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added in API level 1

MemoryFile

public class MemoryFile
extends Object

java.lang.Object
   ↳ android.os.MemoryFile


MemoryFile is a wrapper for SharedMemory which can optionally be set to purgeable. Applications should generally prefer to use SharedMemory which offers more flexible access & control over the shared memory region than MemoryFile does. 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)

Allocates a new ashmem region.

Public methods

boolean allowPurging(boolean allowPurging)

This method was deprecated in API level 27. Purgable is considered generally fragile and hard to use safely. Applications are recommend to instead use onTrimMemory(int) to react to memory events and release shared memory regions as appropriate.

void close()

Closes 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()

This method was deprecated in API level 27. Purgable is considered generally fragile and hard to use safely. Applications are recommend to instead use onTrimMemory(int) to react to memory events and release shared memory regions as appropriate.

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.

Inherited methods

Public constructors

MemoryFile

added in API level 1
MemoryFile (String name, 
                int length)

Allocates a new ashmem region. The region is initially not purgable.

Parameters
name String: optional name for the file (can be null).

length int: of the memory file in bytes, must be positive.

Throws
IOException if the memory file could not be created.

Public methods

allowPurging

added in API level 1
boolean allowPurging (boolean allowPurging)

This method was deprecated in API level 27.
Purgable is considered generally fragile and hard to use safely. Applications are recommend to instead use onTrimMemory(int) to react to memory events and release shared memory regions as appropriate.

Enables or disables purging of the memory file.

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

Returns
boolean previous value of allowPurging

Throws
IOException

close

added in API level 1
void close ()

Closes the memory file. If there are no other open references to the memory file, it will be deleted.

getInputStream

added in API level 1
InputStream getInputStream ()

Creates a new InputStream for reading from the memory file.

Returns
InputStream InputStream

getOutputStream

added in API level 1
OutputStream getOutputStream ()

Creates a new OutputStream for writing to the memory file.

Returns
OutputStream OutputStream

isPurgingAllowed

added in API level 1
boolean isPurgingAllowed ()

This method was deprecated in API level 27.
Purgable is considered generally fragile and hard to use safely. Applications are recommend to instead use onTrimMemory(int) to react to memory events and release shared memory regions as appropriate.

Is memory file purging enabled?

Returns
boolean true if the file may be purged.

length

added in API level 1
int length ()

Returns the length of the memory file.

Returns
int file length.

readBytes

added in API level 1
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: byte array to read bytes into.

srcOffset int: offset into the memory file to read from.

destOffset int: offset into the byte array buffer to read into.

count int: number of bytes to read.

Returns
int number of bytes read.

Throws
IOException if the memory file has been purged or deactivated.

writeBytes

added in API level 1
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: byte array to write bytes from.

srcOffset int: offset into the byte array buffer to write from.

destOffset int: offset into the memory file to write to.

count int: number of bytes to write.

Throws
IOException if the memory file has been purged or deactivated.
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