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#ifndef OBSERVER_LIST_HH
#define OBSERVER_LIST_HH
#include "common.hh"
#include <algorithm>
#include <vector>
template<typename T>
class ObserverList {
public:
class iterator {
public:
iterator()
: list_(nullptr), index_(0), end_(0) {}
~iterator() {
if (list_)
list_->release();
}
iterator(iterator const& it)
: list_(it.list_), index_(it.index_), end_(it.end_) {
if (list_) {
list_->aquire();
while (index_ < end_ && !list_->observers_[index_])
++index_;
}
}
iterator& operator=(iterator const& it) {
if (list_ != it.list_) {
if (list_)
list_->release();
list_ = it.list_;
if (list_)
list_->aquire();
}
index_ = it.index_;
end_ = it.end_;
return *this;
}
explicit operator bool() {
return index_ < end_;
}
T& operator*() {
return *list_->observers_[index_];
}
T* operator->() {
return list_->observers_[index_];
}
iterator operator++(int) {
iterator ret(*this);
++(*this);
return ret;
}
iterator& operator++() {
if (index_ < end_) {
do {
++index_;
} while (index_ < end_ && !list_->observers_[index_]);
}
return *this;
}
private:
friend class ObserverList;
iterator(ObserverList* list, size_t index, size_t end)
: list_(list), index_(index), end_(end) {
list_->aquire();
while (index_ < end_ && !list_->observers_[index_])
++index_;
}
ObserverList* list_;
size_t index_;
size_t end_;
};
ObserverList() = default;
~ObserverList() {
assert(active_ == 0);
}
bool empty() const {
return observers_.empty();
}
void add(T* observer) {
assert(std::find(observers_.begin(), observers_.end(), observer)
== observers_.end());
observers_.push_back(observer);
}
void remove(T* observer) {
auto it = std::find(observers_.begin(), observers_.end(), observer);
if (it != observers_.end()) {
if (active_) {
*it = nullptr;
++deleted_;
} else {
observers_.erase(it);
}
} else {
assert(false);
}
}
iterator notify() {
return iterator(this, 0, observers_.size());
}
private:
void aquire() {
++active_;
}
void release() {
assert(active_ > 0);
--active_;
if (active_ == 0 && deleted_)
cleanup();
}
void cleanup() {
size_t i = observers_.size();
while (deleted_ && i > 0) {
--i;
if (!observers_[i]) {
--deleted_;
observers_.erase(observers_.begin() + i);
}
}
assert(deleted_ == 0);
}
std::vector<T*> observers_;
unsigned active_{0};
unsigned deleted_{0};
};
#endif // OBSERVER_LIST_HH
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