└── stack_allocator.hpp


/stack_allocator.hpp:
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  1 | /* 
  2 |  *
  3 |  * The MIT License (MIT)
  4 |  * 
  5 |  * Copyright (c) 2015 Charles Salvia
  6 |  * 
  7 |  * Permission is hereby granted, free of charge, to any person obtaining a copy
  8 |  * of this software and associated documentation files (the "Software"), to deal
  9 |  * in the Software without restriction, including without limitation the rights
 10 |  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 11 |  * copies of the Software, and to permit persons to whom the Software is
 12 |  * furnished to do so, subject to the following conditions:
 13 |  * 
 14 |  * The above copyright notice and this permission notice shall be included in
 15 |  * all copies or substantial portions of the Software.
 16 |  * 
 17 |  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 18 |  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 19 |  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 20 |  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 21 |  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 22 |  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 23 |  * THE SOFTWARE.
 24 |  *
 25 | */
 26 | 
 27 | #ifndef INCLUDE_STACK_ALLOCATOR_HPP
 28 | #define INCLUDE_STACK_ALLOCATOR_HPP
 29 | 
 30 | #include <functional>
 31 | #include <memory>
 32 | 
 33 | template <class T, std::size_t N, class Allocator = std::allocator<T>>
 34 | class stack_allocator
 35 | {
 36 | 	public:
 37 | 
 38 | 	typedef typename std::allocator_traits<Allocator>::value_type value_type;
 39 | 	typedef typename std::allocator_traits<Allocator>::pointer pointer;
 40 | 	typedef typename std::allocator_traits<Allocator>::const_pointer const_pointer;
 41 | 	typedef typename Allocator::reference reference;
 42 | 	typedef typename Allocator::const_reference const_reference;
 43 | 	typedef typename std::allocator_traits<Allocator>::size_type size_type;
 44 | 	typedef typename std::allocator_traits<Allocator>::difference_type difference_type;
 45 | 
 46 | 	typedef typename std::allocator_traits<Allocator>::const_void_pointer const_void_pointer;
 47 | 	typedef Allocator allocator_type;
 48 | 	
 49 | 	public:
 50 | 
 51 | 	explicit stack_allocator(const allocator_type& alloc = allocator_type()) 
 52 | 		: m_allocator(alloc), m_begin(nullptr), m_end(nullptr), m_stack_pointer(nullptr)
 53 | 	{ }
 54 | 
 55 | 	explicit stack_allocator(pointer buffer, const allocator_type& alloc = allocator_type())
 56 | 		: m_allocator(alloc), m_begin(buffer), m_end(buffer + N), 
 57 | 			m_stack_pointer(buffer)
 58 | 	{ }
 59 | 
 60 | 	template <class U>
 61 | 	stack_allocator(const stack_allocator<U, N, Allocator>& other)
 62 | 		: m_allocator(other.m_allocator), m_begin(other.m_begin), m_end(other.m_end),
 63 | 			m_stack_pointer(other.m_stack_pointer)
 64 | 	{ }
 65 | 
 66 | 	constexpr static size_type capacity()
 67 | 	{
 68 | 		return N;
 69 | 	}
 70 | 
 71 | 	pointer allocate(size_type n, const_void_pointer hint = const_void_pointer())
 72 | 	{
 73 | 		if (n <= size_type(std::distance(m_stack_pointer, m_end)))
 74 | 		{
 75 | 			pointer result = m_stack_pointer;
 76 | 			m_stack_pointer += n;
 77 | 			return result;
 78 | 		}
 79 | 
 80 | 		return m_allocator.allocate(n, hint);
 81 | 	}
 82 | 
 83 | 	void deallocate(pointer p, size_type n)
 84 | 	{
 85 | 		if (pointer_to_internal_buffer(p))
 86 | 		{
 87 | 			m_stack_pointer -= n;
 88 | 		}
 89 | 		else m_allocator.deallocate(p, n);	
 90 | 	}
 91 | 
 92 | 	size_type max_size() const noexcept
 93 | 	{
 94 | 		return m_allocator.max_size();
 95 | 	}
 96 | 
 97 | 	template <class U, class... Args>
 98 | 	void construct(U* p, Args&&... args)
 99 | 	{
100 | 		m_allocator.construct(p, std::forward<Args>(args)...);
101 | 	}
102 | 
103 | 	template <class U>
104 | 	void destroy(U* p)
105 | 	{
106 | 		m_allocator.destroy(p);
107 | 	}
108 | 
109 | 	pointer address(reference x) const noexcept
110 | 	{
111 | 		if (pointer_to_internal_buffer(std::addressof(x)))
112 | 		{
113 | 			return std::addressof(x);
114 | 		}
115 | 
116 | 		return m_allocator.address(x);
117 | 	}
118 | 	
119 | 	const_pointer address(const_reference x) const noexcept
120 | 	{
121 | 		if (pointer_to_internal_buffer(std::addressof(x)))
122 | 		{
123 | 			return std::addressof(x);
124 | 		}
125 | 
126 | 		return m_allocator.address(x);
127 | 	}
128 | 
129 | 	template <class U>
130 | 	struct rebind { typedef stack_allocator<U, N, allocator_type> other; };
131 | 
132 | 	pointer buffer() const noexcept
133 | 	{
134 | 		return m_begin;
135 | 	}
136 | 
137 | 	private:
138 | 
139 | 	bool pointer_to_internal_buffer(const_pointer p) const
140 | 	{
141 | 		return (!(std::less<const_pointer>()(p, m_begin)) && (std::less<const_pointer>()(p, m_end)));
142 | 	}
143 | 
144 | 	allocator_type m_allocator;
145 | 	pointer m_begin;
146 | 	pointer m_end;
147 | 	pointer m_stack_pointer;
148 | };
149 | 
150 | template <class T1, std::size_t N, class Allocator, class T2>
151 | bool operator == (const stack_allocator<T1, N, Allocator>& lhs, 
152 | 	const stack_allocator<T2, N, Allocator>& rhs) noexcept
153 | {
154 | 	return lhs.buffer() == rhs.buffer();
155 | }
156 | 
157 | template <class T1, std::size_t N, class Allocator, class T2>
158 | bool operator != (const stack_allocator<T1, N, Allocator>& lhs, 
159 | 	const stack_allocator<T2, N, Allocator>& rhs) noexcept
160 | {
161 | 	return !(lhs == rhs);
162 | }
163 | 
164 | // -------- Specialization for void
165 | //
166 | template <std::size_t N, class Allocator>
167 | class stack_allocator<void, N, Allocator>
168 | {
169 | 	public:
170 | 
171 | 	typedef std::size_t size_type;
172 | 	typedef std::ptrdiff_t difference_type;
173 | 	typedef void* pointer;
174 | 	typedef const void* const_pointer;
175 | 	typedef void value_type;
176 | 
177 | 	constexpr pointer buffer() const noexcept
178 | 	{
179 | 		return nullptr;
180 | 	}
181 | 
182 | 	template <class U>
183 | 	struct rebind
184 | 	{
185 | 		typedef stack_allocator<U, N, typename Allocator::template rebind<U>::other> other;
186 | 	};
187 | };
188 | 
189 | #endif
190 | 
191 | 


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