X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FMemory.h;h=ce0ff05d3290605f6dd08ba28ad2caae4aca47b4;hp=09f10f36b351ae79c2aee496b20628c3c8a30304;hb=ba4282e472390a2d9ba23672b8844b9f23db0916;hpb=244a89966aa1bead86e9c2fb1263bbe8d837be28

diff --git a/folly/Memory.h b/folly/Memory.h
index 09f10f36..ce0ff05d 100644
--- a/folly/Memory.h
+++ b/folly/Memory.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,18 +14,19 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_MEMORY_H_
-#define FOLLY_MEMORY_H_
+#pragma once
 
-#include "folly/Traits.h"
+#include <folly/Traits.h>
+#include <folly/functional/Invoke.h>
 
-#include <memory>
-#include <limits>
-#include <utility>
+#include <cstddef>
+#include <cstdlib>
 #include <exception>
+#include <limits>
+#include <memory>
 #include <stdexcept>
-
-#include <cstddef>
+#include <type_traits>
+#include <utility>
 
 namespace folly {
 
@@ -34,43 +35,163 @@ namespace folly {
  * we have std::make_unique().
  *
  * @author Louis Brandy (ldbrandy@fb.com)
+ * @author Xu Ning (xning@fb.com)
  */
 
-template<typename T, typename... Args>
-std::unique_ptr<T> make_unique(Args&&... args) {
+#if __cplusplus >= 201402L || __cpp_lib_make_unique >= 201304L || \
+    (__ANDROID__ && __cplusplus >= 201300L) || _MSC_VER >= 1900
+
+/* using override */ using std::make_unique;
+
+#else
+
+template <typename T, typename... Args>
+typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type
+make_unique(Args&&... args) {
   return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
 }
 
+// Allows 'make_unique<T[]>(10)'. (N3690 s20.9.1.4 p3-4)
+template <typename T>
+typename std::enable_if<std::is_array<T>::value, std::unique_ptr<T>>::type
+make_unique(const size_t n) {
+  return std::unique_ptr<T>(new typename std::remove_extent<T>::type[n]());
+}
+
+// Disallows 'make_unique<T[10]>()'. (N3690 s20.9.1.4 p5)
+template <typename T, typename... Args>
+typename std::enable_if<
+  std::extent<T>::value != 0, std::unique_ptr<T>>::type
+make_unique(Args&&...) = delete;
+
+#endif
+
 /**
- * Wrap a SimpleAllocator into a STL-compliant allocator.
+ * static_function_deleter
+ *
+ * So you can write this:
+ *
+ *      using RSA_deleter = folly::static_function_deleter<RSA, &RSA_free>;
+ *      auto rsa = std::unique_ptr<RSA, RSA_deleter>(RSA_new());
+ *      RSA_generate_key_ex(rsa.get(), bits, exponent, nullptr);
+ *      rsa = nullptr;  // calls RSA_free(rsa.get())
+ *
+ * This would be sweet as well for BIO, but unfortunately BIO_free has signature
+ * int(BIO*) while we require signature void(BIO*). So you would need to make a
+ * wrapper for it:
+ *
+ *      inline void BIO_free_fb(BIO* bio) { CHECK_EQ(1, BIO_free(bio)); }
+ *      using BIO_deleter = folly::static_function_deleter<BIO, &BIO_free_fb>;
+ *      auto buf = std::unique_ptr<BIO, BIO_deleter>(BIO_new(BIO_s_mem()));
+ *      buf = nullptr;  // calls BIO_free(buf.get())
+ */
+
+template <typename T, void(*f)(T*)>
+struct static_function_deleter {
+  void operator()(T* t) const {
+    f(t);
+  }
+};
+
+/**
+ *  to_shared_ptr
+ *
+ *  Convert unique_ptr to shared_ptr without specifying the template type
+ *  parameter and letting the compiler deduce it.
+ *
+ *  So you can write this:
+ *
+ *      auto sptr = to_shared_ptr(getSomethingUnique<T>());
+ *
+ *  Instead of this:
+ *
+ *      auto sptr = shared_ptr<T>(getSomethingUnique<T>());
+ *
+ *  Useful when `T` is long, such as:
+ *
+ *      using T = foobar::FooBarAsyncClient;
+ */
+template <typename T, typename D>
+std::shared_ptr<T> to_shared_ptr(std::unique_ptr<T, D>&& ptr) {
+  return std::shared_ptr<T>(std::move(ptr));
+}
+
+/**
+ *  to_weak_ptr
+ *
+ *  Make a weak_ptr and return it from a shared_ptr without specifying the
+ *  template type parameter and letting the compiler deduce it.
+ *
+ *  So you can write this:
+ *
+ *      auto wptr = to_weak_ptr(getSomethingShared<T>());
+ *
+ *  Instead of this:
+ *
+ *      auto wptr = weak_ptr<T>(getSomethingShared<T>());
+ *
+ *  Useful when `T` is long, such as:
+ *
+ *      using T = foobar::FooBarAsyncClient;
+ */
+template <typename T>
+std::weak_ptr<T> to_weak_ptr(const std::shared_ptr<T>& ptr) {
+  return std::weak_ptr<T>(ptr);
+}
+
+struct SysBufferDeleter {
+  void operator()(void* p) const {
+    ::free(p);
+  }
+};
+
+using SysBufferUniquePtr = std::unique_ptr<void, SysBufferDeleter>;
+inline SysBufferUniquePtr allocate_sys_buffer(size_t size) {
+  return SysBufferUniquePtr(::malloc(size));
+}
+
+/**
+ * A SimpleAllocator must provide two methods:
  *
- * The SimpleAllocator must provide two methods:
  *    void* allocate(size_t size);
  *    void deallocate(void* ptr);
- * which, respectively, allocate a block of size bytes (aligned to the maximum
- * alignment required on your system), throwing std::bad_alloc if the
- * allocation can't be satisfied, and free a previously allocated block.
- *
- * Note that the following allocator resembles the standard allocator
- * quite well:
- *
- * class MallocAllocator {
- *  public:
- *   void* allocate(size_t size) {
- *     void* p = malloc(size);
- *     if (!p) throw std::bad_alloc();
- *     return p;
- *   }
- *   void deallocate(void* p) {
- *     free(p);
- *   }
- * };
  *
- * author: Tudor Bosman <tudorb@fb.com>
+ * which, respectively, allocate a block of size bytes (aligned to the
+ * maximum alignment required on your system), throwing std::bad_alloc
+ * if the allocation can't be satisfied, and free a previously
+ * allocated block.
+ *
+ * SysAlloc resembles the standard allocator.
+ */
+class SysAlloc {
+ public:
+  void* allocate(size_t size) {
+    void* p = ::malloc(size);
+    if (!p) {
+      throw std::bad_alloc();
+    }
+    return p;
+  }
+  void deallocate(void* p) {
+    ::free(p);
+  }
+};
+
+/**
+ * StlAllocator wraps a SimpleAllocator into a STL-compliant
+ * allocator, maintaining an instance pointer to the simple allocator
+ * object.  The underlying SimpleAllocator object must outlive all
+ * instances of StlAllocator using it.
+ *
+ * But note that if you pass StlAllocator<MallocAllocator,...> to a
+ * standard container it will be larger due to the contained state
+ * pointer.
+ *
+ * @author: Tudor Bosman <tudorb@fb.com>
  */
 
