GSL/include/gsl/span
Casey Carter 4e8f95b418 Cleanup include structure, constexpr and noexcept compiler workarounds.
* Nest "gsl" directory inside a new "include" directory.

* Cleanup the _MSC_VER conditionals a bit; use constexpr on VS2017+.

* Don't #define noexcept on non-Microsoft implementations.

* Workaround VS2017 bug in multi_span. (Also implement == and != for static_bounds_dynamic_range_t because I'm an EoP semantic soundness snob.)

Fixes #441.
2017-02-07 15:59:37 -08:00

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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.
//
///////////////////////////////////////////////////////////////////////////////
#pragma once
#ifndef GSL_SPAN_H
#define GSL_SPAN_H
#include <gsl/gsl_assert>
#include <gsl/gsl_byte>
#include <gsl/gsl_util>
#include <array>
#include <iterator>
#include <limits>
#include <stdexcept>
#include <type_traits>
#include <utility>
#include <memory>
#ifdef _MSC_VER
#pragma warning(push)
// turn off some warnings that are noisy about our Expects statements
#pragma warning(disable : 4127) // conditional expression is constant
// blanket turn off warnings from CppCoreCheck for now
// so people aren't annoyed by them when running the tool.
// more targeted suppressions will be added in a future update to the GSL
#pragma warning(disable : 26481 26482 26483 26485 26490 26491 26492 26493 26495)
#if _MSC_VER < 1910
#pragma push_macro("constexpr")
#define constexpr /*constexpr*/
// VS 2013 workarounds
#if _MSC_VER <= 1800
#define GSL_MSVC_HAS_VARIADIC_CTOR_BUG
#define GSL_MSVC_NO_DEFAULT_MOVE_CTOR
#define GSL_MSVC_NO_CPP14_STD_EQUAL
// noexcept is not understood
#pragma push_macro("noexcept")
#define noexcept /*noexcept*/
#pragma push_macro("alignof")
#define alignof __alignof
// turn off some misguided warnings
#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
#pragma warning(disable : 4512) // warns that assignment op could not be generated
#endif // _MSC_VER <= 1800
#endif // _MSC_VER < 1910
#endif // _MSC_VER
#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
#define GSL_NOEXCEPT /*noexcept*/
#else
#define GSL_NOEXCEPT noexcept
#endif // GSL_THROW_ON_CONTRACT_VIOLATION
namespace gsl
{
// [views.constants], constants
constexpr const std::ptrdiff_t dynamic_extent = -1;
template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
class span;
// implementation details
namespace details
{
template <class T>
struct is_span_oracle : std::false_type
{
};
template <class ElementType, std::ptrdiff_t Extent>
struct is_span_oracle<gsl::span<ElementType, Extent>> : std::true_type
{
};
template <class T>
struct is_span : public is_span_oracle<std::remove_cv_t<T>>
{
};
template <class T>
struct is_std_array_oracle : std::false_type
{
};
template <class ElementType, size_t Extent>
struct is_std_array_oracle<std::array<ElementType, Extent>> : std::true_type
{
};
template <class T>
struct is_std_array : public is_std_array_oracle<std::remove_cv_t<T>>
{
};
template <std::ptrdiff_t From, std::ptrdiff_t To>
struct is_allowed_extent_conversion
: public std::integral_constant<bool, From == To || From == gsl::dynamic_extent ||
To == gsl::dynamic_extent>
{
};
template <class From, class To>
struct is_allowed_element_type_conversion
: public std::integral_constant<bool, std::is_convertible<From (*)[], To (*)[]>::value>
{
};
template <class Span, bool IsConst>
