/// <summary>
/// Returns an asynchronous stream over `TagEvent`s generated by `reader` with an optional timeout
/// </summary>
public static async IAsyncEnumerable <TagEvent> EventStream(
ReaderManager reader,
TimeSpan?timeout = null,
[EnumeratorCancellation] CancellationToken enumCancellation = default
)
{
CancellationTokenSource timeoutTokenSource = null;
CancellationTokenSource combinedTokenSource = null;
if (timeout != null)
{
timeoutTokenSource = new CancellationTokenSource();
timeoutTokenSource.CancelAfter(timeout.Value);
combinedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(enumCancellation, timeoutTokenSource.Token);
}
var cancellationToken = combinedTokenSource?.Token ?? enumCancellation;
var buffer = new BufferBlock <TagEvent>();
var tagDataHandler = new TagDataListener(tagData => buffer.Post(tagData));
try
{
reader.reader.OnRoAccessReportReceived += tagDataHandler.OnRoAccessReport;
while (!cancellationToken.IsCancellationRequested)
{
TagEvent tagEvent;
try
{
tagEvent = await buffer.ReceiveAsync(cancellationToken);
}
catch (TaskCanceledException)
{
break;
}
yield return(tagEvent);
}
}
finally
{
reader.reader.OnRoAccessReportReceived -= tagDataHandler.OnRoAccessReport;
timeoutTokenSource?.Dispose();
combinedTokenSource?.Dispose();
}
}
/// Scan for tags using an inventory command, returning a dictionary mapping tagIds
/// to scan results.
///
/// Returns results after all target tags have been read, or the timeout has elapsed
private async Task <Dictionary <ushort, TagMetadata> > ScanTags(ushort[] tags, TimeSpan timeout)
{
this.progress.Info($"Scanning for: {TagString(tags)}\n");
var stopwatch = new Stopwatch();
stopwatch.Start();
var targetTags = new HashSet <ushort>(tags);
var scanResults = new Dictionary <ushort, (TagEvent latest, int count)>();
// Start an inventory command and read tag events from the event stream
_ = this.reader.Inventory(TimeSpan.FromSeconds(1));
await foreach (var tagEvent in TagDataListener.EventStream(this.reader, timeout))
{
if (targetTags.Contains(tagEvent.TagId))
{
var count = 0;
if (scanResults.ContainsKey(tagEvent.TagId))
{
count = scanResults[tagEvent.TagId].count;
}
scanResults[tagEvent.TagId] = (tagEvent, count + 1);
}
if (scanResults.Count == tags.Length)
{
// Received data from every target tag at least once
break;
}
}
var duration = stopwatch.Elapsed.TotalSeconds;
this.progress.Info($"Found {TagString(scanResults.Keys)} in {duration} seconds\n");
return(TagMetadata.FromScanResults(scanResults, duration));
}
