Agora C++ API Reference for All Platforms

AgoraOptional.h
1 // Copyright (c) 2019 Agora.io. All rights reserved
2
3 // This program is confidential and proprietary to Agora.io.
4 // And may not be copied, reproduced, modified, disclosed to others, published
5 // or used, in whole or in part, without the express prior written permission
6 // of Agora.io.
7 #pragma once
8
9 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
10 #include <type_traits>
11 #endif
12 #include <utility>
13
14 #ifndef CONSTEXPR
15 #if __cplusplus >= 201103L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201103L)
16 #define CONSTEXPR constexpr
17 #else
18 #define CONSTEXPR
19 #endif
20 #endif // !CONSTEXPR
21
22 #ifndef NOEXCEPT
23 #if __cplusplus >= 201103L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201103L)
24 #define NOEXCEPT(Expr) noexcept(Expr)
25 #else
26 #define NOEXCEPT(Expr)
27 #endif
28 #endif // !NOEXCEPT
29
30 namespace agora {
31
32 // Specification:
33 // http://en.cppreference.com/w/cpp/utility/optional/in_place_t
34 struct in_place_t {};
35
36 // Specification:
37 // http://en.cppreference.com/w/cpp/utility/optional/nullopt_t
38 struct nullopt_t {
39 CONSTEXPR explicit nullopt_t(int) {}
40 };
41
42 // Specification:
43 // http://en.cppreference.com/w/cpp/utility/optional/in_place
44 /*CONSTEXPR*/ const in_place_t in_place = {};
45
46 // Specification:
47 // http://en.cppreference.com/w/cpp/utility/optional/nullopt
48 /*CONSTEXPR*/ const nullopt_t nullopt(0);
49
50 // Forward declaration, which is refered by following helpers.
51 template <typename T>
52 class Optional;
53
54 namespace internal {
55
56 template <typename T>
57 struct OptionalStorageBase {
58 // Initializing |empty_| here instead of using default member initializing
59 // to avoid errors in g++ 4.8.
60 CONSTEXPR OptionalStorageBase() : is_populated_(false), empty_('\0') {}
61
62 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
63 template <class... Args>
64 CONSTEXPR explicit OptionalStorageBase(in_place_t, Args&&... args)
65 : is_populated_(true), value_(std::forward<Args>(args)...) {}
66 #else
67 CONSTEXPR explicit OptionalStorageBase(in_place_t, const T& _value)
68 : is_populated_(true), value_(_value) {}
69 #endif
70 // When T is not trivially destructible we must call its
71 // destructor before deallocating its memory.
72 // Note that this hides the (implicitly declared) move constructor, which
73 // would be used for constexpr move constructor in OptionalStorage<T>.
74 // It is needed iff T is trivially move constructible. However, the current
75 // is_trivially_{copy,move}_constructible implementation requires
76 // is_trivially_destructible (which looks a bug, cf:
77 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51452 and
78 // http://cplusplus.github.io/LWG/lwg-active.html#2116), so it is not
79 // necessary for this case at the moment. Please see also the destructor
80 // comment in "is_trivially_destructible = true" specialization below.
81 ~OptionalStorageBase() {
82 if (is_populated_)
83 value_.~T();
84 }
85
86 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
87 template <class... Args>
88 void Init(Args&&... args) {
89 ::new (&value_) T(std::forward<Args>(args)...);
90 is_populated_ = true;
91 }
92 #else
93 void Init(const T& _value) {
94 ::new (&value_) T(_value);
95 is_populated_ = true;
96 }
97 #endif
98
99 bool is_populated_;
100
101 union {
102 // |empty_| exists so that the union will always be initialized, even when
103 // it doesn't contain a value. Union members must be initialized for the
104 // constructor to be 'constexpr'.
105 char empty_;
106 T value_;
107 };
108 };
109
110 // Implement conditional constexpr copy and move constructors. These are
111 // constexpr if is_trivially_{copy,move}_constructible<T>::value is true
112 // respectively. If each is true, the corresponding constructor is defined as
113 // "= default;", which generates a constexpr constructor (In this case,
114 // the condition of constexpr-ness is satisfied because the base class also has
115 // compiler generated constexpr {copy,move} constructors). Note that
116 // placement-new is prohibited in constexpr.
117 template <typename T>
118 struct OptionalStorage : OptionalStorageBase<T> {
119 // This is no trivially {copy,move} constructible case. Other cases are
120 // defined below as specializations.
121
122 // Accessing the members of template base class requires explicit
123 // declaration.
124 using OptionalStorageBase<T>::is_populated_;
125 using OptionalStorageBase<T>::value_;
126 using OptionalStorageBase<T>::Init;
127
128 // Inherit constructors (specifically, the in_place constructor).
