com.yahoo.memory

Class AllocMemory

java.lang.Object

com.yahoo.memory.NativeMemory

com.yahoo.memory.MemoryMappedFile

com.yahoo.memory.AllocMemory

All Implemented Interfaces:

Memory

public class AllocMemory
extends MemoryMappedFile

The AllocMemory class is a subclass of NativeMemory and is used to allocate direct, off-heap native memory, which is then accessed by the NativeMemory methods. It is the responsibility of the calling class to free this memory using freeMemory() when done.

The task of direct allocation was moved to this sub-class for performance reasons.

Author:

Lee Rhodes

Field Summary

Fields inherited from class com.yahoo.memory.NativeMemory

byteBuf_, capacityBytes_, memArray_, memReq_, nativeRawStartAddress_, objectBaseOffset_

Constructor Summary

Constructors

Constructor and Description
AllocMemory(long capacityBytes) Constructor for allocate native memory.
AllocMemory(long capacityBytes, MemoryRequest memReq) Constructor for allocate native memory with MemoryRequest.
AllocMemory(NativeMemory origMem, long copyToBytes, long capacityBytes, MemoryRequest memReq) Constructor for allocate native memory, copy and clear.
AllocMemory(NativeMemory origMem, long newCapacityBytes, MemoryRequest memReq) Constructor for reallocate native memory.

Method Summary

Modifier and Type	Method and Description
void	freeMemory() This frees this Memory only if it is required.

Methods inherited from class com.yahoo.memory.MemoryMappedFile

finalize, force, isLoaded, load

Methods inherited from class com.yahoo.memory.NativeMemory

array, asReadOnlyMemory, byteBuffer, clear, clear, clearBits, copy, copy, fill, fill, getAddress, getAndAddInt, getAndAddLong, getAndSetInt, getAndSetLong, getBoolean, getBooleanArray, getByte, getByteArray, getCapacity, getChar, getCharArray, getCumulativeOffset, getDouble, getDoubleArray, getFloat, getFloatArray, getInt, getIntArray, getLong, getLongArray, getMemoryRequest, getNativeMemory, getParent, getShort, getShortArray, hasArray, hasByteBuffer, isAllBitsClear, isAllBitsSet, isAllocated, isAnyBitsClear, isAnyBitsSet, isDirect, isReadOnly, putBoolean, putBooleanArray, putByte, putByteArray, putChar, putCharArray, putDouble, putDoubleArray, putFloat, putFloatArray, putInt, putIntArray, putLong, putLongArray, putShort, putShortArray, requiresFree, setBits, setMemoryRequest, toHexString

Methods inherited from class java.lang.Object

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

Constructor Detail

AllocMemory

public AllocMemory(long capacityBytes)

Constructor for allocate native memory.

Allocates and provides access to capacityBytes directly in native (off-heap) memory leveraging the Memory interface. The MemoryRequest callback is set to null.

Parameters:

capacityBytes - the size in bytes of the native memory

AllocMemory

public AllocMemory(long capacityBytes,
                   MemoryRequest memReq)

Constructor for allocate native memory with MemoryRequest.

Allocates and provides access to capacityBytes directly in native (off-heap) memory leveraging the Memory interface.

Parameters:

capacityBytes - the size in bytes of the native memory

memReq - The MemoryRequest callback

AllocMemory

public AllocMemory(NativeMemory origMem,
                   long newCapacityBytes,
                   MemoryRequest memReq)

Constructor for reallocate native memory.

Reallocates the given off-heap NativeMemory to a new a new native (off-heap) memory location and copies the contents of the original given NativeMemory to the new location. Any memory beyond the capacity of the original given NativeMemory will be uninitialized. Dispose of this new memory by calling NativeMemory.freeMemory().

Parameters:

origMem - The original NativeMemory that needs to be reallocated and must not be null. The OS is free to just expand the capacity of the current allocation at the same native address, or reassign a completely different native address in which case the origMem will be freed by the OS. The origMem capacity will be set to zero and must not be used again.

newCapacityBytes - the desired new capacity of the newly allocated memory in bytes

memReq - The MemoryRequest callback, which may be null.

AllocMemory

public AllocMemory(NativeMemory origMem,
                   long copyToBytes,
                   long capacityBytes,
                   MemoryRequest memReq)

Constructor for allocate native memory, copy and clear.

Allocate a new native (off-heap) memory with capacityBytes; copy the contents of origMem from zero to copyToBytes; clear the new memory from copyToBytes to capacityBytes.

Parameters:

origMem - The original NativeMemory, a portion of which will be copied to the newly allocated Memory. The reference must not be null. This origMem is not modified in any way, may be reused and must be freed appropriately.

copyToBytes - the upper limit of the region to be copied from origMem to the newly allocated memory.

capacityBytes - the desired new capacity of the newly allocated memory in bytes and the upper limit of the region to be cleared.

memReq - The MemoryRequest callback, which may be null.

Method Detail

freeMemory

public void freeMemory()

Description copied from class: NativeMemory

This frees this Memory only if it is required. This always sets the capacity to zero and the reference to MemoryRequest to null, which effectively disables this class.

It is always safe to call this method when you are done with this class.

Overrides:

freeMemory in class MemoryMappedFile