mirror of
https://github.com/microsoft/GSL.git
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312 lines
9.8 KiB
C++
312 lines
9.8 KiB
C++
///////////////////////////////////////////////////////////////////////////////
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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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#pragma once
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#ifndef GSL_SPAN_H
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#define GSL_SPAN_H
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#include "gsl_assert.h"
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#include "gsl_util.h"
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#include <array>
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#include <limits>
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#include <iterator>
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#include <stdexcept>
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#include <type_traits>
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#include <utility>
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#ifdef _MSC_VER
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// turn off some warnings that are noisy about our Expects statements
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#pragma warning(push)
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#pragma warning(disable : 4127) // conditional expression is constant
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// No MSVC does constexpr fully yet
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#pragma push_macro("constexpr")
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#define constexpr
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// VS 2013 workarounds
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#if _MSC_VER <= 1800
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#define GSL_MSVC_HAS_VARIADIC_CTOR_BUG
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#define GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
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// noexcept is not understood
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#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
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#pragma push_macro("noexcept")
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#define noexcept /* nothing */
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#endif
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// turn off some misguided warnings
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#pragma warning(push)
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#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
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#pragma warning(disable : 4512) // warns that assignment op could not be generated
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#endif // _MSC_VER <= 1800
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#endif // _MSC_VER
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#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
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#ifdef _MSC_VER
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#pragma push_macro("noexcept")
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#endif
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#define noexcept /* nothing */
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#endif // GSL_THROW_ON_CONTRACT_VIOLATION
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namespace gsl
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{
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// [views.constants], constants
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constexpr const std::ptrdiff_t dynamic_extent = -1;
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// [span], class template span
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template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
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class span {
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public:
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// constants and types
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using element_type = ElementType;
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using index_type = std::ptrdiff_t;
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using pointer = element_type*;
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using reference = element_type&;
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#if 0 // TODO
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using iterator = /*implementation-defined */;
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using const_iterator = /* implementation-defined */;
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using reverse_iterator = std::reverse_iterator<iterator>;
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using const_reverse_iterator = std::reverse_iterator<const_iterator>;
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#endif
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constexpr static const index_type extent = Extent;
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// [span.cons], span constructors, copy, assignment, and destructor
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constexpr span() noexcept : storage_(nullptr, extent_type<0>())
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{}
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constexpr span(nullptr_t) noexcept : span()
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{}
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constexpr span(pointer ptr, index_type count) : storage_(ptr, count)
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{ Expects(((!ptr && count == 0) || (ptr && count >= 0))); }
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constexpr span(pointer firstElem, pointer lastElem)
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: storage_(firstElem, std::distance(firstElem, lastElem))
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{}
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template <size_t N>
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constexpr span(element_type(&arr)[N])
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: storage_(&arr[0], extent_type<N>())
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{}
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template <size_t N>
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constexpr span(std::array<std::remove_const_t<element_type>, N>& arr)
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: storage_(&arr[0], extent_type<N>())
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{}
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template <size_t N>
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constexpr span(const std::array<std::remove_const_t<element_type>, N>& arr)
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: storage_(&arr[0], extent_type<N>())
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{}
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#if 0 // TODO
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template <class Container>
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constexpr span(Container& cont);
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template <class Container>
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span(const Container&&) = delete;
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constexpr span(const span& other) noexcept = default;
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constexpr span(span&& other) noexcept = default;
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template <class OtherElementType, ptrdiff_t OtherExtent>
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constexpr span(const span<OtherElementType, OtherExtent>& other);
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template <class OtherElementType, ptrdiff_t OtherExtent>
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constexpr span(span<OtherElementType, OtherExtent>&& other);
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~span() noexcept = default;
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constexpr span& operator=(const span& other) noexcept = default;
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constexpr span& operator=(span&& other) noexcept = default;
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// [span.sub], span subviews
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template <ptrdiff_t Count>
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constexpr span<element_type, Count> first() const;
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template <ptrdiff_t Count>
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constexpr span<element_type, Count> last() const;
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template <ptrdiff_t Offset, ptrdiff_t Count = dynamic_extent>
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constexpr span<element_type, Count> subspan() const;
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constexpr span<element_type, dynamic_extent> first(index_type count) const;
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constexpr span<element_type, dynamic_extent> last(index_type count) const;
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constexpr span<element_type, dynamic_extent> subspan(index_type offset, index_type count = dynamic_extent) const;