129 //using OptionalStorageBase<T>::OptionalStorageBase;
130
131 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
132 template <class... Args>
133 CONSTEXPR explicit OptionalStorage(in_place_t in_place, Args&&... args)
134 : OptionalStorageBase<T>(in_place, std::forward<Args>(args)...) {}
135 #else
136 CONSTEXPR explicit OptionalStorage(in_place_t in_place, const T& _value)
137 : OptionalStorageBase<T>(in_place, _value) {}
138 #endif
139
140 // User defined constructor deletes the default constructor.
141 // Define it explicitly.
142 OptionalStorage() {}
143
144 OptionalStorage(const OptionalStorage& other) {
145 if (other.is_populated_)
146 Init(other.value_);
147 }
148
149 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
150 OptionalStorage(OptionalStorage&& other) NOEXCEPT(std::is_nothrow_move_constructible<T>::value) {
151 if (other.is_populated_)
152 Init(std::move(other.value_));
153 }
154 #endif
155 };
156
157 // Base class to support conditionally usable copy-/move- constructors
158 // and assign operators.
159 template <typename T>
160 class OptionalBase {
161 // This class provides implementation rather than public API, so everything
162 // should be hidden. Often we use composition, but we cannot in this case
163 // because of C++ language restriction.
164 protected:
165 CONSTEXPR OptionalBase() {}
166 CONSTEXPR OptionalBase(const OptionalBase& other) : storage_(other.storage_) {}
167 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
168 CONSTEXPR OptionalBase(OptionalBase&& other) : storage_(std::move(other.storage_)) {}
169
170 template <class... Args>
171 CONSTEXPR explicit OptionalBase(in_place_t, Args&&... args)
172 : storage_(in_place, std::forward<Args>(args)...) {}
173 #else
174 CONSTEXPR explicit OptionalBase(in_place_t, const T& _value)
175 : storage_(in_place, _value) {}
176 #endif
177
178 // Implementation of converting constructors.
179 template <typename U>
180 explicit OptionalBase(const OptionalBase<U>& other) {
181 if (other.storage_.is_populated_)
182 storage_.Init(other.storage_.value_);
183 }
184
185 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
186 template <typename U>
187 explicit OptionalBase(OptionalBase<U>&& other) {
188 if (other.storage_.is_populated_)
189 storage_.Init(std::move(other.storage_.value_));
190 }
191 #endif
192
193 ~OptionalBase() {}
194
195 OptionalBase& operator=(const OptionalBase& other) {
196 CopyAssign(other);
197 return *this;
198 }
199
200 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
201 OptionalBase& operator=(OptionalBase&& other) NOEXCEPT(
202 std::is_nothrow_move_assignable<T>::value &&
203 std::is_nothrow_move_constructible<T>::value) {
204 MoveAssign(std::move(other));
205 return *this;
206 }
207 #endif
208
209 template <typename U>
210 void CopyAssign(const OptionalBase<U>& other) {
211 if (other.storage_.is_populated_)
212 InitOrAssign(other.storage_.value_);
213 else
214 FreeIfNeeded();
215 }
216
217 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
218 template <typename U>
219 void MoveAssign(OptionalBase<U>&& other) {
220 if (other.storage_.is_populated_)
221 InitOrAssign(std::move(other.storage_.value_));
222 else
223 FreeIfNeeded();
224 }
225 #endif
226
227 template <typename U>
228 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
229 void InitOrAssign(U&& value) {
230 if (storage_.is_populated_)
231 storage_.value_ = std::forward<U>(value);
232 else
233 storage_.Init(std::forward<U>(value));
234 }
235 #else
236 void InitOrAssign(const U& value) {
237 if (storage_.is_populated_)
238 storage_.value_ = value;
239 else
240 storage_.Init(value);
241 }
242 #endif
243
244
245 void FreeIfNeeded() {
246 if (!storage_.is_populated_)
247 return;
248 storage_.value_.~T();
249 storage_.is_populated_ = false;
250 }
251
252 // For implementing conversion, allow access to other typed OptionalBase
253 // class.
254 template <typename U>
255 friend class OptionalBase;
256
257 OptionalStorage<T> storage_;
258 };
259
260 // The following {Copy,Move}{Constructible,Assignable} structs are helpers to
261 // implement constructor/assign-operator overloading. Specifically, if T is
262 // is not movable but copyable, Optional<T>'s move constructor should not
263 // participate in overload resolution. This inheritance trick implements that.
