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+// 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
+//
+// Define a small subset of tr1 type traits. The traits we define are:
+// is_integral
+// is_floating_point
+// is_pointer
+// is_reference
+// is_pod
+// has_trivial_constructor
+// has_trivial_copy
+// has_trivial_assign
+// has_trivial_destructor
+// remove_const
+// remove_volatile
+// remove_cv
+// remove_reference
+// remove_pointer
+// is_convertible
+// We can add more type traits as required.
+
+#ifndef BASE_TYPE_TRAITS_H_
+#define BASE_TYPE_TRAITS_H_
+
+#include "google/sparsehash/sparseconfig.h"
+#include <utility> // For pair
+
+_START_GOOGLE_NAMESPACE_
+
+// integral_constant, defined in tr1, is a wrapper for an integer
+// value. We don't really need this generality; we could get away
+// with hardcoding the integer type to bool. We use the fully
+// general integer_constant for compatibility with tr1.
+
+template<class T, T v>
+struct integral_constant {
+ static const T value = v;
+ typedef T value_type;
+ typedef integral_constant<T, v> type;
+};
+
+template <class T, T v> const T integral_constant<T, v>::value;
+
+// Abbreviations: true_type and false_type are structs that represent
+// boolean true and false values.
+typedef integral_constant<bool, true> true_type;
+typedef integral_constant<bool, false> false_type;
+
+// Types small_ and big_ are guaranteed such that sizeof(small_) <
+// sizeof(big_)
+typedef char small_;
+
+struct big_ {
+ char dummy[2];
+};
+
+// is_integral is false except for the built-in integer types.
+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
+
+
+// is_floating_point is false except for the built-in floating-point types.
+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 { };
+
+
+// is_pointer is false except for pointer types.
+template <class T> struct is_pointer : false_type { };
+template <class T> struct is_pointer<T*> : true_type { };
+
+
+// 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 and pointers,
+// and const versions thereof. Note that std::pair is not a POD.
+template <class T> struct is_pod
+ : integral_constant<bool, (is_integral<T>::value ||
+ is_floating_point<T>::value ||
+ is_pointer<T>::value)> { };
+template <class T> struct is_pod<const 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]
+template<typename T> struct remove_reference { typedef T type; };
+template<typename T> struct remove_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
+#ifndef _MSC_VER
+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
+
+_END_GOOGLE_NAMESPACE_
+
+#endif // BASE_TYPE_TRAITS_H_