it::d4np::memorypool::PoolAllocator< T > Class Template Reference

STL-compatible allocator vending storage from a Pool. More...

#include <pool_allocator.hpp>

Public Types
using	value_type = T
using	propagate_on_container_copy_assignment = std::false_type
using	propagate_on_container_move_assignment = std::false_type
using	propagate_on_container_swap = std::false_type
using	is_always_equal = std::false_type

Public Member Functions
	PoolAllocator (Pool &pool) noexcept
	Bind the adapter to pool.
template<typename U >
	PoolAllocator (const PoolAllocator< U > &other) noexcept
	Rebinding converting constructor — required by the Cpp17Allocator requirements so a container can build an allocator for its internal node type from the user-supplied PoolAllocator<T>.
T *	allocate (std::size_t n)
	Allocate storage for n objects of T (ADR-0018 §2).
void	deallocate (T *ptr, std::size_t n) noexcept
	Return storage obtained from allocate.
template<typename U >
bool	operator== (const PoolAllocator< U > &rhs) const noexcept
	Two adapters are equal iff they reference the same pool.
template<typename U >
bool	operator!= (const PoolAllocator< U > &rhs) const noexcept
	Negation of operator==.

Detailed Description

template<typename T>
class it::d4np::memorypool::PoolAllocator< T >

STL-compatible allocator vending storage from a Pool.

Routing (ADR-0018 §2). A request routes to the pool iff it is a single block that fits — n == 1, sizeof(T) <= pool.block_size(), and T is not over-aligned. Such requests are served by Pool::allocate (O(1), throwing std::bad_alloc on exhaustion per ADR-0016 §2). Every other request — n > 1, an over-aligned T, or a rebound node larger than the block — is delegated to over-aligned ::operator new / ::operator delete.

Because the standard guarantees deallocate(p, n) is called with the same n (and on the same allocator type, hence the same sizeof(T) / alignof(T)) as the matching allocate(n), and block_size() is invariant for the pool's lifetime, the routing predicate evaluates identically at allocate and deallocate time. Every pointer is therefore freed by exactly the path that allocated it, with no per-pointer bookkeeping.

As a result a single container may, over its lifetime, hold storage from both sources (e.g. a std::vector whose n == 1 initial capacity came from the pool and whose grown buffer came from the heap) — correct, if occasionally surprising.

Propagation (ADR-0018 §4). All three propagate_on_container_* traits are false_type; the adapter is stateful (is_always_equal is false_type) and two instances compare equal iff they reference the same Pool.

Template Parameters

T	Element type the allocator vends. Rebinding to any U (e.g. a container's internal node type) is the single-template-parameter default supplied by std::allocator_traits.

Definition at line 70 of file pool_allocator.hpp.

Member Typedef Documentation

value_type

template<typename T >

using it::d4np::memorypool::PoolAllocator< T >::value_type = T

Definition at line 72 of file pool_allocator.hpp.

propagate_on_container_copy_assignment

template<typename T >

using it::d4np::memorypool::PoolAllocator< T >::propagate_on_container_copy_assignment = std::false_type

Definition at line 77 of file pool_allocator.hpp.

propagate_on_container_move_assignment

template<typename T >

using it::d4np::memorypool::PoolAllocator< T >::propagate_on_container_move_assignment = std::false_type

Definition at line 78 of file pool_allocator.hpp.

propagate_on_container_swap

template<typename T >

using it::d4np::memorypool::PoolAllocator< T >::propagate_on_container_swap = std::false_type

Definition at line 79 of file pool_allocator.hpp.

is_always_equal

template<typename T >

using it::d4np::memorypool::PoolAllocator< T >::is_always_equal = std::false_type

Definition at line 81 of file pool_allocator.hpp.

Constructor & Destructor Documentation

PoolAllocator() [1/2]

template<typename T >

it::d4np::memorypool::PoolAllocator< T >::PoolAllocator ( Pool &  pool )

inlineexplicitnoexcept

Bind the adapter to pool.

The pool is not owned and must out-live this adapter, every copy of it, and every container that uses it (ADR-0018 §1).

Definition at line 88 of file pool_allocator.hpp.

PoolAllocator() [2/2]

template<typename T >

template<typename U >

it::d4np::memorypool::PoolAllocator< T >::PoolAllocator ( const PoolAllocator< U > &  other )

inlinenoexcept

Rebinding converting constructor — required by the Cpp17Allocator requirements so a container can build an allocator for its internal node type from the user-supplied PoolAllocator<T>.

Deliberately implicit (the rebind machinery relies on the implicit conversion); it is a trivial back-reference copy.

Definition at line 98 of file pool_allocator.hpp.

Member Function Documentation

allocate()

template<typename T >

T * it::d4np::memorypool::PoolAllocator< T >::allocate ( std::size_t  n )

inline

Allocate storage for n objects of T (ADR-0018 §2).

Returns

Pointer to uninitialized storage for n contiguous T.

Exceptions

std::bad_alloc

on pool exhaustion (pool-eligible requests), on size_t overflow of n * sizeof(T), or from the fallback ::operator new.

Definition at line 108 of file pool_allocator.hpp.

deallocate()

template<typename T >

void it::d4np::memorypool::PoolAllocator< T >::deallocate ( T *  ptr, std::size_t  n  )

inlinenoexcept

Return storage obtained from allocate.

n must be the value passed to the matching allocate call (a Cpp17Allocator guarantee), which keeps the pool/fallback routing deterministic.

Definition at line 124 of file pool_allocator.hpp.

operator==()

template<typename T >

template<typename U >

bool it::d4np::memorypool::PoolAllocator< T >::operator== ( const PoolAllocator< U > &  rhs ) const

inlinenoexcept

Two adapters are equal iff they reference the same pool.

Definition at line 134 of file pool_allocator.hpp.

operator!=()

template<typename T >

template<typename U >

bool it::d4np::memorypool::PoolAllocator< T >::operator!= ( const PoolAllocator< U > &  rhs ) const

inlinenoexcept

Negation of operator==.

Definition at line 140 of file pool_allocator.hpp.

Friends And Related Symbol Documentation

PoolAllocator

template<typename T >

template<typename U >

friend class PoolAllocator

friend

Definition at line 148 of file pool_allocator.hpp.

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

• src/main/cpp/it/d4np/memorypool/pool_allocator.hpp