class span_iterator
{
using element_type_ = typename Span::element_type;
public:
using iterator_category = std::random_access_iterator_tag;
using value_type = std::remove_const_t<element_type_>;
using difference_type = typename Span::index_type;
using reference =
std::conditional_t<IsConst, const element_type_, element_type_> &;
using pointer = std::add_pointer_t<reference>;
constexpr span_iterator() GSL_NOEXCEPT : span_iterator(nullptr, 0) {}
constexpr span_iterator(const Span* span, typename Span::index_type index)
: span_(span), index_(index)
{
Expects(span == nullptr || (index_ >= 0 && index <= span_->length()));
}
friend class span_iterator<Span, true>;
constexpr span_iterator(const span_iterator<Span, false>& other) GSL_NOEXCEPT
: span_iterator(other.span_, other.index_)
{
}
constexpr span_iterator<Span, IsConst>& operator=(const span_iterator<Span, IsConst>&) GSL_NOEXCEPT = default;
constexpr reference operator*() const
{
Expects(span_);
return (*span_)[index_];
}
constexpr pointer operator->() const
{
Expects(span_);
return &((*span_)[index_]);
}
constexpr span_iterator& operator++()
{
Expects(span_ && index_ >= 0 && index_ < span_->length());
++index_;
return *this;
}
constexpr span_iterator operator++(int) GSL_NOEXCEPT
{
auto ret = *this;
++(*this);
return ret;
}
constexpr span_iterator& operator--()
{
Expects(span_ && index_ > 0 && index_ <= span_->length());
--index_;
return *this;
}
constexpr span_iterator operator--(int) GSL_NOEXCEPT
{
auto ret = *this;
--(*this);
return ret;
}
constexpr span_iterator operator+(difference_type n) const GSL_NOEXCEPT
{
auto ret = *this;
return ret += n;
}
constexpr span_iterator& operator+=(difference_type n)
{
Expects(span_ && (index_ + n) >= 0 && (index_ + n) <= span_->length());
index_ += n;
return *this;
}
constexpr span_iterator operator-(difference_type n) const GSL_NOEXCEPT
{
auto ret = *this;
return ret -= n;
}
constexpr span_iterator& operator-=(difference_type n) GSL_NOEXCEPT { return *this += -n; }
constexpr difference_type operator-(const span_iterator& rhs) const
{
Expects(span_ == rhs.span_);
return index_ - rhs.index_;
}
constexpr reference operator[](difference_type n) const GSL_NOEXCEPT { return *(*this + n); }
constexpr friend bool operator==(const span_iterator& lhs,
const span_iterator& rhs) GSL_NOEXCEPT
{
return lhs.span_ == rhs.span_ && lhs.index_ == rhs.index_;
}
constexpr friend bool operator!=(const span_iterator& lhs,
const span_iterator& rhs) GSL_NOEXCEPT
{
return !(lhs == rhs);
}
constexpr friend bool operator<(const span_iterator& lhs, const span_iterator& rhs)
{
Expects(lhs.span_ == rhs.span_);
return lhs.index_ < rhs.index_;
}
constexpr friend bool operator<=(const span_iterator& lhs,
const span_iterator& rhs) GSL_NOEXCEPT
{
return !(rhs < lhs);
}
constexpr friend bool operator>(const span_iterator& lhs, const span_iterator& rhs) GSL_NOEXCEPT
{
return rhs < lhs;
}
constexpr friend bool operator>=(const span_iterator& lhs,
const span_iterator& rhs) GSL_NOEXCEPT
{
return !(rhs > lhs);
}
void swap(span_iterator& rhs) GSL_NOEXCEPT
{
std::swap(index_, rhs.index_);
std::swap(span_, rhs.span_);
}
protected:
const Span* span_;
std::ptrdiff_t index_;
};
template <class Span, bool IsConst>
inline constexpr span_iterator<Span, IsConst>
operator+(typename span_iterator<Span, IsConst>::difference_type n,
const span_iterator<Span, IsConst>& rhs) GSL_NOEXCEPT
