q. on reading bytes from "BIDIRECTIONAL-TERMINAL-STREAM"
Richard James Panturis Giuly
generates output to stdout. I can read from the stream that
run-shell-command returns with read-char but I need to be reading
bytes, not characters. When I try to use read-byte it says
Error: No methods applicable for generic function
#<STANDARD-GENERIC-FUNCTION STREAM-READ-BYTE> with args
(#<BIDIRECTIONAL-TERMINAL-STREAM fd 16/15 @ #x20256dca>)
of classes
(BIDIRECTIONAL-TERMINAL-STREAM)
how can I read bytes instead efficiently?
--
ricky
rgi...@surfsouth.com
Lieven Marchand
On Unix, character streams and byte streams are fairly
interchangeable. Have you measured READ-CHAR is actually slower than
READ-BYTE?
If this is really the case, you could try doing a CHANGE-CLASS on your
stream to BIDIRECTIONAL-BINARY-SOCKET-STREAM. Alternatively, you can
create your own binary stream and give that as argument to the :output
key argument of RUN-SHELL-COMMAND.
--
Lieven Marchand <m...@bewoner.dma.be>
Lambda calculus - Call us a mad club
Erik Naggum
| how can I read bytes instead efficiently?
Which inefficient solutions have you tried so far? (Since you use
one of those extremely annoying invalid return addresses, I'm not
inclined to provide you with the solution I used ere the dawn of
bivalentน streams in Allegro CL.)
#:Erik
-------
น "multivalent" in recent terminology change, but it sounds silly
--
If this is not what you expected, please alter your expectations.
Richard James Panturis Giuly
the read-byte function works but still gives characters. I need
integers (or numbers of some kind) rather than characters.
I don't know how to create a binary stream, could you fill me in?
(All I found were functions to make streams from existing
streams.)
If you know how I can convert a character to an integer that
would be fine too, I just thought converting every byte might be
inefficient.
>
> On Unix, character streams and byte streams are fairly
> interchangeable. Have you measured READ-CHAR is actually slower than
> READ-BYTE?
> If this is really the case, you could try doing a CHANGE-CLASS on your
> stream to BIDIRECTIONAL-BINARY-SOCKET-STREAM. Alternatively, you can
> create your own binary stream and give that as argument to the :output
> key argument of RUN-SHELL-COMMAND.
--
ricky
rgi...@surfsouth.com
Tim Bradshaw
> If you know how I can convert a character to an integer that
> would be fine too, I just thought converting every byte might be
> inefficient.
CHAR-CODE gets the code of a character. It's unlikely to be
inefficient compared to doing I/O.
--tim
Erik Naggum
| If you know how I can convert a character to an integer that would
| be fine too, I just thought converting every byte might be
| inefficient.
The function char-code returns the integer code of the character.
It's essential a type-changing function, as both characters and
integers are immediate values, and at least in Allegro CL is a
simple bit-shift operation if you declare the character's type.
#:Erik
Lieven Marchand
> I don't know how to create a binary stream, could you fill me in?
> (All I found were functions to make streams from existing
> streams.)
I still think you're optimizing something that will be lost in the
fringe, but one way to do it is like this:
(defun test-function ()
(let ((stream (open "/tmp/foo"
:direction :io
:if-exists :supersede
:element-type 'unsigned-byte))
(output-buffer (make-array 1024 :element-type 'unsigned-byte)))
(run-shell-command "ls" :output stream)
(file-position stream 0)
(read-sequence output-buffer stream)
(close stream)
output-buffer))
Add all apropriate declarations and this could be quite fast.
USER(35): (setf *foo* (test-function))
#(35 46 110 101 119 115 114 99 45 108 ...)
USER(39): (loop for c across *foo*
collect (code-char c))
(#\# #\. #\n #\e #\w #\s #\r #\c #\- #\l ...)
Erik Naggum
| USER(39): (loop for c across *foo*
| collect (code-char c))
| (#\# #\. #\n #\e #\w #\s #\r #\c #\- #\l ...)
(map 'list #'char-code <sequence>)