264 template <bool is_copy_constructible>
265 struct CopyConstructible {};
266
267 template <>
268 struct CopyConstructible<false> {
269 CONSTEXPR CopyConstructible() {}
270 CopyConstructible& operator=(const CopyConstructible&) { return *this; }
271 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
272 CONSTEXPR CopyConstructible(CopyConstructible&&) {}
273 CopyConstructible& operator=(CopyConstructible&&) { return *this; }
274 #endif
275 private:
276 CONSTEXPR CopyConstructible(const CopyConstructible&);
277 };
278
279 template <bool is_move_constructible>
280 struct MoveConstructible {};
281
282 template <>
283 struct MoveConstructible<false> {
284 CONSTEXPR MoveConstructible() {}
285 CONSTEXPR MoveConstructible(const MoveConstructible&) {}
286 MoveConstructible& operator=(const MoveConstructible&) { return *this; }
287 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
288 MoveConstructible& operator=(MoveConstructible&&) { return *this; }
289 private:
290 CONSTEXPR MoveConstructible(MoveConstructible&&);
291 #endif
292 };
293
294 template <bool is_copy_assignable>
295 struct CopyAssignable {};
296
297 template <>
298 struct CopyAssignable<false> {
299 CONSTEXPR CopyAssignable() {}
300 CONSTEXPR CopyAssignable(const CopyAssignable&) {}
301 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
302 CONSTEXPR CopyAssignable(CopyAssignable&&) {}
303 CopyAssignable& operator=(CopyAssignable&&) { return *this; }
304 #endif
305 private:
306 CopyAssignable& operator=(const CopyAssignable&);
307 };
308
309 template <bool is_move_assignable>
310 struct MoveAssignable {};
311
312 template <>
313 struct MoveAssignable<false> {
314 CONSTEXPR MoveAssignable() {}
315 CONSTEXPR MoveAssignable(const MoveAssignable&) {}
316 MoveAssignable& operator=(const MoveAssignable&) { return *this; }
317 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
318 CONSTEXPR MoveAssignable(MoveAssignable&&) {}
319
320 private:
321 MoveAssignable& operator=(MoveAssignable&&);
322 #endif
323 };
324
325 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
326 // Helper to conditionally enable converting constructors and assign operators.
327 template <typename T, typename U>
328 struct IsConvertibleFromOptional
329 : std::integral_constant<
330 bool,
331 std::is_constructible<T, Optional<U>&>::value ||
332 std::is_constructible<T, const Optional<U>&>::value ||
333 std::is_constructible<T, Optional<U>&&>::value ||
334 std::is_constructible<T, const Optional<U>&&>::value ||
335 std::is_convertible<Optional<U>&, T>::value ||
336 std::is_convertible<const Optional<U>&, T>::value ||
337 std::is_convertible<Optional<U>&&, T>::value ||
338 std::is_convertible<const Optional<U>&&, T>::value> {};
339
340 template <typename T, typename U>
341 struct IsAssignableFromOptional
342 : std::integral_constant<
343 bool,
344 IsConvertibleFromOptional<T, U>::value ||
345 std::is_assignable<T&, Optional<U>&>::value ||
346 std::is_assignable<T&, const Optional<U>&>::value ||
347 std::is_assignable<T&, Optional<U>&&>::value ||
348 std::is_assignable<T&, const Optional<U>&&>::value> {};
349
350 // Forward compatibility for C++17.
351 // Introduce one more deeper nested namespace to avoid leaking using std::swap.
352 namespace swappable_impl {
353 using std::swap;
354
355 struct IsSwappableImpl {
356 // Tests if swap can be called. Check<T&>(0) returns true_type iff swap
357 // is available for T. Otherwise, Check's overload resolution falls back
358 // to Check(...) declared below thanks to SFINAE, so returns false_type.
359 template <typename T>
360 static auto Check(int)
361 -> decltype(swap(std::declval<T>(), std::declval<T>()), std::true_type());
362
363 template <typename T>
364 static std::false_type Check(...);
365 };
366 } // namespace swappable_impl
367 template <typename T>
368 struct IsSwappable : decltype(swappable_impl::IsSwappableImpl::Check<T&>(0)) {};
369 #endif
370 } // namespace internal
371
372 // On Windows, by default, empty-base class optimization does not work,
373 // which means even if the base class is empty struct, it still consumes one
374 // byte for its body. __declspec(empty_bases) enables the optimization.
375 // cf)
376 // https://blogs.msdn.microsoft.com/vcblog/2016/03/30/optimizing-the-layout-of-empty-base-classes-in-vs2015-update-2-3/
377 #if defined(_WIN32)
378 #define OPTIONAL_DECLSPEC_EMPTY_BASES __declspec(empty_bases)
379 #else
380 #define OPTIONAL_DECLSPEC_EMPTY_BASES
381 #endif
382
383 // Optional is a Chromium version of the C++17 optional class:
384 // std::optional documentation:
385 // http://en.cppreference.com/w/cpp/utility/optional
386 // Chromium documentation:
387 // https://chromium.googlesource.com/chromium/src/+/master/docs/optional.md
388 //
389 // These are the differences between the specification and the implementation:
390 // - Constructors do not use 'constexpr' as it is a C++14 extension.
391 // - 'constexpr' might be missing in some places for reasons specified locally.
392 // - No exceptions are thrown, because they are banned from Chromium.
393 // Marked noexcept for only move constructor and move assign operators.
394 // - All the non-members are in the 'base' namespace instead of 'std'.
395 //
396 // Note that T cannot have a constructor T(Optional<T>) etc. Optional<T> checks
397 // T's constructor (specifically via IsConvertibleFromOptional), and in the
398 // check whether T can be constructible from Optional<T>, which is recursive
399 // so it does not work. As of Feb 2018, std::optional C++17 implementation in
400 // both clang and gcc has same limitation. MSVC SFINAE looks to have different
401 // behavior, but anyway it reports an error, too.
