X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FTraits.h;h=16aab8d6ef1e9011b195e44f35d04e69b00144cc;hb=49e4875c1e7d55df5913410539d299b7aa3c62bc;hp=566036bb77774b8d7a8f62b3f1ed95eb34ac406d;hpb=27494a20393fa45072e7d526d358835f3abe312a;p=folly.git

diff --git a/folly/Traits.h b/folly/Traits.h
index 566036bb..16aab8d6 100644
--- a/folly/Traits.h
+++ b/folly/Traits.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,11 +19,28 @@
 #ifndef FOLLY_BASE_TRAITS_H_
 #define FOLLY_BASE_TRAITS_H_
 
+#include <memory>
+#include <limits>
+#include <type_traits>
+#include <functional>
+
+#include <folly/Portability.h>
+
+// libc++ doesn't provide this header, nor does msvc
+#ifdef FOLLY_HAVE_BITS_CXXCONFIG_H
+// 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>
+#include <boost/mpl/has_xxx.hpp>
 #include <boost/mpl/not.hpp>
-#include <memory>
-#include <bits/c++config.h>
 
 namespace folly {
 
@@ -41,7 +58,7 @@ namespace folly {
  * }
  *
  * void move2(T * from, T * to) {
- *   memcpy(from, to, sizeof(T));
+ *   memcpy(to, from, sizeof(T));
  * }
  *
  * Most C++ types are relocatable; the ones that aren't would include
@@ -57,9 +74,64 @@ namespace folly {
  * types. You may want to add your own specializations. Do so in
  * namespace folly and make sure you keep the specialization of
  * IsRelocatable<SomeStruct> in the same header as SomeStruct.
+ *
+ * You may also declare a type to be relocatable by including
+ *    `typedef std::true_type IsRelocatable;`
+ * in the class header.
+ *
+ * It may be unset in a base class by overriding the typedef to false_type.
  */
-template <class T> struct IsRelocatable : boost::mpl::not_<boost::is_class<T> >
-{};
+/*
+ * IsTriviallyCopyable describes the value semantics property. C++11 contains
+ * the type trait is_trivially_copyable; however, it is not yet implemented
+ * in gcc (as of 4.7.1), and the user may wish to specify otherwise.
+ */
+/*
+ * IsZeroInitializable describes the property that default construction is the
+ * same as memset(dst, 0, sizeof(T)).
+ */
+
+namespace traits_detail {
+
+#define FOLLY_HAS_TRUE_XXX(name)                          \
+  BOOST_MPL_HAS_XXX_TRAIT_DEF(name);                      \
+  template <class T> struct name ## _is_true              \
+    : std::is_same<typename T::name, std::true_type> {};  \
+  template <class T> struct has_true_ ## name             \
+    : std::conditional<                                   \
+        has_ ## name <T>::value,                          \
+        name ## _is_true<T>,                              \
+        std::false_type                                   \
+      >:: type {};
+
+FOLLY_HAS_TRUE_XXX(IsRelocatable)
+FOLLY_HAS_TRUE_XXX(IsZeroInitializable)
+FOLLY_HAS_TRUE_XXX(IsTriviallyCopyable)
+
+#undef FOLLY_HAS_TRUE_XXX
+}
+
+template <class T> struct IsTriviallyCopyable
+  : std::integral_constant<bool,
+      !std::is_class<T>::value ||
+      // TODO: add alternate clause is_trivially_copyable, when available
+      traits_detail::has_true_IsTriviallyCopyable<T>::value
+    > {};
+
+template <class T> struct IsRelocatable
+  : std::integral_constant<bool,
+      !std::is_class<T>::value ||
+      // TODO add this line (and some tests for it) when we upgrade to gcc 4.7
+      //std::is_trivially_move_constructible<T>::value ||
+      IsTriviallyCopyable<T>::value ||
+      traits_detail::has_true_IsRelocatable<T>::value
+    > {};
+
+template <class T> struct IsZeroInitializable
+  : std::integral_constant<bool,
+      !std::is_class<T>::value ||
+      traits_detail::has_true_IsZeroInitializable<T>::value
+    > {};
 
