/*
- * Copyright 2013 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.
#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 {
* 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;
+
/**
- * 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.
*
- * 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);
- * }
- * };
+ * 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>
+ * @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> {
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_;
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()) { }
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>
);
}
+/**
+ * IsArenaAllocator<T>::value describes whether SimpleAllocator has
+ * no-op deallocate().
+ */
+template <class T> struct IsArenaAllocator : std::false_type { };
+
} // namespace folly
#endif /* FOLLY_MEMORY_H_ */
projects / folly.git / blobdiff