public IEnumerable <Task <Possible <StrongFingerprint, Failure> > > EnumerateStrongFingerprints(WeakFingerprintHash weak, UrgencyHint urgencyHint, Guid activityId)
{
Contract.Requires(!IsClosed);
using (var counter = m_counters.EnumerateStrongFingerprintsCounter())
{
using (var eventing = new EnumerateStrongFingerprintsActivity(BasicFilesystemCache.EventSource, activityId, this))
{
eventing.Start(weak, urgencyHint);
// It's possible the cache could encounter an IO error when attempting to enumerate the fingerprints.
// This shouldn't be a fatal error. we just want to catch and record it, then continue on.
// Due to the use of yield a foreach loop can't be used here while still handling the error,
// so the enumation must be done manually.
using (var enumerator = m_cache.EnumerateStrongFingerprints(weak).GetEnumerator())
{
while (true)
{
StrongFingerprint strong = null;
try
{
if (!enumerator.MoveNext())
{
break;
}
strong = enumerator.Current;
}
catch (IOException ex)
{
eventing.StopFailure(new StrongFingerprintEnumerationFailure(m_cache.CacheId, weak, ex));
yield break;
}
catch (UnauthorizedAccessException ex)
{
eventing.StopFailure(new StrongFingerprintEnumerationFailure(m_cache.CacheId, weak, ex));
yield break;
}
counter.YieldReturn();
yield return(Task.FromResult(new Possible <StrongFingerprint, Failure>(strong)));
}
}
eventing.Stop();
}
}
}