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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>{};
struct monostate {};
template<typename...> struct conjunction : std::true_type { };
template<typename B0> struct conjunction<B0> : B0 { };
template<typename B0, typename... Bs>
struct conjunction<B0, Bs...> : std::conditional<bool(B0::value), conjunction<Bs...>, B0>::type { };
} // 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>