libcruft-util/alloc/arena.hpp

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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2015 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_ALLOC_ARENA_HPP
#define __UTIL_ALLOC_ARENA_HPP
#include "../memory/deleter.hpp"
#include <memory>
#include <utility>
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namespace util::alloc {
/// wraps a block allocator with an interface suitable for allocating
/// individual objects.
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template <class T>
class arena {
public:
explicit arena (T &store):
m_store (store)
{ ; }
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//---------------------------------------------------------------------
template <typename U, typename ...Args>
U*
acquire (Args&&... args)
{
U *data = reinterpret_cast<U*> (
m_store.allocate (sizeof (U), alignof (U))
);
try {
new (data) U (std::forward<Args> (args)...);
} catch (...) {
m_store.deallocate (data, sizeof (U));
throw;
}
return data;
}
//---------------------------------------------------------------------
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template <typename U>
void
release (U *u)
{
u->~U ();
m_store.deallocate (reinterpret_cast<void*> (u), sizeof (U));
}
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//---------------------------------------------------------------------
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template <typename U>
using deleter_t = util::memory::owner_deleter<
U,arena<T>,&arena::release
>;
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template <typename U>
using unique_t = std::unique_ptr<U,deleter_t<U>>;
// the return type must be auto and the implementation must be inline
// otherwise we trigger an internal compiler error in gcc-5.2.0
// "sorry, unimplemented: mangling offset_ref"
template <typename U, typename ...Args>
auto
unique (Args&& ...args)
{
return unique_t<U> {
acquire<U> (std::forward<Args> (args)...),
deleter_t<U> (*this)
};
}
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private:
T &m_store;
};
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}
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#endif