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CHAPTER 22

Transport Interface

22-12 Using the Transport Interface

Handling Requests When the Transport Is Active 22

While the transport is actively sending or receiving data in the background, the user

might request another send or receive operation from the In/Out Box. One way to

handle such requests is to queue them up and append them to the current communi-

cation transaction or to start another connection when the transport is ﬁnished.

You can use the transport method

QueueRequest to queue up requests for

sending or receiving, if the transport already has an active communication session

in progress. Call

QueueRequest from the SendRequest or ReceiveRequest

method, whichever one you receive as a result of a user request.

Depending on how you call it, you can make

QueueRequest append the new

request to a request in progress or start another connection when the current

request is ﬁnished. To append the new request to one in progress, for the ﬁrst

parameter, specify the request frame of a request already in progress. A request

frame is the frame passed to

SendRequest or ReceiveRequest to begin the

request in progress. The second parameter is the new request frame.

The following is an example of a

SendRequest method in which

QueueRequest is called to append the new request to the one in progress.

// SendRequest method

func (newRequest)

begin

if status <> 'idle then // check if I’m active

// append to current request

:QueueRequest(currentRequest, newRequest);

else

// do a normal send here

end,

When a new request is appended to an in-progress request, items from the new

request are returned from the

ItemRequest method after all items from the

in-progress request are exhausted. In this way, new items are sent as part of the

current communication session.

To queue a new request so that the transport ﬁnishes its current transaction before

beginning a new one, specify a symbol for the ﬁrst parameter of

QueueRequest.

The symbol should be the name of a method that you want the system to call when

the transport state returns to idle. Usually this is another

SendRequest or

ReceiveRequest method. The following is an example of a SendRequest

method in which

QueueRequest is called to defer a new request until the

transport returns to the idle state.

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Apple Newton Utilities Guía de usuario Pagina 800

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