2 * Copyright 2015 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.
17 #ifndef FOLLY_MEMORY_H_
18 #define FOLLY_MEMORY_H_
20 #include <folly/Traits.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
42 /* using override */ using std::make_unique;
46 template<typename T, typename... Args>
47 typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type
48 make_unique(Args&&... args) {
49 return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
52 // Allows 'make_unique<T[]>(10)'. (N3690 s20.9.1.4 p3-4)
54 typename std::enable_if<std::is_array<T>::value, std::unique_ptr<T>>::type
55 make_unique(const size_t n) {
56 return std::unique_ptr<T>(new typename std::remove_extent<T>::type[n]());
59 // Disallows 'make_unique<T[10]>()'. (N3690 s20.9.1.4 p5)
60 template<typename T, typename... Args>
61 typename std::enable_if<
62 std::extent<T>::value != 0, std::unique_ptr<T>>::type
63 make_unique(Args&&...) = delete;
68 * static_function_deleter
70 * So you can write this:
72 * using RSA_deleter = folly::static_function_deleter<RSA, &RSA_free>;
73 * auto rsa = std::unique_ptr<RSA, RSA_deleter>(RSA_new());
74 * RSA_generate_key_ex(rsa.get(), bits, exponent, nullptr);
75 * rsa = nullptr; // calls RSA_free(rsa.get())
77 * This would be sweet as well for BIO, but unfortunately BIO_free has signature
78 * int(BIO*) while we require signature void(BIO*). So you would need to make a
81 * inline void BIO_free_fb(BIO* bio) { CHECK_EQ(1, BIO_free(bio)); }
82 * using BIO_deleter = folly::static_function_deleter<BIO, &BIO_free_fb>;
83 * auto buf = std::unique_ptr<BIO, BIO_deleter>(BIO_new(BIO_s_mem()));
84 * buf = nullptr; // calls BIO_free(buf.get())
87 template <typename T, void(*f)(T*)>
88 struct static_function_deleter {
89 void operator()(T* t) { f(t); }
95 * Convert unique_ptr to shared_ptr without specifying the template type
96 * parameter and letting the compiler deduce it.
98 * So you can write this:
100 * auto sptr = to_shared_ptr(getSomethingUnique<T>());
104 * auto sptr = shared_ptr<T>(getSomethingUnique<T>());
106 * Useful when `T` is long, such as:
108 * using T = foobar::cpp2::FooBarServiceAsyncClient;
110 template <typename T, typename D>
111 std::shared_ptr<T> to_shared_ptr(std::unique_ptr<T, D>&& ptr) {
112 return std::shared_ptr<T>(std::move(ptr));
116 * A SimpleAllocator must provide two methods:
118 * void* allocate(size_t size);
119 * void deallocate(void* ptr);
121 * which, respectively, allocate a block of size bytes (aligned to the
122 * maximum alignment required on your system), throwing std::bad_alloc
123 * if the allocation can't be satisfied, and free a previously
126 * SysAlloc resembles the standard allocator.
130 void* allocate(size_t size) {
131 void* p = ::malloc(size);
132 if (!p) throw std::bad_alloc();
135 void deallocate(void* p) {
141 * StlAllocator wraps a SimpleAllocator into a STL-compliant
142 * allocator, maintaining an instance pointer to the simple allocator
143 * object. The underlying SimpleAllocator object must outlive all
144 * instances of StlAllocator using it.
146 * But note that if you pass StlAllocator<MallocAllocator,...> to a
147 * standard container it will be larger due to the contained state
150 * @author: Tudor Bosman <tudorb@fb.com>
153 // This would be so much simpler with std::allocator_traits, but gcc 4.6.2
154 // doesn't support it.
155 template <class Alloc, class T> class StlAllocator;
157 template <class Alloc> class StlAllocator<Alloc, void> {
159 typedef void value_type;
160 typedef void* pointer;
161 typedef const void* const_pointer;
163 StlAllocator() : alloc_(nullptr) { }
164 explicit StlAllocator(Alloc* a) : alloc_(a) { }
166 Alloc* alloc() const {
170 template <class U> struct rebind {
171 typedef StlAllocator<Alloc, U> other;
174 bool operator!=(const StlAllocator<Alloc, void>& other) const {
175 return alloc_ != other.alloc_;
178 bool operator==(const StlAllocator<Alloc, void>& other) const {
179 return alloc_ == other.alloc_;
186 template <class Alloc, class T>
189 typedef T value_type;
191 typedef const T* const_pointer;
192 typedef T& reference;
193 typedef const T& const_reference;
195 typedef ptrdiff_t difference_type;
196 typedef size_t size_type;
198 StlAllocator() : alloc_(nullptr) { }
199 explicit StlAllocator(Alloc* a) : alloc_(a) { }
201 template <class U> StlAllocator(const StlAllocator<Alloc, U>& other)
202 : alloc_(other.alloc()) { }
204 T* allocate(size_t n, const void* hint = nullptr) {
205 return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
208 void deallocate(T* p, size_t n) {
209 alloc_->deallocate(p);
212 size_t max_size() const {
213 return std::numeric_limits<size_t>::max();
216 T* address(T& x) const {
217 return std::addressof(x);
220 const T* address(const T& x) const {
221 return std::addressof(x);
224 template <class... Args>
225 void construct(T* p, Args&&... args) {
226 new (p) T(std::forward<Args>(args)...);
233 Alloc* alloc() const {
237 template <class U> struct rebind {
238 typedef StlAllocator<Alloc, U> other;
241 bool operator!=(const StlAllocator<Alloc, T>& other) const {
242 return alloc_ != other.alloc_;
245 bool operator==(const StlAllocator<Alloc, T>& other) const {
246 return alloc_ == other.alloc_;
254 * Helper function to obtain rebound allocators
256 * @author: Marcelo Juchem <marcelo@fb.com>
258 template <typename T, typename Allocator>
259 typename Allocator::template rebind<T>::other rebind_allocator(
260 Allocator const& allocator
262 return typename Allocator::template rebind<T>::other(allocator);
266 * Helper classes/functions for creating a unique_ptr using a custom
269 * @author: Marcelo Juchem <marcelo@fb.com>
272 // Derives from the allocator to take advantage of the empty base
273 // optimization when possible.
