bungeman@google.com | f5cc5b1 | 2013-07-12 18:22:49 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2013 Google Inc. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license that can be |
| 5 | * found in the LICENSE file. |
| 6 | * |
| 7 | * |
| 8 | * This header provides some of the helpers (std::integral_constant) and |
| 9 | * type transformations (std::conditional) which will become available with |
| 10 | * C++11 in the type_traits header. |
| 11 | * |
| 12 | * Because we lack constexpr, we cannot mimic |
| 13 | * std::integral_constant::'constexpr operator T()'. |
| 14 | * As a result we introduce SkTBool and SkTIf similar to Boost in order to |
| 15 | * minimize the visual noise of many uses of '::value'. |
| 16 | */ |
| 17 | |
| 18 | #ifndef SkTLogic_DEFINED |
| 19 | #define SkTLogic_DEFINED |
| 20 | |
| 21 | /** Represents a templated integer constant. |
| 22 | * Pre-C++11 version of std::integral_constant. |
| 23 | */ |
| 24 | template <typename T, T v> struct SkTIntegralConstant { |
| 25 | static const T value = v; |
| 26 | typedef T value_type; |
| 27 | typedef SkTIntegralConstant<T, v> type; |
| 28 | }; |
| 29 | |
| 30 | /** Convenience specialization of SkTIntegralConstant. */ |
| 31 | template <bool b> struct SkTBool : SkTIntegralConstant<bool, b> { }; |
| 32 | |
| 33 | /** Pre-C++11 version of std::true_type. */ |
| 34 | typedef SkTBool<true> SkTrue; |
| 35 | |
| 36 | /** Pre-C++11 version of std::false_type. */ |
| 37 | typedef SkTBool<false> SkFalse; |
| 38 | |
| 39 | /** SkTIf_c::type = (condition) ? T : F; |
| 40 | * Pre-C++11 version of std::conditional. |
| 41 | */ |
| 42 | template <bool condition, typename T, typename F> struct SkTIf_c { |
| 43 | typedef F type; |
| 44 | }; |
| 45 | template <typename T, typename F> struct SkTIf_c<true, T, F> { |
| 46 | typedef T type; |
| 47 | }; |
| 48 | |
| 49 | /** SkTIf::type = (Condition::value) ? T : F; */ |
| 50 | template <typename Condition, typename T, typename F> struct SkTIf { |
| 51 | typedef typename SkTIf_c<static_cast<bool>(Condition::value), T, F>::type type; |
| 52 | }; |
| 53 | |
| 54 | /** SkTMux::type = (a && b) ? Both : (a) ? A : (b) ? B : Neither; */ |
| 55 | template <typename a, typename b, typename Both, typename A, typename B, typename Neither> |
| 56 | struct SkTMux { |
| 57 | typedef typename SkTIf<a, typename SkTIf<b, Both, A>::type, |
| 58 | typename SkTIf<b, B, Neither>::type>::type type; |
| 59 | }; |
| 60 | |
bungeman@google.com | 4b3ef5a | 2013-07-12 18:31:59 +0000 | [diff] [blame] | 61 | #endif |