402 template <typename T>
403 class OPTIONAL_DECLSPEC_EMPTY_BASES Optional
404 : public internal::OptionalBase<T>
405 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
406 , public internal::CopyConstructible<std::is_copy_constructible<T>::value>,
407 public internal::MoveConstructible<std::is_move_constructible<T>::value>,
408 public internal::CopyAssignable<std::is_copy_constructible<T>::value &&
409 std::is_copy_assignable<T>::value>,
410 public internal::MoveAssignable<std::is_move_constructible<T>::value &&
411 std::is_move_assignable<T>::value>
412 #endif
413 {
414 public:
415 #undef OPTIONAL_DECLSPEC_EMPTY_BASES
416
417 typedef T value_type;
418
419 // Defer default/copy/move constructor implementation to OptionalBase.
420 CONSTEXPR Optional() {}
421 CONSTEXPR Optional(const Optional& other) : internal::OptionalBase<T>(other) {}
422
423 CONSTEXPR Optional(nullopt_t) {} // NOLINT(runtime/explicit)
424
425 // Converting copy constructor. "explicit" only if
426 // std::is_convertible<const U&, T>::value is false. It is implemented by
427 // declaring two almost same constructors, but that condition in enable_if_t
428 // is different, so that either one is chosen, thanks to SFINAE.
429 template <typename U>
430 Optional(const Optional<U>& other) : internal::OptionalBase<T>(other) {}
431
432 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
433 // Converting move constructor. Similar to converting copy constructor,
434 // declaring two (explicit and non-explicit) constructors.
435 template <typename U>
436 Optional(Optional<U>&& other) : internal::OptionalBase<T>(std::move(other)) {}
437
438 template <class... Args>
439 CONSTEXPR explicit Optional(in_place_t, Args&&... args)
440 : internal::OptionalBase<T>(in_place, std::forward<Args>(args)...) {}
441
442 template <class U, class... Args>
443 CONSTEXPR explicit Optional(in_place_t,
444 std::initializer_list<U> il,
445 Args&&... args)
446 : internal::OptionalBase<T>(in_place, il, std::forward<Args>(args)...) {}
447 #else
448 CONSTEXPR explicit Optional(in_place_t, const T& _value)
449 : internal::OptionalBase<T>(in_place, _value) {}
450 template <class U>
451 CONSTEXPR explicit Optional(in_place_t,
452 const U il[],
453 const T& _value)
454 : internal::OptionalBase<T>(in_place, il, _value) {}
455 #endif
456
457 // Forward value constructor. Similar to converting constructors,
458 // conditionally explicit.
459 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
460 template <typename U = value_type>
461 CONSTEXPR Optional(U&& value)
462 : internal::OptionalBase<T>(in_place, std::forward<U>(value)) {}
463 #else
464 template <typename U>
465 CONSTEXPR Optional(const U& value)
466 : internal::OptionalBase<T>(in_place, value) {}
467 #endif
468
469 ~Optional() {}
470
471 // Defer copy-/move- assign operator implementation to OptionalBase.
472 Optional& operator=(const Optional& other) {
473 if (&other == this) {
474 return *this;
475 }
476
477 internal::OptionalBase<T>::operator=(other);
478 return *this;
479 }
480
481 Optional& operator=(nullopt_t) {
482 FreeIfNeeded();
483 return *this;
484 }
485
486 // Perfect-forwarded assignment.
487 template <typename U>
488 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
489 Optional& operator=(U&& value) {
490 InitOrAssign(std::forward<U>(value));
491 return *this;
492 }
493 #else
494 Optional& operator=(const U& value) {
495 InitOrAssign(value);
496 return *this;
497 }
498 #endif
499
500 // Copy assign the state of other.
501 template <typename U>
502 Optional& operator=(const Optional<U>& other) {
503 CopyAssign(other);
504 return *this;
505 }
506
507 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
508 // Move assign the state of other.
