storage_ptr

A smart pointer to a memory_resource.

Synopsis

Defined in header <boost/json/storage_ptr.hpp>

class storage_ptr

Member Functions

Name	Description
get	Return a pointer to the memory resource.
is_deallocate_trivial	Return `true` if calling `deallocate` on the memory resource has no effect.
is_not_shared_and_deallocate_is_trivial	Return `true` if ownership of the memory resource is not shared and deallocate is trivial.
is_shared	Return `true` if ownership of the memory resource is shared.
operator *	Return a reference to the memory resource.
operator->	Return a pointer to the memory resource.
operator=	Move assignment. — Copy assignment.
storage_ptr [constructor]	Constructor. — Move constructor. — Copy constructor.
~storage_ptr [destructor]	Destructor.

Friends

Name	Description
make_shared_resource	Return shared ownership of a new, dynamically allocated memory resource.

This container is used to hold a pointer to a memory resource. The pointed-to resource is always valid; default-constructed pointers use the default memory resource, which calls into the standard global system heap. Depending on the means of construction, the ownership will be either:

Non-owning, when constructing from a raw pointer to memory_resource or from a polymorphic_allocator. In this case the caller is responsible for ensuring that the lifetime of the memory resource extends until there are no more calls to allocate or deallocate.
Owning, when constructing using the function make_shared_resource. In this case ownership is shared; the lifetime of the memory resource extends until the last copy of the storage_ptr is destroyed.

Examples

These statements create a memory resource on the stack and construct a pointer from it without taking ownership:

monotonic_resource mr;                  // Create our memory resource on the stack
storage_ptr sp( &mr );                  // Construct a non-owning pointer to the resource

This function creates a pointer to a memory resource using shared ownership and returns it. The lifetime of the memory resource extends until the last copy of the pointer is destroyed:

// Create a counted memory resource and return it
storage_ptr make_storage()
{
    return make_shared_resource< monotonic_resource >();
}

Thread Safety

Instances of this type provide the default level of thread safety for all C++ objects. Specifically, it conforms to 16.4.6.10 Data race avoidance.

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