 // This would be so much simpler with std::allocator_traits, but gcc 4.6.2
-// doesn't support it
+// doesn't support it.
 template <class Alloc, class T> class StlAllocator;
 
 template <class Alloc> class StlAllocator<Alloc, void> {
@@ -78,9 +199,28 @@ template <class Alloc> class StlAllocator<Alloc, void> {
   typedef void value_type;
   typedef void* pointer;
   typedef const void* const_pointer;
+
+  StlAllocator() : alloc_(nullptr) { }
+  explicit StlAllocator(Alloc* a) : alloc_(a) { }
+
+  Alloc* alloc() const {
+    return alloc_;
+  }
+
   template <class U> struct rebind {
     typedef StlAllocator<Alloc, U> other;
   };
+
+  bool operator!=(const StlAllocator<Alloc, void>& other) const {
+    return alloc_ != other.alloc_;
+  }
+
+  bool operator==(const StlAllocator<Alloc, void>& other) const {
+    return alloc_ == other.alloc_;
+  }
+
+ private:
+  Alloc* alloc_;
 };
 
 template <class Alloc, class T>
@@ -96,18 +236,16 @@ class StlAllocator {
   typedef size_t size_type;
 
   StlAllocator() : alloc_(nullptr) { }
-  explicit StlAllocator(Alloc* alloc) : alloc_(alloc) { }
+  explicit StlAllocator(Alloc* a) : alloc_(a) { }
 
   template <class U> StlAllocator(const StlAllocator<Alloc, U>& other)
     : alloc_(other.alloc()) { }
 
-  T* allocate(size_t n, const void* hint = nullptr) {
+  T* allocate(size_t n, const void* /* hint */ = nullptr) {
     return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
   }
 
-  void deallocate(T* p, size_t n) {
-    alloc_->deallocate(p);
-  }
+  void deallocate(T* p, size_t /* n */) { alloc_->deallocate(p); }
 
   size_t max_size() const {
     return std::numeric_limits<size_t>::max();
@@ -150,69 +288,95 @@ class StlAllocator {
   Alloc* alloc_;
 };
 
