Android example source code file (BackupHelperDispatcher.java)

This example Android source code file (BackupHelperDispatcher.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, backuphelper, backuphelperdispatcher, couldn't, entity, filedescriptor, header, io, ioexception, os, parcelfiledescriptor, string, tag, treemap, util, utilities, utils

The BackupHelperDispatcher.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.os.ParcelFileDescriptor;
import android.util.Log;

import java.io.FileDescriptor;
import java.io.IOException;
import java.util.Map;
import java.util.TreeMap;

/** @hide */
public class BackupHelperDispatcher {
    private static final String TAG = "BackupHelperDispatcher";

    private static class Header {
        int chunkSize; // not including the header
        String keyPrefix;
    }

    TreeMap<String,BackupHelper> mHelpers = new TreeMap();
    
    public BackupHelperDispatcher() {
    }

    public void addHelper(String keyPrefix, BackupHelper helper) {
        mHelpers.put(keyPrefix, helper);
    }

    public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
             ParcelFileDescriptor newState) throws IOException {
        // First, do the helpers that we've already done, since they're already in the state
        // file.
        int err;
        Header header = new Header();
        TreeMap<String,BackupHelper> helpers = (TreeMap)mHelpers.clone();
        FileDescriptor oldStateFD = null;
        FileDescriptor newStateFD = newState.getFileDescriptor();

        if (oldState != null) {
            oldStateFD = oldState.getFileDescriptor();
            while ((err = readHeader_native(header, oldStateFD)) >= 0) {
                if (err == 0) {
                    BackupHelper helper = helpers.get(header.keyPrefix);
                    Log.d(TAG, "handling existing helper '" + header.keyPrefix + "' " + helper);
                    if (helper != null) {
                        doOneBackup(oldState, data, newState, header, helper);
                        helpers.remove(header.keyPrefix);
                    } else {
                        skipChunk_native(oldStateFD, header.chunkSize);
                    }
                }
            }
        }

        // Then go through and do the rest that we haven't done.
        for (Map.Entry<String,BackupHelper> entry: helpers.entrySet()) {
            header.keyPrefix = entry.getKey();
            Log.d(TAG, "handling new helper '" + header.keyPrefix + "'");
            BackupHelper helper = entry.getValue();
            doOneBackup(oldState, data, newState, header, helper);
        }
    }

    private void doOneBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
            ParcelFileDescriptor newState, Header header, BackupHelper helper) 
            throws IOException {
        int err;
        FileDescriptor newStateFD = newState.getFileDescriptor();

        // allocate space for the header in the file
        int pos = allocateHeader_native(header, newStateFD);
        if (pos < 0) {
            throw new IOException("allocateHeader_native failed (error " + pos + ")");
        }

        data.setKeyPrefix(header.keyPrefix);

        // do the backup
        helper.performBackup(oldState, data, newState);

        // fill in the header (seeking back to pos).  The file pointer will be returned to
        // where it was at the end of performBackup.  Header.chunkSize will not be filled in.
        err = writeHeader_native(header, newStateFD, pos);
        if (err != 0) {
            throw new IOException("writeHeader_native failed (error " + err + ")");
        }
    }

    public void performRestore(BackupDataInput input, int appVersionCode,
            ParcelFileDescriptor newState)
            throws IOException {
        boolean alreadyComplained = false;

        BackupDataInputStream stream = new BackupDataInputStream(input);
        while (input.readNextHeader()) {

            String rawKey = input.getKey();
            int pos = rawKey.indexOf(':');
            if (pos > 0) {
                String prefix = rawKey.substring(0, pos);
                BackupHelper helper = mHelpers.get(prefix);
                if (helper != null) {
                    stream.dataSize = input.getDataSize();
                    stream.key = rawKey.substring(pos+1);
                    helper.restoreEntity(stream);
                } else {
                    if (!alreadyComplained) {
                        Log.w(TAG, "Couldn't find helper for: '" + rawKey + "'");
                        alreadyComplained = true;
                    }
                }
            } else {
                if (!alreadyComplained) {
                    Log.w(TAG, "Entity with no prefix: '" + rawKey + "'");
                    alreadyComplained = true;
                }
            }
            input.skipEntityData(); // In case they didn't consume the data.
        }

        // Write out the state files -- mHelpers is a TreeMap, so the order is well defined.
        for (BackupHelper helper: mHelpers.values()) {
            helper.writeNewStateDescription(newState);
        }
    }

    private static native int readHeader_native(Header h, FileDescriptor fd);
    private static native int skipChunk_native(FileDescriptor fd, int bytesToSkip);

    private static native int allocateHeader_native(Header h, FileDescriptor fd);
    private static native int writeHeader_native(Header h, FileDescriptor fd, int pos);
}