Re: I/O efficiency question

[Doug Cutting <cutting@parc.xerox.com>]

> Date:   Tue, 23 Feb 1993 08:46:50 -0800
> From:   Peter Shell <pshell@nl.cs.cmu.edu>
> 
>   By calling EXCL::STM-FILE-BUFFERED-READ-CHAR and
> EXCL::STM-FILE-BUFFERED-WRITE-CHAR  directly I was able to bypass
> the method stuff, speeding up my program considerably (45%).

If you really want to make your program burn, try the following:

(defmacro fast-read-char (stream)
  #+(and allegro (version>= 4)) `(stream:stream-read-char ,stream)
  #+lucid`(lcl:fast-read-char ,stream nil :eof)
  #-(or (and allegro (version>= 4)) lucid) `(read-char ,stream nil :eof))

(defmacro fast-read-file-char (stream) `(fast-read-char ,stream))

#+(and allegro (version>= 4))
(define-compiler-macro fast-read-file-char (stream)
  `(macrolet ((stream-slots (stream)
		`(the simple-vector (svref ,stream 1)))
	      (stream-buffer (slots)
		`(the simple-string (svref ,slots 11)))
	      (stream-buffpos (slots)
		`(the fixnum (svref ,slots 12)))
	      (stream-maxbuffpos (slots)
		`(the fixnum (svref ,slots 13))))
     (declare (optimize (speed 3) (safety 0)))
     (let* ((stream ,stream)
	    (slots (stream-slots stream))
	    (buffpos (stream-buffpos slots))
	    (maxbuffpos (stream-maxbuffpos slots)))
       (declare (fixnum buffpos maxbuffpos))
       (if (>= buffpos maxbuffpos)
	   (stream:stream-read-char stream)
	 (prog1 (schar (stream-buffer slots) buffpos)
	   (when (= (setf (stream-buffpos slots) (the fixnum (1+ buffpos)))
		    maxbuffpos)
	     (setf (stream-maxbuffpos slots) 0)))))))