/*
- * 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.
* limitations under the License.
*/
-#ifndef FOLLY_MEMORY_H_
-#define FOLLY_MEMORY_H_
+#pragma once
-#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)
*/
+#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>
-std::unique_ptr<T> make_unique(Args&&... 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
+
+/**
+ * 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);
+}
+
+namespace detail {
+/**
+ * Not all STL implementations define ::free in a way that its address can be
+ * determined at compile time. So we must wrap ::free in a function whose
+ * address can be determined.
+ */
+inline void SysFree(void* p) {
+ ::free(p);
+}
+}
+
+using SysBufferDeleter = static_function_deleter<void, &detail::SysFree>;
+using SysBufferUniquePtr = std::unique_ptr<void, SysBufferDeleter>;
+inline SysBufferUniquePtr allocate_sys_buffer(size_t size) {
+ return SysBufferUniquePtr(::malloc(size));
+}
+
/**
- * 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:
- *
- * 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> {
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()) { }
- 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();
*/
template <typename T, typename Allocator>
typename Allocator::template rebind<T>::other rebind_allocator(
- Allocator const &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>
);
}
-} // 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;
-#endif /* FOLLY_MEMORY_H_ */
+#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
+
+} // namespace folly
projects / folly.git / blobdiff