src/zserio/pmr/PolymorphicAllocator.h

Source
#ifndef ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC
#define ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC

#include <cstddef>
#include <limits>
#include <type_traits>
#include <utility>

#include "zserio/Types.h"
#include "zserio/pmr/MemoryResource.h"

namespace zserio
{
namespace pmr
{
namespace detail
{

/**
 * Polymorphic allocator inspired by C++17 standard.
 */
template <class T = uint8_t>
class PolymorphicAllocatorBase
{
public:
    using value_type = T;

    // Following typedefs are only present for compatibility with older std. libraries, that does not fully
    // conform to C++11. [old-compiler-support]
    using pointer = value_type*;
    using const_pointer = const value_type*;
    using size_type = std::size_t;
    using difference_type = std::ptrdiff_t;
    using reference = value_type&;
    using const_reference = const value_type&;

    /**
     * Constructor.
     *
     * Note that this is intentionally non-explicit to allow to pass MemoryResource wherever
     * the PolymorphicAllocator is required.
     *
     * \param resource Memory resource. According to the C++ standard the resource may not be NULL. Since it
     *                 implies undefined behaviour, we define a non-standard extension here. When the resource
     *                 is NULL, getDefaultResource() is used instead!
     */
    PolymorphicAllocatorBase(MemoryResource* resource = getDefaultResource()) noexcept :
            m_resource(resource != nullptr ? resource : getDefaultResource()) // non-standard extension
    {}

    /**
     * Method generated by default.
     * \{
     */
    ~PolymorphicAllocatorBase() = default;

    PolymorphicAllocatorBase(const PolymorphicAllocatorBase& other) noexcept = default;
    PolymorphicAllocatorBase& operator=(const PolymorphicAllocatorBase& other) noexcept = default;

    PolymorphicAllocatorBase(PolymorphicAllocatorBase&& other) noexcept = default;
    PolymorphicAllocatorBase& operator=(PolymorphicAllocatorBase&& other) noexcept = default;
    /**
     * \}
     */

    /**
     * Copy constructor from PolymorphicAllocator with another value_type.
     *
     * \param other Other PolymorphicAllocator.
     */
    template <class U>
    PolymorphicAllocatorBase(const PolymorphicAllocatorBase<U>& other) noexcept :
            m_resource(other.resource())
    {}

    /**
     * Assignment operator from PolymorphicAllocator with another value_type.
     *
     * \param other Other PolymorphicAllocator.
     */
    template <class U>
    PolymorphicAllocatorBase& operator=(const PolymorphicAllocatorBase<U>& other) noexcept
    {
        m_resource = other.resource();
        return *this;
    }

    /**
     * Allocates memory for n values.
     *
     * \param size Number of values to allocate memory for.
     */
    value_type* allocate(std::size_t size)
    {
        return static_cast<value_type*>(m_resource->allocate(size * sizeof(value_type), alignof(value_type)));
    }

    /**
     * Deallocates memory for n values.
     *
     * \param memory Pointer to the memory to deallocate.
     * \param size Number of values held by the memory pointed to by memory.
     *         Shall be the same size as was used for allocation of memory.
     */
    void deallocate(value_type* memory, std::size_t size) noexcept
    {
        m_resource->deallocate(memory, size * sizeof(value_type), alignof(value_type));
    }

    /**
     * Gets the underlying memory resource.
     */
    MemoryResource* resource() const noexcept
    {
        return m_resource;
    }

    /**
     * Constructs an object in allocated memory.
     *
     * \param ptr Pointer to memory where the object will be constructed.
     * \param args Parameters to be forwarded to the object constructor.
     * \note This is only necessary for compatibility with older std. libraries, that does not fully
     * conform to C++11. [old-compiler-support]
     */
    template <typename U, typename... Args>
    void construct(U* ptr, Args&&... args) noexcept(
            noexcept(new (static_cast<void*>(ptr)) U(std::forward<Args>(args)...)))
    {
        new (static_cast<void*>(ptr)) U(std::forward<Args>(args)...);
    }

