/include/google/protobuf/stubs/type_traits.h
C Header | 336 lines | 175 code | 39 blank | 122 comment | 12 complexity | f67f37d7756e3185d5b3728c6fe0e77e MD5 | raw file
- // Copyright (c) 2006, Google Inc.
- // All rights reserved.
- //
- // Redistribution and use in source and binary forms, with or without
- // modification, are permitted provided that the following conditions are
- // met:
- //
- // * Redistributions of source code must retain the above copyright
- // notice, this list of conditions and the following disclaimer.
- // * Redistributions in binary form must reproduce the above
- // copyright notice, this list of conditions and the following disclaimer
- // in the documentation and/or other materials provided with the
- // distribution.
- // * Neither the name of Google Inc. nor the names of its
- // contributors may be used to endorse or promote products derived from
- // this software without specific prior written permission.
- //
- // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- // ----
- // Author: Matt Austern
- //
- // This code is compiled directly on many platforms, including client
- // platforms like Windows, Mac, and embedded systems. Before making
- // any changes here, make sure that you're not breaking any platforms.
- //
- // Define a small subset of tr1 type traits. The traits we define are:
- // is_integral
- // is_floating_point
- // is_pointer
- // is_enum
- // is_reference
- // is_pod
- // has_trivial_constructor
- // has_trivial_copy
- // has_trivial_assign
- // has_trivial_destructor
- // remove_const
- // remove_volatile
- // remove_cv
- // remove_reference
- // add_reference
- // remove_pointer
- // is_same
- // is_convertible
- // We can add more type traits as required.
- #ifndef GOOGLE_PROTOBUF_TYPE_TRAITS_H_
- #define GOOGLE_PROTOBUF_TYPE_TRAITS_H_
- #include <utility> // For pair
- #include <google/protobuf/stubs/template_util.h> // For true_type and false_type
- namespace google {
- namespace protobuf {
- namespace internal {
- template <class T> struct is_integral;
- template <class T> struct is_floating_point;
- template <class T> struct is_pointer;
- // MSVC can't compile this correctly, and neither can gcc 3.3.5 (at least)
- #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
- // is_enum uses is_convertible, which is not available on MSVC.
- template <class T> struct is_enum;
- #endif
- template <class T> struct is_reference;
- template <class T> struct is_pod;
- template <class T> struct has_trivial_constructor;
- template <class T> struct has_trivial_copy;
- template <class T> struct has_trivial_assign;
- template <class T> struct has_trivial_destructor;
- template <class T> struct remove_const;
- template <class T> struct remove_volatile;
- template <class T> struct remove_cv;
- template <class T> struct remove_reference;
- template <class T> struct add_reference;
- template <class T> struct remove_pointer;
- template <class T, class U> struct is_same;
- #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
- template <class From, class To> struct is_convertible;
- #endif
- // is_integral is false except for the built-in integer types. A
- // cv-qualified type is integral if and only if the underlying type is.
- template <class T> struct is_integral : false_type { };
- template<> struct is_integral<bool> : true_type { };
- template<> struct is_integral<char> : true_type { };
- template<> struct is_integral<unsigned char> : true_type { };
- template<> struct is_integral<signed char> : true_type { };
- #if defined(_MSC_VER)
- // wchar_t is not by default a distinct type from unsigned short in
- // Microsoft C.
- // See http://msdn2.microsoft.com/en-us/library/dh8che7s(VS.80).aspx
- template<> struct is_integral<__wchar_t> : true_type { };
- #else
- template<> struct is_integral<wchar_t> : true_type { };
- #endif
- template<> struct is_integral<short> : true_type { };
- template<> struct is_integral<unsigned short> : true_type { };
- template<> struct is_integral<int> : true_type { };
- template<> struct is_integral<unsigned int> : true_type { };
- template<> struct is_integral<long> : true_type { };
- template<> struct is_integral<unsigned long> : true_type { };
- #ifdef HAVE_LONG_LONG
- template<> struct is_integral<long long> : true_type { };
- template<> struct is_integral<unsigned long long> : true_type { };
- #endif
- template <class T> struct is_integral<const T> : is_integral<T> { };
- template <class T> struct is_integral<volatile T> : is_integral<T> { };
- template <class T> struct is_integral<const volatile T> : is_integral<T> { };
- // is_floating_point is false except for the built-in floating-point types.
- // A cv-qualified type is integral if and only if the underlying type is.