509 template <typename U>
510 Optional& operator=(Optional<U>&& other) {
511 MoveAssign(std::move(other));
512 return *this;
513 }
514 #endif
515
516 const T* operator->() const {
517 return &storage_.value_;
518 }
519
520 T* operator->() {
521 return &storage_.value_;
522 }
523
524 const T& operator*() const {
525 return storage_.value_;
526 }
527
528 T& operator*() {
529 return storage_.value_;
530 }
531
532
533 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
534 CONSTEXPR explicit operator bool() const { return storage_.is_populated_; }
535 #else
536 CONSTEXPR operator bool() const { return storage_.is_populated_; }
537 #endif
538
539 CONSTEXPR bool has_value() const { return storage_.is_populated_; }
540
541 #if 1
542 const T& value() const {
543 return storage_.value_;
544 }
545
546 template <class U>
547 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
548 CONSTEXPR T value_or(U&& default_value) const {
549 // TODO(mlamouri): add the following assert when possible:
550 // static_assert(std::is_copy_constructible<T>::value,
551 // "T must be copy constructible");
552 static_assert(std::is_convertible<U, T>::value,
553 "U must be convertible to T");
554 return storage_.is_populated_
555 ? value()
556 : static_cast<T>(std::forward<U>(default_value));
557 }
558 #else
559 CONSTEXPR T value_or(const U& default_value) const {
560 return storage_.is_populated_
561 ? value()
562 : static_cast<T>(default_value);
563 }
564 #endif
565 #else
566 const T& value() const & {
567 return storage_.value_;
568 }
569
570 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
571 const T&& value() const && {
572 return std::move(storage_.value_);
573 }
574 #endif
575
576 template <class U>
577 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
578 CONSTEXPR T value_or(U&& default_value) const & {
579 // TODO(mlamouri): add the following assert when possible:
580 // static_assert(std::is_copy_constructible<T>::value,
581 // "T must be copy constructible");
582 static_assert(std::is_convertible<U, T>::value,
583 "U must be convertible to T");
584 return storage_.is_populated_
585 ? value()
586 : static_cast<T>(std::forward<U>(default_value));
587 }
588 #else
589 CONSTEXPR T value_or(const U& default_value) const & {
590 // TODO(mlamouri): add the following assert when possible:
591 // static_assert(std::is_copy_constructible<T>::value,
592 // "T must be copy constructible");
593 static_assert(std::is_convertible<U, T>::value,
594 "U must be convertible to T");
595 return storage_.is_populated_
596 ? value()
597 : static_cast<T>(default_value);
598 }
599 #endif
600
601 template <class U>
602 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
603 CONSTEXPR T value_or(U&& default_value) const && {
604 // TODO(mlamouri): add the following assert when possible:
605 // static_assert(std::is_move_constructible<T>::value,
606 // "T must be move constructible");
607 static_assert(std::is_convertible<U, T>::value,
608 "U must be convertible to T");
609 return storage_.is_populated_
610 ? std::move(value())
611 : static_cast<T>(std::forward<U>(default_value));
612 }
613 #endif
614 #endif // 1
615
616 void swap(Optional& other) {
617 if (!storage_.is_populated_ && !other.storage_.is_populated_)
618 return;
619
620 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
621 if (storage_.is_populated_ != other.storage_.is_populated_) {
622 if (storage_.is_populated_) {
623 other.storage_.Init(std::move(storage_.value_));
624 FreeIfNeeded();
625 } else {
626 storage_.Init(std::move(other.storage_.value_));
627 other.FreeIfNeeded();
628 }
629 return;
630 }
631 #endif
632 using std::swap;
633 swap(**this, *other);
634 }
635
636 void reset() { FreeIfNeeded(); }
637
638 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
639 template <class... Args>
640 T& emplace(Args&&... args) {
641 FreeIfNeeded();
642 storage_.Init(std::forward<Args>(args)...);
643 return storage_.value_;
644 }
645
646 template <class U, class... Args>
647 T& emplace(std::initializer_list<U> il, Args&&... args) {
648 FreeIfNeeded();
649 storage_.Init(il, std::forward<Args>(args)...);
650 return storage_.value_;
651 }
652 #else
653 T& emplace(const T& _value) {
654 FreeIfNeeded();
655 storage_.Init(_value);
656 return storage_.value_;
657 }
658 template <class U>
659 T& emplace(const U il[], const T& _value) {
660 FreeIfNeeded();
661 storage_.Init(il, _value);
662 return storage_.value_;
663 }
664 #endif
665
666 private:
667 // Accessing template base class's protected member needs explicit
668 // declaration to do so.
669 using internal::OptionalBase<T>::CopyAssign;
670 using internal::OptionalBase<T>::FreeIfNeeded;
671 using internal::OptionalBase<T>::InitOrAssign;
672 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
673 using internal::OptionalBase<T>::MoveAssign;
674 #endif
675 using internal::OptionalBase<T>::storage_;
676 };
677
678 // Here after defines comparation operators. The definition follows
679 // http://en.cppreference.com/w/cpp/utility/optional/operator_cmp
680 // while bool() casting is replaced by has_value() to meet the chromium
681 // style guide.
