private IDisposable GetDocumentParseCounter(IDocument doc, out int count)
{
VolatileCounter counter;
lock (_pendingParse) {
if (!_pendingParse.TryGetValue(doc, out counter))
{
_pendingParse[doc] = counter = new VolatileCounter();
// Automatically remove counter from the dictionary when it reaches zero.
counter.WaitForChangeToZeroAsync().ContinueWith(t => RemoveDocumentParseCounter(t, doc, counter));
}
var res = counter.Incremented();
count = counter.Count;
return(res);
}
}
private void RemoveDocumentParseCounter(Task t, IDocument doc, VolatileCounter counter)
{
if (t.IsCompleted)
{
lock (_pendingParse) {
if (counter.IsZero)
{
if (_pendingParse.TryGetValue(doc, out var existing) && existing == counter)
{
_pendingParse.Remove(doc);
}
return;
}
}
}
counter.WaitForChangeToZeroAsync().ContinueWith(t2 => RemoveDocumentParseCounter(t, doc, counter));
}