274 template <typename Allocator>
275 class allocator_delete
276 : private std::remove_reference<Allocator>::type
278 typedef typename std::remove_reference<Allocator>::type allocator_type;
281 typedef typename Allocator::pointer pointer;
283 allocator_delete() = default;
285 explicit allocator_delete(const allocator_type& allocator)
286 : allocator_type(allocator)
289 explicit allocator_delete(allocator_type&& allocator)
290 : allocator_type(std::move(allocator))
293 template <typename U>
294 allocator_delete(const allocator_delete<U>& other)
295 : allocator_type(other.get_allocator())
298 allocator_type& get_allocator() const {
299 return *const_cast<allocator_delete*>(this);
302 void operator()(pointer p) const {
304 const_cast<allocator_delete*>(this)->destroy(p);
305 const_cast<allocator_delete*>(this)->deallocate(p, 1);
309 template <typename T, typename Allocator>
310 class is_simple_allocator {
311 FOLLY_CREATE_HAS_MEMBER_FN_TRAITS(has_destroy, destroy);
313 typedef typename std::remove_const<
314 typename std::remove_reference<Allocator>::type
316 typedef typename std::remove_reference<T>::type value_type;
317 typedef value_type* pointer;
320 constexpr static bool value = !has_destroy<allocator, void(pointer)>::value
321 && !has_destroy<allocator, void(void*)>::value;
324 template <typename T, typename Allocator>
325 struct as_stl_allocator {
326 typedef typename std::conditional<
327 is_simple_allocator<T, Allocator>::value,
329 typename std::remove_reference<Allocator>::type,
330 typename std::remove_reference<T>::type
332 typename std::remove_reference<Allocator>::type
336 template <typename T, typename Allocator>
337 typename std::enable_if<
338 is_simple_allocator<T, Allocator>::value,
340 typename std::remove_reference<Allocator>::type,
341 typename std::remove_reference<T>::type
343 >::type make_stl_allocator(Allocator&& allocator) {
344 return folly::StlAllocator<
345 typename std::remove_reference<Allocator>::type,
346 typename std::remove_reference<T>::type
350 template <typename T, typename Allocator>
351 typename std::enable_if<
352 !is_simple_allocator<T, Allocator>::value,
353 typename std::remove_reference<Allocator>::type
354 >::type make_stl_allocator(Allocator&& allocator) {
355 return std::move(allocator);
359 * AllocatorUniquePtr: a unique_ptr that supports both STL-style
360 * allocators and SimpleAllocator
362 * @author: Marcelo Juchem <marcelo@fb.com>
365 template <typename T, typename Allocator>
366 struct AllocatorUniquePtr {
367 typedef std::unique_ptr<T,
368 folly::allocator_delete<
369 typename std::conditional<
370 is_simple_allocator<T, Allocator>::value,
371 folly::StlAllocator<typename std::remove_reference<Allocator>::type, T>,
372 typename std::remove_reference<Allocator>::type
379 * Functions to allocate a unique_ptr / shared_ptr, supporting both
380 * STL-style allocators and SimpleAllocator, analog to std::allocate_shared
382 * @author: Marcelo Juchem <marcelo@fb.com>
385 template <typename T, typename Allocator, typename ...Args>
386 typename AllocatorUniquePtr<T, Allocator>::type allocate_unique(
387 Allocator&& allocator, Args&&... args
389 auto stlAllocator = folly::make_stl_allocator<T>(
390 std::forward<Allocator>(allocator)
392 auto p = stlAllocator.allocate(1);
395 stlAllocator.construct(p, std::forward<Args>(args)...);
398 folly::allocator_delete<decltype(stlAllocator)>(std::move(stlAllocator))
401 stlAllocator.deallocate(p, 1);
406 template <typename T, typename Allocator, typename ...Args>
407 std::shared_ptr<T> allocate_shared(Allocator&& allocator, Args&&... args) {
408 return std::allocate_shared<T>(
409 folly::make_stl_allocator<T>(std::forward<Allocator>(allocator)),
410 std::forward<Args>(args)...
415 * IsArenaAllocator<T>::value describes whether SimpleAllocator has
416 * no-op deallocate().
418 template <class T> struct IsArenaAllocator : std::false_type { };
422 #endif /* FOLLY_MEMORY_H_ */