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#endif
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// [span.obs], span observers
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constexpr index_type length() const noexcept { return size(); }
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constexpr index_type size() const noexcept { return storage_.size(); }
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constexpr index_type length_bytes() const noexcept { return size_bytes(); }
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constexpr index_type size_bytes() const noexcept { return size() * sizeof(element_type); }
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constexpr bool empty() const noexcept { return size() == 0; }
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// [span.elem], span element access
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constexpr reference operator[](index_type idx) const
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{
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Expects(idx >= 0 && idx < storage_.size());
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return storage_.data()[idx];
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}
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constexpr reference operator()(index_type idx) const { return this->operator[](idx); }
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constexpr pointer data() const noexcept { return storage_.data(); }
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#if 0 // TODO
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// [span.iter], span iterator support
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iterator begin() const noexcept;
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iterator end() const noexcept;
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const_iterator cbegin() const noexcept;
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const_iterator cend() const noexcept;
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reverse_iterator rbegin() const noexcept;
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reverse_iterator rend() const noexcept;
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const_reverse_iterator crbegin() const noexcept;
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const_reverse_iterator crend() const noexcept;
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#endif
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private:
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template <index_type Extent>
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class extent_type;
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template <index_type Extent>
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class extent_type
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{
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public:
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static_assert(Extent >= 0, "A fixed-size span must be >= 0 in size.");
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constexpr extent_type() noexcept {}
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template <index_type Other>
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constexpr extent_type(extent_type<Other>) noexcept
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{
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static_assert(Other == Extent,
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"Mismatch between fixed-size extent and size of initializing data.");
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}
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constexpr extent_type(index_type size)
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{ Expects(size == Extent); }
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constexpr inline index_type size() const noexcept { return Extent; }
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};
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template <>
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class extent_type<dynamic_extent>
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{
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public:
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template <index_type Other>
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explicit constexpr extent_type(extent_type<Other> ext) : size_(ext.size())
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{}
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explicit constexpr extent_type(index_type size) : size_(size)
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{ Expects(size >= 0); }
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constexpr inline index_type size() const noexcept
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{ return size_; }
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private:
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index_type size_;
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};
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// this implementation detail class lets us take advantage of the
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// empty base class optimization to pay for only storage of a single
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// pointer in the case of fixed-size spans
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template <class ExtentType>
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class storage_type : public ExtentType
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{
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public:
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template <class OtherExtentType>
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storage_type(pointer data, OtherExtentType ext)
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: ExtentType(ext), data_(data) {}
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//storage_type(pointer data, ExtentType ext)
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// : ExtentType(ext), data_(data) {}
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constexpr inline pointer data() const noexcept
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{ return data_; }
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private:
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pointer data_;
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};
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storage_type<extent_type<Extent>> storage_;
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};
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#if 0 // TODO
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// [span.comparison], span comparison operators
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator==(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator<(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr bool operator>=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
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#endif
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#if 0 // TODO
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// [span.objectrep], views of object representation
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template <class ElementType, ptrdiff_t Extent>
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constexpr span<const char, ((Extent == dynamic_extent) ? dynamic_extent : (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
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template <class ElementType, ptrdiff_t Extent>
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constexpr span<char, ((Extent == dynamic_extent) ? dynamic_extent : (sizeof(ElementType) * Extent))> as_writeable_bytes(span<ElementType, Extent>) noexcept;
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#endif
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} // namespace gsl
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#ifdef _MSC_VER
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#undef constexpr
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#pragma pop_macro("constexpr")
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#if _MSC_VER <= 1800
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#pragma warning(pop)
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#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
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#undef noexcept
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#pragma pop_macro("noexcept")
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#endif // GSL_THROW_ON_CONTRACT_VIOLATION
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#undef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
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#endif // _MSC_VER <= 1800
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#endif // _MSC_VER
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#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
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#undef noexcept
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#ifdef _MSC_VER
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#pragma warning(pop)
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#pragma pop_macro("noexcept")
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#endif
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#endif // GSL_THROW_ON_CONTRACT_VIOLATION
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#endif // GSL_SPAN_H
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