Avoid character to byte conversions in motion subroutines.

* indent.h (compute_motion, vmotion): Add byte position argument.
* indent.c (compute_motion): Use it and avoid CHAR_TO_BYTE.
Add eassert.
(Fcompute_motion): Break long line.  Adjust call to compute_motion.
Use list5 for return value.
(vmotion): Use byte position argument and avoid call to CHAR_TO_BYTE.
Adjust comments, style and calls to compute_motion.
(Fvertical_motion): Adjust call to vmotion.
* window.c (Fdelete_other_windows_internal): Record window start
byte position and adjust call to vmotion.
(window_scroll_line_based): Likewise with call to compute_motion.
Use SET_PT_BOTH.
(Frecenter): Adjust calls to vmotion.

4 files changed, 66 insertions, 61 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index eee20d998d..bc106df0cb 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,22 @@
 2013-03-07  Dmitry Antipov  <dmantipov@yandex.ru>
 
+	Avoid character to byte conversions in motion subroutines.
+	* indent.h (compute_motion, vmotion): Add byte position argument.
+	* indent.c (compute_motion): Use it and avoid CHAR_TO_BYTE.
+	Add eassert.
+	(Fcompute_motion): Break long line.  Adjust call to compute_motion.
+	Use list5 for return value.
+	(vmotion): Use byte position argument and avoid call to CHAR_TO_BYTE.
+	Adjust comments, style and calls to compute_motion.
+	(Fvertical_motion): Adjust call to vmotion.
+	* window.c (Fdelete_other_windows_internal): Record window start
+	byte position and adjust call to vmotion.
+	(window_scroll_line_based): Likewise with call to compute_motion.
+	Use SET_PT_BOTH.
+	(Frecenter): Adjust calls to vmotion.
+
+2013-03-07  Dmitry Antipov  <dmantipov@yandex.ru>
+
 	* lisp.h (list2i, list3i): New functions.
 	(list4i): Move from window.c and make LISP_INLINE.
 	* editfns.c (make_lisp_time):
diff --git a/src/indent.c b/src/indent.c
index abb4e08ad0..fd692f0b14 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -1102,8 +1102,8 @@ static struct position val_compute_motion;
    the scroll bars if they are turned on.  */
 
 struct position *
-compute_motion (ptrdiff_t from, EMACS_INT fromvpos, EMACS_INT fromhpos,
-		bool did_motion, ptrdiff_t to,
+compute_motion (ptrdiff_t from, ptrdiff_t frombyte, EMACS_INT fromvpos,
+		EMACS_INT fromhpos, bool did_motion, ptrdiff_t to,
 		EMACS_INT tovpos, EMACS_INT tohpos, EMACS_INT width,
 		ptrdiff_t hscroll, int tab_offset, struct window *win)
 {
@@ -1186,8 +1186,11 @@ compute_motion (ptrdiff_t from, EMACS_INT fromvpos, EMACS_INT fromhpos,
   immediate_quit = 1;
   QUIT;
 
+  /* It's just impossible to be too paranoid here.  */
+  eassert (from == BYTE_TO_CHAR (frombyte) && frombyte == CHAR_TO_BYTE (from));
+
   pos = prev_pos = from;
-  pos_byte = prev_pos_byte = CHAR_TO_BYTE (from);
+  pos_byte = prev_pos_byte = frombyte;
   contin_hpos = 0;
   prev_tab_offset = tab_offset;
   memset (&cmp_it, 0, sizeof cmp_it);
@@ -1724,7 +1727,8 @@ of a certain window, pass the window's starting location as FROM
 and the window's upper-left coordinates as FROMPOS.
 Pass the buffer's (point-max) as TO, to limit the scan to the end of the
 visible section of the buffer, and pass LINE and COL as TOPOS.  */)
-  (Lisp_Object from, Lisp_Object frompos, Lisp_Object to, Lisp_Object topos, Lisp_Object width, Lisp_Object offsets, Lisp_Object window)
+  (Lisp_Object from, Lisp_Object frompos, Lisp_Object to, Lisp_Object topos,
+   Lisp_Object width, Lisp_Object offsets, Lisp_Object window)
 {
   struct window *w;
   Lisp_Object bufpos, hpos, vpos, prevhpos;
@@ -1767,7 +1771,8 @@ visible section of the buffer, and pass LINE and COL as TOPOS.  */)
   if (XINT (to) < BEGV || XINT (to) > ZV)
     args_out_of_range_3 (to, make_number (BEGV), make_number (ZV));
 