682 template <class T, class U>
683 bool operator==(const Optional<T>& lhs, const Optional<U>& rhs) {
684 if (lhs.has_value() != rhs.has_value())
685 return false;
686 if (!lhs.has_value())
687 return true;
688 return *lhs == *rhs;
689 }
690
691 template <class T, class U>
692 bool operator!=(const Optional<T>& lhs, const Optional<U>& rhs) {
693 if (lhs.has_value() != rhs.has_value())
694 return true;
695 if (!lhs.has_value())
696 return false;
697 return *lhs != *rhs;
698 }
699
700 template <class T, class U>
701 bool operator<(const Optional<T>& lhs, const Optional<U>& rhs) {
702 if (!rhs.has_value())
703 return false;
704 if (!lhs.has_value())
705 return true;
706 return *lhs < *rhs;
707 }
708
709 template <class T, class U>
710 bool operator<=(const Optional<T>& lhs, const Optional<U>& rhs) {
711 if (!lhs.has_value())
712 return true;
713 if (!rhs.has_value())
714 return false;
715 return *lhs <= *rhs;
716 }
717
718 template <class T, class U>
719 bool operator>(const Optional<T>& lhs, const Optional<U>& rhs) {
720 if (!lhs.has_value())
721 return false;
722 if (!rhs.has_value())
723 return true;
724 return *lhs > *rhs;
725 }
726
727 template <class T, class U>
728 bool operator>=(const Optional<T>& lhs, const Optional<U>& rhs) {
729 if (!rhs.has_value())
730 return true;
731 if (!lhs.has_value())
732 return false;
733 return *lhs >= *rhs;
734 }
735
736 template <class T>
737 CONSTEXPR bool operator==(const Optional<T>& opt, nullopt_t) {
738 return !opt;
739 }
740
741 template <class T>
742 CONSTEXPR bool operator==(nullopt_t, const Optional<T>& opt) {
743 return !opt;
744 }
745
746 template <class T>
747 CONSTEXPR bool operator!=(const Optional<T>& opt, nullopt_t) {
748 return opt.has_value();
749 }
750
751 template <class T>
752 CONSTEXPR bool operator!=(nullopt_t, const Optional<T>& opt) {
753 return opt.has_value();
754 }
755
756 template <class T>
757 CONSTEXPR bool operator<(const Optional<T>& , nullopt_t) {
758 return false;
759 }
760
761 template <class T>
762 CONSTEXPR bool operator<(nullopt_t, const Optional<T>& opt) {
763 return opt.has_value();
764 }
765
766 template <class T>
767 CONSTEXPR bool operator<=(const Optional<T>& opt, nullopt_t) {
768 return !opt;
769 }
770
771 template <class T>
772 CONSTEXPR bool operator<=(nullopt_t, const Optional<T>& ) {
773 return true;
774 }
775
776 template <class T>
777 CONSTEXPR bool operator>(const Optional<T>& opt, nullopt_t) {
778 return opt.has_value();
779 }
780
781 template <class T>
782 CONSTEXPR bool operator>(nullopt_t, const Optional<T>& ) {
783 return false;
784 }
785
786 template <class T>
787 CONSTEXPR bool operator>=(const Optional<T>& , nullopt_t) {
788 return true;
789 }
790
791 template <class T>
792 CONSTEXPR bool operator>=(nullopt_t, const Optional<T>& opt) {
793 return !opt;
794 }
795
796 template <class T, class U>
797 CONSTEXPR bool operator==(const Optional<T>& opt, const U& value) {
798 return opt.has_value() ? *opt == value : false;
799 }
800
801 template <class T, class U>
802 CONSTEXPR bool operator==(const U& value, const Optional<T>& opt) {
803 return opt.has_value() ? value == *opt : false;
804 }
805
806 template <class T, class U>
807 CONSTEXPR bool operator!=(const Optional<T>& opt, const U& value) {
808 return opt.has_value() ? *opt != value : true;
809 }
810
811 template <class T, class U>
812 CONSTEXPR bool operator!=(const U& value, const Optional<T>& opt) {
813 return opt.has_value() ? value != *opt : true;
814 }
815
816 template <class T, class U>
817 CONSTEXPR bool operator<(const Optional<T>& opt, const U& value) {
818 return opt.has_value() ? *opt < value : true;
819 }
820
821 template <class T, class U>
822 CONSTEXPR bool operator<(const U& value, const Optional<T>& opt) {
823 return opt.has_value() ? value < *opt : false;
824 }
825
826 template <class T, class U>
827 CONSTEXPR bool operator<=(const Optional<T>& opt, const U& value) {
828 return opt.has_value() ? *opt <= value : true;
829 }
830
831 template <class T, class U>
832 CONSTEXPR bool operator<=(const U& value, const Optional<T>& opt) {
833 return opt.has_value() ? value <= *opt : false;
834 }
835
836 template <class T, class U>
837 CONSTEXPR bool operator>(const Optional<T>& opt, const U& value) {
838 return opt.has_value() ? *opt > value : false;
839 }
840
841 template <class T, class U>
842 CONSTEXPR bool operator>(const U& value, const Optional<T>& opt) {
843 return opt.has_value() ? value > *opt : true;
844 }
845
846 template <class T, class U>
847 CONSTEXPR bool operator>=(const Optional<T>& opt, const U& value) {
848 return opt.has_value() ? *opt >= value : false;
849 }
850
851 template <class T, class U>
852 CONSTEXPR bool operator>=(const U& value, const Optional<T>& opt) {
853 return opt.has_value() ? value >= *opt : true;
854 }
855
856 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
857 template <class T, class... Args>
858 CONSTEXPR Optional<T> make_optional(Args&&... args) {
859 return Optional<T>(in_place, std::forward<Args>(args)...);
860 }
861
862 template <class T, class U, class... Args>
863 CONSTEXPR Optional<T> make_optional(std::initializer_list<U> il,
864 Args&&... args) {
865 return Optional<T>(in_place, il, std::forward<Args>(args)...);
866 }
867 #endif
868
869 // Partial specialization for a function template is not allowed. Also, it is
870 // not allowed to add overload function to std namespace, while it is allowed
871 // to specialize the template in std. Thus, swap() (kind of) overloading is
872 // defined in base namespace, instead.
