Apple Newton Utilities Podręcznik Użytkownika Pobierz pdf (Strona 843)

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CHAPTER 23

Endpoint Interface

Using the Endpoint Interface 23-15

termination sequence, or an array of items, any one of which will cause the input to

terminate. A termination sequence can be a single character, a string, a number, or

an array of bytes. If you don't want to look for a termination sequence, don't deﬁne

this slot.

For the

'binary data form, you cannot use the endSequence slot to specify a

termination condition.

Note

Note that the system executes byte-by-byte comparisons between

the termination sequence and the input stream. To facilitate this

process, the termination sequence (or elements within the

endSequence array) is converted to a byte or binary format to

speed the comparison. Internally, single characters are converted

to single bytes using the translation table speciﬁed by the

endpoint

encoding slot. Numbers are converted to single bytes;

strings are converted to binary objects. An array of bytes is also

treated as a binary object. For large numbers, you must encode

your number as an array of bytes if there are signiﬁcant digits

beyond the high order byte of the number.

◆

If you want to terminate input based on a transport-level end-of-packet (EOP)

indicator, then you can set the

useEOP slot in the termination frame. This slot

holds a Boolean value specifying whether or not to look for EOP indicators.

Specify this slot only if the input spec

rcvFlags slot includes the kPacket ﬂag.

Moreover, if the

rcvFlags slot includes the kPacket ﬂag and you do not specify

the

termination.useEOP slot, the system effectively sets useEOP to the

default value

true. For more information, see the following section, “Specifying

Flags for Receiving.”

It is not appropriate to specify the

termination slot for data forms other than

'string, 'bytes, and 'binary. The 'char and 'number data forms

automatically terminate after 1 and 4 bytes, respectively. The

'frame data form is

terminated automatically when a complete frame has been received, and the

'template data form terminates when the number of bytes received matches the

typelist specification in the target frame.

To limit the amount of accumulated data in the input buffer, you can deﬁne a

discardAfter slot in the input spec. You can do this only when you have not

speciﬁed a

termination.byteCount slot for 'string and 'bytes data

forms. The

discardAfter slot sets the input buffer size. If the buffer overﬂows,

older bytes are discarded in favor of more recently received bytes.

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