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/*
* 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.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <folly/Traits.h>
#include <cstddef>
#include <cstdlib>
#include <exception>
#include <limits>
#include <memory>
#include <stdexcept>
#include <utility>
namespace folly {
/**
* For exception safety and consistency with make_shared. Erase me when
* 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>
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));
}
/**
* A 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.
*
* 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.
template <class Alloc, class T> class StlAllocator;
template <class Alloc> class StlAllocator<Alloc, void> {
public:
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>
class StlAllocator {
public:
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef ptrdiff_t difference_type;
typedef size_t size_type;
StlAllocator() : alloc_(nullptr) { }
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) {
return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
}
void deallocate(T* p, size_t /* n */) { alloc_->deallocate(p); }
size_t max_size() const {
return std::numeric_limits<size_t>::max();
}
T* address(T& x) const {
return std::addressof(x);
}
const T* address(const T& x) const {
return std::addressof(x);
}
template <class... Args>
void construct(T* p, Args&&... args) {
new (p) T(std::forward<Args>(args)...);
}
void destroy(T* p) {
p->~T();
}
Alloc* alloc() const {
return alloc_;
}
template <class U> struct rebind {
typedef StlAllocator<Alloc, U> other;
};
bool operator!=(const StlAllocator<Alloc, T>& other) const {
return alloc_ != other.alloc_;
}
bool operator==(const StlAllocator<Alloc, T>& other) const {
return alloc_ == other.alloc_;
}
private:
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.
*
* @author: Marcelo Juchem <marcelo@fb.com>
*/
// Derives from the allocator to take advantage of the empty base
// optimization when possible.
template <typename Allocator>
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_type(allocator)
{}
explicit allocator_delete(allocator_type&& allocator)
: allocator_type(std::move(allocator))
{}
template <typename U>
allocator_delete(const allocator_delete<U>& other)
: allocator_type(other.get_allocator())
{}
allocator_type& get_allocator() const {
return *const_cast<allocator_delete*>(this);
}
void operator()(pointer p) const {
if (!p) return;
const_cast<allocator_delete*>(this)->destroy(p);
const_cast<allocator_delete*>(this)->deallocate(p, 1);
}
};
template <typename T, typename Allocator>
class is_simple_allocator {
FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_destroy, destroy);
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;
public:
constexpr static bool value = !has_destroy<allocator, void(pointer)>::value
&& !has_destroy<allocator, void(void*)>::value;
};
template <typename T, typename Allocator>
struct as_stl_allocator {
typedef typename std::conditional<
is_simple_allocator<T, Allocator>::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,
folly::StlAllocator<
typename std::remove_reference<Allocator>::type,
typename std::remove_reference<T>::type
>
>::type make_stl_allocator(Allocator&& allocator) {
return folly::StlAllocator<
typename std::remove_reference<Allocator>::type,
typename std::remove_reference<T>::type
>(&allocator);
}
template <typename T, typename Allocator>
typename std::enable_if<
!is_simple_allocator<T, Allocator>::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,
folly::StlAllocator<typename std::remove_reference<Allocator>::type, T>,
typename std::remove_reference<Allocator>::type
>::type
>
> 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
) {
auto stlAllocator = folly::make_stl_allocator<T>(
std::forward<Allocator>(allocator)
);
auto p = stlAllocator.allocate(1);
try {
stlAllocator.construct(p, std::forward<Args>(args)...);
return {p,
folly::allocator_delete<decltype(stlAllocator)>(std::move(stlAllocator))
};
} catch (...) {
stlAllocator.deallocate(p, 1);
throw;
}
}
template <typename T, typename Allocator, typename ...Args>
std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
return std::allocate_shared<T>(
folly::make_stl_allocator<T>(std::forward<Allocator>(allocator)),
std::forward<Args>(args)...
);
}
/**
* 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
} // namespace folly