Apple Newton Programmer’s Newton 2.0 (for Newton 2.0) - Manual (Page 842)

C H A P T E R 2 3
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