protected override async Task <bool> OnNextAsync(CancellationToken cancellationToken)
{
// if we are in a batch, iterate over it
// if not, wait for the next batch
while (!cancellationToken.IsCancellationRequested)
{
if (m_batch == null)
{
if (!await m_iterator.MoveNextAsync(cancellationToken).ConfigureAwait(false))
{ // inner completed
return(Completed());
}
if (cancellationToken.IsCancellationRequested)
{
break;
}
IEnumerable <TResult> sequence;
if (!m_selector.Async)
{
sequence = m_selector.Invoke(m_iterator.Current);
}
else
{
sequence = await m_selector.InvokeAsync(m_iterator.Current, cancellationToken).ConfigureAwait(false);
}
if (sequence == null)
{
throw new InvalidOperationException("The inner sequence returned a null collection");
}
m_batch = sequence.GetEnumerator();
Contract.Assert(m_batch != null);
}
if (!m_batch.MoveNext())
{ // the current batch is exhausted, move to the next
m_batch.Dispose();
m_batch = null;
continue;
}
return(Publish(m_batch.Current));
}
return(Canceled(cancellationToken));
}
protected override async Task <bool> OnNextAsync(CancellationToken cancellationToken)
{
if (m_remaining != null && m_remaining.Value <= 0)
{ // reached limit!
return(Completed());
}
while (!cancellationToken.IsCancellationRequested)
{
if (!await m_iterator.MoveNext(cancellationToken).ConfigureAwait(false))
{ // completed
return(Completed());
}
if (cancellationToken.IsCancellationRequested)
{
break;
}
#region Filtering...
TSource current = m_iterator.Current;
if (m_filter != null)
{
if (!m_filter.Async)
{
if (!m_filter.Invoke(current))
{
continue;
}
}
else
{
if (!await m_filter.InvokeAsync(current, cancellationToken).ConfigureAwait(false))
{
continue;
}
}
}
#endregion
#region Skipping...
if (m_skipped != null)
{
if (m_skipped.Value > 0)
{ // skip this result
m_skipped = m_skipped.Value - 1;
continue;
}
// we can now start outputing results...
m_skipped = null;
}
#endregion
#region Transforming...
TResult result;
if (!m_transform.Async)
{
result = m_transform.Invoke(current);
}
else
{
result = await m_transform.InvokeAsync(current, cancellationToken).ConfigureAwait(false);
}
#endregion
#region Publishing...
if (m_remaining != null)
{ // decrement remaining quota
m_remaining = m_remaining.Value - 1;
}
return(Publish(result));
#endregion
}
return(Canceled(cancellationToken));
}