{
return rhs + n;
}
template <class Span, bool IsConst>
inline constexpr span_iterator<Span, IsConst>
operator-(typename span_iterator<Span, IsConst>::difference_type n,
const span_iterator<Span, IsConst>& rhs) GSL_NOEXCEPT
{
return rhs - n;
}
template <std::ptrdiff_t Ext>
class extent_type
{
public:
using index_type = std::ptrdiff_t;
static_assert(Ext >= 0, "A fixed-size span must be >= 0 in size.");
constexpr extent_type() GSL_NOEXCEPT {}
template <index_type Other>
constexpr extent_type(extent_type<Other> ext)
{
static_assert(Other == Ext || Other == dynamic_extent,
"Mismatch between fixed-size extent and size of initializing data.");
Expects(ext.size() == Ext);
}
constexpr extent_type(index_type size) { Expects(size == Ext); }
constexpr index_type size() const GSL_NOEXCEPT { return Ext; }
};
template <>
class extent_type<dynamic_extent>
{
public:
using index_type = std::ptrdiff_t;
template <index_type Other>
explicit constexpr extent_type(extent_type<Other> ext) : size_(ext.size())
{
}
explicit constexpr extent_type(index_type size) : size_(size) { Expects(size >= 0); }
constexpr index_type size() const GSL_NOEXCEPT { return size_; }
private:
index_type size_;
};
} // namespace details
// [span], class template span
template <class ElementType, std::ptrdiff_t Extent>
class span
{
public:
// constants and types
using element_type = ElementType;
using index_type = std::ptrdiff_t;
using pointer = element_type*;
using reference = element_type&;
using iterator = details::span_iterator<span<ElementType, Extent>, false>;
using const_iterator = details::span_iterator<span<ElementType, Extent>, true>;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
constexpr static const index_type extent = Extent;
// [span.cons], span constructors, copy, assignment, and destructor
template <bool Dependent = false,
// "Dependent" is needed to make "std::enable_if_t<Dependent || Extent <= 0>" SFINAE,
// since "std::enable_if_t<Extent <= 0>" is ill-formed when Extent is greater than 0.
class = std::enable_if_t<(Dependent || Extent <= 0)>>
constexpr span() GSL_NOEXCEPT : storage_(nullptr, details::extent_type<0>()) {}
constexpr span(std::nullptr_t) GSL_NOEXCEPT : span() {}
constexpr span(pointer ptr, index_type count) : storage_(ptr, count) {}
constexpr span(pointer firstElem, pointer lastElem)
: storage_(firstElem, std::distance(firstElem, lastElem))
{
}
template <size_t N>
constexpr span(element_type (&arr)[N]) GSL_NOEXCEPT : storage_(&arr[0], details::extent_type<N>())
{
}
template <size_t N, class ArrayElementType = std::remove_const_t<element_type>>
constexpr span(std::array<ArrayElementType, N>& arr) GSL_NOEXCEPT
: storage_(&arr[0], details::extent_type<N>())
{
}
template <size_t N>
constexpr span(const std::array<std::remove_const_t<element_type>, N>& arr) GSL_NOEXCEPT
: storage_(&arr[0], details::extent_type<N>())
{
}
template<class ArrayElementType = std::add_pointer<element_type>>
constexpr span(const std::unique_ptr<ArrayElementType>& ptr, index_type count) : storage_(ptr.get(), count) {}
constexpr span(const std::unique_ptr<ElementType>& ptr) : storage_(ptr.get(), ptr.get() ? 1 : 0) {}
constexpr span(const std::shared_ptr<ElementType>& ptr) : storage_(ptr.get(), ptr.get() ? 1 : 0) {}
// NB: the SFINAE here uses .data() as a incomplete/imperfect proxy for the requirement
// on Container to be a contiguous sequence container.