+/**
+ * Helper function to obtain rebound allocators
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+template <typename T, typename Allocator>
+typename Allocator::template rebind<T>::other rebind_allocator(
+  Allocator const& allocator
+) {
+  return typename Allocator::template rebind<T>::other(allocator);
+}
+
 /*
- * Helper classes/functions for creating a unique_ptr using a custom allocator
+ * Helper classes/functions for creating a unique_ptr using a custom
+ * allocator.
  *
  * @author: Marcelo Juchem <marcelo@fb.com>
  */
 
-// A deleter implementation based on std::default_delete,
-// which uses a custom allocator to free memory
+// Derives from the allocator to take advantage of the empty base
+// optimization when possible.
 template <typename Allocator>
-class allocator_delete {
+class allocator_delete
+  : private std::remove_reference<Allocator>::type
+{
   typedef typename std::remove_reference<Allocator>::type allocator_type;
 
-public:
+ public:
+  typedef typename Allocator::pointer pointer;
+
   allocator_delete() = default;
 
-  explicit allocator_delete(const allocator_type& allocator):
-    allocator_(allocator)
+  explicit allocator_delete(const allocator_type& allocator)
+    : allocator_type(allocator)
   {}
 
-  explicit allocator_delete(allocator_type&& allocator):
-    allocator_(std::move(allocator))
+  explicit allocator_delete(allocator_type&& allocator)
+    : allocator_type(std::move(allocator))
   {}
 
   template <typename U>
-  allocator_delete(const allocator_delete<U>& other):
-    allocator_(other.get_allocator())
+  allocator_delete(const allocator_delete<U>& other)
+    : allocator_type(other.get_allocator())
   {}
 
   allocator_type& get_allocator() const {
-    return allocator_;
+    return *const_cast<allocator_delete*>(this);
   }
 
-  void operator()(typename allocator_type::pointer p) const {
+  void operator()(pointer p) const {
     if (!p) {
       return;
     }
-
-    allocator_.destroy(p);
-    allocator_.deallocate(p, 1);
+    const_cast<allocator_delete*>(this)->destroy(p);
+    const_cast<allocator_delete*>(this)->deallocate(p, 1);
   }
-
-private:
-  mutable allocator_type allocator_;
 };
 
-template <typename T, typename Allocator>
-class is_simple_allocator {
-  FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_destroy, destroy);
+namespace detail {
 
-  typedef typename std::remove_const<
-    typename std::remove_reference<Allocator>::type
-  >::type allocator;
-  typedef typename std::remove_reference<T>::type value_type;
-  typedef value_type* pointer;
+FOLLY_CREATE_MEMBER_INVOKE_TRAITS(destroy_invoke_traits, destroy);
+
+} // namespace detail
 
-public:
-  constexpr static bool value = !has_destroy<allocator, void(pointer)>::value
-    && !has_destroy<allocator, void(void*)>::value;
+template <typename Allocator, typename Value>
+using is_simple_allocator =
+    Negation<detail::destroy_invoke_traits::is_invocable<Allocator, Value*>>;
+
+template <typename T, typename Allocator>
+struct as_stl_allocator {
+  typedef typename std::conditional<
+    is_simple_allocator<
+      typename std::remove_reference<Allocator>::type,
+      typename std::remove_reference<T>::type
+    >::value,
+    folly::StlAllocator<
+      typename std::remove_reference<Allocator>::type,
+      typename std::remove_reference<T>::type
+    >,
+    typename std::remove_reference<Allocator>::type
+  >::type type;
 };
 
 template <typename T, typename Allocator>
 typename std::enable_if<
-  is_simple_allocator<T, Allocator>::value,
+  is_simple_allocator<
+    typename std::remove_reference<Allocator>::type,
+    typename std::remove_reference<T>::type
+  >::value,
   folly::StlAllocator<
     typename std::remove_reference<Allocator>::type,
     typename std::remove_reference<T>::type
@@ -226,18 +390,31 @@ typename std::enable_if<
 
 template <typename T, typename Allocator>
 typename std::enable_if<
-  !is_simple_allocator<T, Allocator>::value,
+  !is_simple_allocator<
+    typename std::remove_reference<Allocator>::type,
+    typename std::remove_reference<T>::type
+  >::value,
   typename std::remove_reference<Allocator>::type
 >::type make_stl_allocator(Allocator&& allocator) {
   return std::move(allocator);
 }
 
