File	Doc	Category	Size	Date	Package
MemoryFile.java	API Doc	Android 5.1 API	11314	Thu Mar 12 22:22:10 GMT 2015	android.os

MemoryFile

• java.lang.Object

Fields Summary
private static String	TAG
private static final int	PROT_READ
private static final int	PROT_WRITE
private FileDescriptor	mFD
private long	mAddress
private int	mLength
private boolean	mAllowPurging

Constructors Summary

public MemoryFile(String name, int length) Allocates a new ashmem region. The region is initially not purgable. param name optional name for the file (can be null). param length of the memory file in bytes, must be non-negative. throws IOException if the memory file could not be created. // true if our ashmem region is unpinned mLength = length; if (length >= 0) { mFD = native_open(name, length); } else { throw new IOException("Invalid length: " + length); } if (length > 0) { mAddress = native_mmap(mFD, length, PROT_READ | PROT_WRITE); } else { mAddress = 0; }

Methods Summary
public synchronized boolean	allowPurging(boolean allowPurging) Enables or disables purging of the memory file. param allowPurging true if the operating system can purge the contents of the file in low memory situations return previous value of allowPurging boolean oldValue = mAllowPurging; if (oldValue != allowPurging) { native_pin(mFD, !allowPurging); mAllowPurging = allowPurging; } return oldValue;
public void	close() Closes the memory file. If there are no other open references to the memory file, it will be deleted. deactivate(); if (!isClosed()) { native_close(mFD); }
void	deactivate() Unmaps the memory file from the process's memory space, but does not close it. After this method has been called, read and write operations through this object will fail, but {@link #getFileDescriptor()} will still return a valid file descriptor. hide if (!isDeactivated()) { try { native_munmap(mAddress, mLength); mAddress = 0; } catch (IOException ex) { Log.e(TAG, ex.toString()); } }
protected void	finalize() if (!isClosed()) { Log.e(TAG, "MemoryFile.finalize() called while ashmem still open"); close(); }
public java.io.FileDescriptor	getFileDescriptor() Gets a FileDescriptor for the memory file. The returned file descriptor is not duplicated. throws IOException If the memory file has been closed. hide return mFD;
public java.io.InputStream	getInputStream() Creates a new InputStream for reading from the memory file. return InputStream return new MemoryInputStream();
public java.io.OutputStream	getOutputStream() Creates a new OutputStream for writing to the memory file. return OutputStream return new MemoryOutputStream();
public static int	getSize(java.io.FileDescriptor fd) Returns the size of the memory file that the file descriptor refers to, or -1 if the file descriptor does not refer to a memory file. throws IOException If fd is not a valid file descriptor. hide return native_get_size(fd);
private boolean	isClosed() Checks whether the memory file has been closed. return !mFD.valid();
private boolean	isDeactivated() Checks whether the memory file has been deactivated. return mAddress == 0;
public boolean	isPurgingAllowed() Is memory file purging enabled? return true if the file may be purged. return mAllowPurging;
public int	length() Returns the length of the memory file. return file length. return mLength;
private static native void	native_close(java.io.FileDescriptor fd)
private static native int	native_get_size(java.io.FileDescriptor fd)
private static native long	native_mmap(java.io.FileDescriptor fd, int length, int mode)
private static native void	native_munmap(long addr, int length)
private static native java.io.FileDescriptor	native_open(java.lang.String name, int length)
private static native void	native_pin(java.io.FileDescriptor fd, boolean pin)
private static native int	native_read(java.io.FileDescriptor fd, long address, byte[] buffer, int srcOffset, int destOffset, int count, boolean isUnpinned)
private static native void	native_write(java.io.FileDescriptor fd, long address, byte[] buffer, int srcOffset, int destOffset, int count, boolean isUnpinned)
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. param buffer byte array to read bytes into. param srcOffset offset into the memory file to read from. param destOffset offset into the byte array buffer to read into. param count number of bytes to read. return number of bytes read. throws IOException if the memory file has been purged or deactivated. if (isDeactivated()) { throw new IOException("Can't read from deactivated memory file."); } if (destOffset < 0 || destOffset > buffer.length || count < 0 || count > buffer.length - destOffset || srcOffset < 0 || srcOffset > mLength || count > mLength - srcOffset) { throw new IndexOutOfBoundsException(); } return native_read(mFD, mAddress, buffer, srcOffset, destOffset, count, mAllowPurging);
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. param buffer byte array to write bytes from. param srcOffset offset into the byte array buffer to write from. param destOffset offset into the memory file to write to. param count number of bytes to write. throws IOException if the memory file has been purged or deactivated. if (isDeactivated()) { throw new IOException("Can't write to deactivated memory file."); } if (srcOffset < 0 || srcOffset > buffer.length || count < 0 || count > buffer.length - srcOffset || destOffset < 0 || destOffset > mLength || count > mLength - destOffset) { throw new IndexOutOfBoundsException(); } native_write(mFD, mAddress, buffer, srcOffset, destOffset, count, mAllowPurging);