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///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef GSL_POINTERS_H
#define GSL_POINTERS_H
#include <gsl/gsl_assert> // for Ensures, Expects
#include <algorithm> // for forward
#include <iosfwd> // for ptrdiff_t, nullptr_t, ostream, size_t
#include <memory> // for shared_ptr, unique_ptr
#include <system_error> // for hash
#include <type_traits> // for enable_if_t, is_convertible, is_assignable
#if defined(_MSC_VER) && _MSC_VER < 1910 && !defined(__clang__)
#pragma push_macro("constexpr")
#define constexpr /*constexpr*/
#endif // defined(_MSC_VER) && _MSC_VER < 1910
namespace gsl
{
//
// GSL.owner: ownership pointers
//
using std::unique_ptr;
using std::shared_ptr;
//
// owner
//
// owner<T> is designed as a bridge for code that must deal directly with owning pointers for some reason
//
// T must be a pointer type
// - disallow construction from any type other than pointer type
//
template <class T, class = std::enable_if_t<std::is_pointer<T>::value>>
using owner = T;
//
// not_null
//
// Restricts a pointer or smart pointer to only hold non-null values.
//
// Has zero size overhead over T.
//
// If T is a pointer (i.e. T == U*) then
// - allow construction from U*
// - disallow construction from nullptr_t
// - disallow default construction
// - ensure construction from null U* fails
// - allow implicit conversion to U*
//
template <class T>
class not_null
{
public:
static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
constexpr not_null(U&& u) : ptr_(std::forward<U>(u))
{
Expects(ptr_ != nullptr);
}
template <typename = std::enable_if_t<!std::is_same<std::nullptr_t, T>::value>>
constexpr not_null(T u) : ptr_(u)
{
Expects(ptr_ != nullptr);
}
template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
constexpr not_null(const not_null<U>& other) : not_null(other.get())
{
}
not_null(not_null&& other) = default;
not_null(const not_null& other) = default;
not_null& operator=(const not_null& other) = default;
constexpr T get() const
{
Ensures(ptr_ != nullptr);
return ptr_;
}
constexpr operator T() const { return get(); }
constexpr T operator->() const { return get(); }
constexpr decltype(auto) operator*() const { return *get(); }
// prevents compilation when someone attempts to assign a null pointer constant
not_null(std::nullptr_t) = delete;
not_null& operator=(std::nullptr_t) = delete;
// unwanted operators...pointers only point to single objects!
not_null& operator++() = delete;
not_null& operator--() = delete;
not_null operator++(int) = delete;
not_null operator--(int) = delete;
not_null& operator+=(std::ptrdiff_t) = delete;
not_null& operator-=(std::ptrdiff_t) = delete;
void operator[](std::ptrdiff_t) const = delete;
private:
T ptr_;
};
template <class T>
auto make_not_null(T&& t) {
return not_null<std::remove_cv_t<std::remove_reference_t<T>>>{std::forward<T>(t)};
}
template <class T>
std::ostream& operator<<(std::ostream& os, const not_null<T>& val)
{
os << val.get();
return os;
}
template <class T, class U>
auto operator==(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() == rhs.get())
{
return lhs.get() == rhs.get();
}
template <class T, class U>
auto operator!=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() != rhs.get())
{
return lhs.get() != rhs.get();
}
template <class T, class U>
auto operator<(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() < rhs.get())
{
return lhs.get() < rhs.get();
}
template <class T, class U>
auto operator<=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() <= rhs.get())
{
return lhs.get() <= rhs.get();
}
template <class T, class U>
auto operator>(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() > rhs.get())
{
return lhs.get() > rhs.get();
}
template <class T, class U>
auto operator>=(const not_null<T>& lhs, const not_null<U>& rhs) -> decltype(lhs.get() >= rhs.get())
{
return lhs.get() >= rhs.get();
}
// more unwanted operators
template <class T, class U>
std::ptrdiff_t operator-(const not_null<T>&, const not_null<U>&) = delete;
template <class T>
not_null<T> operator-(const not_null<T>&, std::ptrdiff_t) = delete;
template <class T>
not_null<T> operator+(const not_null<T>&, std::ptrdiff_t) = delete;
template <class T>
not_null<T> operator+(std::ptrdiff_t, const not_null<T>&) = delete;
} // namespace gsl
namespace std
{
template <class T>
struct hash<gsl::not_null<T>>
{
std::size_t operator()(const gsl::not_null<T>& value) const { return hash<T>{}(value); }
};
} // namespace std
namespace gsl
{
//
// strict_not_null
//
// Restricts a pointer or smart pointer to only hold non-null values,
//
// - provides a strict (i.e. explicit contructor from T) wrapper of not_null
// - to be used for new code that wishes the design to be cleaner and make not_null
// checks intentional, or in old code that would like to make the transition.
