ArenaSharedHeapSTLAllocator.h File Reference

STL-style allocator wrapper for ArenaHeapAllocator allowing the heap to be shared between containers. More...

#include "AthAllocators/ArenaHeapAllocator.h"
#include "AthAllocators/ArenaHeapSTLAllocator.h"
#include "AthAllocators/ArenaAllocatorRegistry.h"
#include "CxxUtils/concepts.h"
#include <string>
#include <vector>
#include "AthAllocators/ArenaSharedHeapSTLAllocator.icc"

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Classes
class	SG::ArenaSharedHeapSTLAllocator< T >
	Forward declaration. More...
class	SG::ArenaSharedHeapSTLHeader
	Common header class for ArenaSharedHeapSTLAllocator. More...
class	SG::ArenaSharedHeapSTLAllocator< T >
	Forward declaration. More...
struct	SG::ArenaSharedHeapSTLAllocator< T >::rebind< U >
	Standard STL allocator rebinder. More...

Namespaces
	SG
	Forward declaration.

Functions
template<class T >
void	SG::swap (ArenaSharedHeapSTLAllocator< T > &a, ArenaSharedHeapSTLAllocator< T > &b)
template<class T >
void	SG::maybeUnprotect (ArenaSharedHeapSTLAllocator< T > &a)
	Hook for unprotecting an arena. More...

Detailed Description

STL-style allocator wrapper for ArenaHeapAllocator allowing the heap to be shared between containers.

Author

scott snyder snyde.nosp@m.r@bn.nosp@m.l.gov

Date

Nov, 2011 This class defines a STL-style allocator for types T with the following special properties.

• We use an ArenaHeapAllocator for allocations.
• Only one object at a time may be allocated.
• The memory from several allocators may be grouped together in the same memory pool.

So, this allocator is suitable for an STL container which allocates lots of fixed-size objects, such as std::list, and further, you want to be able to have multiple list instances use the same pool.

Note that this allocator will not work for containers that make variable-sized allocations, such as vector and the hash table containers.

To use it, you should first explicitly create the allocator class, and then pass it to the constructors of the containers. The memory pool will be deleted when the original allocator instance is deleted. Example:

{
  typedef SG::ArenaSharedHeapSTLAllocator<int> alloc_t;
  typedef std::list<int> list_t;
 
  alloc_t allocator;
  list_t list1 (allocator);
  list_t list2 (allocator);
  ... Now list1 and list2 will both use the same memory pool.
}
... The memory pool is freed when the object `allocator' is deleted.

Implementation: Each allocator references a Header object, which is common to all allocators in the pool. When an allocator is copied, the header pointer is copied too. The Header object remembers the address of the allocator which originally created it, so that we can clean things up when that allocator goes away.

A Header contains a list of ArenaHeapAllocator objects, one per payload type. We use ArenaAllocatorRegistry to assign indices to the different allocator types.

Definition in file ArenaSharedHeapSTLAllocator.h.