[Chicken-users] fix for read-string

[Joerg F. Wittenberger]

Hi all,

the read-string procedure in extras.scm is broken when it comes to
length terminated reads (one of those nice off-by-one's).  Here a
fixed version:

(define read-string
  (let ([read-char read-char]
        [write-char write-char]
        [open-output-string open-output-string]
        [get-output-string get-output-string] )
    (lambda (n . port)
      (let ([p (if (pair? port) (car port) ##sys#standard-input)]
            [str (open-output-string)] )
        (when n (##sys#check-exact n 'read-string))
        (let loop ([n n])
          (or (and (eq? n 0) (get-output-string str))
              (let ([c (read-char p)])
                (cond [(eof-object? c) (get-output-string str)]
                      [else
                       (write-char c str)
                       (loop (and n (fx- n 1))) ] ) )) ) ) ) ) )

One remark: I'd tend to use `if' instead of the `or/and' construction
I used here, but I noticed (in some different context) that `or/and'
is faster with chicken than `if'.  To me this is something between
surprizing, strange and suspicious.  I'm not sure whether my test
benchmark was broken or that's really the truth, anybody who can
comment?

Regards

/Jörg

-- 
The worst of harm may often result from the best of intentions.