org.apache.drill.exec.memory

Interface AllocationReservation

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

BaseAllocator.Reservation

public interface AllocationReservation
extends AutoCloseable

Supports cumulative allocation reservation. Clients may increase the size of the reservation repeatedly until they call for an allocation of the current total size. The reservation can only be used once, and will throw an exception if it is used more than once.

For the purposes of airtight memory accounting, the reservation must be close()d whether it is used or not. This is not threadsafe.

Method Summary

Modifier and Type	Method and Description
boolean	add(int nBytes) Add to the current reservation.
DrillBuf	allocateBuffer() Allocate a buffer whose size is the total of all the add()s made.
void	close()
int	getSize() Get the current size of the reservation (the sum of all the add()s).
boolean	isClosed() Return whether or not the reservation has been closed.
boolean	isUsed() Return whether or not the reservation has been used.
boolean	reserve(int nBytes) Requests a reservation of additional space.

Method Detail

add

boolean add(int nBytes)

Add to the current reservation.

Adding may fail if the allocator is not allowed to consume any more space.

Parameters:

nBytes - the number of bytes to add

Returns:

true if the addition is possible, false otherwise

Throws:

IllegalStateException - if called after buffer() is used to allocate the reservation

reserve

boolean reserve(int nBytes)

Requests a reservation of additional space.

The implementation of the allocator's inner class provides this.

Parameters:

nBytes - the amount to reserve

Returns:

true if the reservation can be satisfied, false otherwise

allocateBuffer

DrillBuf allocateBuffer()

Allocate a buffer whose size is the total of all the add()s made.

The allocation request can still fail, even if the amount of space requested is available, if the allocation cannot be made contiguously.

Returns:

the buffer, or null, if the request cannot be satisfied

Throws:

IllegalStateException - if called called more than once

getSize

int getSize()

Get the current size of the reservation (the sum of all the add()s).

Returns:

size of the current reservation

isUsed

boolean isUsed()

Return whether or not the reservation has been used.

Returns:

whether or not the reservation has been used

isClosed

boolean isClosed()

Return whether or not the reservation has been closed.

Returns:

whether or not the reservation has been closed

close

void close()

Specified by:

close in interface AutoCloseable