IT. Expert System.

public class BackupDataInput
extends Object

 public void onRestore(BackupDataInput data, int appVersionCode,
                       ParcelFileDescriptor newState) {
     while (data.readNextHeader()) {
         String key = data.getKey();
         int dataSize = data.getDataSize();

         if (key.equals(MY_BACKUP_KEY_ONE)) {
             // process this kind of record here
             byte[] buffer = new byte[dataSize];
             data.readEntityData(buffer, 0, dataSize); // reads the entire entity at once

             // now 'buffer' holds the raw data and can be processed however
             // the agent wishes
             processBackupKeyOne(buffer);
         } else if (key.equals(MY_BACKUP_KEY_TO_IGNORE) {
             // a key we recognize but wish to discard
             data.skipEntityData();
         } // ... etc.
    }
 }

• Constructor Summary

  Constructors

  Constructor and Description
  BackupDataInput(FileDescriptor fd)

• Method Summary

  Methods

  Modifier and Type	Method and Description
  protected void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
  int	getDataSize() Report the size in bytes of the data associated with the current entity in the restore stream.
  String	getKey() Report the key associated with the current entity in the restore stream
  int	readEntityData(byte[] data, int offset, int size) Read a record's raw data from the restore stream.
  boolean	readNextHeader() Extract the next entity header from the restore stream.
  void	skipEntityData() Consume the current entity's data without extracting it into a buffer for further processing.

  • Methods inherited from class java.lang.Object

    clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

• Constructor Detail

  • BackupDataInput

    public BackupDataInput(FileDescriptor fd)

• Method Detail

  • finalize

    protected void finalize()
                     throws Throwable

    Description copied from class: Object
    Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

    Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

    If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

    Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

    Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

    Overrides:

    finalize in class Object

    Throws:

    Throwable

  • readNextHeader

    public boolean readNextHeader()
                           throws IOException

    Extract the next entity header from the restore stream. After this method return success, the getKey() and getDataSize() methods can be used to inspect the entity that is now available for processing.

    Returns:

    true when there is an entity ready for consumption from the restore stream, false if the restore stream has been fully consumed.

    Throws:

    IOException - if an error occurred while reading the restore stream

  • getKey

    public String getKey()

    Report the key associated with the current entity in the restore stream

    Returns:

    the current entity's key string

    Throws:

    IllegalStateException - if the next record header has not yet been read

  • getDataSize

    public int getDataSize()

    Report the size in bytes of the data associated with the current entity in the restore stream.

    Returns:

    The size of the record's raw data, in bytes

    Throws:

    IllegalStateException - if the next record header has not yet been read

  • readEntityData

    public int readEntityData(byte[] data,
                     int offset,
                     int size)
                       throws IOException

    Read a record's raw data from the restore stream. The record's header must first have been processed by the readNextHeader() method. Multiple calls to this method may be made in order to process the data in chunks; not all of it must be read in a single call. Once all of the raw data for the current entity has been read, further calls to this method will simply return zero.

    Parameters:

    data - An allocated byte array of at least 'size' bytes

    offset - Offset within the 'data' array at which the data will be placed when read from the stream

    size - The number of bytes to read in this pass

    Returns:

    The number of bytes of data read. Once all of the data for this entity has been read, further calls to this method will return zero.

    Throws:

    IOException - if an error occurred when trying to read the restore data stream

  • skipEntityData

    public void skipEntityData()
                        throws IOException

    Consume the current entity's data without extracting it into a buffer for further processing. This allows a BackupAgent to efficiently discard obsolete or otherwise uninteresting records during the restore operation.

    Throws:

    IOException - if an error occurred when trying to read the restore data stream