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));
118 * A SimpleAllocator must provide two methods:
120 * void* allocate(size_t size);
121 * void deallocate(void* ptr);
123 * which, respectively, allocate a block of size bytes (aligned to the
124 * maximum alignment required on your system), throwing std::bad_alloc
125 * if the allocation can't be satisfied, and free a previously
128 * SysAlloc resembles the standard allocator.
132 void* allocate(size_t size) {
133 void* p = ::malloc(size);
134 if (!p) throw std::bad_alloc();
137 void deallocate(void* p) {
143 * StlAllocator wraps a SimpleAllocator into a STL-compliant
144 * allocator, maintaining an instance pointer to the simple allocator
145 * object. The underlying SimpleAllocator object must outlive all
146 * instances of StlAllocator using it.
148 * But note that if you pass StlAllocator<MallocAllocator,...> to a
149 * standard container it will be larger due to the contained state
152 * @author: Tudor Bosman <tudorb@fb.com>
155 // This would be so much simpler with std::allocator_traits, but gcc 4.6.2
156 // doesn't support it.
157 template <class Alloc, class T> class StlAllocator;
159 template <class Alloc> class StlAllocator<Alloc, void> {
161 typedef void value_type;
162 typedef void* pointer;
163 typedef const void* const_pointer;
165 StlAllocator() : alloc_(nullptr) { }
166 explicit StlAllocator(Alloc* a) : alloc_(a) { }
168 Alloc* alloc() const {
172 template <class U> struct rebind {
173 typedef StlAllocator<Alloc, U> other;
176 bool operator!=(const StlAllocator<Alloc, void>& other) const {
177 return alloc_ != other.alloc_;
180 bool operator==(const StlAllocator<Alloc, void>& other) const {
181 return alloc_ == other.alloc_;
188 template <class Alloc, class T>
191 typedef T value_type;
193 typedef const T* const_pointer;
194 typedef T& reference;
195 typedef const T& const_reference;
197 typedef ptrdiff_t difference_type;
198 typedef size_t size_type;
200 StlAllocator() : alloc_(nullptr) { }
201 explicit StlAllocator(Alloc* a) : alloc_(a) { }
203 template <class U> StlAllocator(const StlAllocator<Alloc, U>& other)
204 : alloc_(other.alloc()) { }
206 T* allocate(size_t n, const void* /* hint */ = nullptr) {
207 return static_cast<T*>(alloc_->allocate(n * sizeof(T)));
210 void deallocate(T* p, size_t /* n */) { 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 { };