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public class

MemoryFile

extends Object
java.lang.Object
   ↳ android.os.MemoryFile

Class Overview

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.
[Expand]
Inherited Methods
From class java.lang.Object

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.