skia2/include/private/SkTLogic.h
Mike Klein dc976a96ea update skstd
- Lots of skstd::foo is now std::foo since C++14.
- Get rid of SK_WHEN(cond,T); std::enable_if_t<cond,T> is pithy enough.
- Move SkBitmaskEnum.h contents into sknonstd.

Change-Id: Ie5dc459405b1ff55e5b3ac57e70df7edd7cf38c0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/286315
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2020-04-30 15:05:43 +00:00

67 lines
2.6 KiB
C++

/*
* 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 std:: features early in the skstd namespace
* and several Skia-specific additions in the sknonstd namespace.
*/
#ifndef SkTLogic_DEFINED
#define SkTLogic_DEFINED
#include <cstddef>
#include <type_traits>
#include <utility>
namespace skstd {
// C++17, <variant>
struct monostate {};
// C++17, <type_traits>
template<typename...> struct conjunction : std::true_type { };
template<typename T> struct conjunction<T> : T { };
template<typename T, typename... Ts>
struct conjunction<T, Ts...> : std::conditional<bool(T::value), conjunction<Ts...>, T>::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 = std::conditional_t<std::is_const<S>::value, std::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 = std::conditional_t<std::is_volatile<S>::value, std::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<std::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<std::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<std::remove_cv_t<D>, S>;
template <typename D, typename S> using same_cv_t = typename same_cv<D, S>::type;
} // namespace sknonstd
#endif