-  pos = compute_motion (XINT (from), XINT (XCDR (frompos)),
+  pos = compute_motion (XINT (from), CHAR_TO_BYTE (XINT (from)),
+			XINT (XCDR (frompos)),
 			XINT (XCAR (frompos)), 0,
 			XINT (to),
 			(NILP (topos)
@@ -1789,28 +1794,23 @@ visible section of the buffer, and pass LINE and COL as TOPOS.  */)
   XSETINT (vpos, pos->vpos);
   XSETINT (prevhpos, pos->prevhpos);
 
-  return Fcons (bufpos,
-		Fcons (hpos,
-		       Fcons (vpos,
-			      Fcons (prevhpos,
-				     Fcons (pos->contin ? Qt : Qnil, Qnil)))));
-
+  return list5 (bufpos, hpos, vpos, prevhpos, pos->contin ? Qt : Qnil);
 }
-
-/* Fvertical_motion and vmotion */
+
+/* Fvertical_motion and vmotion.  */
 
 static struct position val_vmotion;
 
 struct position *
-vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
+vmotion (register ptrdiff_t from, register ptrdiff_t from_byte,
+	 register EMACS_INT vtarget, struct window *w)
 {
   ptrdiff_t hscroll = w->hscroll;
   struct position pos;
-  /* vpos is cumulative vertical position, changed as from is changed */
+  /* VPOS is cumulative vertical position, changed as from is changed.  */
   register EMACS_INT vpos = 0;
   ptrdiff_t prevline;
   register ptrdiff_t first;
-  ptrdiff_t from_byte;
   ptrdiff_t lmargin = hscroll > 0 ? 1 - hscroll : 0;
   ptrdiff_t selective
     = (INTEGERP (BVAR (current_buffer, selective_display))
@@ -1854,29 +1854,24 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
 						       text_prop_object),
 			 TEXT_PROP_MEANS_INVISIBLE (propval))))
 	    prevline = find_newline_no_quit (prevline - 1, -1, &bytepos);
-	  pos = *compute_motion (prevline, 0,
-				 lmargin,
-				 0,
-				 from,
+	  pos = *compute_motion (prevline, bytepos, 0, lmargin, 0, from,
 				 /* Don't care for VPOS...  */
 				 1 << (BITS_PER_SHORT - 1),
 				 /* ... nor HPOS.  */
 				 1 << (BITS_PER_SHORT - 1),
-				 -1, hscroll,
-				 0,
-				 w);
+				 -1, hscroll, 0, w);
 	  vpos -= pos.vpos;
 	  first = 0;
 	  from = prevline;
+	  from_byte = bytepos;
 	}
 
-      /* If we made exactly the desired vertical distance,
-	 or if we hit beginning of buffer,
-	 return point found */
+      /* If we made exactly the desired vertical distance, or
+	 if we hit beginning of buffer, return point found.  */
       if (vpos >= vtarget)
 	{
 	  val_vmotion.bufpos = from;
-	  val_vmotion.bytepos = CHAR_TO_BYTE (from);
+	  val_vmotion.bytepos = from_byte;
 	  val_vmotion.vpos = vpos;
 	  val_vmotion.hpos = lmargin;
 	  val_vmotion.contin = 0;
@@ -1884,11 +1879,12 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
 	  return &val_vmotion;
 	}
 
