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Extends the DeferredQueue to allow out-of-order enqueing.

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Thomas Harte 2020-01-29 21:49:52 -05:00
parent baa51853c4
commit 8c4fb0f688
1 changed files with 40 additions and 19 deletions
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53
ClockReceiver/DeferredQueue.hpp
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@ -16,6 +16,8 @@
A DeferredQueue maintains a list of ordered actions and the times at which
they should happen, and divides a total execution period up into the portions
that occur between those actions, triggering each action when it is reached.
This list is efficient only for short queues.
*/
template <typename TimeUnit> class DeferredQueue {
public:
@ -24,13 +26,31 @@ template <typename TimeUnit> class DeferredQueue {
/*!
Schedules @c action to occur in @c delay units of time.
Actions must be scheduled in the order they will occur. It is undefined behaviour
to schedule them out of order.
*/
void defer(TimeUnit delay, const std::function<void(void)> &action) {
// Apply immediately if there's no delay (or a negative delay).
if(delay <= 0) {
action();
return;
}
if(!pending_actions_.empty()) {
// Otherwise enqueue, having subtracted the delay for any preceding events,
// and subtracting from the subsequent, if any.
auto insertion_point = pending_actions_.begin();
while(insertion_point != pending_actions_.end() && insertion_point->delay < delay) {
delay -= insertion_point->delay;
++insertion_point;
}
if(insertion_point != pending_actions_.end()) {
insertion_point->delay -= delay;
}
pending_actions_.emplace(insertion_point, delay, action);
} else {
pending_actions_.emplace_back(delay, action);
}
}
/*!
Runs for @c length units of time.
@ -47,22 +67,23 @@ template <typename TimeUnit> class DeferredQueue {
}
// Divide the time to run according to the pending actions.
while(length > TimeUnit(0)) {
TimeUnit next_period = pending_actions_.empty() ? length : std::min(length, pending_actions_[0].delay);
target_(next_period);
length -= next_period;
off_t performances = 0;
for(auto &action: pending_actions_) {
action.delay -= next_period;
if(!action.delay) {
action.action();
++performances;
auto erase_iterator = pending_actions_.begin();
while(erase_iterator != pending_actions_.end()) {
erase_iterator->delay -= length;
if(erase_iterator->delay <= TimeUnit(0)) {
target_(length + erase_iterator->delay);
length = -erase_iterator->delay;
erase_iterator->action();
++erase_iterator;
} else {
break;
}
}
if(performances) {
pending_actions_.erase(pending_actions_.begin(), pending_actions_.begin() + performances);
if(erase_iterator != pending_actions_.begin()) {
pending_actions_.erase(pending_actions_.begin(), erase_iterator);
}
if(length != TimeUnit(0)) {
target_(length);
}
}