github.com/unicornultrafoundation/go-u2u@v1.0.0-rc1.0.20240205080301-e74a83d3fadc/gossip/execqueue.go (about)

     1  package gossip
     2  
     3  import "sync"
     4  
     5  // execQueue implements a queue that executes function calls in a single thread,
     6  // in the same order as they have been queued.
     7  type execQueue struct {
     8  	mu        sync.Mutex
     9  	cond      *sync.Cond
    10  	funcs     []func()
    11  	closeWait chan struct{}
    12  }
    13  
    14  // newExecQueue creates a new execution queue.
    15  func newExecQueue(capacity int) *execQueue {
    16  	q := &execQueue{funcs: make([]func(), 0, capacity)}
    17  	q.cond = sync.NewCond(&q.mu)
    18  	go q.loop()
    19  	return q
    20  }
    21  
    22  func (q *execQueue) loop() {
    23  	for f := q.waitNext(false); f != nil; f = q.waitNext(true) {
    24  		f()
    25  	}
    26  	close(q.closeWait)
    27  }
    28  
    29  func (q *execQueue) waitNext(drop bool) (f func()) {
    30  	q.mu.Lock()
    31  	if drop && len(q.funcs) > 0 {
    32  		// Remove the function that just executed. We do this here instead of when
    33  		// dequeuing so len(q.funcs) includes the function that is running.
    34  		q.funcs = append(q.funcs[:0], q.funcs[1:]...)
    35  	}
    36  	for !q.isClosed() {
    37  		if len(q.funcs) > 0 {
    38  			f = q.funcs[0]
    39  			break
    40  		}
    41  		q.cond.Wait()
    42  	}
    43  	q.mu.Unlock()
    44  	return f
    45  }
    46  
    47  func (q *execQueue) isClosed() bool {
    48  	return q.closeWait != nil
    49  }
    50  
    51  // canQueue returns true if more function calls can be added to the execution queue.
    52  func (q *execQueue) canQueue() bool {
    53  	q.mu.Lock()
    54  	ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
    55  	q.mu.Unlock()
    56  	return ok
    57  }
    58  
    59  // queue adds a function call to the execution queue. Returns true if successful.
    60  func (q *execQueue) queue(f func()) bool {
    61  	q.mu.Lock()
    62  	ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
    63  	if ok {
    64  		q.funcs = append(q.funcs, f)
    65  		q.cond.Signal()
    66  	}
    67  	q.mu.Unlock()
    68  	return ok
    69  }
    70  
    71  // clear drops all queued functions
    72  func (q *execQueue) clear() {
    73  	q.mu.Lock()
    74  	q.funcs = q.funcs[:0]
    75  	q.mu.Unlock()
    76  }
    77  
    78  // quit stops the exec queue.
    79  // quit waits for the current execution to finish before returning.
    80  func (q *execQueue) quit() {
    81  	q.mu.Lock()
    82  	if !q.isClosed() {
    83  		q.closeWait = make(chan struct{})
    84  		q.cond.Signal()
    85  	}
    86  	q.mu.Unlock()
    87  	<-q.closeWait
    88  }