java.lang.Object
- org.apache.druid.frame.allocation.ArenaMemoryAllocator

All Implemented Interfaces:

MemoryAllocator
```
public class ArenaMemoryAllocator
extends Object
implements MemoryAllocator
```
Allocator that uses a reusable WritableMemory arena. The allocator maintains a high watermark that is reset to zero when all outstanding allocations have been freed.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Optional<ResourceHolder<org.apache.datasketches.memory.WritableMemory>>`	`allocate(long size)`	Allocates a block of memory of capacity {@param size}.
`long`	`available()`	Returns the number of bytes available for allocations.
`long`	`capacity()`	Returns the number of bytes managed by this allocator.
`static ArenaMemoryAllocator`	`create(ByteBuffer buffer)`	Creates an allocator based on a specific `ByteBuffer`.
`static ArenaMemoryAllocator`	`createOnHeap(int capacity)`	Creates an allocator of a specific size using an on-heap `ByteBuffer`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - create
```
public static ArenaMemoryAllocator create(ByteBuffer buffer)
```
    Creates an allocator based on a specific ByteBuffer. The buffer is never freed, so to ensure proper cleanup when the allocator is discarded, this buffer must be on-heap (so it can be garbage collected) rather than off-heap.
  - createOnHeap
```
public static ArenaMemoryAllocator createOnHeap(int capacity)
```
    Creates an allocator of a specific size using an on-heap ByteBuffer.
  - allocate
```
public Optional<ResourceHolder<org.apache.datasketches.memory.WritableMemory>> allocate(long size)
```
    Description copied from interface: MemoryAllocator
    
    Allocates a block of memory of capacity {@param size}. Returns empty if no more memory is available. The memory can be freed by closing the returned ResourceHolder. The returned WritableMemory object will use little-endian byte order.
    
    Specified by:
    
    allocate in interface MemoryAllocator
  - available
```
public long available()
```
    Description copied from interface: MemoryAllocator
    
    Returns the number of bytes available for allocations. May return Long.MAX_VALUE if there is no inherent limit. This generally does not mean you can actually allocate 9 exabytes.
    
    Specified by:
    
    available in interface MemoryAllocator
  - capacity
```
public long capacity()
```
    Description copied from interface: MemoryAllocator
    
    Returns the number of bytes managed by this allocator. When no memory has been allocated yet, this is identical to MemoryAllocator.available(). May return Long.MAX_VALUE if there is no inherent limit. This generally does not mean you can actually allocate 9 exabytes.
    
    Specified by:
    
    capacity in interface MemoryAllocator

Class ArenaMemoryAllocator

Method Summary

Methods inherited from class java.lang.Object

Method Detail

create

createOnHeap

allocate

available

capacity