template <class Container,
class = std::enable_if_t<
!details::is_span<Container>::value && !details::is_std_array<Container>::value &&
std::is_convertible<typename Container::pointer, pointer>::value &&
std::is_convertible<typename Container::pointer,
decltype(std::declval<Container>().data())>::value>>
constexpr span(Container& cont) : span(cont.data(), narrow<index_type>(cont.size()))
{
}
template <class Container,
class = std::enable_if_t<
std::is_const<element_type>::value && !details::is_span<Container>::value &&
std::is_convertible<typename Container::pointer, pointer>::value &&
std::is_convertible<typename Container::pointer,
decltype(std::declval<Container>().data())>::value>>
constexpr span(const Container& cont) : span(cont.data(), narrow<index_type>(cont.size()))
{
}
constexpr span(const span& other) GSL_NOEXCEPT = default;
#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
constexpr span(span&& other) GSL_NOEXCEPT = default;
#else
constexpr span(span&& other) GSL_NOEXCEPT : storage_(std::move(other.storage_)) {}
#endif
template <
class OtherElementType, std::ptrdiff_t OtherExtent,
class = std::enable_if_t<
details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
details::is_allowed_element_type_conversion<OtherElementType, element_type>::value>>
constexpr span(const span<OtherElementType, OtherExtent>& other)
: storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
{
}
template <
class OtherElementType, std::ptrdiff_t OtherExtent,
class = std::enable_if_t<
details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
details::is_allowed_element_type_conversion<OtherElementType, element_type>::value>>
constexpr span(span<OtherElementType, OtherExtent>&& other)
: storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
{
}
~span() GSL_NOEXCEPT = default;
constexpr span& operator=(const span& other) GSL_NOEXCEPT = default;
#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
constexpr span& operator=(span&& other) GSL_NOEXCEPT = default;
#else
constexpr span& operator=(span&& other) GSL_NOEXCEPT
{
storage_ = std::move(other.storage_);
return *this;
}
#endif
// [span.sub], span subviews
template <std::ptrdiff_t Count>
constexpr span<element_type, Count> first() const
{
Expects(Count >= 0 && Count <= size());
return {data(), Count};
}
template <std::ptrdiff_t Count>
constexpr span<element_type, Count> last() const
{
Expects(Count >= 0 && Count <= size());
return {data() + (size() - Count), Count};
}
template <std::ptrdiff_t Offset, std::ptrdiff_t Count = dynamic_extent>
constexpr span<element_type, Count> subspan() const
{
Expects((Offset == 0 || (Offset > 0 && Offset <= size())) &&
(Count == dynamic_extent || (Count >= 0 && Offset + Count <= size())));
return {data() + Offset, Count == dynamic_extent ? size() - Offset : Count};
}
constexpr span<element_type, dynamic_extent> first(index_type count) const
{
Expects(count >= 0 && count <= size());
return {data(), count};
}
constexpr span<element_type, dynamic_extent> last(index_type count) const
{
Expects(count >= 0 && count <= size());
return {data() + (size() - count), count};
}
constexpr span<element_type, dynamic_extent> subspan(index_type offset,
index_type count = dynamic_extent) const
{
Expects((offset == 0 || (offset > 0 && offset <= size())) &&
(count == dynamic_extent || (count >= 0 && offset + count <= size())));
return {data() + offset, count == dynamic_extent ? size() - offset : count};
}
// [span.obs], span observers
constexpr index_type length() const GSL_NOEXCEPT { return size(); }
constexpr index_type size() const GSL_NOEXCEPT { return storage_.size(); }
constexpr index_type length_bytes() const GSL_NOEXCEPT { return size_bytes(); }
constexpr index_type size_bytes() const GSL_NOEXCEPT { return size() * narrow_cast<index_type>(sizeof(element_type)); }
constexpr bool empty() const GSL_NOEXCEPT { return size() == 0; }
// [span.elem], span element access
constexpr reference operator[](index_type idx) const
{
Expects(idx >= 0 && idx < storage_.size());
return data()[idx];
}
constexpr reference at(index_type idx) const { return this->operator[](idx); }
constexpr reference operator()(index_type idx) const { return this->operator[](idx); }
constexpr pointer data() const GSL_NOEXCEPT { return storage_.data(); }
// [span.iter], span iterator support
iterator begin() const GSL_NOEXCEPT { return {this, 0}; }
iterator end() const GSL_NOEXCEPT { return {this, length()}; }
const_iterator cbegin() const GSL_NOEXCEPT { return {this, 0}; }
const_iterator cend() const GSL_NOEXCEPT { return {this, length()}; }
reverse_iterator rbegin() const GSL_NOEXCEPT { return reverse_iterator{end()}; }
reverse_iterator rend() const GSL_NOEXCEPT { return reverse_iterator{begin()}; }
const_reverse_iterator crbegin() const GSL_NOEXCEPT { return const_reverse_iterator{cend()}; }
