mirror of
https://github.com/matrix-construct/construct
synced 2024-11-29 18:22:50 +01:00
113 lines
2.7 KiB
C++
113 lines
2.7 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2023 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_ALLOCATOR_CALLBACK_H
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namespace ircd::allocator
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{
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template<class T = void>
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struct callback;
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}
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/// The callback allocator is a shell around the pre-c++17/20 boilerplate
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/// jumble for allocator template creation. This is an alternative to virtual
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/// functions to accomplish the same thing here. Implement the principal
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/// allocate and deallocate functions and maintain an instance of
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/// allocator::callback with them somewhere.
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template<class T>
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struct ircd::allocator::callback
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{
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struct allocator;
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public:
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using allocate_callback = std::function<T *(const size_t &, const T *const &)>;
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using deallocate_callback = std::function<void (T *const &, const size_t &)>;
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allocate_callback ac;
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deallocate_callback dc;
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allocator operator()();
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operator allocator();
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callback(allocate_callback ac, deallocate_callback dc)
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:ac{std::move(ac)}
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,dc{std::move(dc)}
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{}
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};
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template<class T>
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struct ircd::allocator::callback<T>::allocator
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{
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using value_type = T;
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using size_type = std::size_t;
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using difference_type = std::ptrdiff_t;
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using is_always_equal = std::true_type;
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using propagate_on_container_move_assignment = std::true_type;
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callback *s;
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public:
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template<class U> struct rebind
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{
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typedef ircd::allocator::callback<T>::allocator other;
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};
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T *
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__attribute__((malloc, returns_nonnull, warn_unused_result))
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allocate(const size_type n, const T *const hint = nullptr)
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{
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assert(s && s->ac);
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return s->ac(n, hint);
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}
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void deallocate(T *const p, const size_type n = 1)
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{
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assert(s && s->dc);
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return s->dc(p, n);
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}
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template<class U>
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allocator(const typename ircd::allocator::callback<U>::allocator &s) noexcept
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:s{s.s}
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{}
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allocator(callback &s) noexcept
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:s{&s}
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{}
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allocator(allocator &&) = default;
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allocator(const allocator &) = default;
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friend bool operator==(const allocator &a, const allocator &b)
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{
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return &a == &b;
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}
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friend bool operator!=(const allocator &a, const allocator &b)
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{
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return &a == &b;
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}
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};
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template<class T>
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inline typename ircd::allocator::callback<T>::allocator
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ircd::allocator::callback<T>::operator()()
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{
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return ircd::allocator::callback<T>::allocator(*this);
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}
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template<class T>
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inline ircd::allocator::callback<T>::operator
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allocator()
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{
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return ircd::allocator::callback<T>::allocator(*this);
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}
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