Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 846)

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CHAPTER 23

Endpoint Interface

23-18 Using the Endpoint Interface

Handling Normal Termination of Input 23

The InputScript message is sent to the input spec frame when one of the

termination conditions is met. You deﬁne the

InputScript method in the input

spec frame.

The received data is passed as a parameter to the

InputScript method. Another

parameter describes the speciﬁc condition that caused the input to terminate, in

case you had speciﬁed more than one in the input spec.

When the

InputScript method returns, the system automatically posts another

receive request for you using the same input spec as the last one. You can prevent

this by calling

SetInputSpec within the InputScript method. In the

SetInputSpec method, you can set a different input spec, or you can prevent a

new input spec from being posted by setting the

inputSpec parameter to nil. Note

that while the input spec is

nil, incoming data may be lost.

Periodically Sampling Incoming Data 23

You can sample the incoming data without meeting any of the termination

conditions by specifying a

PartialScript method in the input spec. The system

sends the

PartialScript message to the input spec frame periodically, at the

frequency you deﬁne in the

partialFrequency slot in the input spec, as long as

there are one or more bytes of data in the input buffer. The system passes to the

PartialScript method all of the data currently in the input buffer, but the data

is not removed from the input buffer. If you want to remove this data from the input

buffer, you can call the

FlushPartial method.

Note that the sending of

PartialScript messages is controlled by system idle

events and is in no way triggered by receive request completions. The current input

spec remains in effect after the

PartialScript method returns.

You typically would use a

PartialScript method to detect abnormal or

out-of-band data not found by any of the usual input termination conditions.

You can specify

PartialScript methods only for those input data forms that

allow termination conditions —speciﬁcally, the

'string and 'bytes data forms.

To use the

PartialScript method, you must also include the

partialFrequency slot in the input spec. The partialFrequency slot

speciﬁes the frequency, in milliseconds, at which the input data buffer should be

checked. If new data exists in the buffer, the

PartialScript message is sent to

the input spec frame.

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