2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include <folly/Traits.h>
20 #include <folly/portability/Memory.h>
33 * For exception safety and consistency with make_shared. Erase me when
34 * we have std::make_unique().
36 * @author Louis Brandy (ldbrandy@fb.com)
37 * @author Xu Ning (xning@fb.com)
40 #if __cplusplus >= 201402L || \
41 (defined __cpp_lib_make_unique && __cpp_lib_make_unique >= 201304L) || \
42 (defined(_MSC_VER) && _MSC_VER >= 1900)
44 /* using override */ using std::make_unique;
48 template<typename T, typename... Args>
49 typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type
50 make_unique(Args&&... args) {
51 return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
54 // Allows 'make_unique<T[]>(10)'. (N3690 s20.9.1.4 p3-4)
56 typename std::enable_if<std::is_array<T>::value, std::unique_ptr<T>>::type
57 make_unique(const size_t n) {
58 return std::unique_ptr<T>(new typename std::remove_extent<T>::type[n]());
61 // Disallows 'make_unique<T[10]>()'. (N3690 s20.9.1.4 p5)
62 template<typename T, typename... Args>
63 typename std::enable_if<
64 std::extent<T>::value != 0, std::unique_ptr<T>>::type
65 make_unique(Args&&...) = delete;
70 * static_function_deleter
72 * So you can write this:
74 * using RSA_deleter = folly::static_function_deleter<RSA, &RSA_free>;
75 * auto rsa = std::unique_ptr<RSA, RSA_deleter>(RSA_new());
76 * RSA_generate_key_ex(rsa.get(), bits, exponent, nullptr);
77 * rsa = nullptr; // calls RSA_free(rsa.get())
79 * This would be sweet as well for BIO, but unfortunately BIO_free has signature
80 * int(BIO*) while we require signature void(BIO*). So you would need to make a
83 * inline void BIO_free_fb(BIO* bio) { CHECK_EQ(1, BIO_free(bio)); }
84 * using BIO_deleter = folly::static_function_deleter<BIO, &BIO_free_fb>;
85 * auto buf = std::unique_ptr<BIO, BIO_deleter>(BIO_new(BIO_s_mem()));
86 * buf = nullptr; // calls BIO_free(buf.get())
89 template <typename T, void(*f)(T*)>
90 struct static_function_deleter {
91 void operator()(T* t) { f(t); }
97 * Convert unique_ptr to shared_ptr without specifying the template type
98 * parameter and letting the compiler deduce it.
100 * So you can write this:
102 * auto sptr = to_shared_ptr(getSomethingUnique<T>());
106 * auto sptr = shared_ptr<T>(getSomethingUnique<T>());
108 * Useful when `T` is long, such as:
110 * using T = foobar::cpp2::FooBarServiceAsyncClient;
112 template <typename T, typename D>
113 std::shared_ptr<T> to_shared_ptr(std::unique_ptr<T, D>&& ptr) {
114 return std::shared_ptr<T>(std::move(ptr));
117 using SysBufferDeleter = static_function_deleter<void, ::free>;
118 using SysBufferUniquePtr = std::unique_ptr<void, SysBufferDeleter>;
119 inline SysBufferUniquePtr allocate_sys_buffer(size_t size) {
120 return SysBufferUniquePtr(::malloc(size));
124 * A SimpleAllocator must provide two methods:
126 * void* allocate(size_t size);
127 * void deallocate(void* ptr);
129 * which, respectively, allocate a block of size bytes (aligned to the
130 * maximum alignment required on your system), throwing std::bad_alloc
131 * if the allocation can't be satisfied, and free a previously
134 * SysAlloc resembles the standard allocator.
138 void* allocate(size_t size) {
139 void* p = ::malloc(size);
140 if (!p) throw std::bad_alloc();
143 void deallocate(void* p) {
149 * StlAllocator wraps a SimpleAllocator into a STL-compliant
150 * allocator, maintaining an instance pointer to the simple allocator
151 * object. The underlying SimpleAllocator object must outlive all
152 * instances of StlAllocator using it.
154 * But note that if you pass StlAllocator<MallocAllocator,...> to a
155 * standard container it will be larger due to the contained state
158 * @author: Tudor Bosman <tudorb@fb.com>
161 // This would be so much simpler with std::allocator_traits, but gcc 4.6.2
162 // doesn't support it.
