mirror of
https://github.com/microsoft/GSL.git
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685 lines
22 KiB
C++
685 lines
22 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 "gsl_byte.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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#pragma warning(push)
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// turn off some warnings that are noisy about our Expects statements
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#pragma warning(disable : 4127) // conditional expression is constant
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// blanket turn off warnings from CppCoreCheck for now
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// so people aren't annoyed by them when running the tool.
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// more targeted suppressions will be added in a future update to the GSL
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#pragma warning(disable: 26481 26482 26483 26485 26490 26491 26492 26493 26495)
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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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template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
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class span;
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// [views.constants], constants
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constexpr const std::ptrdiff_t dynamic_extent = -1;
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// implementation details
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namespace details
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{
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template <class T>
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struct is_span_oracle : std::false_type
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{
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};
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template <class ElementType, std::ptrdiff_t Extent>
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struct is_span_oracle<gsl::span<ElementType, Extent>> : std::true_type
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{
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};
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template <class T>
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struct is_span : is_span_oracle<std::remove_cv_t<T>>
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{
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};
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template <class From, class To>
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struct is_allowed_pointer_conversion
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: std::bool_constant<
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std::is_pointer<From>::value &&
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std::is_pointer<To>::value &&
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std::is_convertible<From, To>::value
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>
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{
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};
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template <class From, class To>
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struct is_allowed_integral_conversion
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: std::bool_constant<
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std::is_integral<From>::value &&
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std::is_integral<To>::value &&
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sizeof(From) == sizeof(To) &&
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alignof(From) == alignof(To) &&
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std::is_convertible<From, To>::value
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>
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{
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};
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template <std::ptrdiff_t From, std::ptrdiff_t To>
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struct is_allowed_extent_conversion
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: std::bool_constant<
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From == To ||
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From == gsl::dynamic_extent ||
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To == gsl::dynamic_extent
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>
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{
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};
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template <class From, class To>
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struct is_allowed_element_type_conversion
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: std::bool_constant<
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std::is_same<From, std::remove_cv_t<To>>::value ||
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is_allowed_pointer_conversion<From, To>::value ||
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is_allowed_integral_conversion<From, To>::value
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>
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{
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};
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template <class From>
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struct is_allowed_element_type_conversion<From, byte>
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: std::bool_constant<!std::is_const<From>::value>
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{
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};
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template <class From>
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struct is_allowed_element_type_conversion<From, const byte>
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: std::true_type
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{
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};
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template <class Span>
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class const_span_iterator
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{
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public:
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using iterator_category = std::random_access_iterator_tag;
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using value_type = typename Span::element_type;
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using difference_type = std::ptrdiff_t;
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using const_pointer = std::add_const_t<value_type*>;
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using pointer = const_pointer;
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using const_reference = std::add_const_t<value_type&>;
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using reference = const_reference;
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constexpr const_span_iterator() : const_span_iterator(nullptr, 0) {}
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constexpr const_span_iterator(const Span* span, typename Span::index_type index) : span_(span), index_(index)
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{
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Expects(span == nullptr || (index_ >= 0 && index <= span_->length()));
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}
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constexpr reference operator*() const { Expects(span_); return (*span_)[index_]; }
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constexpr pointer operator->() const { Expects(span_); return &((*span_)[index_]); }
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constexpr const_span_iterator& operator++() noexcept
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{
