Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 850)

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CHAPTER 23

Endpoint Interface

23-22 Using the Endpoint Interface

The cancellation itself can be invoked asynchronously or synchronously, and is

handled differently in the system depending on how it’s done. The details are

explained in the following subsections.

Asynchronous Cancellation 23

Cancellation can be invoked asynchronously in the following ways:

■ calling the Cancel method asynchronously, or calling the Disconnect

method asynchronously with the

cancelPending parameter set to true

■ having a time-out expire for an asynchronous request

When cancellation is invoked asynchronously, the system ﬁrst cancels all pending

asynchronous requests. This means that the

CompletionScript message is sent

to the callback spec for each of these requests, and the

CompletionScript

result parameter is set to –16005.

Note

When calling Cancel asynchronously, it is possible that

additional asynchronous requests might be queued (by a

CompletionScript method) after the Cancel request is

queued but before it is executed. These additional requests will

fail with error –36003 since they will be processed after the

cancel process begins. In fact, any endpoint request that is made

while a cancel is in progress will fail with error –36003.

◆

Next, the cancel request itself completes by sending the CompletionScript

message. This message is sent to the callback spec passed to the

Cancel (or

Disconnect) method. Or, if the cancellation was invoked as the result of a

time-out expiration, the

CompletionScript message is sent to the callback spec

of whatever method timed out (or to the input spec, if input was in progress).

Finally, any pending synchronous request is canceled by throwing an exception that

contains error code –16005.

Synchronous Cancellation 23

Cancellation can be invoked synchronously in the following ways:

■ calling the Cancel method synchronously, or calling the Disconnect method

synchronously with the

cancelPending parameter set to true

■ having a time-out expire for a synchronous request

When cancellation is invoked synchronously, the system ﬁrst cancels any pending

asynchronous requests. This means that the

CompletionScript message is sent

to the callback spec for each of these requests, and the

CompletionScript

result parameter is set to –16005.

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Apple Newton Utilities Guide de l'utilisateur Page 850

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