+/**
+ * AllocatorUniquePtr: a unique_ptr that supports both STL-style
+ * allocators and SimpleAllocator
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+
 template <typename T, typename Allocator>
 struct AllocatorUniquePtr {
   typedef std::unique_ptr<T,
     folly::allocator_delete<
       typename std::conditional<
-        is_simple_allocator<T, Allocator>::value,
+        is_simple_allocator<
+          typename std::remove_reference<Allocator>::type,
+          typename std::remove_reference<T>::type
+        >::value,
         folly::StlAllocator<typename std::remove_reference<Allocator>::type, T>,
         typename std::remove_reference<Allocator>::type
       >::type
@@ -245,6 +422,13 @@ struct AllocatorUniquePtr {
   > type;
 };
 
+/**
+ * Functions to allocate a unique_ptr / shared_ptr, supporting both
+ * STL-style allocators and SimpleAllocator, analog to std::allocate_shared
+ *
+ * @author: Marcelo Juchem <marcelo@fb.com>
+ */
+
 template <typename T, typename Allocator, typename ...Args>
 typename AllocatorUniquePtr<T, Allocator>::type allocate_unique(
   Allocator&& allocator, Args&&... args
@@ -274,6 +458,99 @@ std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
   );
 }
 
-}  // namespace folly
+/**
+ * IsArenaAllocator<T>::value describes whether SimpleAllocator has
+ * no-op deallocate().
+ */
+template <class T> struct IsArenaAllocator : std::false_type { };
+
+/*
+ * folly::enable_shared_from_this
+ *
+ * To be removed once C++17 becomes a minimum requirement for folly.
+ */
+#if __cplusplus >= 201700L || \
+    __cpp_lib_enable_shared_from_this >= 201603L
+
+// Guaranteed to have std::enable_shared_from_this::weak_from_this(). Prefer
+// type alias over our own class.
+/* using override */ using std::enable_shared_from_this;
+
+#else
+
+/**
+ * Extends std::enabled_shared_from_this. Offers weak_from_this() to pre-C++17
+ * code. Use as drop-in replacement for std::enable_shared_from_this.
+ *
+ * C++14 has no direct means of creating a std::weak_ptr, one must always
+ * create a (temporary) std::shared_ptr first. C++17 adds weak_from_this() to
+ * std::enable_shared_from_this to avoid that overhead. Alas code that must
+ * compile under different language versions cannot call
+ * std::enable_shared_from_this::weak_from_this() directly. Hence this class.
+ *
+ * @example
+ *   class MyClass : public folly::enable_shared_from_this<MyClass> {};
+ *
+ *   int main() {
+ *     std::shared_ptr<MyClass> sp = std::make_shared<MyClass>();
+ *     std::weak_ptr<MyClass> wp = sp->weak_from_this();
+ *   }
+ */
+template <typename T>
+class enable_shared_from_this : public std::enable_shared_from_this<T> {
+ public:
+  constexpr enable_shared_from_this() noexcept = default;
+
+  std::weak_ptr<T> weak_from_this() noexcept {
+    return weak_from_this_<T>(this);
+  }
+
+  std::weak_ptr<T const> weak_from_this() const noexcept {
+    return weak_from_this_<T>(this);
+  }
+
+ private:
+  // Uses SFINAE to detect and call
+  // std::enable_shared_from_this<T>::weak_from_this() if available. Falls
+  // back to std::enable_shared_from_this<T>::shared_from_this() otherwise.
+  template <typename U>
+  auto weak_from_this_(std::enable_shared_from_this<U>* base_ptr)
+  noexcept -> decltype(base_ptr->weak_from_this()) {
+    return base_ptr->weak_from_this();
+  }
+
+  template <typename U>
+  auto weak_from_this_(std::enable_shared_from_this<U> const* base_ptr)
+  const noexcept -> decltype(base_ptr->weak_from_this()) {
+    return base_ptr->weak_from_this();
+  }
+
+  template <typename U>
+  std::weak_ptr<U> weak_from_this_(...) noexcept {
+    try {
+      return this->shared_from_this();
+    } catch (std::bad_weak_ptr const&) {
+      // C++17 requires that weak_from_this() on an object not owned by a
+      // shared_ptr returns an empty weak_ptr. Sadly, in C++14,
+      // shared_from_this() on such an object is undefined behavior, and there
+      // is nothing we can do to detect and handle the situation in a portable
+      // manner. But in case a compiler is nice enough to implement C++17
+      // semantics of shared_from_this() and throws a bad_weak_ptr, we catch it
+      // and return an empty weak_ptr.
+      return std::weak_ptr<U>{};
+    }
+  }
+
+  template <typename U>
+  std::weak_ptr<U const> weak_from_this_(...) const noexcept {
+    try {
+      return this->shared_from_this();
+    } catch (std::bad_weak_ptr const&) {
+      return std::weak_ptr<U const>{};
+    }
+  }
+};
+
+#endif
 
-#endif /* FOLLY_MEMORY_H_ */
+} // namespace folly