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) const {
99 * Convert unique_ptr to shared_ptr without specifying the template type
100 * parameter and letting the compiler deduce it.
102 * So you can write this:
104 * auto sptr = to_shared_ptr(getSomethingUnique<T>());
108 * auto sptr = shared_ptr<T>(getSomethingUnique<T>());
110 * Useful when `T` is long, such as:
112 * using T = foobar::cpp2::FooBarServiceAsyncClient;
114 template <typename T, typename D>
115 std::shared_ptr<T> to_shared_ptr(std::unique_ptr<T, D>&& ptr) {
116 return std::shared_ptr<T>(std::move(ptr));
119 using SysBufferDeleter = static_function_deleter<void, ::free>;
120 using SysBufferUniquePtr = std::unique_ptr<void, SysBufferDeleter>;
121 inline SysBufferUniquePtr allocate_sys_buffer(size_t size) {
122 return SysBufferUniquePtr(::malloc(size));
126 * A SimpleAllocator must provide two methods:
128 * void* allocate(size_t size);
129 * void deallocate(void* ptr);
131 * which, respectively, allocate a block of size bytes (aligned to the
132 * maximum alignment required on your system), throwing std::bad_alloc
133 * if the allocation can't be satisfied, and free a previously
136 * SysAlloc resembles the standard allocator.
140 void* allocate(size_t size) {
141 void* p = ::malloc(size);
142 if (!p) throw std::bad_alloc();
145 void deallocate(void* p) {
151 * StlAllocator wraps a SimpleAllocator into a STL-compliant
152 * allocator, maintaining an instance pointer to the simple allocator
153 * object. The underlying SimpleAllocator object must outlive all
154 * instances of StlAllocator using it.
156 * But note that if you pass StlAllocator<MallocAllocator,...> to a
157 * standard container it will be larger due to the contained state
160 * @author: Tudor Bosman <tudorb@fb.com>
163 // This would be so much simpler with std::allocator_traits, but gcc 4.6.2
164 // doesn't support it.
165 template <class Alloc, class T> class StlAllocator;
167 template <class Alloc> class StlAllocator<Alloc, void> {
169 typedef void value_type;
170 typedef void* pointer;
171 typedef const void* const_pointer;
173 StlAllocator() : alloc_(nullptr) { }
174 explicit StlAllocator(Alloc* a) : alloc_(a) { }
176 Alloc* alloc() const {
180 template <class U> struct rebind {
181 typedef StlAllocator<Alloc, U> other;
184 bool operator!=(const StlAllocator<Alloc, void>& other) const {
185 return alloc_ != other.alloc_;
188 bool operator==(const StlAllocator<Alloc, void>& other) const {
189 return alloc_ == other.alloc_;
196 template <class Alloc, class T>
199 typedef T value_type;
201 typedef const T* const_pointer;
202 typedef T& reference;
203 typedef const T& const_reference;
205 typedef ptrdiff_t difference_type;
206 typedef size_t size_type;
208 StlAllocator() : alloc_(nullptr) { }
209 explicit StlAllocator(Alloc* a) : alloc_(a) { }
211 template <class U> StlAllocator(const StlAllocator<Alloc, U>& other)
212 : alloc_(other.alloc()) { }
214 T* allocate(size_t n, const void* /* hint */ = nullptr) {
215 return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
218 void deallocate(T* p, size_t /* n */) { alloc_->deallocate(p); }
220 size_t max_size() const {
221 return std::numeric_limits<size_t>::max();
224 T* address(T& x) const {
225 return std::addressof(x);
228 const T* address(const T& x) const {
229 return std::addressof(x);
232 template <class... Args>
233 void construct(T* p, Args&&... args) {
234 new (p) T(std::forward<Args>(args)...);
241 Alloc* alloc() const {
245 template <class U> struct rebind {
246 typedef StlAllocator<Alloc, U> other;
249 bool operator!=(const StlAllocator<Alloc, T>& other) const {
250 return alloc_ != other.alloc_;
253 bool operator==(const StlAllocator<Alloc, T>& other) const {
254 return alloc_ == other.alloc_;
262 * Helper function to obtain rebound allocators
264 * @author: Marcelo Juchem <marcelo@fb.com>
266 template <typename T, typename Allocator>
267 typename Allocator::template rebind<T>::other rebind_allocator(
268 Allocator const& allocator
270 return typename Allocator::template rebind<T>::other(allocator);
274 * Helper classes/functions for creating a unique_ptr using a custom
277 * @author: Marcelo Juchem <marcelo@fb.com>
280 // Derives from the allocator to take advantage of the empty base
281 // optimization when possible.
