The following method for
stream-write-char
uses
write-char
to write a character to the stream. If the character written to
unicode-ls-stream
is a
#\Newline
, then the method writes a
#\Line-Separator
to the file stream.
(defmethod stream:stream-write-char ((stream unicode-ls-stream)
char)
(write-char (if (eq char #\Newline)
#\Line-Separator
char)
(ls-stream-file-stream stream)))
The default method for
stream-write-string
calls
stream-write-char
repeatedly to write a string to the stream. However, the following is a more efficient implementation for our stream.
(defmethod stream:stream-write-string ((stream unicode-ls-stream)
string &optional (start 0)
(end (length string)))
(loop with i = start
until (>= i end)
do (let* ((newline (position #\Newline
string :start i :end end))
(this-end (or newline end)))
(write-string string (ls-stream-file-stream stream)
:start i :end this-end)
(incf i this-end)
(when newline
(stream:stream-terpri stream)
(incf i)))
finally (return string)))
We do not need to define our own method for
stream-terpri
, as the default uses
stream-write-char
, and therefore works appropriately
To be useful, the
stream-line-column
and
stream-start-line-p
generic functions need to know the number of characters preceding a
#\Line-Separator
. However, since the LispWorks file stream records line position only by
#\Newline
characters, this information is not available. Hence we define the two generic functions to return
nil
:
(defmethod stream:stream-line-column
((stream unicode-ls-stream))
nil)
(defmethod stream:stream-start-line-p
((stream unicode-ls-stream))
nil)
Finally, the methods for
stream-force-output
,
stream-finish-output
and
stream-clear-output
are "trampolined" from the standard
force-output
,
finish-output
and
clear-output
functions.
(defmethod stream:stream-force-output ((stream
unicode-ls-stream))
(force-output (ls-stream-file-stream stream)))
(defmethod stream:stream-finish-output ((stream
unicode-ls-stream))
(finish-output (ls-stream-file-stream stream)))
(defmethod stream:stream-clear-output ((stream
unicode-ls-stream))
(clear-output (ls-stream-file-stream stream)))
LispWorks User Guide and Reference Manual - 21 Dec 2011