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- /*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- *
- *
- * This header provides some of the helpers (like std::enable_if_t) which will
- * become available with C++14 in the type_traits header (in the skstd
- * namespace). This header also provides several Skia specific additions such
- * as SK_WHEN and the sknonstd namespace.
- */
- #ifndef SkTLogic_DEFINED
- #define SkTLogic_DEFINED
- #include <cstddef>
- #include <type_traits>
- namespace skstd {
- template <bool B> using bool_constant = std::integral_constant<bool, B>;
- template <bool B, typename T, typename F> using conditional_t = typename std::conditional<B, T, F>::type;
- template <bool B, typename T = void> using enable_if_t = typename std::enable_if<B, T>::type;
- template <typename T> using remove_const_t = typename std::remove_const<T>::type;
- template <typename T> using remove_volatile_t = typename std::remove_volatile<T>::type;
- template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
- template <typename T> using remove_pointer_t = typename std::remove_pointer<T>::type;
- template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
- template <typename T> using remove_extent_t = typename std::remove_extent<T>::type;
- template <typename T> using add_const_t = typename std::add_const<T>::type;
- template <typename T> using add_volatile_t = typename std::add_volatile<T>::type;
- template <typename T> using add_cv_t = typename std::add_cv<T>::type;
- template <typename T> using add_pointer_t = typename std::add_pointer<T>::type;
- template <typename T> using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
- template <typename T> using result_of_t = typename std::result_of<T>::type;
- template <typename... T> using common_type_t = typename std::common_type<T...>::type;
- template <std::size_t... Ints> struct index_sequence {
- using type = index_sequence;
- using value_type = std::size_t;
- static constexpr std::size_t size() noexcept { return sizeof...(Ints); }
- };
- template <typename S1, typename S2> struct make_index_sequence_combine;
- template <std::size_t... I1, std::size_t... I2>
- struct make_index_sequence_combine<skstd::index_sequence<I1...>, skstd::index_sequence<I2...>>
- : skstd::index_sequence<I1..., (sizeof...(I1)+I2)...>
- { };
- template <std::size_t N> struct make_index_sequence
- : make_index_sequence_combine<typename skstd::make_index_sequence< N/2>::type,
- typename skstd::make_index_sequence<N - N/2>::type>{};
- template<> struct make_index_sequence<0> : skstd::index_sequence< >{};
- template<> struct make_index_sequence<1> : skstd::index_sequence<0>{};
- } // namespace skstd
- // The sknonstd namespace contains things we would like to be proposed and feel std-ish.
- namespace sknonstd {
- // The name 'copy' here is fraught with peril. In this case it means 'append', not 'overwrite'.
- // Alternate proposed names are 'propagate', 'augment', or 'append' (and 'add', but already taken).
- // std::experimental::propagate_const already exists for other purposes in TSv2.
- // These also follow the <dest, source> pattern used by boost.
- template <typename D, typename S> struct copy_const {
- using type = skstd::conditional_t<std::is_const<S>::value, skstd::add_const_t<D>, D>;
- };
- template <typename D, typename S> using copy_const_t = typename copy_const<D, S>::type;
- template <typename D, typename S> struct copy_volatile {
- using type = skstd::conditional_t<std::is_volatile<S>::value, skstd::add_volatile_t<D>, D>;
- };
- template <typename D, typename S> using copy_volatile_t = typename copy_volatile<D, S>::type;
- template <typename D, typename S> struct copy_cv {
- using type = copy_volatile_t<copy_const_t<D, S>, S>;
- };
- template <typename D, typename S> using copy_cv_t = typename copy_cv<D, S>::type;
- // The name 'same' here means 'overwrite'.
- // Alternate proposed names are 'replace', 'transfer', or 'qualify_from'.
- // same_xxx<D, S> can be written as copy_xxx<remove_xxx_t<D>, S>
- template <typename D, typename S> using same_const = copy_const<skstd::remove_const_t<D>, S>;
- template <typename D, typename S> using same_const_t = typename same_const<D, S>::type;
- template <typename D, typename S> using same_volatile =copy_volatile<skstd::remove_volatile_t<D>,S>;
- template <typename D, typename S> using same_volatile_t = typename same_volatile<D, S>::type;
- template <typename D, typename S> using same_cv = copy_cv<skstd::remove_cv_t<D>, S>;
- template <typename D, typename S> using same_cv_t = typename same_cv<D, S>::type;
- } // namespace sknonstd
- // Just a pithier wrapper for enable_if_t.
- #define SK_WHEN(condition, T) skstd::enable_if_t<!!(condition), T>
- #endif
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