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Expects(span_ && index_ >= 0 && index_ < span_->length());
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++index_;
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return *this;
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}
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constexpr const_span_iterator operator++(int) noexcept
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{
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auto ret = *this;
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++(*this);
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return ret;
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}
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constexpr const_span_iterator& operator--() noexcept
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{
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Expects(span_ && index_ > 0 && index_ <= span_->length());
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--index_;
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return *this;
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}
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constexpr const_span_iterator operator--(int) noexcept
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{
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auto ret = *this;
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--(*this);
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return ret;
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}
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constexpr const_span_iterator operator+(difference_type n) const noexcept
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{
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auto ret{*this};
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return ret += n;
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}
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constexpr const_span_iterator& operator+=(difference_type n) noexcept
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{
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Expects(span_ && (index_ + n) >= 0 && (index_ + n) <= span_->length());
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index_ += n;
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return *this;
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}
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constexpr const_span_iterator operator-(difference_type n) const noexcept
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{
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auto ret{*this};
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return ret -= n;
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}
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constexpr const_span_iterator& operator-=(difference_type n) noexcept
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{
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return *this += -n;
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}
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constexpr difference_type operator-(const const_span_iterator& rhs) const noexcept
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{
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Expects(span_ == rhs.span_);
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return index_ - rhs.index_;
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}
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constexpr reference operator[](difference_type n) const noexcept
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{
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return *(*this + n);
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}
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constexpr bool operator==(const const_span_iterator& rhs) const noexcept
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{
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return span_ == rhs.span_ && index_ == rhs.index_;
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}
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constexpr bool operator!=(const const_span_iterator& rhs) const noexcept { return !(*this == rhs); }
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constexpr bool operator<(const const_span_iterator& rhs) const noexcept
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{
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Expects(span_ == rhs.span_);
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return index_ < rhs.index_;
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}
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constexpr bool operator<=(const const_span_iterator& rhs) const noexcept { return !(rhs < *this); }
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constexpr bool operator>(const const_span_iterator& rhs) const noexcept { return rhs < *this; }
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constexpr bool operator>=(const const_span_iterator& rhs) const noexcept { return !(rhs > *this); }
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void swap(const_span_iterator& rhs) noexcept
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{
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std::swap(index_, rhs.index_);
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std::swap(m_span, rhs.m_span);
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}
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private:
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const Span* span_;
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ptrdiff_t index_;
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};
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template <class Span>
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class span_iterator : public const_span_iterator<Span>
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{
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using base_type = const_span_iterator<Span>;
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public:
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using iterator_category = std::random_access_iterator_tag;
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using value_type = typename Span::element_type;
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using difference_type = std::ptrdiff_t;
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using pointer = value_type*;
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using reference = value_type&;
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constexpr span_iterator() : base_type() {}
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constexpr span_iterator(const Span* span, typename Span::index_type index) : base_type(span, index) {}
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constexpr reference operator*() const { return const_cast<reference>(base_type::operator*()); }
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constexpr pointer operator->() const { return const_cast<pointer>(base_type::operator->()); }
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constexpr span_iterator& operator++() noexcept { base_type::operator++(); return *this; }
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constexpr span_iterator operator++(int) noexcept { return base_type::operator++(1); }
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constexpr span_iterator& operator--() noexcept { base_type::operator--(); return *this; }
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constexpr span_iterator operator--(int) noexcept { return base_type::operator--(1); }
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constexpr span_iterator operator+(difference_type n) const noexcept { return base_type::operator+(n); }
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constexpr span_iterator& operator+=(difference_type n) noexcept { return base_type::operator+=(n); }
