private async Task <bool> ReadAnotherBatchAsync(CancellationToken cancellationToken)
{
Contract.Requires(m_itemsRemainingInChunk == 0 && m_currentOffsetInChunk == -1 && !m_outOfChunks);
// start reading the next batch
if (await m_chunkIterator.MoveNext(cancellationToken).ConfigureAwait(false))
{ // we got a new chunk !
var chunk = m_chunkIterator.Current;
//note: if the range is empty, we may have an empty chunk, that is equivalent to no chunk
if (chunk != null && chunk.Length > 0)
{
#if DEBUG_RANGE_ITERATOR
Debug.WriteLine("Got a new chunk from page iterator: " + chunk.Length);
#endif
m_chunk = chunk;
m_itemsRemainingInChunk = chunk.Length;
// transform the first one
return(ProcessNextItem());
}
#if DEBUG_RANGE_ITERATOR
Debug.WriteLine("Got empty chunk from page iterator!");
#endif
}
#if DEBUG_RANGE_ITERATOR
Debug.WriteLine("No more chunks from page iterator");
#endif
m_outOfChunks = true;
return(Completed());
}
/// <summary>Run the pump until the inner iterator is done, an error occurs, or the cancellation token is fired</summary>
public async Task PumpAsync(CancellationToken ct)
{
if (m_state != STATE_IDLE)
{
if (m_state >= STATE_FAILED)
{
throw new InvalidOperationException("The iterator pump has already completed once");
}
else
{
throw new InvalidOperationException("The iterator pump is already running");
}
}
try
{
while (!ct.IsCancellationRequested)
{
LogDebug("waiting for next");
m_state = STATE_WAITING_FOR_NEXT;
if (!(await m_iterator.MoveNext(ct).ConfigureAwait(false)))
{
LogDebug("completed");
m_state = STATE_DONE;
m_target.OnCompleted();
return;
}
LogDebug("got item, publishing...");
m_state = STATE_PUBLISHING_TO_TARGET;
await m_target.OnNextAsync(m_iterator.Current, ct).ConfigureAwait(false);
}
// push the cancellation on the queue
OnError(ExceptionDispatchInfo.Capture(new OperationCanceledException(ct)));
// and throw!
}
catch (Exception e)
{
LogDebug("failed... (" + m_state + ") : " + e.Message);
if (m_state == STATE_FAILED)
{ // already signaled the target, just throw
throw;
}
// push the error on the queue, and eat the error
OnError(ExceptionDispatchInfo.Capture(e));
}
finally
{
if (m_state != STATE_FAILED)
{
m_state = STATE_DONE;
}
LogDebug("stopped (" + m_state + ")");
}
}
public Task<bool> MoveNext(CancellationToken cancellationToken)
{
return m_iterator.MoveNext(cancellationToken);
}