[slime-devel] [PATCH] fix for bad source position in ACL6.2/win32

[Matthew Danish]

Allegro 6.2 reports source position of definitions by file-position,
which does not properly account for line-ending encoding.  This means
that a file with carriage returns will cause all reported positions to
appear to be offset from the actual definition in the emacs buffer.
This is assuming that your emacs is properly understanding the
line-ending encoding and is not displaying a bunch of ^Ms at the end
of every line.

This quick hack counts the number of carriage returns that need to be
subtracted from the file-position.  It runs quickly enough on large
(15msec to count CRs for 4481 lines in a file I am testing) files that
I think it should be acceptable, unless someone has a better idea.  I
don't know if 7.0 has this problem as well; if not then this could be
conditionalized.

diff -u -r1.61 swank-allegro.lisp
--- swank-allegro.lisp  25 Oct 2004 16:17:11 -0000      1.61
+++ swank-allegro.lisp  18 Nov 2004 22:12:25 -0000
@@ -274,10 +274,22 @@
     (symbol (string fspec))
     (list (string (second fspec)))))
 
+(defun count-cr (file pos)
+  (let* ((bufsize 256)
+         (buf (make-array bufsize :element-type '(unsigned-byte 8)))
+         (cr-count 0))
+    (with-open-file (stream file :direction :input)
+      (loop for bytes-read = (read-sequence buf stream) do
+           (incf cr-count (count (char-code #\return) buf 
+                                 :end (min pos bytes-read)))
+           (decf pos bytes-read)
+           (when (<= pos 0)
+             (return cr-count))))))
+
 (defun find-definition-in-file (fspec type file)
   (let* ((start (scm:find-definition-in-file fspec type file))
          (pos (if start
-                  (list :position (1+ start))
+                  (list :position (1+ (- start (count-cr file start))))
                   (list :function-name (fspec-primary-name fspec)))))
          (make-location (list :file (namestring (truename file)))
                         pos)))


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