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55 lines
1.3 KiB
C
55 lines
1.3 KiB
C
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_TypeTraits_h_
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#define mozilla_TypeTraits_h_
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/* Template-based metaprogramming and type-testing facilities. */
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namespace mozilla {
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/*
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* IsBaseOf allows to know whether a given class is derived from another.
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*
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* Consider the following class definitions:
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*
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* class A {};
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* class B : public A {};
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* class C {};
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*
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* mozilla::IsBaseOf<A, B>::value is true;
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* mozilla::IsBaseOf<A, C>::value is false;
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*/
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template <class Base, class Derived>
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class IsBaseOf
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{
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private:
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static char Test(Base *);
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static int Test(...);
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public:
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static const bool value = (sizeof(Test(static_cast<Derived *>(0))) == sizeof(char));
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};
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/*
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* Conditional selects a class between two, depending on a given boolean value.
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*
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* mozilla::Conditional<true, A, B>::Type is A;
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* mozilla::Conditional<false, A, B>::Type is B;
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*/
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template <bool condition, class A, class B>
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struct Conditional
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{
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typedef A Type;
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};
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template <class A, class B>
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struct Conditional<false, A, B>
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{
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typedef B Type;
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};
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} /* namespace mozilla */
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#endif /* mozilla_TypeTraits_h_ */
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