    /**
     * Destroys an object
     *
     * \param ptr Pointer to the object to be destroyed.
     * \note This is only necessary for compatibility with older std. libraries, that does not fully
     * conform to C++11. [old-compiler-support]
     */
    template <typename U>
    void destroy(U* ptr) noexcept(noexcept(ptr->~U()))
    {
        ptr->~U();
    }

    /**
     * Returns theoretical maximal limit for allocation.
     *
     * \return Theoretical maximal limit for allocation.
     * \note This is only necessary for compatibility with older std. libraries, that does not fully
     * conform to C++11. [old-compiler-support]
     */
    size_type max_size() const noexcept
    {
        return std::numeric_limits<size_type>::max() / sizeof(value_type);
    }

private:
    MemoryResource* m_resource;
};

template <class T, class U>
bool operator==(const PolymorphicAllocatorBase<T>& lhs, const PolymorphicAllocatorBase<U>& rhs) noexcept
{
    return *lhs.resource() == *rhs.resource();
}

template <class T, class U>
bool operator!=(const PolymorphicAllocatorBase<T>& lhs, const PolymorphicAllocatorBase<U>& rhs) noexcept
{
    return !(lhs == rhs);
}

} // namespace detail

/**
 * Non-propagating version of the polymorphic allocator. This allocator behaves as the polymorphic_allocator
 * from C++17.
 */
template <class T = uint8_t>
class PolymorphicAllocator : public detail::PolymorphicAllocatorBase<T>
{
public:
    using detail::PolymorphicAllocatorBase<T>::PolymorphicAllocatorBase;

    using propagate_on_container_copy_assignment = std::false_type;
    using propagate_on_container_move_assignment = std::false_type;
    using propagate_on_container_swap = std::false_type;

    /**
     * Returns instance of the allocator to be used when a container gets copied.
     */
    PolymorphicAllocator select_on_container_copy_construction() const
    {
        return PolymorphicAllocator();
    }

    /**
     * Rebind template.
     * \note This is only necessary for compatibility with older std. libraries, that does not fully
     * conform to C++11. [old-compiler-support]
     */
    template <typename U>
    struct rebind
    {
        using other = PolymorphicAllocator<U>;
    };
};

/**
 * Propagating version of the polymorphic allocator. This one is propagated on container copy and assignment.
 */
template <class T = uint8_t>
class PropagatingPolymorphicAllocator : public detail::PolymorphicAllocatorBase<T>
{
public:
    using detail::PolymorphicAllocatorBase<T>::PolymorphicAllocatorBase;

    using propagate_on_container_copy_assignment = std::true_type;
    using propagate_on_container_move_assignment = std::true_type;
    using propagate_on_container_swap = std::true_type;

    /**
     * Returns instance of the allocator to be used when a container gets copied.
     */
    PropagatingPolymorphicAllocator select_on_container_copy_construction() const
    {
        return *this;
    }

    /**
     * Rebind template.
     * \note This is only necessary for compatibility with older std. libraries, that does not fully
     * conform to C++11. [old-compiler-support]
     */
    template <typename U>
    struct rebind
    {
        using other = PropagatingPolymorphicAllocator<U>;
    };
};