282 template <typename Allocator>
283 class allocator_delete
284 : private std::remove_reference<Allocator>::type
286 typedef typename std::remove_reference<Allocator>::type allocator_type;
289 typedef typename Allocator::pointer pointer;
291 allocator_delete() = default;
293 explicit allocator_delete(const allocator_type& allocator)
294 : allocator_type(allocator)
297 explicit allocator_delete(allocator_type&& allocator)
298 : allocator_type(std::move(allocator))
301 template <typename U>
302 allocator_delete(const allocator_delete<U>& other)
303 : allocator_type(other.get_allocator())
306 allocator_type& get_allocator() const {
307 return *const_cast<allocator_delete*>(this);
310 void operator()(pointer p) const {
312 const_cast<allocator_delete*>(this)->destroy(p);
313 const_cast<allocator_delete*>(this)->deallocate(p, 1);
317 template <typename T, typename Allocator>
318 class is_simple_allocator {
319 FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_destroy, destroy);
321 typedef typename std::remove_const<
322 typename std::remove_reference<Allocator>::type
324 typedef typename std::remove_reference<T>::type value_type;
325 typedef value_type* pointer;
328 constexpr static bool value = !has_destroy<allocator, void(pointer)>::value
329 && !has_destroy<allocator, void(void*)>::value;
332 template <typename T, typename Allocator>
333 struct as_stl_allocator {
334 typedef typename std::conditional<
335 is_simple_allocator<T, Allocator>::value,
337 typename std::remove_reference<Allocator>::type,
338 typename std::remove_reference<T>::type
340 typename std::remove_reference<Allocator>::type
344 template <typename T, typename Allocator>
345 typename std::enable_if<
346 is_simple_allocator<T, Allocator>::value,
348 typename std::remove_reference<Allocator>::type,
349 typename std::remove_reference<T>::type
351 >::type make_stl_allocator(Allocator&& allocator) {
352 return folly::StlAllocator<
353 typename std::remove_reference<Allocator>::type,
354 typename std::remove_reference<T>::type
358 template <typename T, typename Allocator>
359 typename std::enable_if<
360 !is_simple_allocator<T, Allocator>::value,
361 typename std::remove_reference<Allocator>::type
362 >::type make_stl_allocator(Allocator&& allocator) {
363 return std::move(allocator);
367 * AllocatorUniquePtr: a unique_ptr that supports both STL-style
368 * allocators and SimpleAllocator
370 * @author: Marcelo Juchem <marcelo@fb.com>
373 template <typename T, typename Allocator>
374 struct AllocatorUniquePtr {
375 typedef std::unique_ptr<T,
376 folly::allocator_delete<
377 typename std::conditional<
378 is_simple_allocator<T, Allocator>::value,
379 folly::StlAllocator<typename std::remove_reference<Allocator>::type, T>,
380 typename std::remove_reference<Allocator>::type
387 * Functions to allocate a unique_ptr / shared_ptr, supporting both
388 * STL-style allocators and SimpleAllocator, analog to std::allocate_shared
390 * @author: Marcelo Juchem <marcelo@fb.com>
393 template <typename T, typename Allocator, typename ...Args>
394 typename AllocatorUniquePtr<T, Allocator>::type allocate_unique(
395 Allocator&& allocator, Args&&... args
397 auto stlAllocator = folly::make_stl_allocator<T>(
398 std::forward<Allocator>(allocator)
400 auto p = stlAllocator.allocate(1);
403 stlAllocator.construct(p, std::forward<Args>(args)...);
406 folly::allocator_delete<decltype(stlAllocator)>(std::move(stlAllocator))
409 stlAllocator.deallocate(p, 1);
414 template <typename T, typename Allocator, typename ...Args>
415 std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
416 return std::allocate_shared<T>(
417 folly::make_stl_allocator<T>(std::forward<Allocator>(allocator)),
418 std::forward<Args>(args)...
423 * IsArenaAllocator<T>::value describes whether SimpleAllocator has
424 * no-op deallocate().
426 template <class T> struct IsArenaAllocator : std::false_type { };