42db87a8c2
Here, transferring is defined as moving an object to a new location (either via a move or copy constructor) and destroying the source. This is useful when implementing containers.
55 lines
1.6 KiB
C++
55 lines
1.6 KiB
C++
/*
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* Copyright (C) 2014 Cloudius Systems, Ltd.
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*/
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#ifndef TRANSFER_HH_
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#define TRANSFER_HH_
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// Helper functions for copying or moving multiple objects in an exception
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// safe manner, then destroying the sources.
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//
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// To transfer, call transfer_pass1(allocator, &from, &to) on all object pairs,
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// (this copies the object from @from to @to). If no exceptions are encountered,
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// call transfer_pass2(allocator, &from, &to). This destroys the object at the
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// origin. If exceptions were encountered, simply destroy all copied objects.
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//
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// As an optimization, if the objects are moveable without throwing (noexcept)
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// transfer_pass1() simply moves the objects and destroys the source, and
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// transfer_pass2() does nothing.
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#include <type_traits>
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template <typename T, typename Alloc>
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inline
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void
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transfer_pass1(Alloc& a, T* from, T* to,
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typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
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a.construct(to, std::move(*from));
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a.destroy(from);
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}
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template <typename T, typename Alloc>
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inline
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void
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transfer_pass2(Alloc& a, T* from, T* to,
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typename std::enable_if<std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
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}
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template <typename T, typename Alloc>
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inline
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void
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transfer_pass1(Alloc& a, T* from, T* to,
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typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
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a.construct(to, *from);
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}
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template <typename T, typename Alloc>
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inline
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void
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transfer_pass2(Alloc& a, T* from, T* to,
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typename std::enable_if<!std::is_nothrow_move_constructible<T>::value>::type* = nullptr) {
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a.destroy(from);
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}
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#endif /* TRANSFER_HH_ */
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