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193 lines
5.6 KiB
Plaintext
193 lines
5.6 KiB
Plaintext
///////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
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//
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// This code is licensed under the MIT License (MIT).
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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///////////////////////////////////////////////////////////////////////////////
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#ifndef GSL_POINTERS_H
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#define GSL_POINTERS_H
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#include <gsl/gsl_assert> // for Ensures, Expects
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#include <algorithm> // for forward
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#include <iosfwd> // for ptrdiff_t, nullptr_t, ostream, size_t
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#include <memory> // for shared_ptr, unique_ptr
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#include <system_error> // for hash
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#include <type_traits> // for enable_if_t, is_convertible, is_assignable
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#if defined(_MSC_VER) && _MSC_VER < 1910
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#pragma push_macro("constexpr")
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#define constexpr /*constexpr*/
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#endif // defined(_MSC_VER) && _MSC_VER < 1910
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namespace gsl
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{
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//
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// GSL.owner: ownership pointers
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//
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using std::unique_ptr;
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using std::shared_ptr;
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//
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// owner
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//
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// owner<T> is designed as a bridge for code that must deal directly with owning pointers for some reason
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//
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// T must be a pointer type
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// - disallow construction from any type other than pointer type
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//
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template <class T, class = std::enable_if_t<std::is_pointer<T>::value>>
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using owner = T;
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//
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// not_null
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//
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// Restricts a pointer or smart pointer to only hold non-null values.
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//
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// Has zero size overhead over T.
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//
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// If T is a pointer (i.e. T == U*) then
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// - allow construction from U*
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// - disallow construction from nullptr_t
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// - disallow default construction
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// - ensure construction from null U* fails
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// - allow implicit conversion to U*
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//
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template <class T>
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class not_null
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{
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public:
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static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
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template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
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constexpr not_null(U&& u) : ptr_(std::forward<U>(u))
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{
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Expects(ptr_ != nullptr);
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}
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template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
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constexpr not_null(const not_null<U>& other) : not_null(other.get())
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{
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}
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not_null(not_null&& other) = default;
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not_null(const not_null& other) = default;
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not_null& operator=(const not_null& other) = default;
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constexpr T get() const
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{
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/*
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not_null constructors and assignment operators always verify ptr_ is
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not set to null. As long as references to ptr_ are not exposed publicly
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it is not additionally necessary to check the value against nullptr here.
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*/
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// Ensures(ptr_ != nullptr);
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return ptr_;
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}
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constexpr operator T() const { return get(); }
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constexpr T operator->() const { return get(); }
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constexpr decltype(auto) operator*() const { return *get(); }
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// prevents compilation when someone attempts to assign a null pointer constant
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not_null(std::nullptr_t) = delete;
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not_null& operator=(std::nullptr_t) = delete;
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// unwanted operators...pointers only point to single objects!
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not_null& operator++() = delete;
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not_null& operator--() = delete;
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not_null operator++(int) = delete;
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not_null operator--(int) = delete;
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not_null& operator+=(std::ptrdiff_t) = delete;
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not_null& operator-=(std::ptrdiff_t) = delete;
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void operator[](std::ptrdiff_t) const = delete;
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private:
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T ptr_;
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};
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template <class T>
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std::ostream& operator<<(std::ostream& os, const not_null<T>& val)
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{
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os << val.get();
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return os;
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}
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template <class T, class U>
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auto operator==(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() == rhs.get())
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{
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return lhs.get() == rhs.get();
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}
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template <class T, class U>
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auto operator!=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() != rhs.get())
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{
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return lhs.get() != rhs.get();
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}
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template <class T, class U>
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auto operator<(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() < rhs.get())
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{
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return lhs.get() < rhs.get();
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}
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template <class T, class U>
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auto operator<=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() <= rhs.get())
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{
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return lhs.get() <= rhs.get();
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}
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template <class T, class U>
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auto operator>(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() > rhs.get())
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{
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return lhs.get() > rhs.get();
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}
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template <class T, class U>
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auto operator>=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() >= rhs.get())
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{
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return lhs.get() >= rhs.get();
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}
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// more unwanted operators
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template <class T, class U>
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std::ptrdiff_t operator-(const not_null<T>&, const not_null<U>&) = delete;
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template <class T>
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not_null<T> operator-(const not_null<T>&, std::ptrdiff_t) = delete;
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template <class T>
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not_null<T> operator+(const not_null<T>&, std::ptrdiff_t) = delete;
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template <class T>
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not_null<T> operator+(std::ptrdiff_t, const not_null<T>&) = delete;
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} // namespace gsl
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namespace std
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{
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template <class T>
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struct hash<gsl::not_null<T>>
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{
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std::size_t operator()(const gsl::not_null<T>& value) const { return hash<T>{}(value); }
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};
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} // namespace std
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#if defined(_MSC_VER) && _MSC_VER < 1910
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#undef constexpr
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#pragma pop_macro("constexpr")
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#endif // defined(_MSC_VER) && _MSC_VER < 1910
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#endif // GSL_POINTERS_H
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