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87 lines
3.4 KiB
87 lines
3.4 KiB
/*
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* Copyright 2013 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*
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*
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* This header provides some std:: features early in the skstd namespace
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* and several Skia-specific additions in the sknonstd namespace.
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*/
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#ifndef SkTLogic_DEFINED
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#define SkTLogic_DEFINED
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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#include "include/private/SkTo.h"
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namespace skstd {
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// C++17, <variant>
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struct monostate {};
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// C++17, <type_traits>
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template<typename...> struct conjunction : std::true_type { };
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template<typename T> struct conjunction<T> : T { };
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template<typename T, typename... Ts>
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struct conjunction<T, Ts...> : std::conditional<bool(T::value), conjunction<Ts...>, T>::type { };
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// C++17, std::data, std::size
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template<typename Container>
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constexpr auto data(Container& c) -> decltype(c.data()) { return c.data(); }
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template<typename Container>
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constexpr auto data(const Container& c) -> decltype(c.data()) { return c.data(); }
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template<typename Array, size_t N>
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constexpr auto data(Array(&a)[N]) -> decltype(a) { return a; }
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template<typename T>
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constexpr const T* data(std::initializer_list<T> i) { return i.begin(); }
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template<typename Container>
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constexpr auto size(Container& c) -> decltype(c.size()) { return c.size(); }
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template<typename Array, size_t N>
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constexpr size_t size(Array(&)[N]) { return N; }
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template<typename T>
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constexpr const T* size(std::initializer_list<T> i) { return i.end() - i.begin(); }
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} // namespace skstd
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// The sknonstd namespace contains things we would like to be proposed and feel std-ish.
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namespace sknonstd {
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// The name 'copy' here is fraught with peril. In this case it means 'append', not 'overwrite'.
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// Alternate proposed names are 'propagate', 'augment', or 'append' (and 'add', but already taken).
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// std::experimental::propagate_const already exists for other purposes in TSv2.
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// These also follow the <dest, source> pattern used by boost.
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template <typename D, typename S> struct copy_const {
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using type = std::conditional_t<std::is_const<S>::value, std::add_const_t<D>, D>;
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};
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template <typename D, typename S> using copy_const_t = typename copy_const<D, S>::type;
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template <typename D, typename S> struct copy_volatile {
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using type = std::conditional_t<std::is_volatile<S>::value, std::add_volatile_t<D>, D>;
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};
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template <typename D, typename S> using copy_volatile_t = typename copy_volatile<D, S>::type;
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template <typename D, typename S> struct copy_cv {
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using type = copy_volatile_t<copy_const_t<D, S>, S>;
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};
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template <typename D, typename S> using copy_cv_t = typename copy_cv<D, S>::type;
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// The name 'same' here means 'overwrite'.
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// Alternate proposed names are 'replace', 'transfer', or 'qualify_from'.
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// same_xxx<D, S> can be written as copy_xxx<remove_xxx_t<D>, S>
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template <typename D, typename S> using same_const = copy_const<std::remove_const_t<D>, S>;
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template <typename D, typename S> using same_const_t = typename same_const<D, S>::type;
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template <typename D, typename S> using same_volatile =copy_volatile<std::remove_volatile_t<D>,S>;
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template <typename D, typename S> using same_volatile_t = typename same_volatile<D, S>::type;
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template <typename D, typename S> using same_cv = copy_cv<std::remove_cv_t<D>, S>;
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template <typename D, typename S> using same_cv_t = typename same_cv<D, S>::type;
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} // namespace sknonstd
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template <typename Container>
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constexpr int SkCount(const Container& c) { return SkTo<int>(skstd::size(c)); }
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#endif
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