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127 lines
5.8 KiB
127 lines
5.8 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 of the helpers (like std::enable_if_t) which will
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* become available with C++14 in the type_traits header (in the skstd
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* namespace). This header also provides several Skia specific additions such
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* as SK_WHEN and 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 <array>
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#include <stddef.h>
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#include <stdint.h>
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#include <type_traits>
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#include <utility>
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namespace skstd {
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template <bool B> using bool_constant = std::integral_constant<bool, B>;
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template <bool B, typename T, typename F> using conditional_t = typename std::conditional<B, T, F>::type;
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template <bool B, typename T = void> using enable_if_t = typename std::enable_if<B, T>::type;
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template <typename T> using remove_const_t = typename std::remove_const<T>::type;
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template <typename T> using remove_volatile_t = typename std::remove_volatile<T>::type;
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template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
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template <typename T> using remove_pointer_t = typename std::remove_pointer<T>::type;
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template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
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template <typename T> using remove_extent_t = typename std::remove_extent<T>::type;
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template <typename T> using add_const_t = typename std::add_const<T>::type;
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template <typename T> using add_volatile_t = typename std::add_volatile<T>::type;
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template <typename T> using add_cv_t = typename std::add_cv<T>::type;
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template <typename T> using add_pointer_t = typename std::add_pointer<T>::type;
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template <typename T> using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
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template <typename T> using result_of_t = typename std::result_of<T>::type;
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template <typename... T> using common_type_t = typename std::common_type<T...>::type;
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// Chromium currently requires gcc 4.8.2 or a recent clang compiler, but uses libstdc++4.6.4.
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// Note that Precise actually uses libstdc++4.6.3.
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// Unfortunately, libstdc++ STL before libstdc++4.7 do not define std::underlying_type.
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// Newer gcc and clang compilers have __underlying_type which does not depend on runtime support.
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// See https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html for __GLIBCXX__ values.
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// Unfortunately __GLIBCXX__ is a date, but no updates to versions before 4.7 are now anticipated.
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#define SK_GLIBCXX_4_7_0 20120322
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// Updates to versions before 4.7 but released after 4.7 was released.
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#define SK_GLIBCXX_4_5_4 20120702
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#define SK_GLIBCXX_4_6_4 20121127
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#if defined(__GLIBCXX__) && (__GLIBCXX__ < SK_GLIBCXX_4_7_0 || \
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__GLIBCXX__ == SK_GLIBCXX_4_5_4 || \
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__GLIBCXX__ == SK_GLIBCXX_4_6_4)
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template <typename T> struct underlying_type {
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using type = __underlying_type(T);
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};
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#else
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template <typename T> using underlying_type = std::underlying_type<T>;
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#endif
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template <typename T> using underlying_type_t = typename skstd::underlying_type<T>::type;
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template <std::size_t... Ints> struct index_sequence {
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using type = index_sequence;
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using value_type = size_t;
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static constexpr std::size_t size() noexcept { return sizeof...(Ints); }
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};
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template <typename S1, typename S2> struct make_index_sequence_combine;
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template <size_t... I1, size_t... I2>
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struct make_index_sequence_combine<skstd::index_sequence<I1...>, skstd::index_sequence<I2...>>
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: skstd::index_sequence<I1..., (sizeof...(I1)+I2)...>
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{ };
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template <size_t N> struct make_index_sequence
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: make_index_sequence_combine<typename skstd::make_index_sequence< N/2>::type,
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typename skstd::make_index_sequence<N - N/2>::type>{};
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template<> struct make_index_sequence<0> : skstd::index_sequence< >{};
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template<> struct make_index_sequence<1> : skstd::index_sequence<0>{};
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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 = skstd::conditional_t<std::is_const<S>::value, skstd::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 = skstd::conditional_t<std::is_volatile<S>::value, skstd::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<skstd::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<skstd::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<skstd::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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// Just a pithier wrapper for enable_if_t.
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#define SK_WHEN(condition, T) skstd::enable_if_t<!!(condition), T>
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#endif
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