mirror of https://github.com/jorio/Pomme.git
612 lines
18 KiB
C++
612 lines
18 KiB
C++
/*
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This is an implementation of C++20's std::span
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http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/n4820.pdf
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*/
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// Copyright Tristan Brindle 2018.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file ../../LICENSE_1_0.txt or copy at
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// https://www.boost.org/LICENSE_1_0.txt)
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#ifndef TCB_SPAN_HPP_INCLUDED
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#define TCB_SPAN_HPP_INCLUDED
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#include <array>
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#include <cstddef>
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#include <cstdint>
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#include <type_traits>
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#ifndef TCB_SPAN_NO_EXCEPTIONS
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// Attempt to discover whether we're being compiled with exception support
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#if !(defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
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#define TCB_SPAN_NO_EXCEPTIONS
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#endif
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#endif
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#ifndef TCB_SPAN_NO_EXCEPTIONS
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#include <cstdio>
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#include <stdexcept>
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#endif
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// Various feature test macros
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#ifndef TCB_SPAN_NAMESPACE_NAME
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#define TCB_SPAN_NAMESPACE_NAME std
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#endif
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#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
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#define TCB_SPAN_HAVE_CPP17
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#endif
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#if __cplusplus >= 201402L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201402L)
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#define TCB_SPAN_HAVE_CPP14
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#endif
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namespace TCB_SPAN_NAMESPACE_NAME {
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// Establish default contract checking behavior
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#if !defined(TCB_SPAN_THROW_ON_CONTRACT_VIOLATION) && \
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!defined(TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION) && \
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!defined(TCB_SPAN_NO_CONTRACT_CHECKING)
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#if defined(NDEBUG) || !defined(TCB_SPAN_HAVE_CPP14)
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#define TCB_SPAN_NO_CONTRACT_CHECKING
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#else
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#define TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION
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#endif
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#endif
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#if defined(TCB_SPAN_THROW_ON_CONTRACT_VIOLATION)
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struct contract_violation_error : std::logic_error {
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explicit contract_violation_error(const char* msg) : std::logic_error(msg)
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{}
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};
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inline void contract_violation(const char* msg)
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{
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throw contract_violation_error(msg);
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}
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#elif defined(TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION)
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[[noreturn]] inline void contract_violation(const char* /*unused*/)
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{
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std::terminate();
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}
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#endif
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#if !defined(TCB_SPAN_NO_CONTRACT_CHECKING)
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#define TCB_SPAN_STRINGIFY(cond) #cond
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#define TCB_SPAN_EXPECT(cond) \
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cond ? (void) 0 : contract_violation("Expected " TCB_SPAN_STRINGIFY(cond))
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#else
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#define TCB_SPAN_EXPECT(cond)
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#endif
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#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_inline_variables)
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#define TCB_SPAN_INLINE_VAR inline
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#else
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#define TCB_SPAN_INLINE_VAR
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#endif
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#if defined(TCB_SPAN_HAVE_CPP14) || \
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(defined(__cpp_constexpr) && __cpp_constexpr >= 201304)
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#define TCB_SPAN_HAVE_CPP14_CONSTEXPR
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#endif
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#if defined(TCB_SPAN_HAVE_CPP14_CONSTEXPR)
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#define TCB_SPAN_CONSTEXPR14 constexpr
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#else
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#define TCB_SPAN_CONSTEXPR14
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#endif
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#if defined(TCB_SPAN_HAVE_CPP14_CONSTEXPR) && \
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(!defined(_MSC_VER) || _MSC_VER > 1900)
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#define TCB_SPAN_CONSTEXPR_ASSIGN constexpr
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#else
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#define TCB_SPAN_CONSTEXPR_ASSIGN
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#endif
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#if defined(TCB_SPAN_NO_CONTRACT_CHECKING)
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#define TCB_SPAN_CONSTEXPR11 constexpr
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#else
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#define TCB_SPAN_CONSTEXPR11 TCB_SPAN_CONSTEXPR14
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#endif
