119 lines
3.3 KiB
C
119 lines
3.3 KiB
C
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/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_TRAITS_H
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#define ANDROID_TRAITS_H
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// -----------------------------------------------------------------------
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// Typelists
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namespace android {
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// end-of-list marker
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class NullType {};
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// type-list node
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template <typename T, typename U>
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struct TypeList {
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typedef T Head;
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typedef U Tail;
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};
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// helpers to build typelists
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#define TYPELIST_1(T1) TypeList<T1, NullType>
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#define TYPELIST_2(T1, T2) TypeList<T1, TYPELIST_1(T2)>
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#define TYPELIST_3(T1, T2, T3) TypeList<T1, TYPELIST_2(T2, T3)>
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#define TYPELIST_4(T1, T2, T3, T4) TypeList<T1, TYPELIST_3(T2, T3, T4)>
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// typelists algorithms
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namespace TL {
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template <typename TList, typename T> struct IndexOf;
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template <typename T>
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struct IndexOf<NullType, T> {
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enum { value = -1 };
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};
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template <typename T, typename Tail>
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struct IndexOf<TypeList<T, Tail>, T> {
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enum { value = 0 };
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};
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template <typename Head, typename Tail, typename T>
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struct IndexOf<TypeList<Head, Tail>, T> {
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private:
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enum { temp = IndexOf<Tail, T>::value };
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public:
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enum { value = temp == -1 ? -1 : 1 + temp };
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};
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}; // namespace TL
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// type selection based on a boolean
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template <bool flag, typename T, typename U>
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struct Select {
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typedef T Result;
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};
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template <typename T, typename U>
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struct Select<false, T, U> {
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typedef U Result;
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};
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// -----------------------------------------------------------------------
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// Type traits
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template <typename T>
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class TypeTraits {
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typedef TYPELIST_4(
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unsigned char, unsigned short,
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unsigned int, unsigned long int) UnsignedInts;
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typedef TYPELIST_4(
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signed char, signed short,
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signed int, signed long int) SignedInts;
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typedef TYPELIST_1(
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bool) OtherInts;
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typedef TYPELIST_3(
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float, double, long double) Floats;
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template<typename U> struct PointerTraits {
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enum { result = false };
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typedef NullType PointeeType;
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};
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template<typename U> struct PointerTraits<U*> {
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enum { result = true };
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typedef U PointeeType;
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};
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public:
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enum { isStdUnsignedInt = TL::IndexOf<UnsignedInts, T>::value >= 0 };
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enum { isStdSignedInt = TL::IndexOf<SignedInts, T>::value >= 0 };
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enum { isStdIntegral = TL::IndexOf<OtherInts, T>::value >= 0 || isStdUnsignedInt || isStdSignedInt };
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enum { isStdFloat = TL::IndexOf<Floats, T>::value >= 0 };
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enum { isPointer = PointerTraits<T>::result };
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enum { isStdArith = isStdIntegral || isStdFloat };
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// best parameter type for given type
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typedef typename Select<isStdArith || isPointer, T, const T&>::Result ParameterType;
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};
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// -----------------------------------------------------------------------
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}; // namespace android
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#endif /* ANDROID_TRAITS_H */
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