 } // namespace folly
 
@@ -73,11 +145,11 @@ template <class T> struct IsRelocatable : boost::mpl::not_<boost::is_class<T> >
  * When using it with a template type, use it like this:
  *
  * // Make sure you're at namespace ::folly scope
- * template<class T, class T2>
+ * template<class T1, class T2>
  * FOLLY_ASSUME_RELOCATABLE(MyType<T1, T2>)
  */
 #define FOLLY_ASSUME_RELOCATABLE(...) \
-  struct IsRelocatable<  __VA_ARGS__ > : ::boost::true_type {};
+  struct IsRelocatable<  __VA_ARGS__ > : std::true_type {};
 
 /**
  * Use this macro ONLY inside namespace boost. When using it with a
@@ -89,7 +161,7 @@ template <class T> struct IsRelocatable : boost::mpl::not_<boost::is_class<T> >
  * When using it with a template type, use it like this:
  *
  * // Make sure you're at namespace ::boost scope
- * template<class T, class T2>
+ * template<class T1, class T2>
  * FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(MyType<T1, T2>)
  */
 #define FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(...) \
@@ -163,13 +235,15 @@ template <class T> struct IsRelocatable : boost::mpl::not_<boost::is_class<T> >
  * 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
+FOLLY_GLIBCXX_NAMESPACE_CXX11_BEGIN
 template <class T, class R, class A>
   class basic_string;
+FOLLY_GLIBCXX_NAMESPACE_CXX11_END
 #else
 template <class T, class R, class A, class S>
   class basic_string;
@@ -178,8 +252,10 @@ template <class T, class A>
   class vector;
 template <class T, class A>
   class deque;
+FOLLY_GLIBCXX_NAMESPACE_CXX11_BEGIN
 template <class T, class A>
   class list;
+FOLLY_GLIBCXX_NAMESPACE_CXX11_END
 template <class T, class C, class A>
   class set;
 template <class K, class V, class C, class A>
@@ -187,7 +263,7 @@ template <class K, class V, class C, class A>
 template <class T>
   class shared_ptr;
 
-}
+FOLLY_NAMESPACE_STD_END
 
 namespace boost {
 
@@ -218,14 +294,102 @@ struct IsOneOf<T, T1, Ts...> {
   enum { value = std::is_same<T, T1>::value || IsOneOf<T, Ts...>::value };
 };
 
+/*
+ * 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) { return false; }
+};
+
+// folly::to integral specializations can end up generating code
+// inside what are really static ifs (not executed because of the templated
+// types) that violate -Wsign-compare so suppress them in order to not prevent
+// all calling code from using it.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wsign-compare"
+
+template <typename RHS, RHS rhs, typename LHS>
+bool less_than_impl(LHS const lhs) {
+  return
+    rhs > std::numeric_limits<LHS>::max() ? true :
+    rhs <= std::numeric_limits<LHS>::min() ? false :
+    lhs < rhs;
+}
+
+#pragma GCC diagnostic pop
+
+template <typename RHS, RHS rhs, typename LHS>
+bool greater_than_impl(LHS const lhs) {
+  return
+    rhs > std::numeric_limits<LHS>::max() ? false :
+    rhs < std::numeric_limits<LHS>::min() ? true :
+    lhs > rhs;
+}
+
+} // 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);
+}
+
+/**
+ * Like std::piecewise_construct, a tag type & instance used for in-place
+ * construction of non-movable contained types, e.g. by Synchronized.
+ */
+struct construct_in_place_t {};
+constexpr construct_in_place_t construct_in_place{};
+
 } // 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);
@@ -233,4 +397,86 @@ FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(std::function);
 // Boost
 FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(boost::shared_ptr);
 
+#define FOLLY_CREATE_HAS_MEMBER_TYPE_TRAITS(classname, type_name) \
+  template <typename T> \
+  struct classname { \
+    template <typename C> \
+    constexpr static bool test(typename C::type_name*) { return true; } \
+    template <typename> \
+    constexpr static bool test(...) { return false; } \
+    constexpr static bool value = test<T>(nullptr); \
+  }
+
+#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, /* nolint */ volatile); \
+  FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL( \
+      classname, func_name, /* nolint */ volatile const)
+
 #endif //FOLLY_BASE_TRAITS_H_