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Optimize base::weak_ptr.

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This commit is contained in:
John Preston 2018-09-29 09:42:42 +03:00
parent 4f43f1dd0f
commit 1c79f85d00
1 changed files with 28 additions and 26 deletions
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54
Telegram/SourceFiles/base/weak_ptr.h
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@ -14,8 +14,11 @@ namespace base {
namespace details {
struct alive_tracker {
explicit alive_tracker(const void *value) : value(value) {
}
std::atomic<int> counter = 1;
std::atomic<bool> dead = false;
std::atomic<const void*> value;
};
inline alive_tracker *check_and_increment(alive_tracker *tracker) noexcept {
@ -54,7 +57,7 @@ public:
~has_weak_ptr() {
if (auto alive = _alive.load()) {
alive->dead.store(true);
alive->value.store(nullptr);
details::decrement(alive);
}
}
@ -66,7 +69,8 @@ private:
details::alive_tracker *incrementAliveTracker() const {
auto current = _alive.load();
if (!current) {
auto alive = std::make_unique<details::alive_tracker>();
auto alive = std::make_unique<details::alive_tracker>(
static_cast<const void*>(this));
if (_alive.compare_exchange_strong(current, alive.get())) {
return alive.release();
}
@ -84,8 +88,7 @@ class weak_ptr {
public:
weak_ptr() = default;
weak_ptr(T *value)
: _alive(value ? value->incrementAliveTracker() : nullptr)
, _value(value) {
: _alive(value ? value->incrementAliveTracker() : nullptr) {
}
weak_ptr(const std::unique_ptr<T> &value)
: weak_ptr(value.get()) {
@ -97,28 +100,24 @@ public:
: weak_ptr(value.lock().get()) {
}
weak_ptr(const weak_ptr &other) noexcept
: _alive(details::check_and_increment(other._alive))
, _value(other._value) {
: _alive(details::check_and_increment(other._alive)) {
}
weak_ptr(weak_ptr &&other) noexcept
: _alive(std::exchange(other._alive, nullptr))
, _value(std::exchange(other._value, nullptr)) {
: _alive(std::exchange(other._alive, nullptr)) {
}
template <
typename Other,
typename = std::enable_if_t<
std::is_base_of_v<T, Other> && !std::is_same_v<T, Other>>>
weak_ptr(const weak_ptr<Other> &other) noexcept
: _alive(details::check_and_increment(other._alive))
, _value(other._value) {
: _alive(details::check_and_increment(other._alive)) {
}
template <
typename Other,
typename = std::enable_if_t<
std::is_base_of_v<T, Other> && !std::is_same_v<T, Other>>>
weak_ptr(weak_ptr<Other> &&other) noexcept
: _alive(std::exchange(other._alive, nullptr))
, _value(std::exchange(other._value, nullptr)) {
: _alive(std::exchange(other._alive, nullptr)) {
}
weak_ptr &operator=(T *value) {
@ -138,18 +137,16 @@ public:
return *this;
}
weak_ptr &operator=(const weak_ptr &other) noexcept {
if (_value != other._value) {
if (_alive != other._alive) {
destroy();
_alive = details::check_and_increment(other._alive);
_value = other._value;
}
return *this;
}
weak_ptr &operator=(weak_ptr &&other) noexcept {
if (_value != other._value) {
if (_alive != other._alive) {
destroy();
_alive = std::exchange(other._alive, nullptr);
_value = std::exchange(other._value, nullptr);
}
return *this;
}
@ -158,10 +155,9 @@ public:
typename = std::enable_if_t<
std::is_base_of_v<T, Other> && !std::is_same_v<T, Other>>>
weak_ptr &operator=(const weak_ptr<Other> &other) noexcept {
if (_value != other._value) {
if (_alive != other._alive) {
destroy();
_alive = details::check_and_increment(other._alive);
_value = other._value;
}
return *this;
}
@ -170,10 +166,9 @@ public:
typename = std::enable_if_t<
std::is_base_of_v<T, Other> && !std::is_same_v<T, Other>>>
weak_ptr &operator=(weak_ptr<Other> &&other) noexcept {
if (_value != other._value) {
if (_alive != other._alive) {
destroy();
_alive = std::exchange(other._alive, nullptr);
_value = std::exchange(other._value, nullptr);
}
return *this;
}
@ -183,10 +178,19 @@ public:
}
T *get() const noexcept {
return (_alive && !_alive->dead) ? _value : nullptr;
if constexpr (std::is_const_v<T>) {
return _alive
? static_cast<T*>(_alive->value.load())
: nullptr;
} else {
return _alive
? const_cast<T*>(
static_cast<const T*>(_alive->value.load()))
: nullptr;
}
}
explicit operator bool() const noexcept {
return (_alive && !_alive->dead);
return (_alive && _alive->value);
}
T &operator*() const noexcept {
return *get();
@ -196,10 +200,9 @@ public:
}
void reset(T *value = nullptr) {
if (_value != value) {
if (get() != value) {
destroy();
_alive = value ? value->incrementAliveTracker() : nullptr;
_value = value;
}
}
@ -211,7 +214,6 @@ private:
}
details::alive_tracker *_alive = nullptr;
T *_value = nullptr;
template <typename Other>
friend class weak_ptr;