// Peeks message (first/application-specified correlationId) from status queue
private Message PeekFromStatusQueue(string correlationId)
{
string statusQueuePath = "FormatName:DIRECT=OS:" + this.queue.MachineName + @"\" + Parameters.STATUS_QUEUE;
MessageQueue statusQueue = new MessageQueue(statusQueuePath);
statusQueue.Formatter = new BinaryMessageFormatter();
statusQueue.MessageReadPropertyFilter.AppSpecific = true;
statusQueue.MessageReadPropertyFilter.CorrelationId = true;
Message statusMessage = null;
try
{
if (correlationId == null)
{
statusMessage = statusQueue.PeekByLookupId(MessageLookupAction.First, 0);
}
else
{
statusMessage = statusQueue.PeekByCorrelationId(correlationId, TimeSpan.Zero);
}
}
catch (MessageQueueException)
{
// If status queue is empty, peek will throw MessageQueueException
throw new InvalidOperationException();
}
statusQueue.Dispose();
statusQueue.Close();
return statusMessage;
}
// throws exception if hole is found in the large message sequence
// If not found, message is moved to the subqueue if moveMessage flag is true
private int CheckReceiveMessage(MessageQueue subQueue, string correlationId, string largeSequenceId)
{
LargeMessageProperties largeMessageProperties = null;
IMessageFormatter formatter = new BinaryMessageFormatter();
// If AppSpecific is zero, it is first fragment
if (this.message.AppSpecific != Parameters.HEADER_FRAGMENT_ID)
{
try
{
Message lastMessageInSubQueue = subQueue.PeekByLookupId(MessageLookupAction.Last, 0);
lastMessageInSubQueue.Formatter = formatter;
if (this.message.AppSpecific == Parameters.TRAILER_FRAGMENT_ID)
{
// If message in main queue is a trailer fragment, check if the last message in subqueue
// corresponds to the last expected message with application data
largeMessageProperties = this.GetLargeMessageHeader(this.message);
if (lastMessageInSubQueue.AppSpecific != largeMessageProperties.FragmentCount)
{
// Fragment(s) in the middle (before the trailer fragment) missing, send delete status message
this.SendToStatusQueue(correlationId, (int)Parameters.ReceiveAction.Delete, largeSequenceId);
return (int)Parameters.ReceiveAction.Restart;
}
}
else if (((this.message.AppSpecific != (lastMessageInSubQueue.AppSpecific + 1)) &&
(lastMessageInSubQueue.AppSpecific != Parameters.HEADER_FRAGMENT_ID)) ||
((this.message.AppSpecific != 1) && (lastMessageInSubQueue.AppSpecific == Parameters.HEADER_FRAGMENT_ID)))
{
// Fragment(s) in the middle missing, send delete status message
this.SendToStatusQueue(correlationId, (int)Parameters.ReceiveAction.Delete, largeSequenceId);
return (int)Parameters.ReceiveAction.Restart;
}
}
catch (InvalidOperationException)
{
// No message in subqueue, send delete status message
this.SendToStatusQueue(correlationId, (int)Parameters.ReceiveAction.Delete, largeSequenceId);
return (int)Parameters.ReceiveAction.Restart;
}
}
else
{
largeMessageProperties = this.GetLargeMessageHeader(this.message);
}
// Move message to sub-queue
try
{
NativeMethods.MoveLargeMessage(this.queue, subQueue.FormatName, this.message.LookupId);
}
catch (InvalidOperationException)
{
// look for another large message sequence
return ((int)Parameters.ReceiveAction.Restart);
}
if (this.message.AppSpecific == Parameters.TRAILER_FRAGMENT_ID)
{
// All fragments available in subqueue
return ((int)Parameters.ReceiveAction.Complete);
}
// More fragments are expected
return ((int)Parameters.ReceiveAction.Pending);
}
// this.message is set to the first message in queue that is not same as large message id
// If queue is empty, peek will throw MessageQueueException
private void GetNextMessageSequenceInQueue(MessageQueue mq, string largeSequenceId)
{
int nextSequenceFlag = 0;
try
{
if (this.message == null)
{
this.message = mq.PeekByLookupId(MessageLookupAction.First, 0);
nextSequenceFlag = 1;
}
else
{
do
{
string currentLargeSequenceId = null;
long prevLookupId = this.message.LookupId;
this.message = mq.PeekByLookupId(MessageLookupAction.Next, prevLookupId);
if (this.message.AppSpecific == Parameters.HEADER_FRAGMENT_ID)
{
currentLargeSequenceId = this.message.Id;
}
else
{
currentLargeSequenceId = this.message.CorrelationId;
}
nextSequenceFlag = String.Compare(currentLargeSequenceId, 0, largeSequenceId, 0, currentLargeSequenceId.Length, StringComparison.OrdinalIgnoreCase);
} while (nextSequenceFlag == 0);
}
}
catch (MessageQueueException)
{
throw new InvalidOperationException();
}
}
// Returns true if the large message sequence in the sub-queue is completed
private bool CheckCompleteMessage(MessageQueue subQueue)
{
Message firstMessageInSubQueue = subQueue.PeekByLookupId(MessageLookupAction.First, 0);
firstMessageInSubQueue.Formatter = new BinaryMessageFormatter();
if (firstMessageInSubQueue.AppSpecific == Parameters.HEADER_FRAGMENT_ID)
{
Message lastMessageInSubQueue = subQueue.PeekByLookupId(MessageLookupAction.Last, 0);
if (lastMessageInSubQueue.AppSpecific == Parameters.TRAILER_FRAGMENT_ID)
{
return true;
}
}
return false;
}