Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 842)

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CHAPTER 23

Endpoint Interface

23-14 Using the Endpoint Interface

If you specify the form 'template or 'binary, you also must specify a target

slot in the input spec. The

target slot is a frame used to deﬁne additional

information pertaining to the data form.

If your input form is

'template, then you must set the arglist and typelist

slots in the

target frame. The arglist array contains placeholder data, which

is ﬁlled in with actual data when it is received, and the

typelist array contains

the template’s array of types.

If your input form is

'binary, data is written directly into the binary object that

you specify in the

data slot of the target frame. You can specify a binary object,

virtual binary object, or string. Note that the binary object must be the same size as

the received data; the system will not expand or shrink the object. For information

on virtual binary objects, see Chapter 11, “Data Storage and Retrieval.”

The

offset slot in the target frame allows you to specify an offset in the binary

object at which to write incoming data. For instance, if you want to write the

received data in consecutive blocks in a binary object that already exists, you must

set the

data slot to the binary object, and set the offset slot to the byte offset at

which you want the new data to be written for each block.

Specifying Data Termination Conditions 23

For 'string and 'bytes data forms, you must indicate when the input

terminates by specifying a

termination slot. You can terminate the input on

these conditions:

■ when a certain number of bytes has been received (set the byteCount slot)

■ when a speciﬁc set of characters in the input stream has been found (set the

endSequence slot)

■ when the communication tool returns an end-of-packet indicator (set the

useEOP slot)

Normally with the

'binary data form, the input is terminated when the target

object ﬁlls up. However, you can also use the

termination slot with binary data

to specify a byte count that causes the input to terminate after a certain number of

bytes has been received. This feature is useful when you want to provide user

feedback as a large binary object is being received. Set the

byteCount slot in the

termination frame, and, when the input terminates, repost the input spec with the

target.offset slot offset by the value of the termination.byteCount slot.

If you want to receive data that ends with a particular sequence of data, deﬁne

that sequence in the

endSequence slot in the termination frame. The

endSequence slot allows you to terminate input based on a particular sequence

of incoming data called the termination sequence. You can specify a single

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