- template <class T> struct is_floating_point : false_type { };
- template<> struct is_floating_point<float> : true_type { };
- template<> struct is_floating_point<double> : true_type { };
- template<> struct is_floating_point<long double> : true_type { };
- template <class T> struct is_floating_point<const T>
- : is_floating_point<T> { };
- template <class T> struct is_floating_point<volatile T>
- : is_floating_point<T> { };
- template <class T> struct is_floating_point<const volatile T>
- : is_floating_point<T> { };
- // is_pointer is false except for pointer types. A cv-qualified type (e.g.
- // "int* const", as opposed to "int const*") is cv-qualified if and only if
- // the underlying type is.
- template <class T> struct is_pointer : false_type { };
- template <class T> struct is_pointer<T*> : true_type { };
- template <class T> struct is_pointer<const T> : is_pointer<T> { };
- template <class T> struct is_pointer<volatile T> : is_pointer<T> { };
- template <class T> struct is_pointer<const volatile T> : is_pointer<T> { };
- #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
- namespace internal {
- template <class T> struct is_class_or_union {
- template <class U> static small_ tester(void (U::*)());
- template <class U> static big_ tester(...);
- static const bool value = sizeof(tester<T>(0)) == sizeof(small_);
- };
- // is_convertible chokes if the first argument is an array. That's why
- // we use add_reference here.
- template <bool NotUnum, class T> struct is_enum_impl
- : is_convertible<typename add_reference<T>::type, int> { };
- template <class T> struct is_enum_impl<true, T> : false_type { };
- } // namespace internal
- // Specified by TR1 [4.5.1] primary type categories.
- // Implementation note:
- //
- // Each type is either void, integral, floating point, array, pointer,
- // reference, member object pointer, member function pointer, enum,
- // union or class. Out of these, only integral, floating point, reference,
- // class and enum types are potentially convertible to int. Therefore,
- // if a type is not a reference, integral, floating point or class and
- // is convertible to int, it's a enum. Adding cv-qualification to a type
- // does not change whether it's an enum.
- //
- // Is-convertible-to-int check is done only if all other checks pass,
- // because it can't be used with some types (e.g. void or classes with
- // inaccessible conversion operators).
- template <class T> struct is_enum
- : internal::is_enum_impl<
- is_same<T, void>::value ||
- is_integral<T>::value ||
- is_floating_point<T>::value ||
- is_reference<T>::value ||
- internal::is_class_or_union<T>::value,
- T> { };
- template <class T> struct is_enum<const T> : is_enum<T> { };
- template <class T> struct is_enum<volatile T> : is_enum<T> { };
- template <class T> struct is_enum<const volatile T> : is_enum<T> { };
- #endif
- // is_reference is false except for reference types.
- template<typename T> struct is_reference : false_type {};
- template<typename T> struct is_reference<T&> : true_type {};
- // We can't get is_pod right without compiler help, so fail conservatively.
- // We will assume it's false except for arithmetic types, enumerations,
- // pointers and cv-qualified versions thereof. Note that std::pair<T,U>
- // is not a POD even if T and U are PODs.
- template <class T> struct is_pod
- : integral_constant<bool, (is_integral<T>::value ||
- is_floating_point<T>::value ||
- #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
- // is_enum is not available on MSVC.
- is_enum<T>::value ||
- #endif
- is_pointer<T>::value)> { };
- template <class T> struct is_pod<const T> : is_pod<T> { };
- template <class T> struct is_pod<volatile T> : is_pod<T> { };
- template <class T> struct is_pod<const volatile T> : is_pod<T> { };
- // We can't get has_trivial_constructor right without compiler help, so
- // fail conservatively. We will assume it's false except for: (1) types
- // for which is_pod is true. (2) std::pair of types with trivial
- // constructors. (3) array of a type with a trivial constructor.
- // (4) const versions thereof.
- template <class T> struct has_trivial_constructor : is_pod<T> { };
- template <class T, class U> struct has_trivial_constructor<std::pair<T, U> >
- : integral_constant<bool,
- (has_trivial_constructor<T>::value &&
- has_trivial_constructor<U>::value)> { };
- template <class A, int N> struct has_trivial_constructor<A[N]>
- : has_trivial_constructor<A> { };
- template <class T> struct has_trivial_constructor<const T>
- : has_trivial_constructor<T> { };
- // We can't get has_trivial_copy right without compiler help, so fail
- // conservatively. We will assume it's false except for: (1) types
- // for which is_pod is true. (2) std::pair of types with trivial copy
- // constructors. (3) array of a type with a trivial copy constructor.