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#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_deduction_guides)
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#define TCB_SPAN_HAVE_DEDUCTION_GUIDES
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#endif
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#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_byte)
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#define TCB_SPAN_HAVE_STD_BYTE
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#endif
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#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_array_constexpr)
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#define TCB_SPAN_HAVE_CONSTEXPR_STD_ARRAY_ETC
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#endif
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#if defined(TCB_SPAN_HAVE_CONSTEXPR_STD_ARRAY_ETC)
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#define TCB_SPAN_ARRAY_CONSTEXPR constexpr
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#else
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#define TCB_SPAN_ARRAY_CONSTEXPR
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#endif
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#ifdef TCB_SPAN_HAVE_STD_BYTE
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using byte = std::byte;
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#else
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using byte = unsigned char;
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#endif
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#if defined(TCB_SPAN_HAVE_CPP17)
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#define TCB_SPAN_NODISCARD [[nodiscard]]
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#else
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#define TCB_SPAN_NODISCARD
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#endif
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TCB_SPAN_INLINE_VAR constexpr std::size_t dynamic_extent = SIZE_MAX;
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template <typename ElementType, std::size_t Extent = dynamic_extent>
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class span;
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namespace detail {
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template <typename E, std::size_t S>
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struct span_storage {
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constexpr span_storage() noexcept = default;
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constexpr span_storage(E* p_ptr, std::size_t /*unused*/) noexcept
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: ptr(p_ptr)
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{}
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E* ptr = nullptr;
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static constexpr std::size_t size = S;
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};
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template <typename E>
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struct span_storage<E, dynamic_extent> {
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constexpr span_storage() noexcept = default;
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constexpr span_storage(E* p_ptr, std::size_t p_size) noexcept
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: ptr(p_ptr), size(p_size)
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{}
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E* ptr = nullptr;
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std::size_t size = 0;
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};
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// Reimplementation of C++17 std::size() and std::data()
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#if defined(TCB_SPAN_HAVE_CPP17) || \
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defined(__cpp_lib_nonmember_container_access)
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using std::data;
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using std::size;
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#else
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template <class C>
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constexpr auto size(const C& c) -> decltype(c.size())
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{
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return c.size();
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}
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template <class T, std::size_t N>
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constexpr std::size_t size(const T (&)[N]) noexcept
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{
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return N;
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}
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template <class C>
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constexpr auto data(C& c) -> decltype(c.data())
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{
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return c.data();
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}
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template <class C>
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constexpr auto data(const C& c) -> decltype(c.data())
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{
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return c.data();
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}
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template <class T, std::size_t N>
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constexpr T* data(T (&array)[N]) noexcept
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{
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return array;
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}
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template <class E>
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constexpr const E* data(std::initializer_list<E> il) noexcept
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{
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return il.begin();
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}
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#endif // TCB_SPAN_HAVE_CPP17
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#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_void_t)
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using std::void_t;
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#else
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template <typename...>
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using void_t = void;
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#endif
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template <typename T>
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using uncvref_t =
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typename std::remove_cv<typename std::remove_reference<T>::type>::type;
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template <typename>
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struct is_span : std::false_type {};
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template <typename T, std::size_t S>
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struct is_span<span<T, S>> : std::true_type {};
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template <typename>
