/*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#define FOLLY_BASE_TRAITS_H_
#include <memory>
+#include <limits>
#include <type_traits>
+#include "folly/Portability.h"
+
+// libc++ doesn't provide this header
+#if !FOLLY_USE_LIBCPP
+// This file appears in two locations: inside fbcode and in the
+// libstdc++ source code (when embedding fbstring as std::string).
+// To aid in this schizophrenic use, two macros are defined in
+// c++config.h:
+// _LIBSTDCXX_FBSTRING - Set inside libstdc++. This is useful to
+// gate use inside fbcode v. libstdc++
#include <bits/c++config.h>
+#endif
#include <boost/type_traits.hpp>
#include <boost/mpl/and.hpp>
* although that is not guaranteed by the standard.
*/
-namespace std {
+FOLLY_NAMESPACE_STD_BEGIN
template <class T, class U>
- class pair;
+ struct pair;
#ifndef _GLIBCXX_USE_FB
template <class T, class R, class A>
class basic_string;
template <class T>
class shared_ptr;
-}
+FOLLY_NAMESPACE_STD_END
namespace boost {
enum { value = std::is_same<T, T1>::value || IsOneOf<T, Ts...>::value };
};
+/**
+ * A traits class to check for incomplete types.
+ *
+ * Example:
+ *
+ * struct FullyDeclared {}; // complete type
+ * struct ForwardDeclared; // incomplete type
+ *
+ * is_complete<int>::value // evaluates to true
+ * is_complete<FullyDeclared>::value // evaluates to true
+ * is_complete<ForwardDeclared>::value // evaluates to false
+ *
+ * struct ForwardDeclared {}; // declared, at last
+ *
+ * is_complete<ForwardDeclared>::value // now it evaluates to true
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+template <typename T>
+class is_complete {
+ template <unsigned long long> struct sfinae {};
+ template <typename U>
+ constexpr static bool test(sfinae<sizeof(U)>*) { return true; }
+ template <typename> constexpr static bool test(...) { return false; }
+public:
+ constexpr static bool value = test<T>(nullptr);
+};
+
+/*
+ * Complementary type traits for integral comparisons.
+ *
+ * For instance, `if(x < 0)` yields an error in clang for unsigned types
+ * when -Werror is used due to -Wtautological-compare
+ *
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+
+namespace detail {
+
+template <typename T, bool>
+struct is_negative_impl {
+ constexpr static bool check(T x) { return x < 0; }
+};
+
+template <typename T>
+struct is_negative_impl<T, false> {
+ constexpr static bool check(T x) { return false; }
+};
+
+template <typename RHS, RHS rhs, typename LHS>
+bool less_than_impl(
+ typename std::enable_if<
+ (rhs <= std::numeric_limits<LHS>::max()
+ && rhs > std::numeric_limits<LHS>::min()),
+ LHS
+ >::type const lhs
+) {
+ return lhs < rhs;
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool less_than_impl(
+ typename std::enable_if<
+ (rhs > std::numeric_limits<LHS>::max()),
+ LHS
+ >::type const
+) {
+ return true;
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool less_than_impl(
+ typename std::enable_if<
+ (rhs <= std::numeric_limits<LHS>::min()),
+ LHS
+ >::type const
+) {
+ return false;
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool greater_than_impl(
+ typename std::enable_if<
+ (rhs <= std::numeric_limits<LHS>::max()
+ && rhs >= std::numeric_limits<LHS>::min()),
+ LHS
+ >::type const lhs
+) {
+ return lhs > rhs;
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool greater_than_impl(
+ typename std::enable_if<
+ (rhs > std::numeric_limits<LHS>::max()),
+ LHS
+ >::type const
+) {
+ return false;
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool greater_than_impl(
+ typename std::enable_if<
+ (rhs < std::numeric_limits<LHS>::min()),
+ LHS
+ >::type const
+) {
+ return true;
+}
+
+} // namespace detail {
+
+// same as `x < 0`
+template <typename T>
+constexpr bool is_negative(T x) {
+ return folly::detail::is_negative_impl<T, std::is_signed<T>::value>::check(x);
+}
+
+// same as `x <= 0`
+template <typename T>
+constexpr bool is_non_positive(T x) { return !x || folly::is_negative(x); }
+
+// same as `x > 0`
+template <typename T>
+constexpr bool is_positive(T x) { return !is_non_positive(x); }
+
+// same as `x >= 0`