} // namespace pmr
} // namespace zserio

#endif // ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC

Coverage Report

Created: 2024-12-05 10:39

Line	Count	Source
1		#ifndef ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC
2		#define ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC
3
4		#include <cstddef>
5		#include <limits>
6		#include <type_traits>
7		#include <utility>
8
9		#include "zserio/Types.h"
10		#include "zserio/pmr/MemoryResource.h"
11
12		namespace zserio
13		{
14		namespace pmr
15		{
16		namespace detail
17		{
18
19		/**
20		* Polymorphic allocator inspired by C++17 standard.
21		*/
22		template <class T = uint8_t>
23		class PolymorphicAllocatorBase
24		{
25		public:
26		using value_type = T;
27
28		// Following typedefs are only present for compatibility with older std. libraries, that does not fully
29		// conform to C++11. [old-compiler-support]
30		using pointer = value_type*;
31		using const_pointer = const value_type*;
32		using size_type = std::size_t;
33		using difference_type = std::ptrdiff_t;
34		using reference = value_type&;
35		using const_reference = const value_type&;
36
37		/**
38		* Constructor.
39		*
40		* Note that this is intentionally non-explicit to allow to pass MemoryResource wherever
41		* the PolymorphicAllocator is required.
42		*
43		* \param resource Memory resource. According to the C++ standard the resource may not be NULL. Since it
44		* implies undefined behaviour, we define a non-standard extension here. When the resource
45		* is NULL, getDefaultResource() is used instead!
46		*/
47		PolymorphicAllocatorBase(MemoryResource* resource = getDefaultResource()) noexcept :
48		m_resource(resource != nullptr ? resource : getDefaultResource()) // non-standard extension
49	142	{}
50
51		/**
52		* Method generated by default.
53		* \{
54		*/
55		~PolymorphicAllocatorBase() = default;
56
57		PolymorphicAllocatorBase(const PolymorphicAllocatorBase& other) noexcept = default;
58		PolymorphicAllocatorBase& operator=(const PolymorphicAllocatorBase& other) noexcept = default;
59
60		PolymorphicAllocatorBase(PolymorphicAllocatorBase&& other) noexcept = default;
61		PolymorphicAllocatorBase& operator=(PolymorphicAllocatorBase&& other) noexcept = default;
62		/**
63		* \}
64		*/
65
66		/**
67		* Copy constructor from PolymorphicAllocator with another value_type.
68		*
69		* \param other Other PolymorphicAllocator.
70		*/
71		template <class U>
72		PolymorphicAllocatorBase(const PolymorphicAllocatorBase<U>& other) noexcept :
73		m_resource(other.resource())
74	402	{}
75
76		/**
77		* Assignment operator from PolymorphicAllocator with another value_type.
78		*
79		* \param other Other PolymorphicAllocator.
80		*/
81		template <class U>
82		PolymorphicAllocatorBase& operator=(const PolymorphicAllocatorBase<U>& other) noexcept
83		{
84		m_resource = other.resource();
85		return *this;
86		}
87
88		/**
89		* Allocates memory for n values.
90		*
91		* \param size Number of values to allocate memory for.
92		*/
93		value_type* allocate(std::size_t size)
94	196	{
95	196	return static_cast<value_type>(m_resource->allocate(size sizeof(value_type), alignof(value_type)));
96	196	}
97
98		/**
99		* Deallocates memory for n values.
100		*
101		* \param memory Pointer to the memory to deallocate.
102		* \param size Number of values held by the memory pointed to by memory.
103		* Shall be the same size as was used for allocation of memory.
104		*/
105		void deallocate(value_type* memory, std::size_t size) noexcept
106	196	{
107	196	m_resource->deallocate(memory, size * sizeof(value_type), alignof(value_type));
108	196	}
109
110		/**
111		* Gets the underlying memory resource.
112		*/
113		MemoryResource* resource() const noexcept
114	554	{
115	554	return m_resource;
116	554	}
117
118		/**
119		* Constructs an object in allocated memory.
120		*
121		* \param ptr Pointer to memory where the object will be constructed.
122		* \param args Parameters to be forwarded to the object constructor.
