Android
android.os
public class

android.os.MemoryFile

java.lang.Object
android.os.MemoryFile

MemoryFile is a wrapper for the Linux ashmem driver. MemoryFiles are backed by shared memory, which can be optionally set to be purgeable. Purgeable files may have their contents reclaimed by the kernel in low memory conditions (only if allowPurging is set to true). After a file is purged, attempts to read or write the file will cause an IOException to be thrown.

Summary

Public Constructors

            MemoryFile(String name, int length)
MemoryFile constructor.

Public Methods

  synchronized        boolean  allowPurging(boolean allowPurging)
Enables or disables purging of the memory file.
          void  close()
Closes and releases all resources for the memory file.
          InputStream  getInputStream()
Creates a new InputStream for reading from the memory file.
          OutputStream  getOutputStream()
Creates a new OutputStream for writing to the memory file.
          boolean  isPurgingAllowed()
Is memory file purging enabled?
          int  length()
Returns the length of the memory file.
          int  readBytes(byte[] buffer, int srcOffset, int destOffset, int count)
Reads bytes from the memory file.
          void  writeBytes(byte[] buffer, int srcOffset, int destOffset, int count)
Write bytes to the memory file.

Protected Methods

          void  finalize()
Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
Methods inherited from class java.lang.Object

Details

Public Constructors

public MemoryFile(String name, int length)

MemoryFile constructor.

Parameters

name optional name for the file (can be null).
length of the memory file in bytes.

Public Methods

public synchronized boolean allowPurging(boolean allowPurging)

Enables or disables purging of the memory file.

Parameters

allowPurging true if the operating system can purge the contents of the file in low memory situations

Returns

  • previous value of allowPurging

Throws

IOException

public void close()

Closes and releases all resources for the memory file.

public InputStream getInputStream()

Creates a new InputStream for reading from the memory file.

Returns

  • InputStream

public OutputStream getOutputStream()

Creates a new OutputStream for writing to the memory file.

Returns

  • OutputStream

public boolean isPurgingAllowed()

Is memory file purging enabled?

Returns

  • true if the file may be purged.

public int length()

Returns the length of the memory file.

Returns

  • file length.

public int readBytes(byte[] buffer, int srcOffset, int destOffset, int count)

Reads bytes from the memory file. Will throw an IOException if the file has been purged.

Parameters

buffer byte array to read bytes into.
srcOffset offset into the memory file to read from.
destOffset offset into the byte array buffer to read into.
count number of bytes to read.

Returns

  • number of bytes read.

Throws

IOException

public void writeBytes(byte[] buffer, int srcOffset, int destOffset, int count)

Write bytes to the memory file. Will throw an IOException if the file has been purged.

Parameters

buffer byte array to write bytes from.
srcOffset offset into the byte array buffer to write from.
destOffset offset into the memory file to write to.
count number of bytes to write.

Throws

IOException

Protected Methods

protected void finalize()

Called by the virtual machine when there are no longer any (non-weak) references to the receiver. Subclasses can use this facility to guarantee that any associated resources are cleaned up before the receiver is garbage collected. Uncaught exceptions which are thrown during the running of the method cause it to terminate immediately, but are otherwise ignored.

Note: The virtual machine assumes that the implementation in class Object is empty.

Copyright 2007 Google Inc. Build 0.9_r1-98467 - 14 Aug 2008 18:56