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constexpr span_iterator operator-(difference_type n) const noexcept { return base_type::operator-(n); }
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constexpr span_iterator& operator-=(difference_type n) noexcept { return base_type::operator-=(n); }
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constexpr difference_type operator-(const span_iterator& rhs) const noexcept { return base_type::operator-(rhs); }
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constexpr reference operator[](difference_type n) const noexcept { return *(*this + n); }
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constexpr bool operator==(const span_iterator& rhs) const noexcept { return base_type::operator==(rhs); }
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constexpr bool operator!=(const span_iterator& rhs) const noexcept { return !(*this == rhs); }
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constexpr bool operator<(const span_iterator& rhs) const noexcept { return base_type::operator<(rhs); }
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constexpr bool operator<=(const span_iterator& rhs) const noexcept { return !(rhs < *this); }
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constexpr bool operator>(const span_iterator& rhs) const noexcept { return rhs < *this; }
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constexpr bool operator>=(const span_iterator& rhs) const noexcept { return !(rhs > *this); }
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void swap(span_iterator& rhs) noexcept { base_type::swap(rhs); }
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};
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template <typename Span>
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constexpr const_span_iterator<Span> operator+(typename const_span_iterator<Span>::difference_type n,
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const const_span_iterator<Span>& rhs) noexcept
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{
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return rhs + n;
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}
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template <typename Span>
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constexpr const_span_iterator<Span> operator-(typename const_span_iterator<Span>::difference_type n,
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const const_span_iterator<Span>& rhs) noexcept
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{
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return rhs - n;
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}
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template <typename Span>
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constexpr span_iterator<Span> operator+(typename span_iterator<Span>::difference_type n,
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const span_iterator<Span>& rhs) noexcept
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{
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return rhs + n;
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}
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template <typename Span>
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constexpr span_iterator<Span> operator-(typename span_iterator<Span>::difference_type n,
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const span_iterator<Span>& rhs) noexcept
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{
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return rhs - n;
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}
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} // namespace details
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// [span], class template span
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template <class ElementType, std::ptrdiff_t 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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using iterator = details::span_iterator<span<ElementType, Extent>>;
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using const_iterator = details::const_span_iterator<span>;
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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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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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{}
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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]) noexcept
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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<element_type, N>& arr) noexcept
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: storage_(&arr[0], extent_type<N>())
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{}
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template <size_t N, class = std::enable_if_t<is_const<element_type>::value>>
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constexpr span(std::array<std::remove_const_t<element_type>, N>& arr) noexcept
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: storage_(&arr[0], extent_type<N>())
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{}
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template <size_t N, class = std::enable_if_t<is_const<element_type>::value>>
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constexpr span(const std::array<std::remove_const_t<element_type>, N>& arr) noexcept
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: storage_(&arr[0], extent_type<N>())
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{}
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// NB: the SFINAE here uses .data() as a incomplete/imperfect proxy for the requirement
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// on Container to be a contiguous sequence container.
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template <class Container,
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class = std::enable_if_t<!details::is_span<Container>::value &&
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std::is_convertible<Container::pointer, pointer>::value &&
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std::is_convertible<Container::pointer, decltype(std::declval<Container>().data())>::value>
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>
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constexpr span(Container& cont) : span(cont.data(), cont.size()) {}
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template <class Container,
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class = std::enable_if_t<std::is_const<element_type>::value &&
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!details::is_span<Container>::value &&
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std::is_convertible<Container::pointer, pointer>::value &&
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std::is_convertible<Container::pointer, decltype(std::declval<Container>().data())>::value>
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>
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constexpr span(const Container& cont) : span(cont.data(), cont.size()) {}
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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, std::ptrdiff_t OtherExtent,
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class = std::enable_if_t<
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details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
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details::is_allowed_element_type_conversion<OtherElementType, element_type>::value
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>
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>
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constexpr span(const span<OtherElementType, OtherExtent>& other)
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: storage_(reinterpret_cast<pointer>(other.data()), extent_type<OtherExtent>(other.size()))
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{}
