138 lines
4.0 KiB
C++
138 lines
4.0 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2015-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_UTIL_ALLOC_ARENA_HPP
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#define CRUFT_UTIL_ALLOC_ARENA_HPP
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#include "../memory/deleter.hpp"
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#include "../cast.hpp"
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#include "../view.hpp"
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#include <memory>
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#include <utility>
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namespace cruft::alloc {
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/// wraps a block allocator with an interface suitable for allocating
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/// individual objects.
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template <class T>
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class arena {
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public:
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explicit arena (T &store):
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m_store (store)
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{ ; }
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//---------------------------------------------------------------------
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template <typename U, typename ...Args>
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U*
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acquire (Args&&... args)
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{
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U *data = m_store.template allocate<U> (1).data ();
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try {
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new (data) U (std::forward<Args> (args)...);
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} catch (...) {
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m_store.template deallocate<U> ({data,1});
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throw;
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}
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return data;
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}
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//---------------------------------------------------------------------
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template <typename U>
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void
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release (U *u)
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{
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u->~U ();
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m_store.template deallocate<U> (cruft::view {u,1u});
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}
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//---------------------------------------------------------------------
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template <typename U>
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using deleter_t = cruft::memory::owner_deleter<
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U,arena<T>,&arena::release
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>;
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template <typename U>
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using unique_t = std::unique_ptr<U,deleter_t<U>>;
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// the return type must be auto and the implementation must be inline
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// otherwise we trigger an internal compiler error in gcc-5.2.0
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// "sorry, unimplemented: mangling offset_ref"
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template <typename U, typename ...Args>
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auto
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unique (Args&& ...args)
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{
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return unique_t<U> {
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acquire<U> (std::forward<Args> (args)...),
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deleter_t<U> (*this)
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};
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}
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private:
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T &m_store;
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};
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/// A simple allocator that contains a raw allocator and a forwarded
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/// allocator.
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///
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/// The raw allocator handles the memory allocation, the forwarded
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/// allocator performs the initialisation, and we control the construction
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/// of both.
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///
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/// Ideally we wouldn't forward calls manually and instead do something
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/// like inherit from arena<T>, but that makes it difficult to initialise
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/// the raw allocator before we have to supply the reference to the arena.
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template <typename AllocT>
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class owned {
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public:
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template <typename ...ArgsT>
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explicit owned (ArgsT &&...args)
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: m_store (std::forward<ArgsT> (args)...)
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, m_arena {m_store}
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{ ; }
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owned (owned &&rhs)
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: m_store (std::move (rhs.m_store))
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, m_arena (m_store)
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{ ; }
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owned& operator= (owned &&rhs)
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{
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m_store = std::move (rhs.m_store);
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}
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owned (owned const&) = delete;
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owned& operator= (owned const&) = delete;
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template <typename T, typename ...ArgsT>
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decltype(auto) acquire (ArgsT &&...args)
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{ return m_arena.template acquire<T,ArgsT...> (std::forward<ArgsT> (args)...); }
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template <typename ...ArgsT>
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decltype(auto) release (ArgsT &&...args)
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{ return m_arena.release (std::forward<ArgsT> (args)...); }
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template <typename T, typename ...ArgsT>
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decltype(auto) unique (ArgsT &&...args)
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{ return m_arena.template unique<T,ArgsT...> (std::forward<ArgsT> (args)...); }
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template <typename ...Args>
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decltype(auto) reset (Args&&...args)
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{ return m_store.reset (std::forward<Args> (args)...); }
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private:
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AllocT m_store;
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arena<AllocT> m_arena;
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};
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}
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#endif
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