| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
Arguments: stream blocking action
Performs record-oriented operations on
stream. Simple-streams have a record-end slot
that normally has a nil
value. When the slot
is set to a numeric value, it is interpreted by the read or write
operation as the location in the buffer of the record-end or
break. device-finish-record
is then called, and the return value is interpreted based on the
action specified and the value of
blocking. action is typically one of
:input
, :output
, or
:prime-input
(see the discussion on
"priming" in the second bulleted paragraph below).
blocking is a boolean which specifies whether
or not the method should block during its
operation, or else return immediately.
The return value is either true, meaning success,
or nil
, meaning failure. The interpretation
of the nil
return depends on the value
of the blocking argument; if nil
, then device-finish-record failed to
complete the requested task. If blocking was
true, then a return of nil
means an eof was encountered (if
action was :input
or
:prime-input
), or an error occurred (if
action was :output
).
Allegro CL offers calls to device-finish-record under the following circumstances:
string-output-simple-stream
: An
xp-simple-stream is a subclass of string-output-stream, and thus has
character orientation. The pretty printer sets the record-end slot of
the xp-simple-stream to the value of *print-right-margin*
. Then, when that many
characters have been output, the device-finish-record
method is called which makes formatting decisions about how and where
the accumulated output will be sent to the base stream. dual-channel-simple-stream
A socket-simple-stream that might do "chunking" sets the
record-end slot to a true value while input
chunking is occurring (output-chunking does not use
record-orientation, but writes chunks out whenever the buffer becomes
full or when force-output or
finish-output is called). A special value indicates a
"priming", and device-finish-record is
called with :prime-input
as action just before the
first character is read. This call causes chunking to temporarily be
suspended: bytes are read until the #\return #\linefeed combination,
and the bytes read indicate the chunk length. The record-end slot is
set based on the chunk length. When the chunk length is reached,
device-finish-record is called with
:input
action, which reads bytes and expects a
terminating #\return #\linefeed combination. If either of these calls
to device-finish-record
return nil
, end-of-file processing is
done. There are no usable methods defined.
See streams.htm for information on the simple-streams implementation in Allegro CL. The older but still supported Gray streams implementation is described in gray-streams.htm.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |