mirror of
https://github.com/matrix-construct/construct
synced 2024-07-02 08:48:18 +02:00
136 lines
3.5 KiB
C++
136 lines
3.5 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_DYNAMIC_H
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namespace ircd::allocator
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{
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template<class T = char>
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struct dynamic;
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}
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/// The dynamic allocator provides a pool of a fixed size known at runtime.
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///
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/// This allocator conducts a single new and delete for a pool allowing an STL
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/// container to operate without interacting with the rest of the system and
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/// without fragmentation. This is not as useful as the allocator::fixed in
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/// practice as the standard allocator is as good as this in many cases. This
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/// is still available as an analog to the fixed allocator in this suite.
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///
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template<class T>
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struct ircd::allocator::dynamic
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:state
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{
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struct allocator;
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size_t head_size, data_size;
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std::unique_ptr<uint8_t[]> arena;
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T *buf;
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public:
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allocator operator()();
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operator allocator();
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dynamic(const size_t &size)
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:state{size}
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,head_size{size / 8}
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,data_size{sizeof(T) * size + 16}
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,arena
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{
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new __attribute__((aligned(16))) uint8_t[head_size + data_size]
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}
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,buf
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{
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reinterpret_cast<T *>(arena.get() + head_size + (head_size % 16))
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}
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{
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state::avail = reinterpret_cast<word_t *>(arena.get());
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}
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};
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/// The actual template passed to containers for using the dynamic allocator.
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///
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/// See the notes for ircd::allocator::fixed::allocator for details.
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///
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template<class T>
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struct ircd::allocator::dynamic<T>::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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dynamic *s;
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public:
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template<class U> struct rebind
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{
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using other = typename dynamic<U>::allocator;
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};
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size_type max_size() const { return s->size; }
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auto address(reference x) const { return &x; }
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auto address(const_reference x) const { return &x; }
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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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const uint hintpos(hint? hint - s->buf : -1);
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return s->buf + s->state::allocate(n, hintpos);
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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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const uint pos(p - s->buf);
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s->state::deallocate(pos, n);
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}
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template<class U>
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allocator(const typename dynamic<U>::allocator &s) noexcept
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:s{reinterpret_cast<dynamic *>(s.s)}
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{}
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allocator(dynamic &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::dynamic<T>::allocator
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ircd::allocator::dynamic<T>::operator()()
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{
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return ircd::allocator::dynamic<T>::allocator(*this);
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}
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template<class T>
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inline ircd::allocator::dynamic<T>::operator
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allocator()
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{
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return ircd::allocator::dynamic<T>::allocator(*this);
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}
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