Re: file i/o and clos objects...

[bill (Bill St. Clair)]

> Date: Sun, 3 Nov 91 17:11:08 PST
> From: mmeehan@eesof.com (Mike Meehan)
> To: Info-MCL@cambridge.apple.com
> Subject: file i/o and clos objects...
> 
> 
>   Is there a way, (without resorting to the toolbox) to increase the buffer
>   size used with "read-line"?  Using read-line to count the number of lines
>   in the file seems to be a real disk basher...read-line is hitting the disk
>   about every 3rd read-line, which for a 4-5k line file is a real workout...
> 
>   Is there a straightforward way to use binary file i/o using :element-type
>   '(unsigned-byte 8192) to read in, say 1k???

read-line uses the standard buffers that any file I/O uses.  I believe
they are 512 bytes long.  I doubt that the buffer size is your
problem, however.  READ-LINE has a fair amount of overhead in order
to do rubout handling on interactive streams.  See if the following
works faster for you:

(defun make-read-line-string ()
  (make-array 256 :element-type 'character :fill-pointer 0 :adjustable t))

(defvar *read-line-string* (make-read-line-string))
  
(defun non-interactive-read-line (stream &optional
                                        (eof-error-p t) eof-value)
  (let ((s *read-line-string*)
        (*read-line-string* nil)
        ch)
    (unless s (setq s (make-read-line-string)))
    (if (stream-eofp stream)
      (if eof-error-p
        (error "EOF on ~s" stream)
        eof-value)
      (multiple-value-bind (reader arg) (stream-reader stream)
        (setf (fill-pointer s) 0)
        (loop
          (when (or (null (setq ch (funcall reader arg)))
                    (eq ch #\newline))
            (return))
          (vector-push-extend ch s))
        (values (ensure-simple-string s) (null ch))))))