163 template <class Alloc, class T> class StlAllocator;
165 template <class Alloc> class StlAllocator<Alloc, void> {
167 typedef void value_type;
168 typedef void* pointer;
169 typedef const void* const_pointer;
171 StlAllocator() : alloc_(nullptr) { }
172 explicit StlAllocator(Alloc* a) : alloc_(a) { }
174 Alloc* alloc() const {
178 template <class U> struct rebind {
179 typedef StlAllocator<Alloc, U> other;
182 bool operator!=(const StlAllocator<Alloc, void>& other) const {
183 return alloc_ != other.alloc_;
186 bool operator==(const StlAllocator<Alloc, void>& other) const {
187 return alloc_ == other.alloc_;
194 template <class Alloc, class T>
197 typedef T value_type;
199 typedef const T* const_pointer;
200 typedef T& reference;
201 typedef const T& const_reference;
203 typedef ptrdiff_t difference_type;
204 typedef size_t size_type;
206 StlAllocator() : alloc_(nullptr) { }
207 explicit StlAllocator(Alloc* a) : alloc_(a) { }
209 template <class U> StlAllocator(const StlAllocator<Alloc, U>& other)
210 : alloc_(other.alloc()) { }
212 T* allocate(size_t n, const void* /* hint */ = nullptr) {
213 return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
216 void deallocate(T* p, size_t /* n */) { alloc_->deallocate(p); }
218 size_t max_size() const {
219 return std::numeric_limits<size_t>::max();
222 T* address(T& x) const {
223 return std::addressof(x);
226 const T* address(const T& x) const {
227 return std::addressof(x);
230 template <class... Args>
231 void construct(T* p, Args&&... args) {
232 new (p) T(std::forward<Args>(args)...);
239 Alloc* alloc() const {
243 template <class U> struct rebind {
244 typedef StlAllocator<Alloc, U> other;
247 bool operator!=(const StlAllocator<Alloc, T>& other) const {
248 return alloc_ != other.alloc_;
251 bool operator==(const StlAllocator<Alloc, T>& other) const {
252 return alloc_ == other.alloc_;
260 * Helper function to obtain rebound allocators
262 * @author: Marcelo Juchem <marcelo@fb.com>
264 template <typename T, typename Allocator>
265 typename Allocator::template rebind<T>::other rebind_allocator(
266 Allocator const& allocator
268 return typename Allocator::template rebind<T>::other(allocator);
272 * Helper classes/functions for creating a unique_ptr using a custom
275 * @author: Marcelo Juchem <marcelo@fb.com>
278 // Derives from the allocator to take advantage of the empty base
279 // optimization when possible.
280 template <typename Allocator>
281 class allocator_delete
282 : private std::remove_reference<Allocator>::type
284 typedef typename std::remove_reference<Allocator>::type allocator_type;
287 typedef typename Allocator::pointer pointer;
289 allocator_delete() = default;
291 explicit allocator_delete(const allocator_type& allocator)
292 : allocator_type(allocator)
295 explicit allocator_delete(allocator_type&& allocator)
296 : allocator_type(std::move(allocator))
299 template <typename U>
300 allocator_delete(const allocator_delete<U>& other)
301 : allocator_type(other.get_allocator())
304 allocator_type& get_allocator() const {
305 return *const_cast<allocator_delete*>(this);
308 void operator()(pointer p) const {
310 const_cast<allocator_delete*>(this)->destroy(p);
311 const_cast<allocator_delete*>(this)->deallocate(p, 1);
315 template <typename T, typename Allocator>
316 class is_simple_allocator {
317 FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_destroy, destroy);
319 typedef typename std::remove_const<
320 typename std::remove_reference<Allocator>::type
322 typedef typename std::remove_reference<T>::type value_type;
323 typedef value_type* pointer;
326 constexpr static bool value = !has_destroy<allocator, void(pointer)>::value
327 && !has_destroy<allocator, void(void*)>::value;
330 template <typename T, typename Allocator>
331 struct as_stl_allocator {
332 typedef typename std::conditional<
333 is_simple_allocator<T, Allocator>::value,
335 typename std::remove_reference<Allocator>::type,
336 typename std::remove_reference<T>::type
338 typename std::remove_reference<Allocator>::type
342 template <typename T, typename Allocator>
343 typename std::enable_if<
344 is_simple_allocator<T, Allocator>::value,
346 typename std::remove_reference<Allocator>::type,
347 typename std::remove_reference<T>::type
349 >::type make_stl_allocator(Allocator&& allocator) {
350 return folly::StlAllocator<
351 typename std::remove_reference<Allocator>::type,
352 typename std::remove_reference<T>::type
356 template <typename T, typename Allocator>
357 typename std::enable_if<
358 !is_simple_allocator<T, Allocator>::value,
359 typename std::remove_reference<Allocator>::type
360 >::type make_stl_allocator(Allocator&& allocator) {
361 return std::move(allocator);
365 * AllocatorUniquePtr: a unique_ptr that supports both STL-style
366 * allocators and SimpleAllocator
368 * @author: Marcelo Juchem <marcelo@fb.com>
371 template <typename T, typename Allocator>
372 struct AllocatorUniquePtr {
373 typedef std::unique_ptr<T,
374 folly::allocator_delete<
375 typename std::conditional<
376 is_simple_allocator<T, Allocator>::value,
377 folly::StlAllocator<typename std::remove_reference<Allocator>::type, T>,
378 typename std::remove_reference<Allocator>::type
385 * Functions to allocate a unique_ptr / shared_ptr, supporting both
386 * STL-style allocators and SimpleAllocator, analog to std::allocate_shared
388 * @author: Marcelo Juchem <marcelo@fb.com>
391 template <typename T, typename Allocator, typename ...Args>
392 typename AllocatorUniquePtr<T, Allocator>::type allocate_unique(
393 Allocator&& allocator, Args&&... args
395 auto stlAllocator = folly::make_stl_allocator<T>(
396 std::forward<Allocator>(allocator)
398 auto p = stlAllocator.allocate(1);
401 stlAllocator.construct(p, std::forward<Args>(args)...);
404 folly::allocator_delete<decltype(stlAllocator)>(std::move(stlAllocator))
407 stlAllocator.deallocate(p, 1);
412 template <typename T, typename Allocator, typename ...Args>
413 std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
414 return std::allocate_shared<T>(
415 folly::make_stl_allocator<T>(std::forward<Allocator>(allocator)),
416 std::forward<Args>(args)...
421 * IsArenaAllocator<T>::value describes whether SimpleAllocator has
422 * no-op deallocate().
424 template <class T> struct IsArenaAllocator : std::false_type { };