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struct is_std_array : std::false_type {};
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template <typename T, std::size_t N>
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struct is_std_array<std::array<T, N>> : std::true_type {};
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template <typename, typename = void>
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struct has_size_and_data : std::false_type {};
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template <typename T>
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struct has_size_and_data<T, void_t<decltype(detail::size(std::declval<T>())),
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decltype(detail::data(std::declval<T>()))>>
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: std::true_type {};
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template <typename C, typename U = uncvref_t<C>>
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struct is_container {
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static constexpr bool value =
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!is_span<U>::value && !is_std_array<U>::value &&
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!std::is_array<U>::value && has_size_and_data<C>::value;
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};
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template <typename T>
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using remove_pointer_t = typename std::remove_pointer<T>::type;
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template <typename, typename, typename = void>
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struct is_container_element_type_compatible : std::false_type {};
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template <typename T, typename E>
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struct is_container_element_type_compatible<
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T, E,
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typename std::enable_if<
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!std::is_same<typename std::remove_cv<decltype(
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detail::data(std::declval<T>()))>::type,
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void>::value>::type>
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: std::is_convertible<
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remove_pointer_t<decltype(detail::data(std::declval<T>()))> (*)[],
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E (*)[]> {};
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template <typename, typename = size_t>
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struct is_complete : std::false_type {};
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template <typename T>
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struct is_complete<T, decltype(sizeof(T))> : std::true_type {};
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} // namespace detail
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template <typename ElementType, std::size_t Extent>
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class span {
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static_assert(std::is_object<ElementType>::value,
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"A span's ElementType must be an object type (not a "
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"reference type or void)");
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static_assert(detail::is_complete<ElementType>::value,
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"A span's ElementType must be a complete type (not a forward "
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"declaration)");
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static_assert(!std::is_abstract<ElementType>::value,
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"A span's ElementType cannot be an abstract class type");
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using storage_type = detail::span_storage<ElementType, Extent>;
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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 value_type = typename std::remove_cv<ElementType>::type;
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using size_type = std::size_t;
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using difference_type = std::ptrdiff_t;
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using pointer = element_type*;
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using const_pointer = const element_type*;
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using reference = element_type&;
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using const_reference = const element_type&;
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using iterator = pointer;
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using reverse_iterator = std::reverse_iterator<iterator>;
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static constexpr size_type extent = Extent;
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// [span.cons], span constructors, copy, assignment, and destructor
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template <
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std::size_t E = Extent,
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typename std::enable_if<(E == dynamic_extent || E <= 0), int>::type = 0>
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constexpr span() noexcept
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{}
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TCB_SPAN_CONSTEXPR11 span(pointer ptr, size_type count)
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: storage_(ptr, count)
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{
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TCB_SPAN_EXPECT(extent == dynamic_extent || count == extent);
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}
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TCB_SPAN_CONSTEXPR11 span(pointer first_elem, pointer last_elem)
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: storage_(first_elem, last_elem - first_elem)
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{
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TCB_SPAN_EXPECT(extent == dynamic_extent ||
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last_elem - first_elem ==
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static_cast<std::ptrdiff_t>(extent));
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}
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template <std::size_t N, std::size_t E = Extent,
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typename std::enable_if<
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(E == dynamic_extent || N == E) &&
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detail::is_container_element_type_compatible<
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element_type (&)[N], ElementType>::value,
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int>::type = 0>
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constexpr span(element_type (&arr)[N]) noexcept : storage_(arr, N)
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{}
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template <std::size_t N, std::size_t E = Extent,
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typename std::enable_if<
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(E == dynamic_extent || N == E) &&
