511 lines
10 KiB
C++
511 lines
10 KiB
C++
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//
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// Copyright (c) 2022 Vinnie Falco (vinnie.falco@gmail.com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/url
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//
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#ifndef BOOST_URL_GRAMMAR_RECYCLED_HPP
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#define BOOST_URL_GRAMMAR_RECYCLED_HPP
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#include <boost/url/detail/config.hpp>
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#include <boost/url/grammar/detail/recycled.hpp>
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#include <atomic>
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#include <cstddef>
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#include <type_traits>
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#include <stddef.h> // ::max_align_t
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#if !defined(BOOST_URL_DISABLE_THREADS)
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# include <mutex>
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#endif
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namespace boost {
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namespace urls {
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namespace grammar {
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/** Provides an aligned storage buffer aligned for T
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*/
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#ifdef BOOST_URL_DOCS
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template<class T>
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struct aligned_storage
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{
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/** Return a pointer to the aligned storage area
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*/
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void* addr() noexcept;
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/** Return a pointer to the aligned storage area
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*/
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void const* addr() const noexcept;
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};
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#else
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template<class T>
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using aligned_storage =
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detail::aligned_storage_impl<
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detail::nearest_pow2(sizeof(T), 64),
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(alignof(::max_align_t) > alignof(T)) ?
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alignof(::max_align_t) : alignof(T)>;
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#endif
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//------------------------------------------------
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/** A thread-safe collection of instances of T
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Instances of this type may be used to control
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where recycled instances of T come from when
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used with @ref recycled_ptr.
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@par Example
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@code
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static recycled< std::string > bin;
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recycled_ptr< std::string > ps( bin );
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// Put the string into a known state
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ps->clear();
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@endcode
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@see
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@ref recycled_ptr.
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*/
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template<class T>
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class recycled
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{
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public:
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/** Destructor
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All recycled instances of T are destroyed.
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Undefined behavior results if there are
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any @ref recycled_ptr which reference
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this recycle bin.
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*/
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~recycled();
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/** Constructor
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*/
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constexpr recycled() = default;
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private:
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template<class>
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friend class recycled_ptr;
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struct U
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{
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T t;
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U* next = nullptr;
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#if !defined(BOOST_URL_DISABLE_THREADS)
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std::atomic<
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std::size_t> refs;
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#else
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std::size_t refs;
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#endif
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U()
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: refs{1}
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{
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}
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};
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struct report;
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U* acquire();
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void release(U* u) noexcept;
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U* head_ = nullptr;
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#if !defined(BOOST_URL_DISABLE_THREADS)
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std::mutex m_;
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#endif
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};
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//------------------------------------------------
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/** A pointer to shared instance of T
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This is a smart pointer container which can
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acquire shared ownership of an instance of
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`T` upon or after construction. The instance
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is guaranteed to be in a valid, but unknown
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state. Every recycled pointer references
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a valid recycle bin.
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@par Example
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@code
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static recycled< std::string > bin;
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recycled_ptr< std::string > ps( bin );
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// Put the string into a known state
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ps->clear();
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@endcode
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@tparam T the type of object to
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acquire, which must be
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<em>DefaultConstructible</em>.
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*/
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template<class T>
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class recycled_ptr
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{
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// T must be default constructible!
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static_assert(
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std::is_default_constructible<T>::value,
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"T must be DefaultConstructible");
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friend class recycled<T>;
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using B = recycled<T>;
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using U = typename B::U;
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B* bin_ = nullptr;
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U* p_ = nullptr;
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public:
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/** Destructor
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If this is not empty, shared ownership
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of the pointee is released. If this was
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the last reference, the object is
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returned to the original recycle bin.
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@par Effects
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@code
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this->release();
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@endcode
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*/
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~recycled_ptr();
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/** Constructor
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Upon construction, this acquires
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exclusive access to an object of type
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`T` which is either recycled from the
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specified bin, or newly allocated.
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The object is in an unknown but
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valid state.
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@par Example
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@code
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static recycled< std::string > bin;
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recycled_ptr< std::string > ps( bin );
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// Put the string into a known state
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ps->clear();
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@endcode
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@par Postconditions
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@code
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&this->bin() == &bin && ! this->empty()
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@endcode
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@param bin The recycle bin to use
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@see
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@ref recycled.
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*/
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explicit
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recycled_ptr(recycled<T>& bin);
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/** Constructor
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After construction, this is empty and
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refers to the specified recycle bin.
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@par Example
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@code
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static recycled< std::string > bin;
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recycled_ptr< std::string > ps( bin, nullptr );
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// Acquire a string and put it into a known state
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ps->acquire();
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ps->clear();
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@endcode
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@par Postconditions
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@code
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&this->bin() == &bin && this->empty()
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@endcode
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@par Exception Safety
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Throws nothing.
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@param bin The recycle bin to use
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@see
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@ref acquire,
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@ref recycled,
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@ref release.
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*/
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recycled_ptr(
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recycled<T>& bin,
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std::nullptr_t) noexcept;
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/** Constructor
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Upon construction, this acquires
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exclusive access to an object of type
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`T` which is either recycled from a
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global recycle bin, or newly allocated.
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The object is in an unknown but
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valid state.
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@par Example
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@code
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recycled_ptr< std::string > ps;
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// Put the string into a known state
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ps->clear();
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@endcode
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@par Postconditions
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@code
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&this->bin() != nullptr && ! this->empty()
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@endcode
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@see
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@ref recycled.
