X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FMemory.h;h=70bc451cb2221bad6ef984f4018613bdc4859135;hb=0f383c3789e8ca0caa5b086fde1a28af44e0a450;hp=e4db242ba22edc24065a249e67bc5416f47944b3;hpb=36b366265da55fc26201870d1c5c2477ccc12600;p=folly.git

diff --git a/folly/Memory.h b/folly/Memory.h
index e4db242b..70bc451c 100644
--- a/folly/Memory.h
+++ b/folly/Memory.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 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.
@@ -17,15 +17,15 @@
 #ifndef FOLLY_MEMORY_H_
 #define FOLLY_MEMORY_H_
 
-#include "folly/Traits.h"
+#include <folly/Traits.h>
 
-#include <memory>
-#include <limits>
-#include <utility>
+#include <cstddef>
+#include <cstdlib>
 #include <exception>
+#include <limits>
+#include <memory>
 #include <stdexcept>
-
-#include <cstddef>
+#include <utility>
 
 namespace folly {
 
@@ -34,43 +34,91 @@ 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) {
-  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+template<typename T, typename Dp = std::default_delete<T>, typename... Args>
+typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T, Dp>>::type
+make_unique(Args&&... args) {
+  return std::unique_ptr<T, Dp>(new T(std::forward<Args>(args)...));
+}
+
+// Allows 'make_unique<T[]>(10)'. (N3690 s20.9.1.4 p3-4)
+template<typename T, typename Dp = std::default_delete<T>>
+typename std::enable_if<std::is_array<T>::value, std::unique_ptr<T, Dp>>::type
+make_unique(const size_t n) {
+  return std::unique_ptr<T, Dp>(new typename std::remove_extent<T>::type[n]());
+}
+
+// Disallows 'make_unique<T[10]>()'. (N3690 s20.9.1.4 p5)
+template<typename T, typename Dp = std::default_delete<T>, typename... Args>
+typename std::enable_if<
+  std::extent<T>::value != 0, std::unique_ptr<T, Dp>>::type
+make_unique(Args&&...) = delete;
+
+/**
+ *  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::cpp2::FooBarServiceAsyncClient;
+ */
+template <typename T>
+std::shared_ptr<T> to_shared_ptr(std::unique_ptr<T>&& ptr) {
+  return std::shared_ptr<T>(std::move(ptr));
 }
 
 /**
- * Wrap a SimpleAllocator into a STL-compliant allocator.
+ * 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:
+ * 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.
  *
- * 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);
- *   }
- * };
+ * 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>
+ * @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> {
@@ -80,7 +128,7 @@ template <class Alloc> class StlAllocator<Alloc, void> {
   typedef const void* const_pointer;
 
   StlAllocator() : alloc_(nullptr) { }
-  explicit StlAllocator(Alloc* alloc) : alloc_(alloc) { }
+  explicit StlAllocator(Alloc* a) : alloc_(a) { }
 
   Alloc* alloc() const {
     return alloc_;
@@ -115,7 +163,7 @@ 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()) { }
@@ -169,49 +217,60 @@ 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:
+  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 {
-    if (!p) {
-      return;
-    }
-
-    allocator_.destroy(p);
-    allocator_.deallocate(p, 1);
+  void operator()(pointer p) const {
+    if (!p) return;
+    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>
@@ -319,6 +378,12 @@ std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
   );
 }
 
+/**
+ * IsArenaAllocator<T>::value describes whether SimpleAllocator has
+ * no-op deallocate().
+ */
+template <class T> struct IsArenaAllocator : std::false_type { };
+
 }  // namespace folly
 
 #endif /* FOLLY_MEMORY_H_ */