- // (4) const versions thereof.
- template <class T> struct has_trivial_copy : is_pod<T> { };
- template <class T, class U> struct has_trivial_copy<std::pair<T, U> >
- : integral_constant<bool,
- (has_trivial_copy<T>::value &&
- has_trivial_copy<U>::value)> { };
- template <class A, int N> struct has_trivial_copy<A[N]>
- : has_trivial_copy<A> { };
- template <class T> struct has_trivial_copy<const T> : has_trivial_copy<T> { };
- // We can't get has_trivial_assign right without compiler help, so fail
- // conservatively. We will assume it's false except for: (1) types
- // for which is_pod is true. (2) std::pair of types with trivial copy
- // constructors. (3) array of a type with a trivial assign constructor.
- template <class T> struct has_trivial_assign : is_pod<T> { };
- template <class T, class U> struct has_trivial_assign<std::pair<T, U> >
- : integral_constant<bool,
- (has_trivial_assign<T>::value &&
- has_trivial_assign<U>::value)> { };
- template <class A, int N> struct has_trivial_assign<A[N]>
- : has_trivial_assign<A> { };
- // We can't get has_trivial_destructor right without compiler help, so
- // fail conservatively. We will assume it's false except for: (1) types
- // for which is_pod is true. (2) std::pair of types with trivial
- // destructors. (3) array of a type with a trivial destructor.
- // (4) const versions thereof.
- template <class T> struct has_trivial_destructor : is_pod<T> { };
- template <class T, class U> struct has_trivial_destructor<std::pair<T, U> >
- : integral_constant<bool,
- (has_trivial_destructor<T>::value &&
- has_trivial_destructor<U>::value)> { };
- template <class A, int N> struct has_trivial_destructor<A[N]>
- : has_trivial_destructor<A> { };
- template <class T> struct has_trivial_destructor<const T>
- : has_trivial_destructor<T> { };
- // Specified by TR1 [4.7.1]
- template<typename T> struct remove_const { typedef T type; };
- template<typename T> struct remove_const<T const> { typedef T type; };
- template<typename T> struct remove_volatile { typedef T type; };
- template<typename T> struct remove_volatile<T volatile> { typedef T type; };
- template<typename T> struct remove_cv {
- typedef typename remove_const<typename remove_volatile<T>::type>::type type;
- };
- // Specified by TR1 [4.7.2] Reference modifications.
- template<typename T> struct remove_reference { typedef T type; };
- template<typename T> struct remove_reference<T&> { typedef T type; };
- template <typename T> struct add_reference { typedef T& type; };
- template <typename T> struct add_reference<T&> { typedef T& type; };
- // Specified by TR1 [4.7.4] Pointer modifications.
- template<typename T> struct remove_pointer { typedef T type; };
- template<typename T> struct remove_pointer<T*> { typedef T type; };
- template<typename T> struct remove_pointer<T* const> { typedef T type; };
- template<typename T> struct remove_pointer<T* volatile> { typedef T type; };
- template<typename T> struct remove_pointer<T* const volatile> {
- typedef T type; };
- // Specified by TR1 [4.6] Relationships between types
- template<typename T, typename U> struct is_same : public false_type { };
- template<typename T> struct is_same<T, T> : public true_type { };
- // Specified by TR1 [4.6] Relationships between types
- #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
- namespace internal {
- // This class is an implementation detail for is_convertible, and you
- // don't need to know how it works to use is_convertible. For those
- // who care: we declare two different functions, one whose argument is
- // of type To and one with a variadic argument list. We give them
- // return types of different size, so we can use sizeof to trick the
- // compiler into telling us which function it would have chosen if we
- // had called it with an argument of type From. See Alexandrescu's
- // _Modern C++ Design_ for more details on this sort of trick.
- template <typename From, typename To>
- struct ConvertHelper {
- static small_ Test(To);
- static big_ Test(...);
- static From Create();
- };
- } // namespace internal
- // Inherits from true_type if From is convertible to To, false_type otherwise.
- template <typename From, typename To>
- struct is_convertible
- : integral_constant<bool,
- sizeof(internal::ConvertHelper<From, To>::Test(
- internal::ConvertHelper<From, To>::Create()))
- == sizeof(small_)> {
- };
- #endif
- } // namespace internal
- } // namespace protobuf
- } // namespace google
- #endif // GOOGLE_PROTOBUF_TYPE_TRAITS_H_