//
// To make the transition from not_null, incrementally replace not_null
// by strict_not_null and fix compilation errors
//
// Expect to
// - remove all unneded conversions from raw pointer to not_null and back
// - make API clear by specifyning not_null in parameters where needed
// - remove unnesessary asserts
//
template <class T>
class strict_not_null: public not_null<T>
{
public:
template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
constexpr explicit strict_not_null(U&& u) :
not_null<T>(std::forward<U>(u))
{}
template <typename = std::enable_if_t<!std::is_same<std::nullptr_t, T>::value>>
constexpr explicit strict_not_null(T u) :
not_null<T>(u)
{}
template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
constexpr strict_not_null(const not_null<U>& other) :
not_null<T>(other)
{}
template <typename U, typename = std::enable_if_t<std::is_convertible<U, T>::value>>
constexpr strict_not_null(const strict_not_null<U>& other) :
not_null<T>(other)
{}
strict_not_null(strict_not_null&& other) = default;
strict_not_null(const strict_not_null& other) = default;
strict_not_null& operator=(const strict_not_null& other) = default;
strict_not_null& operator=(const not_null<T>& other)
{
not_null<T>::operator=(other);
return *this;
}
// prevents compilation when someone attempts to assign a null pointer constant
strict_not_null(std::nullptr_t) = delete;
strict_not_null& operator=(std::nullptr_t) = delete;
// unwanted operators...pointers only point to single objects!
strict_not_null& operator++() = delete;
strict_not_null& operator--() = delete;
strict_not_null operator++(int) = delete;
strict_not_null operator--(int) = delete;
strict_not_null& operator+=(std::ptrdiff_t) = delete;
strict_not_null& operator-=(std::ptrdiff_t) = delete;
void operator[](std::ptrdiff_t) const = delete;
};
// more unwanted operators
template <class T, class U>
std::ptrdiff_t operator-(const strict_not_null<T>&, const strict_not_null<U>&) = delete;
template <class T>
strict_not_null<T> operator-(const strict_not_null<T>&, std::ptrdiff_t) = delete;
template <class T>
strict_not_null<T> operator+(const strict_not_null<T>&, std::ptrdiff_t) = delete;
template <class T>
strict_not_null<T> operator+(std::ptrdiff_t, const strict_not_null<T>&) = delete;
template <class T>
auto make_strict_not_null(T&& t) {
return strict_not_null<std::remove_cv_t<std::remove_reference_t<T>>>{std::forward<T>(t)};
}
} // namespace gsl
namespace std
{
template <class T>
struct hash<gsl::strict_not_null<T>>
{
std::size_t operator()(const gsl::strict_not_null<T>& value) const { return hash<T>{}(value); }
};
} // namespace std
#if defined(_MSC_VER) && _MSC_VER < 1910 && !defined(__clang__)
#undef constexpr
#pragma pop_macro("constexpr")
#endif // defined(_MSC_VER) && _MSC_VER < 1910 && !defined(__clang__)
#endif // GSL_POINTERS_H