const_reverse_iterator crend() const GSL_NOEXCEPT { return const_reverse_iterator{cbegin()}; }
private:
// this implementation detail class lets us take advantage of the
// empty base class optimization to pay for only storage of a single
// pointer in the case of fixed-size spans
template <class ExtentType>
class storage_type : public ExtentType
{
public:
template <class OtherExtentType>
constexpr storage_type(pointer data, OtherExtentType ext) : ExtentType(ext), data_(data)
{
Expects((!data && ExtentType::size() == 0) || (data && ExtentType::size() >= 0));
}
constexpr pointer data() const GSL_NOEXCEPT { return data_; }
private:
pointer data_;
};
storage_type<details::extent_type<Extent>> storage_;
};
// [span.comparison], span comparison operators
template <class ElementType, std::ptrdiff_t FirstExtent, std::ptrdiff_t SecondExtent>
inline constexpr bool operator==(const span<ElementType, FirstExtent>& l,
const span<ElementType, SecondExtent>& r)
{
#ifdef GSL_MSVC_NO_CPP14_STD_EQUAL
return (l.size() == r.size()) && std::equal(l.begin(), l.end(), r.begin());
#else
return std::equal(l.begin(), l.end(), r.begin(), r.end());
#endif
}
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
{
return !(l == r);
}
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr bool operator<(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
{
return std::lexicographical_compare(l.begin(), l.end(), r.begin(), r.end());
}
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
{
return !(l > r);
}
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
{
return r < l;
}
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr bool operator>=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
{
return !(l < r);
}
namespace details
{
// if we only supported compilers with good constexpr support then
// this pair of classes could collapse down to a constexpr function
// we should use a narrow_cast<> to go to size_t, but older compilers may not see it as
// constexpr
// and so will fail compilation of the template
template <class ElementType, std::ptrdiff_t Extent>
struct calculate_byte_size
: std::integral_constant<std::ptrdiff_t,
static_cast<std::ptrdiff_t>(sizeof(ElementType) *
static_cast<std::size_t>(Extent))>
{
};
template <class ElementType>
struct calculate_byte_size<ElementType, dynamic_extent>
: std::integral_constant<std::ptrdiff_t, dynamic_extent>
{
};
}
// [span.objectrep], views of object representation
template <class ElementType, std::ptrdiff_t Extent>
span<const byte, details::calculate_byte_size<ElementType, Extent>::value>
as_bytes(span<ElementType, Extent> s) GSL_NOEXCEPT
{
return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
}
template <class ElementType, std::ptrdiff_t Extent,
class = std::enable_if_t<!std::is_const<ElementType>::value>>
span<byte, details::calculate_byte_size<ElementType, Extent>::value>
as_writeable_bytes(span<ElementType, Extent> s) GSL_NOEXCEPT
{
return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
}
//
// make_span() - Utility functions for creating spans
//
template <class ElementType>
span<ElementType>
make_span(ElementType* ptr, typename span<ElementType>::index_type count)
{ return span<ElementType>(ptr, count); }
template <class ElementType>
span<ElementType>
make_span(ElementType* firstElem, ElementType* lastElem)
{ return span<ElementType>(firstElem, lastElem); }
template <class ElementType, size_t N>
span<ElementType>
make_span(ElementType (&arr)[N])
{ return span<ElementType>(arr); }
template <class Container>
span<typename Container::value_type>
make_span(Container &cont)
{ return span<typename Container::value_type>(cont); }
template <class Container>
span<const typename Container::value_type>
make_span(const Container &cont)
{ return span<const typename Container::value_type>(cont); }
template <class Ptr>
span<typename Ptr::element_type>
make_span(Ptr& cont, std::ptrdiff_t count)
{ return span<typename Ptr::element_type>(cont, count); }
template <class Ptr>
span<typename Ptr::element_type>
make_span(Ptr& cont)
{ return span<typename Ptr::element_type>(cont); }
// Specialization of gsl::at for span
template <class ElementType, std::ptrdiff_t Extent>
inline constexpr ElementType& at(const span<ElementType, Extent>& s, std::ptrdiff_t index)
{
// No bounds checking here because it is done in span::operator[] called below
return s[index];
}
} // namespace gsl
#undef GSL_NOEXCEPT
#ifdef _MSC_VER
#if _MSC_VER < 1910
#undef constexpr
#pragma pop_macro("constexpr")
#if _MSC_VER <= 1800
#undef noexcept
#pragma pop_macro("noexcept")
#undef alignof
#pragma pop_macro("alignof")
#undef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
#undef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
#undef GSL_MSVC_NO_CPP14_STD_EQUAL
#endif // _MSC_VER <= 1800
#endif // _MSC_VER < 1910
#pragma warning(pop)
#endif // _MSC_VER
#endif // GSL_SPAN_H