Bug with file I/O

[cornell@unix1.cs.umass.edu (Matthew Cornell)]

I believe the following code should write a sequence of 256 a's b's
and c's. Instead we get various incorrect results. I remember someone
reporting a similar problem not too long ago. I would be *very*
grateful for any patches that correct this problem.

matt


==== Start sample code ====
(defun file-test (file-name list-name)
  (with-open-file (file-stream file-name
                               :direction :output
                               :if-exists :overwrite
                               :if-does-not-exist :create)
    (write-it file-stream list-name)))


(defun write-it (file-stream list-name)
  (dolist (cur-elem list-name)
    (write-string-at-pos file-stream (cdr cur-elem) (car cur-elem))))




(defun write-string-at-pos (file-stream input-string position)
  (declare (optimize speed))
  (file-position file-stream position)
  (with-input-from-string (my-stream input-string)
    (let ((eof (list 'eof)))
      (do ((current-object (read-char my-stream nil eof)
                           (read-char my-stream nil eof)))
          ((eq current-object eof) t)
        (format file-stream "~a" current-object)))))

(setq tmpp 
      '((0 .
         
         "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
        (256 .
         
         "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb")
        (512 .
         
         "cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc")
        (768 .
        
         "dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd")
))

==== End sample code ====