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template <class OtherElementType, std::ptrdiff_t OtherExtent,
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class = std::enable_if_t<
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details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
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details::is_allowed_element_type_conversion<OtherElementType, element_type>::value
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>
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>
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constexpr span(span<OtherElementType, OtherExtent>&& other)
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: storage_(reinterpret_cast<pointer>(other.data()), extent_type<OtherExtent>(other.size()))
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{}
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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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{
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Expects(Count >= 0 && Count <= size());
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return { data(), Count };
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}
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template <ptrdiff_t Count>
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constexpr span<element_type, Count> last() const
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{
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Expects(Count >= 0 && Count <= size());
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return{ data() + (size() - Count), Count };
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}
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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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{
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Expects((Offset == 0 || Offset > 0 && Offset <= size()) &&
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(Count == dynamic_extent || Count >= 0 && Offset + Count <= size()));
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return { data() + Offset, Count == dynamic_extent ? size() - Offset : Count };
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}
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constexpr span<element_type, dynamic_extent> first(index_type count) const
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{
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Expects(count >= 0 && count <= size());
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return { data(), count };
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}
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constexpr span<element_type, dynamic_extent> last(index_type count) const
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{
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Expects(count >= 0 && count <= size());
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return { data() + (size() - count), count };
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}
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constexpr span<element_type, dynamic_extent> subspan(index_type offset,
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index_type count = dynamic_extent) const
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{
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Expects((offset == 0 || offset > 0 && offset <= size()) &&
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(count == dynamic_extent || count >= 0 && offset + count <= size()));
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return { data() + offset, count == dynamic_extent ? size() - offset : count };
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}
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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 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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// [span.iter], span iterator support
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iterator begin() const noexcept { return {this, 0}; }
|
|
iterator end() const noexcept { return {this, length()}; }
|
|
|
|
const_iterator cbegin() const noexcept { return {this, 0}; }
|
|
const_iterator cend() const noexcept { return {this, length()}; }
|
|
|
|
reverse_iterator rbegin() const noexcept { return reverse_iterator{{this, length()}}; }
|
|
reverse_iterator rend() const noexcept { return reverse_iterator{{this, 0}}; }
|
|
|
|
const_reverse_iterator crbegin() const noexcept { return reverse_iterator{{this, length()}}; }
|
|
const_reverse_iterator crend() const noexcept { return reverse_iterator{{this, 0}}; }
|
|
|
|
private:
|
|
template <index_type Extent>
|
|
class extent_type;
|
|
|
|
template <index_type Extent>
|
|
class extent_type
|
|
{
|
|
public:
|
|
static_assert(Extent >= 0, "A fixed-size span must be >= 0 in size.");
|
|
|
|
constexpr extent_type() noexcept {}
|
|
|
|
template <index_type Other>
|
|
constexpr extent_type(extent_type<Other> ext) noexcept
|
|
{
|
|
static_assert(Other == Extent || Other == dynamic_extent,
|
|
"Mismatch between fixed-size extent and size of initializing data.");
|
|
Expects(ext.size() == Extent);
|
|
}
|
|
|
|
constexpr extent_type(index_type size)
|
|
{ Expects(size == Extent); }
|
|
|
|
constexpr inline index_type size() const noexcept { return Extent; }
|
|
};
|
|
|
|
template <>
|
|
class extent_type<dynamic_extent>
|
|
{
|
|
public:
|
|
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 inline index_type size() const noexcept
|
|
{ return size_; }
|
|
|
|
private:
|
|
index_type size_;
|
|
};
|
|
|
|
// 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 && size() == 0) || (data && size() >= 0)); }
|
|
|
|
constexpr inline pointer data() const noexcept
|
|
{ return data_; }
|
|
|
|
private:
|
|
pointer data_;
|
|
};
|
|
|
|
storage_type<extent_type<Extent>> storage_;
|
|
};
|
|
|
|
|
|
// [span.comparison], span comparison operators
|
|
template <class ElementType, ptrdiff_t Extent>
|
|
constexpr bool operator==(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
|
|
{ return std::equal(l.begin(), l.end(), r.begin(), r.end()); }
|
|
|
|
template <class ElementType, ptrdiff_t Extent>
|
|
constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
|
|
{ return !(l == r); }
|
|
|
|
template <class ElementType, ptrdiff_t Extent>
|
|
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, ptrdiff_t Extent>
|
|
constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
|
|
{ return !(l > r); }
|
|
|
|
template <class ElementType, ptrdiff_t Extent>
|
|
constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
|
|
{ return r < l; }
|
|
|
|
template <class ElementType, ptrdiff_t Extent>
|
|
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, ptrdiff_t Extent>
|
|
struct calculate_byte_size :
|
|
std::integral_constant<std::ptrdiff_t, static_cast<ptrdiff_t>(sizeof(ElementType) * static_cast<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, ptrdiff_t Extent>
|
|
span<const byte, details::calculate_byte_size<ElementType, Extent>::value> as_bytes(span<ElementType, Extent> s) noexcept
|
|
{ return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()}; }
|
|
|
|
template <class ElementType, 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) noexcept
|
|
{ return {reinterpret_cast<byte*>(s.data()), s.size_bytes()}; }
|
|
|
|
} // namespace gsl
|
|
|
|
#ifdef _MSC_VER
|
|
|
|
#undef constexpr
|
|
#pragma pop_macro("constexpr")
|
|
|
|
#if _MSC_VER <= 1800
|
|
#pragma warning(pop)
|
|
|
|
#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
|
|
#undef noexcept
|
|
#pragma pop_macro("noexcept")
|
|
#endif // GSL_THROW_ON_CONTRACT_VIOLATION
|
|
|
|
#undef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
|
|
|
|
#endif // _MSC_VER <= 1800
|
|
|
|
#endif // _MSC_VER
|
|
|
|
#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
|
|
|
|
#undef noexcept
|
|
|
|
#ifdef _MSC_VER
|
|
#pragma warning(pop)
|
|
#pragma pop_macro("noexcept")
|
|
#endif
|
|
|
|
#endif // GSL_THROW_ON_CONTRACT_VIOLATION
|
|
|
|
#endif // GSL_SPAN_H
|