Android example source code file (FileBackupHelperBase.java)

This example Android source code file (FileBackupHelperBase.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, backupdatainputstream, backupdataoutput, content, context, failed, filebackuphelperbase, filedescriptor, io, nullpointerexception, os, parcelfiledescriptor, runtimeexception, string, tag, throwable, utilities, utils

The FileBackupHelperBase.java Android example source code

/*
 * 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 android.app.backup;

import android.content.Context;
import android.os.ParcelFileDescriptor;
import android.util.Log;

import java.io.File;
import java.io.FileDescriptor;

/**
 * Base class for the {@link android.app.backup.FileBackupHelper} implementation.
 */
class FileBackupHelperBase {
    private static final String TAG = "FileBackupHelperBase";

    int mPtr;
    Context mContext;
    boolean mExceptionLogged;
    
    FileBackupHelperBase(Context context) {
        mPtr = ctor();
        mContext = context;
    }

    protected void finalize() throws Throwable {
        try {
            dtor(mPtr);
        } finally {
            super.finalize();
        }
    }

    /**
     * Check the parameters so the native code doesn't have to throw all the exceptions
     * since it's easier to do that from Java.
     */
    static void performBackup_checked(ParcelFileDescriptor oldState, BackupDataOutput data,
            ParcelFileDescriptor newState, String[] files, String[] keys) {
        if (files.length == 0) {
            return;
        }
        // files must be all absolute paths
        for (String f: files) {
            if (f.charAt(0) != '/') {
                throw new RuntimeException("files must have all absolute paths: " + f);
            }
        }
        // the length of files and keys must be the same
        if (files.length != keys.length) {
            throw new RuntimeException("files.length=" + files.length
                    + " keys.length=" + keys.length);
        }
        // oldStateFd can be null
        FileDescriptor oldStateFd = oldState != null ? oldState.getFileDescriptor() : null;
        FileDescriptor newStateFd = newState.getFileDescriptor();
        if (newStateFd == null) {
            throw new NullPointerException();
        }

        int err = performBackup_native(oldStateFd, data.mBackupWriter, newStateFd, files, keys);

        if (err != 0) {
            // TODO: more here
            throw new RuntimeException("Backup failed 0x" + Integer.toHexString(err));
        }
    }

    void writeFile(File f, BackupDataInputStream in) {
        int result = -1;

        // Create the enclosing directory.
        File parent = f.getParentFile();
        parent.mkdirs();

        result = writeFile_native(mPtr, f.getAbsolutePath(), in.mData.mBackupReader);
        if (result != 0) {
            // Bail on this entity.  Only log one failure per helper object.
            if (!mExceptionLogged) {
                Log.e(TAG, "Failed restoring file '" + f + "' for app '"
                        + mContext.getPackageName() + "\' result=0x"
                        + Integer.toHexString(result));
                mExceptionLogged = true;
            }
        }
    }

    public void writeNewStateDescription(ParcelFileDescriptor fd) {
        int result = writeSnapshot_native(mPtr, fd.getFileDescriptor());
        // TODO: Do something with the error.
    }

    boolean isKeyInList(String key, String[] list) {
        for (String s: list) {
            if (s.equals(key)) {
                return true;
            }
        }
        return false;
    }

    private static native int ctor();
    private static native void dtor(int ptr);

    native private static int performBackup_native(FileDescriptor oldState,
            int data, FileDescriptor newState, String[] files, String[] keys);
    
    private static native int writeFile_native(int ptr, String filename, int backupReader);
    private static native int writeSnapshot_native(int ptr, FileDescriptor fd);
}