/// <summary>
/// Attempts to enqueue an item.
/// </summary>
/// <param name="item">The item to enqueue.</param>
/// <param name="cancellationToken">A cancellation token that can be used to abort the enqueue operation. If <paramref name="abort"/> is not <c>null</c>, then this token must include signals from the <paramref name="abort"/> object.</param>
/// <param name="abort">A synchronization object used to cancel related enqueue operations. May be <c>null</c> if this is the only enqueue operation.</param>
internal async Task <AsyncProducerConsumerQueue <T> > TryEnqueueAsync(T item, CancellationToken cancellationToken, TaskCompletionSource abort)
{
try
{
using (var combinedToken = CancellationTokenHelpers.Normalize(_completed.Token, cancellationToken))
using (await _mutex.LockAsync().ConfigureAwait(false))
{
// Wait for the queue to be not full.
while (Full)
{
await _notFull.WaitAsync(combinedToken.Token).ConfigureAwait(false);
}
// Explicitly check whether the queue has been marked complete to prevent a race condition where notFull is signalled at the same time the queue is marked complete.
if (_completed.IsCancellationRequested)
{
return(null);
}
// Set the abort signal. If another queue has already set the abort signal, then abort.
if (abort != null && !abort.TrySetCanceled())
{
return(null);
}
_queue.Enqueue(item);
_completedOrNotEmpty.Notify();
return(this);
}
}
catch (OperationCanceledException)
{
return(null);
}
}
/// <summary>
/// Attempts to enqueue an item. This method may block the calling thread.
/// </summary>
/// <param name="item">The item to enqueue.</param>
/// <param name="cancellationToken">A cancellation token that can be used to abort the enqueue operation.</param>
internal AsyncProducerConsumerQueue <T> DoTryEnqueue(T item, CancellationToken cancellationToken)
{
try
{
using (var combinedToken = CancellationTokenHelpers.Normalize(_completed.Token, cancellationToken))
using (_mutex.Lock())
{
// Wait for the queue to be not full.
while (Full)
{
_notFull.Wait(combinedToken.Token);
}
// Explicitly check whether the queue has been marked complete to prevent a race condition where notFull is signalled at the same time the queue is marked complete.
if (_completed.IsCancellationRequested)
{
return(null);
}
_queue.Enqueue(item);
_completedOrNotEmpty.Notify();
return(this);
}
}
catch (OperationCanceledException)
{
return(null);
}
}
/// <summary>
/// Attempts to enqueue an item to any of a number of producer/consumer queues. Returns the producer/consumer queue that received the item. Returns <c>null</c> if all producer/consumer queues have completed adding.
/// </summary>
/// <param name="queues">The producer/consumer queues.</param>
/// <param name="item">The item to enqueue.</param>
/// <param name="cancellationToken">A cancellation token that can be used to abort the enqueue operation.</param>
/// <returns>The producer/consumer queue that received the item.</returns>
public static async Task <AsyncProducerConsumerQueue <T> > TryEnqueueToAnyAsync <T>(this IEnumerable <AsyncProducerConsumerQueue <T> > queues, T item, CancellationToken cancellationToken)
{
var abort = new TaskCompletionSource();
using (var abortCancellationToken = CancellationTokenHelpers.FromTask(abort.Task))
using (var combinedToken = CancellationTokenHelpers.Normalize(abortCancellationToken.Token, cancellationToken))
{
var token = combinedToken.Token;
var tasks = queues.Select(q => q.TryEnqueueAsync(item, token, abort));
var results = await TaskShim.WhenAll(tasks).ConfigureAwait(false);
var ret = results.FirstOrDefault(x => x != null);
if (ret == null)
{
cancellationToken.ThrowIfCancellationRequested();
}
return(ret);
}
}
/// <summary>
/// Attempts to take an item from any of a number of producer/consumer collections. The operation "fails" if all the producer/consumer collections have completed adding and are empty, or if any take operation on an underlying collection fails.
/// </summary>
/// <param name="collections">The producer/consumer collections.</param>
/// <param name="cancellationToken">A cancellation token that can be used to abort the take operation.</param>
public static async Task <AsyncCollection <T> .TakeResult> TryTakeFromAnyAsync <T>(this IEnumerable <AsyncCollection <T> > collections, CancellationToken cancellationToken)
{
var abort = new TaskCompletionSource();
using (var abortCancellationToken = CancellationTokenHelpers.FromTask(abort.Task))
using (var combinedToken = CancellationTokenHelpers.Normalize(abortCancellationToken.Token, cancellationToken))
{
var token = combinedToken.Token;
var tasks = collections.Select(q => q.TryTakeAsync(token, abort));
var results = await TaskShim.WhenAll(tasks).ConfigureAwait(false);
var result = results.FirstOrDefault(x => x.Success);
if (result != null)
{
return(result);
}
cancellationToken.ThrowIfCancellationRequested();
return(AsyncCollection <T> .FalseResult);
}
}
