link #rollback} to forget the changes. |
| */ |
| @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) |
| 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. |
| */ |
| @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) |
| public void commit() { |
| if (!mWriting) { |
| throw new IllegalStateException("no file to commit"); |
| } |
| mWriting = false; |
| mTemp.renameTo(mReal); |
| } |
| |
| /** |
| * Roll back changes. |
| */ |
| @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) |
| public void rollback() { |
| if (!mWriting) { |
| throw new IllegalStateException("no file to roll back"); |
| } |
| mWriting = false; |
| mTemp.delete(); |
| } |
| } |