michael@0: /*
michael@0:  * Copyright 2013 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  *
michael@0:  *
michael@0:  * This header provides some of the helpers (std::integral_constant) and
michael@0:  * type transformations (std::conditional) which will become available with
michael@0:  * C++11 in the type_traits header.
michael@0:  *
michael@0:  * Because we lack constexpr, we cannot mimic
michael@0:  * std::integral_constant::'constexpr operator T()'.
michael@0:  * As a result we introduce SkTBool and SkTIf similar to Boost in order to
michael@0:  * minimize the visual noise of many uses of '::value'.
michael@0:  */
michael@0: 
michael@0: #ifndef SkTLogic_DEFINED
michael@0: #define SkTLogic_DEFINED
michael@0: 
michael@0: /** Represents a templated integer constant.
michael@0:  *  Pre-C++11 version of std::integral_constant.
michael@0:  */
michael@0: template <typename T, T v> struct SkTIntegralConstant {
michael@0:     static const T value = v;
michael@0:     typedef T value_type;
michael@0:     typedef SkTIntegralConstant<T, v> type;
michael@0: };
michael@0: 
michael@0: /** Convenience specialization of SkTIntegralConstant. */
michael@0: template <bool b> struct SkTBool : SkTIntegralConstant<bool, b> { };
michael@0: 
michael@0: /** Pre-C++11 version of std::true_type. */
michael@0: typedef SkTBool<true> SkTrue;
michael@0: 
michael@0: /** Pre-C++11 version of std::false_type. */
michael@0: typedef SkTBool<false> SkFalse;
michael@0: 
michael@0: /** SkTIf_c::type = (condition) ? T : F;
michael@0:  *  Pre-C++11 version of std::conditional.
michael@0:  */
michael@0: template <bool condition, typename T, typename F> struct SkTIf_c {
michael@0:     typedef F type;
michael@0: };
michael@0: template <typename T, typename F> struct SkTIf_c<true, T, F> {
michael@0:     typedef T type;
michael@0: };
michael@0: 
michael@0: /** SkTIf::type = (Condition::value) ? T : F; */
michael@0: template <typename Condition, typename T, typename F> struct SkTIf {
michael@0:     typedef typename SkTIf_c<static_cast<bool>(Condition::value), T, F>::type type;
michael@0: };
michael@0: 
michael@0: /** SkTMux::type = (a && b) ? Both : (a) ? A : (b) ? B : Neither; */
michael@0: template <typename a, typename b, typename Both, typename A, typename B, typename Neither>
michael@0: struct SkTMux {
michael@0:     typedef typename SkTIf<a, typename SkTIf<b, Both, A>::type,
michael@0:                               typename SkTIf<b, B, Neither>::type>::type type;
michael@0: };
michael@0: 
michael@0: #endif