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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 (std::integral_constant) and
* type transformations (std::conditional) which will become available with
* C++11 in the type_traits header.
*
* Because we lack constexpr, we cannot mimic
* std::integral_constant::'constexpr operator T()'.
* As a result we introduce SkTBool and SkTIf similar to Boost in order to
* minimize the visual noise of many uses of '::value'.
*/
#ifndef SkTLogic_DEFINED
#define SkTLogic_DEFINED
/** Represents a templated integer constant.
* Pre-C++11 version of std::integral_constant.
*/
template <typename T, T v> struct SkTIntegralConstant {
static const T value = v;
typedef T value_type;
typedef SkTIntegralConstant<T, v> type;
};
/** Convenience specialization of SkTIntegralConstant. */
template <bool b> struct SkTBool : SkTIntegralConstant<bool, b> { };
/** Pre-C++11 version of std::true_type. */
typedef SkTBool<true> SkTrue;
/** Pre-C++11 version of std::false_type. */
typedef SkTBool<false> SkFalse;
/** SkTIf_c::type = (condition) ? T : F;
* Pre-C++11 version of std::conditional.
*/
template <bool condition, typename T, typename F> struct SkTIf_c {
typedef F type;
};
template <typename T, typename F> struct SkTIf_c<true, T, F> {
typedef T type;
};
/** SkTIf::type = (Condition::value) ? T : F; */
template <typename Condition, typename T, typename F> struct SkTIf {
typedef typename SkTIf_c<static_cast<bool>(Condition::value), T, F>::type type;
};
/** SkTMux::type = (a && b) ? Both : (a) ? A : (b) ? B : Neither; */
template <typename a, typename b, typename Both, typename A, typename B, typename Neither>
struct SkTMux {
typedef typename SkTIf<a, typename SkTIf<b, Both, A>::type,
typename SkTIf<b, B, Neither>::type>::type type;
};
#endif
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