873 template <class T>
874 void swap(Optional<T>& lhs, Optional<T>& rhs) {
875 lhs.swap(rhs);
876 }
877
878 } // namespace agora
879
880 #if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
881 namespace std {
882 template <class T>
883 struct hash<agora::Optional<T> > {
884 size_t operator()(const agora::Optional<T>& opt) const {
885 return opt == agora::nullopt ? 0 : std::hash<T>()(*opt);
886 }
887 };
888 } // namespace std
889 #endif
890 #undef CONSTEXPR
891 #undef NOEXCEPT
agora::internal::IsConvertibleFromOptional
Definition: AgoraOptional.h:338
agora::internal::CopyConstructible< false >::CopyConstructible
CONSTEXPR CopyConstructible(CopyConstructible &&)
Definition: AgoraOptional.h:272
agora::internal::OptionalStorage::OptionalStorage
OptionalStorage(const OptionalStorage &other)
Definition: AgoraOptional.h:144
agora::nullopt_t::nullopt_t
CONSTEXPR nullopt_t(int)
Definition: AgoraOptional.h:39
agora::internal::CopyAssignable< false >::CopyAssignable
CONSTEXPR CopyAssignable()
Definition: AgoraOptional.h:299
agora::internal::OptionalStorage::OptionalStorage
CONSTEXPR OptionalStorage(in_place_t in_place, Args &&... args)
Definition: AgoraOptional.h:133
agora::internal::MoveAssignable< false >::MoveAssignable
CONSTEXPR MoveAssignable(MoveAssignable &&)
Definition: AgoraOptional.h:318
agora::internal::OptionalStorageBase::OptionalStorageBase
CONSTEXPR OptionalStorageBase(in_place_t, const T &_value)
Definition: AgoraOptional.h:67
agora::internal::OptionalBase::FreeIfNeeded
void FreeIfNeeded()
Definition: AgoraOptional.h:245
agora::internal::MoveConstructible< false >::MoveConstructible
CONSTEXPR MoveConstructible(const MoveConstructible &)
Definition: AgoraOptional.h:285
agora::internal::OptionalStorageBase::is_populated_
bool is_populated_
Definition: AgoraOptional.h:99
agora::internal::swappable_impl::IsSwappableImpl::Check
static std::false_type Check(...)
agora::internal::OptionalBase::InitOrAssign
void InitOrAssign(const U &value)
Definition: AgoraOptional.h:236
agora::internal::MoveConstructible< false >::MoveConstructible
CONSTEXPR MoveConstructible()
Definition: AgoraOptional.h:284
agora::base::operator!=
bool operator!=(const NtpTime &n1, const NtpTime &n2)
Definition: time_utils.h:82
agora::internal::OptionalStorage::OptionalStorage
CONSTEXPR OptionalStorage(in_place_t in_place, const T &_value)
Definition: AgoraOptional.h:136
agora::internal::OptionalStorage::OptionalStorage
OptionalStorage(OptionalStorage &&other) NOEXCEPT(std
Definition: AgoraOptional.h:150
agora::internal::OptionalBase::OptionalBase
OptionalBase(const OptionalBase< U > &other)
Definition: AgoraOptional.h:180
agora::internal::swappable_impl::IsSwappableImpl
Definition: AgoraOptional.h:355
agora::base::operator==
bool operator==(const NtpTime &n1, const NtpTime &n2)
Definition: time_utils.h:78
agora::internal::CopyConstructible
Definition: AgoraOptional.h:265
agora::internal::OptionalStorageBase::Init
void Init(const T &_value)
Definition: AgoraOptional.h:93
agora::internal::MoveAssignable< false >::MoveAssignable
CONSTEXPR MoveAssignable(const MoveAssignable &)
Definition: AgoraOptional.h:315
agora::internal::MoveConstructible< false >::operator=
MoveConstructible & operator=(const MoveConstructible &)
Definition: AgoraOptional.h:286
agora
Definition: AgoraAtomicOps.h:21
agora::internal::CopyAssignable
Definition: AgoraOptional.h:295
agora::internal::OptionalBase::operator=
OptionalBase & operator=(const OptionalBase &other)
Definition: AgoraOptional.h:195
agora::internal::OptionalBase::MoveAssign
void MoveAssign(OptionalBase< U > &&other)
Definition: AgoraOptional.h:219
agora::internal::CopyAssignable< false >::CopyAssignable
CONSTEXPR CopyAssignable(const CopyAssignable &)
Definition: AgoraOptional.h:300
agora::internal::OptionalStorage::OptionalStorage
OptionalStorage()
Definition: AgoraOptional.h:142
agora::internal::MoveConstructible
Definition: AgoraOptional.h:280
agora::nullopt