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detail::is_container_element_type_compatible<
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std::array<value_type, N>&, ElementType>::value,
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int>::type = 0>
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TCB_SPAN_ARRAY_CONSTEXPR span(std::array<value_type, N>& arr) noexcept
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: storage_(arr.data(), N)
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{}
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template <std::size_t N, std::size_t E = Extent,
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typename std::enable_if<
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(E == dynamic_extent || N == E) &&
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detail::is_container_element_type_compatible<
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const std::array<value_type, N>&, ElementType>::value,
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int>::type = 0>
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TCB_SPAN_ARRAY_CONSTEXPR span(const std::array<value_type, N>& arr) noexcept
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: storage_(arr.data(), N)
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{}
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template <
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typename Container, std::size_t E = Extent,
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typename std::enable_if<
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E == dynamic_extent && detail::is_container<Container>::value &&
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detail::is_container_element_type_compatible<
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Container&, ElementType>::value,
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int>::type = 0>
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constexpr span(Container& cont)
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: storage_(detail::data(cont), detail::size(cont))
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{}
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template <
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typename Container, std::size_t E = Extent,
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typename std::enable_if<
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E == dynamic_extent && detail::is_container<Container>::value &&
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detail::is_container_element_type_compatible<
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const Container&, ElementType>::value,
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int>::type = 0>
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constexpr span(const Container& cont)
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: storage_(detail::data(cont), detail::size(cont))
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{}
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constexpr span(const span& other) noexcept = default;
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template <typename OtherElementType, std::size_t OtherExtent,
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typename std::enable_if<
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(Extent == OtherExtent || Extent == dynamic_extent) &&
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std::is_convertible<OtherElementType (*)[],
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ElementType (*)[]>::value,
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int>::type = 0>
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constexpr span(const span<OtherElementType, OtherExtent>& other) noexcept
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: storage_(other.data(), other.size())
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{}
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~span() noexcept = default;
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TCB_SPAN_CONSTEXPR_ASSIGN span&
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operator=(const span& other) noexcept = default;
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// [span.sub], span subviews
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template <std::size_t Count>
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TCB_SPAN_CONSTEXPR11 span<element_type, Count> first() const
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{
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TCB_SPAN_EXPECT(Count <= size());
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return {data(), Count};
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}
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template <std::size_t Count>
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TCB_SPAN_CONSTEXPR11 span<element_type, Count> last() const
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{
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TCB_SPAN_EXPECT(Count <= size());
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return {data() + (size() - Count), Count};
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}
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template <std::size_t Offset, std::size_t Count = dynamic_extent>
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using subspan_return_t =
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span<ElementType, Count != dynamic_extent
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? Count
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: (Extent != dynamic_extent ? Extent - Offset
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: dynamic_extent)>;
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template <std::size_t Offset, std::size_t Count = dynamic_extent>
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TCB_SPAN_CONSTEXPR11 subspan_return_t<Offset, Count> subspan() const
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{
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TCB_SPAN_EXPECT(Offset <= size() &&
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(Count == dynamic_extent || Offset + Count <= size()));
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return {data() + Offset,
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Count != dynamic_extent ? Count : size() - Offset};
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}
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TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
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first(size_type count) const
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{
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TCB_SPAN_EXPECT(count <= size());
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return {data(), count};
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}
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TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
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last(size_type count) const
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{
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TCB_SPAN_EXPECT(count <= size());
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return {data() + (size() - count), count};
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}
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TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