+template <typename T>
+constexpr bool is_non_negative(T x) {
+ return !x || is_positive(x);
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool less_than(LHS const lhs) {
+ return detail::less_than_impl<
+ RHS, rhs, typename std::remove_reference<LHS>::type
+ >(lhs);
+}
+
+template <typename RHS, RHS rhs, typename LHS>
+bool greater_than(LHS const lhs) {
+ return detail::greater_than_impl<
+ RHS, rhs, typename std::remove_reference<LHS>::type
+ >(lhs);
+}
+
} // namespace folly
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_3(std::basic_string);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::vector);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::list);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::deque);
-FOLLY_ASSUME_FBVECTOR_COMPATIBLE_4(std::map);
-FOLLY_ASSUME_FBVECTOR_COMPATIBLE_3(std::set);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::unique_ptr);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(std::shared_ptr);
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(std::function);
// Boost
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(boost::shared_ptr);
+#define FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, cv_qual) \
+ template <typename TTheClass_, typename RTheReturn_, typename... TTheArgs_> \
+ class classname<TTheClass_, RTheReturn_(TTheArgs_...) cv_qual> { \
+ template < \
+ typename UTheClass_, RTheReturn_ (UTheClass_::*)(TTheArgs_...) cv_qual \
+ > struct sfinae {}; \
+ template <typename UTheClass_> \
+ constexpr static bool test(sfinae<UTheClass_, &UTheClass_::func_name>*) \
+ { return true; } \
+ template <typename> \
+ constexpr static bool test(...) { return false; } \
+ public: \
+ constexpr static bool value = test<TTheClass_>(nullptr); \
+ }
+
+/*
+ * The FOLLY_CREATE_HAS_MEMBER_FN_TRAITS is used to create traits
+ * classes that check for the existence of a member function with
+ * a given name and signature. It currently does not support
+ * checking for inherited members.
+ *
+ * Such classes receive two template parameters: the class to be checked
+ * and the signature of the member function. A static boolean field
+ * named `value` (which is also constexpr) tells whether such member
+ * function exists.
+ *
+ * Each traits class created is bound only to the member name, not to
+ * its signature nor to the type of the class containing it.
+ *
+ * Say you need to know if a given class has a member function named
+ * `test` with the following signature:
+ *
+ * int test() const;
+ *
+ * You'd need this macro to create a traits class to check for a member
+ * named `test`, and then use this traits class to check for the signature:
+ *
+ * namespace {
+ *
+ * FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_test_traits, test);
+ *
+ * } // unnamed-namespace
+ *
+ * void some_func() {
+ * cout << "Does class Foo have a member int test() const? "
+ * << boolalpha << has_test_traits<Foo, int() const>::value;
+ * }
+ *
+ * You can use the same traits class to test for a completely different
+ * signature, on a completely different class, as long as the member name
+ * is the same:
+ *
+ * void some_func() {
+ * cout << "Does class Foo have a member int test()? "
+ * << boolalpha << has_test_traits<Foo, int()>::value;
+ * cout << "Does class Foo have a member int test() const? "
+ * << boolalpha << has_test_traits<Foo, int() const>::value;
+ * cout << "Does class Bar have a member double test(const string&, long)? "
+ * << boolalpha << has_test_traits<Bar, double(const string&, long)>::value;
+ * }
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+#define FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(classname, func_name) \
+ template <typename, typename> class classname; \
+ FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, ); \
+ FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, const); \
+ FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, volatile); \
+ FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, volatile const)
+
#endif //FOLLY_BASE_TRAITS_H_
projects / folly.git / blobdiff