const nullopt_t nullopt(0)
agora::in_place_t
Definition: AgoraOptional.h:34
agora::internal::OptionalBase::OptionalBase
CONSTEXPR OptionalBase()
Definition: AgoraOptional.h:165
agora::internal::CopyAssignable< false >::operator=
CopyAssignable & operator=(CopyAssignable &&)
Definition: AgoraOptional.h:303
agora::internal::OptionalBase::~OptionalBase
~OptionalBase()
Definition: AgoraOptional.h:193
agora::internal::MoveAssignable< false >::MoveAssignable
CONSTEXPR MoveAssignable()
Definition: AgoraOptional.h:314
agora::internal::OptionalStorageBase::OptionalStorageBase
CONSTEXPR OptionalStorageBase(in_place_t, Args &&... args)
Definition: AgoraOptional.h:64
agora::internal::OptionalBase::OptionalBase
CONSTEXPR OptionalBase(const OptionalBase &other)
Definition: AgoraOptional.h:166
agora::internal::OptionalStorageBase::~OptionalStorageBase
~OptionalStorageBase()
Definition: AgoraOptional.h:81
agora::internal::MoveConstructible< false >::operator=
MoveConstructible & operator=(MoveConstructible &&)
Definition: AgoraOptional.h:288
agora::internal::OptionalStorageBase::OptionalStorageBase
CONSTEXPR OptionalStorageBase()
Definition: AgoraOptional.h:60
agora::internal::OptionalStorageBase::empty_
char empty_
Definition: AgoraOptional.h:105
agora::internal::CopyConstructible< false >::operator=
CopyConstructible & operator=(CopyConstructible &&)
Definition: AgoraOptional.h:273
agora::internal::MoveAssignable
Definition: AgoraOptional.h:310
std::hash< agora::Optional< T > >::operator()
size_t operator()(const agora::Optional< T > &opt) const
Definition: AgoraOptional.h:884
agora::internal::OptionalBase::OptionalBase
CONSTEXPR OptionalBase(in_place_t, Args &&... args)
Definition: AgoraOptional.h:171
agora::internal::CopyConstructible< false >::operator=
CopyConstructible & operator=(const CopyConstructible &)
Definition: AgoraOptional.h:270
agora::internal::OptionalBase::InitOrAssign
void InitOrAssign(U &&value)
Definition: AgoraOptional.h:229
agora::internal::CopyAssignable< false >::CopyAssignable
CONSTEXPR CopyAssignable(CopyAssignable &&)
Definition: AgoraOptional.h:302
agora::internal::OptionalBase::OptionalBase
OptionalBase(OptionalBase< U > &&other)
Definition: AgoraOptional.h:187
std
Definition: AgoraOptional.h:881
agora::internal::OptionalStorageBase::Init
void Init(Args &&... args)
Definition: AgoraOptional.h:88
agora::internal::OptionalStorage
Definition: AgoraOptional.h:118
agora::in_place
const in_place_t in_place
Definition: AgoraOptional.h:44
agora::internal::OptionalBase
Definition: AgoraOptional.h:160
agora::internal::swappable_impl::IsSwappableImpl::Check
static auto Check(int) -> decltype(swap(std::declval< T >(), std::declval< T >()), std::true_type())
agora::internal::OptionalBase::operator=
OptionalBase & operator=(OptionalBase &&other) NOEXCEPT(std
Definition: AgoraOptional.h:201
agora::nullopt_t
Definition: AgoraOptional.h:38
agora::internal::OptionalBase::storage_
OptionalStorage< T > storage_
Definition: AgoraOptional.h:257
agora::internal::OptionalBase::OptionalBase
CONSTEXPR OptionalBase(in_place_t, const T &_value)
Definition: AgoraOptional.h:174
agora::internal::OptionalBase::OptionalBase
CONSTEXPR OptionalBase(OptionalBase &&other)
Definition: AgoraOptional.h:168
agora::internal::OptionalStorageBase
Definition: AgoraOptional.h:57
agora::internal::OptionalStorageBase::value_
T value_
Definition: AgoraOptional.h:106
agora::internal::MoveAssignable< false >::operator=
MoveAssignable & operator=(const MoveAssignable &)
Definition: AgoraOptional.h:316
agora::internal::CopyConstructible< false >::CopyConstructible
CONSTEXPR CopyConstructible()
Definition: AgoraOptional.h:269
agora::Optional
Definition: AgoraOptional.h:52
agora::internal::IsAssignableFromOptional
Definition: AgoraOptional.h:348
agora::internal::IsSwappable
Definition: AgoraOptional.h:368
agora::internal::OptionalBase::CopyAssign
void CopyAssign(const OptionalBase< U > &other)
Definition: AgoraOptional.h:210