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subspan(size_type offset, size_type count = dynamic_extent) const
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{
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TCB_SPAN_EXPECT(offset <= size() &&
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(count == dynamic_extent || offset + count <= size()));
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return {data() + offset,
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count == dynamic_extent ? size() - offset : count};
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}
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// [span.obs], span observers
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constexpr size_type size() const noexcept { return storage_.size; }
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constexpr size_type size_bytes() const noexcept
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{
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return size() * sizeof(element_type);
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}
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TCB_SPAN_NODISCARD constexpr bool empty() const noexcept
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{
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return size() == 0;
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}
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// [span.elem], span element access
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TCB_SPAN_CONSTEXPR11 reference operator[](size_type idx) const
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{
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TCB_SPAN_EXPECT(idx < size());
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return *(data() + idx);
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}
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TCB_SPAN_CONSTEXPR11 reference front() const
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{
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TCB_SPAN_EXPECT(!empty());
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return *data();
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}
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TCB_SPAN_CONSTEXPR11 reference back() const
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{
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TCB_SPAN_EXPECT(!empty());
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return *(data() + (size() - 1));
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}
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constexpr pointer data() const noexcept { return storage_.ptr; }
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// [span.iterators], span iterator support
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constexpr iterator begin() const noexcept { return data(); }
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constexpr iterator end() const noexcept { return data() + size(); }
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TCB_SPAN_ARRAY_CONSTEXPR reverse_iterator rbegin() const noexcept
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{
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return reverse_iterator(end());
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}
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TCB_SPAN_ARRAY_CONSTEXPR reverse_iterator rend() const noexcept
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{
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return reverse_iterator(begin());
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}
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private:
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storage_type storage_{};
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};
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#ifdef TCB_SPAN_HAVE_DEDUCTION_GUIDES
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/* Deduction Guides */
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template <class T, size_t N>
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span(T (&)[N])->span<T, N>;
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template <class T, size_t N>
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span(std::array<T, N>&)->span<T, N>;
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|
template <class T, size_t N>
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|
span(const std::array<T, N>&)->span<const T, N>;
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|
|
|
template <class Container>
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|
span(Container&)->span<typename Container::value_type>;
|
|
|
|
template <class Container>
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|
span(const Container&)->span<const typename Container::value_type>;
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|
|
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#endif // TCB_HAVE_DEDUCTION_GUIDES
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|
|
|
template <typename ElementType, std::size_t Extent>
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|
constexpr span<ElementType, Extent>
|
|
make_span(span<ElementType, Extent> s) noexcept
|
|
{
|
|
return s;
|
|
}
|
|
|
|
template <typename T, std::size_t N>
|
|
constexpr span<T, N> make_span(T (&arr)[N]) noexcept
|
|
{
|
|
return {arr};
|
|
}
|
|
|
|
template <typename T, std::size_t N>
|
|
TCB_SPAN_ARRAY_CONSTEXPR span<T, N> make_span(std::array<T, N>& arr) noexcept
|
|
{
|
|
return {arr};
|
|
}
|
|
|
|
template <typename T, std::size_t N>
|
|
TCB_SPAN_ARRAY_CONSTEXPR span<const T, N>
|
|
make_span(const std::array<T, N>& arr) noexcept
|
|
{
|
|
return {arr};
|
|
}
|
|
|
|
template <typename Container>
|
|
constexpr span<typename Container::value_type> make_span(Container& cont)
|
|
{
|
|
return {cont};
|
|
}
|
|
|
|
template <typename Container>
|
|
constexpr span<const typename Container::value_type>
|
|
make_span(const Container& cont)
|
|
{
|
|
return {cont};
|
|
}
|
|
|
|
template <typename ElementType, std::size_t Extent>
|
|
span<const byte, ((Extent == dynamic_extent) ? dynamic_extent
|
|
: sizeof(ElementType) * Extent)>
|
|
as_bytes(span<ElementType, Extent> s) noexcept
|
|
{
|
|
return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
|
|
}
|
|
|
|
template <
|
|
class ElementType, size_t Extent,
|
|
typename std::enable_if<!std::is_const<ElementType>::value, int>::type = 0>
|
|
span<byte, ((Extent == dynamic_extent) ? dynamic_extent
|
|
: sizeof(ElementType) * Extent)>
|
|
as_writable_bytes(span<ElementType, Extent> s) noexcept
|
|
{
|
|
return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
|
|
}
|
|
|
|
template <std::size_t N, typename E, std::size_t S>
|
|
constexpr auto get(span<E, S> s) -> decltype(s[N])
|
|
{
|
|
return s[N];
|
|
}
|
|
|
|
} // namespace TCB_SPAN_NAMESPACE_NAME
|
|
|
|
namespace std {
|
|
|
|
template <typename ElementType, size_t Extent>
|
|
class tuple_size<TCB_SPAN_NAMESPACE_NAME::span<ElementType, Extent>>
|
|
: public integral_constant<size_t, Extent> {};
|
|
|
|
template <typename ElementType>
|
|
class tuple_size<TCB_SPAN_NAMESPACE_NAME::span<
|
|
ElementType, TCB_SPAN_NAMESPACE_NAME::dynamic_extent>>; // not defined
|
|
|
|
template <size_t I, typename ElementType, size_t Extent>
|
|
class tuple_element<I, TCB_SPAN_NAMESPACE_NAME::span<ElementType, Extent>> {
|
|
public:
|
|
static_assert(Extent != TCB_SPAN_NAMESPACE_NAME::dynamic_extent &&
|
|
I < Extent,
|
|
"");
|
|
using type = ElementType;
|
|
};
|
|
|
|
} // end namespace std
|
|
|
|
#endif // TCB_SPAN_HPP_INCLUDED
|