123		* \note This is only necessary for compatibility with older std. libraries, that does not fully
124		* conform to C++11. [old-compiler-support]
125		*/
126		template <typename U, typename... Args>
127		void construct(U* ptr, Args&&... args) noexcept(
128		noexcept(new (static_cast<void*>(ptr)) U(std::forward<Args>(args)...)))
129	214	{
130	214	new (static_cast<void*>(ptr)) U(std::forward<Args>(args)...);
131	214	}
132
133		/**
134		* Destroys an object
135		*
136		* \param ptr Pointer to the object to be destroyed.
137		* \note This is only necessary for compatibility with older std. libraries, that does not fully
138		* conform to C++11. [old-compiler-support]
139		*/
140		template <typename U>
141		void destroy(U* ptr) noexcept(noexcept(ptr->~U()))
142	214	{
143	214	ptr->~U();
144	214	}
145
146		/**
147		* Returns theoretical maximal limit for allocation.
148		*
149		* \return Theoretical maximal limit for allocation.
150		* \note This is only necessary for compatibility with older std. libraries, that does not fully
151		* conform to C++11. [old-compiler-support]
152		*/
153		size_type max_size() const noexcept
154	129	{
155	129	return std::numeric_limits<size_type>::max() / sizeof(value_type);
156	129	}
157
158		private:
159		MemoryResource* m_resource;
160		};
161
162		template <class T, class U>
163		bool operator==(const PolymorphicAllocatorBase<T>& lhs, const PolymorphicAllocatorBase<U>& rhs) noexcept
164	68	{
165	68	return lhs.resource() == rhs.resource();
166	68	}
167
168		template <class T, class U>
169		bool operator!=(const PolymorphicAllocatorBase<T>& lhs, const PolymorphicAllocatorBase<U>& rhs) noexcept
170	6	{
171	6	return !(lhs == rhs);
172	6	}
173
174		} // namespace detail
175
176		/**
177		* Non-propagating version of the polymorphic allocator. This allocator behaves as the polymorphic_allocator
178		* from C++17.
179		*/
180		template <class T = uint8_t>
181		class PolymorphicAllocator : public detail::PolymorphicAllocatorBase<T>
182		{
183		public:
184		using detail::PolymorphicAllocatorBase<T>::PolymorphicAllocatorBase;
185
186		using propagate_on_container_copy_assignment = std::false_type;
187		using propagate_on_container_move_assignment = std::false_type;
188		using propagate_on_container_swap = std::false_type;
189
190		/**
191		* Returns instance of the allocator to be used when a container gets copied.
192		*/
193		PolymorphicAllocator select_on_container_copy_construction() const
194	1	{
195	1	return PolymorphicAllocator();
196	1	}
197
198		/**
199		* Rebind template.
200		* \note This is only necessary for compatibility with older std. libraries, that does not fully
201		* conform to C++11. [old-compiler-support]
202		*/
203		template <typename U>
204		struct rebind
205		{
206		using other = PolymorphicAllocator<U>;
207		};
208		};
209
210		/**
211		* Propagating version of the polymorphic allocator. This one is propagated on container copy and assignment.
212		*/
213		template <class T = uint8_t>
214		class PropagatingPolymorphicAllocator : public detail::PolymorphicAllocatorBase<T>
215		{
216		public:
217		using detail::PolymorphicAllocatorBase<T>::PolymorphicAllocatorBase;
218
219		using propagate_on_container_copy_assignment = std::true_type;
220		using propagate_on_container_move_assignment = std::true_type;
221		using propagate_on_container_swap = std::true_type;
222
223		/**
224		* Returns instance of the allocator to be used when a container gets copied.
225		*/
226		PropagatingPolymorphicAllocator select_on_container_copy_construction() const
227	29	{
228	29	return *this;
229	29	}
230
231		/**
232		* Rebind template.
233		* \note This is only necessary for compatibility with older std. libraries, that does not fully
234		* conform to C++11. [old-compiler-support]
235		*/
236		template <typename U>
237		struct rebind
238		{
239		using other = PropagatingPolymorphicAllocator<U>;
240		};
241		};
242
243		} // namespace pmr
244		} // namespace zserio
245
246		#endif // ZSERIO_PMR_POLYMORPHIC_ALLOCATOR_H_INC