mirror of
https://github.com/matrix-construct/construct
synced 2024-11-16 15:00:51 +01:00
137 lines
3.2 KiB
C++
137 lines
3.2 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_TWOLEVEL_H
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namespace ircd::allocator
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{
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template<class T = char,
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size_t L0_SIZE = 512>
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struct twolevel;
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}
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/// The twolevel allocator uses both a fixed allocator (first level) and then
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/// the standard allocator (second level) when the fixed allocator is exhausted.
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/// This has the intent that the fixed allocator will mostly be used, but the
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/// fallback to the standard allocator is seamlessly available for robustness.
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template<class T,
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size_t L0_SIZE>
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struct ircd::allocator::twolevel
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{
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struct allocator;
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fixed<T, L0_SIZE> l0;
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std::allocator<T> l1;
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public:
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allocator operator()();
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operator allocator();
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twolevel() = default;
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};
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template<class T,
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size_t L0_SIZE>
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struct ircd::allocator::twolevel<T, L0_SIZE>::allocator
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{
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using value_type = T;
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using pointer = T *;
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using const_pointer = const T *;
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using reference = T &;
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using const_reference = const 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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twolevel *s;
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public:
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template<class U,
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size_t OTHER_L0_SIZE = L0_SIZE>
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struct rebind
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{
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using other = typename twolevel<U, OTHER_L0_SIZE>::allocator;
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};
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size_type max_size() const
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{
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return std::numeric_limits<size_type>::max();
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}
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auto address(reference x) const
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{
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return &x;
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}
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auto address(const_reference x) const
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{
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return &x;
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}
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pointer
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__attribute__((malloc, returns_nonnull, warn_unused_result))
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allocate(const size_type &n, const const_pointer &hint = nullptr)
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{
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assert(s);
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return
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s->l0.allocate(std::nothrow, n, hint)?:
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s->l1.allocate(n, hint);
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}
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void deallocate(const pointer &p, const size_type &n)
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{
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assert(s);
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if(likely(s->l0.in_range(p)))
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s->l0.deallocate(p, n);
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else
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s->l1.deallocate(p, n);
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}
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template<class U,
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size_t OTHER_L0_SIZE = L0_SIZE>
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allocator(const typename twolevel<U, OTHER_L0_SIZE>::allocator &s) noexcept
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:s{reinterpret_cast<twolevel<T, L0_SIZE> *>(s.s)}
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{
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static_assert(OTHER_L0_SIZE == L0_SIZE);
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}
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allocator(twolevel &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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size_t L0_SIZE>
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inline typename ircd::allocator::twolevel<T, L0_SIZE>::allocator
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ircd::allocator::twolevel<T, L0_SIZE>::operator()()
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{
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return ircd::allocator::twolevel<T, L0_SIZE>::allocator(*this);
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}
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template<class T,
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size_t L0_SIZE>
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inline ircd::allocator::twolevel<T, L0_SIZE>::operator
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allocator()
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{
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return ircd::allocator::twolevel<T, L0_SIZE>::allocator(*this);
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}
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