vecmem::allocator Class Reference

An allocator class that wraps a memory resource. More...

#include <vecmem/memory/allocator.hpp>

Public Member Functions
	allocator (memory_resource &mem)
	Construct an allocator.
void *	allocate_bytes (std::size_t bytes, std::size_t alignment=alignof(std::max_align_t))
	Allocate a given number of bytes.
void	deallocate_bytes (void *p, std::size_t bytes, std::size_t alignment=alignof(std::max_align_t))
	Deallocate a given number of bytes.
template<typename T >
T *	allocate_object (std::size_t n=1)
	Allocate space for (a number of) objects.
template<typename T >
void	deallocate_object (T *p, std::size_t n=1)
	Deallocate space for (a number of) objects.
template<typename T , typename... Args>
T *	new_object (Args &&... args)
	Allocate and construct a new object.
template<typename T >
void	delete_object (T *p)
	Deconstruct and deallocate an object.

Detailed Description

An allocator class that wraps a memory resource.

Sometimes we want to construct objects outside of vectors, and for those cases we need a simpler allocator that uses a memory resource to set the allocation strategy. This class is inspired by std::pmr::polymorphic_allocator but changes some things about it. Firstly, this class is not templated at a class level, and the templating only happens at a method level. This makes the class significantly easier to use. Secondly, this class emulates some of the C++20 functionality offered by the polymorphic allocator in a C++17 context.

Warning

Deallocating memory allocated with a different allocator (or rather, with an allocator using a different upstream memory resource) than the one doing the deallocation is not well-defined and should be avoided.

Constructor & Destructor Documentation

allocator()

vecmem::allocator::allocator

(

memory_resource &

mem

)

Construct an allocator.

Construct a new allocator on a given upstream memory resource.

Parameters

[in]

mem

The memory resource to use for allocations.

Member Function Documentation

allocate_bytes()

void * vecmem::allocator::allocate_bytes	(	std::size_t	bytes,
		std::size_t	alignment = alignof(std::max_align_t)
	)

Allocate a given number of bytes.

The most low-level allocation method provided by the allocator simply allocates a number of untyped bytes, optionally with some alignment. This can be used directly, or by other allocation methods to build more high-level functionality.

Parameters

[in]	bytes	The number of bytes to allocate.
[in]	alignment	The alignment boundary for the allocation.

allocate_object()

template<typename T >

T * vecmem::allocator::allocate_object

(

std::size_t

n = 1

)

Allocate space for (a number of) objects.

A mid-level allocator which abstracts away calculating the size of their allocation. The user simply provides the type and the number of objects to allocate space for.

Note

The space allocated by this method is not initialized in any way.

Template Parameters

T	The type of object to allocate space for.

Parameters

[in]

n

The number of objects of type T to allocate space for.

deallocate_bytes()

void vecmem::allocator::deallocate_bytes	(	void *	p,
		std::size_t	bytes,
		std::size_t	alignment = alignof(std::max_align_t)
	)

Deallocate a given number of bytes.

The most low-level deallocation method simply deallocates a number of bytes.

Warning

The onus is on the user to remember the size of each allocation, and this method might be too low-level for most purposes.

Parameters

[in]	p	The pointer to deallocate.
[in]	bytes	The number of bytes to deallocate.
[in]	alignment	The alignment boundary for the deallocation.

deallocate_object()

template<typename T >

void vecmem::allocator::deallocate_object	(	T *	p,
		std::size_t	n = 1
	)

Deallocate space for (a number of) objects.

A mid-level deallocator which abstracts away calculating the size of the deallocation.

Note

The space deallocated by this method is not deconstructed.

Template Parameters

T	The type of object to deallocater.

Parameters

[in]

n

The number of objects of type T to deallocate.

delete_object()

template<typename T >

void vecmem::allocator::delete_object

(

T *

p

)

Deconstruct and deallocate an object.

The highest-level deallocator we provide, this deconstructs and then deallocates an object.

Template Parameters

T	The type of object to delete.

Parameters

[in]

p

The object to delete.

new_object()

template<typename T , typename... Args>

T * vecmem::allocator::new_object

(

Args &&...

args

)

Allocate and construct a new object.

The highest-level allocator we provide, this allocates memory for and then constructs an object of the given type. Parameters passed to this method are passed on to the constructor for the object.

Template Parameters

T	The type to construct.
Args	The constructor parameter pack.

Parameters

[in]

args

The arguments to pass on to the class constructor.

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The documentation for this class was generated from the following files:

• core/include/vecmem/memory/allocator.hpp
• core/include/vecmem/memory/impl/allocator.ipp
• core/src/memory/allocator.cpp