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*/
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recycled_ptr();
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/** Constructor
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After construction, this is empty
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and refers to a global recycle bin.
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@par Example
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@code
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recycled_ptr< std::string > ps( nullptr );
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// Acquire a string and put it into a known state
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ps->acquire();
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ps->clear();
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@endcode
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@par Postconditions
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@code
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&this->bin() != nullptr && this->empty()
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@endcode
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@par Exception Safety
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Throws nothing.
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@see
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@ref acquire,
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@ref recycled,
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@ref release.
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*/
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recycled_ptr(
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std::nullptr_t) noexcept;
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/** Constructor
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If `other` references an object, the
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newly constructed pointer acquires
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shared ownership. Otherwise this is
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empty. The new pointer references
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the same recycle bin as `other`.
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@par Postconditions
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@code
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&this->bin() == &other->bin() && this->get() == other.get()
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@endcode
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@par Exception Safety
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Throws nothing.
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@param other The pointer to copy
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*/
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recycled_ptr(
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recycled_ptr const& other) noexcept;
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/** Constructor
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If `other` references an object,
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ownership is transferred including
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a reference to the recycle bin. After
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the move, the moved-from object is empty.
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@par Postconditions
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@code
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&this->bin() == &other->bin() && ! this->empty() && other.empty()
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@endcode
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@par Exception Safety
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Throws nothing.
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@param other The pointer to move from
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*/
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recycled_ptr(
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recycled_ptr&& other) noexcept;
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/** Assignment
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If `other` references an object,
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ownership is transferred including
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a reference to the recycle bin. After
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the move, the moved-from object is empty.
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@par Effects
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@code
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this->release()
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@endcode
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@par Postconditions
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@code
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&this->bin() == &other->bin()
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@endcode
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@par Exception Safety
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Throws nothing.
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@param other The pointer to move from
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*/
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recycled_ptr&
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operator=(
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recycled_ptr&& other) noexcept;
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/** Assignment
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If `other` references an object,
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this acquires shared ownership and
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references the same recycle bin as
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`other`. The previous object if any
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is released.
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@par Effects
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@code
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this->release()
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@endcode
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@par Postconditions
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@code
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&this->bin() == &other->bin() && this->get() == other.get()
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@endcode
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@par Exception Safety
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Throws nothing.
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@param other The pointer to copy from
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*/
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recycled_ptr&
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operator=(
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recycled_ptr const& other) noexcept;
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/** Return true if this does not reference an object
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@par Exception Safety
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Throws nothing.
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*/
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bool
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empty() const noexcept
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{
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return p_ == nullptr;
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}
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/** Return true if this references an object
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@par Effects
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@code
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return ! this->empty();
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@endcode
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@par Exception Safety
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Throws nothing.
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*/
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explicit
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operator bool() const noexcept
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{
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return p_ != nullptr;
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}
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/** Return the referenced recycle bin
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@par Exception Safety
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Throws nothing.
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*/
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recycled<T>&
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bin() const noexcept
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{
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return *bin_;
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}
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/** Return the referenced object
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If this is empty, `nullptr` is returned.
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@par Exception Safety
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Throws nothing.
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*/
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T* get() const noexcept
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{
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return &p_->t;
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}
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/** Return the referenced object
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If this is empty, `nullptr` is returned.
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@par Exception Safety
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Throws nothing.
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*/
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|
T* operator->() const noexcept
|
||
|
|
{
|
||
|
|
return get();
|
||
|
|
}
|
||
|
|
|
||
|
|
/** Return the referenced object
|
||
|
|
|
||
|
|
@par Preconditions
|
||
|
|
@code
|
||
|
|
not this->empty()
|
||
|
|
@endcode
|
||
|
|
*/
|
||
|
|
T& operator*() const noexcept
|
||
|
|
{
|
||
|
|
return *get();
|
||
|
|
}
|
||
|
|
|
||
|
|
/** Return the referenced object
|
||
|
|
|
||
|
|
If this references an object, it is
|
||
|
|
returned. Otherwise, exclusive ownership
|
||
|
|
of a new object of type `T` is acquired
|
||
|
|
and returned.
|
||
|
|
|
||
|
|
@par Postconditions
|
||
|
|
@code
|
||
|
|
not this->empty()
|
||
|
|
@endcode
|
||
|
|
*/
|
||
|
|
T& acquire();
|
||
|
|
|
||
|
|
/** Release the referenced object
|
||
|
|
|
||
|
|
If this references an object, it is
|
||
|
|
released to the referenced recycle bin.
|
||
|
|
The pointer continues to reference
|
||
|
|
the same recycle bin.
|
||
|
|
|
||
|
|
@par Postconditions
|
||
|
|
@code
|
||
|
|
this->empty()
|
||
|
|
@endcode
|
||
|
|
|
||
|
|
@par Exception Safety
|
||
|
|
Throws nothing.
|
||
|
|
*/
|
||
|
|
void release() noexcept;
|
||
|
|
};
|
||
|
|
|
||
|
|
} // grammar
|
||
|
|
} // urls
|
||
|
|
} // boost
|
||
|
|
|
||
|
|
#include <boost/url/grammar/impl/recycled.hpp>
|
||
|
|
|
||
|
|
#endif
|