-      /* Otherwise find the correct spot by moving down */
+      /* Otherwise find the correct spot by moving down.  */
     }
-  /* Moving downward is simple, but must calculate from beg of line
-     to determine hpos of starting point */
-  from_byte = CHAR_TO_BYTE (from);
+
+  /* Moving downward is simple, but must calculate from
+     beg of line to determine hpos of starting point.  */
+
   if (from > BEGV && FETCH_BYTE (from_byte - 1) != '\n')
     {
       ptrdiff_t bytepos;
@@ -1905,17 +1901,12 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
 						   text_prop_object),
 		     TEXT_PROP_MEANS_INVISIBLE (propval))))
 	prevline = find_newline_no_quit (prevline - 1, -1, &bytepos);
-      pos = *compute_motion (prevline, 0,
-			     lmargin,
-			     0,
-			     from,
+      pos = *compute_motion (prevline, bytepos, 0, lmargin, 0, from,
 			     /* Don't care for VPOS...  */
 			     1 << (BITS_PER_SHORT - 1),
 			     /* ... nor HPOS.  */
 			     1 << (BITS_PER_SHORT - 1),
-			     -1, hscroll,
-			     0,
-			     w);
+			     -1, hscroll, 0, w);
       did_motion = 1;
     }
   else
@@ -1924,11 +1915,9 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
       pos.vpos = 0;
       did_motion = 0;
     }
-  return compute_motion (from, vpos, pos.hpos, did_motion,
+  return compute_motion (from, from_byte, vpos, pos.hpos, did_motion,
 			 ZV, vtarget, - (1 << (BITS_PER_SHORT - 1)),
-			 -1, hscroll,
-			 0,
-			 w);
+			 -1, hscroll, 0, w);
 }
 
 DEFUN ("vertical-motion", Fvertical_motion, Svertical_motion, 1, 2, 0,
@@ -1995,7 +1984,7 @@ whether or not it is currently displayed in some window.  */)
   if (noninteractive)
     {
       struct position pos;
-      pos = *vmotion (PT, XINT (lines), w);
+      pos = *vmotion (PT, PT_BYTE, XINT (lines), w);
       SET_PT_BOTH (pos.bufpos, pos.bytepos);
     }
   else
diff --git a/src/indent.h b/src/indent.h
index acfd952754..4eb3fed6a1 100644
--- a/src/indent.h
+++ b/src/indent.h
@@ -26,14 +26,14 @@ struct position
     int contin;
   };
 
-struct position *compute_motion (ptrdiff_t from, EMACS_INT fromvpos,
-                                 EMACS_INT fromhpos, bool did_motion,
-                                 ptrdiff_t to, EMACS_INT tovpos,
-                                 EMACS_INT tohpos,
+struct position *compute_motion (ptrdiff_t from, ptrdiff_t frombyte,
+				 EMACS_INT fromvpos, EMACS_INT fromhpos,
+				 bool did_motion, ptrdiff_t to,
+				 EMACS_INT tovpos, EMACS_INT tohpos,
                                  EMACS_INT width, ptrdiff_t hscroll,
                                  int tab_offset, struct window *);
-struct position *vmotion (ptrdiff_t from, EMACS_INT vtarget,
-                          struct window *);
+struct position *vmotion (ptrdiff_t from, ptrdiff_t from_byte,
+			  EMACS_INT vtarget, struct window *);
 ptrdiff_t skip_invisible (ptrdiff_t pos, ptrdiff_t *next_boundary_p,
                           ptrdiff_t to, Lisp_Object window);
 
diff --git a/src/window.c b/src/window.c
index ed0c1283ab..7769613151 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2743,7 +2743,7 @@ window-start value is reasonable when this function is called.  */)
   struct window *w, *r, *s;
   struct frame *f;
   Lisp_Object sibling, pwindow, swindow IF_LINT (= Qnil), delta;
-  ptrdiff_t startpos IF_LINT (= 0);
+  ptrdiff_t startpos IF_LINT (= 0), startbyte IF_LINT (= 0);
   int top IF_LINT (= 0), new_top, resize_failed;
 
   w = decode_valid_window (window);
@@ -2782,6 +2782,7 @@ window-start value is reasonable when this function is called.  */)
   if (!NILP (w->buffer))
     {
       startpos = marker_position (w->start);
+      startbyte = marker_byte_position (w->start);
       top = WINDOW_TOP_EDGE_LINE (w)
 	- FRAME_TOP_MARGIN (XFRAME (WINDOW_FRAME (w)));
       /* Make sure WINDOW is the frame's selected window.  */
@@ -2951,7 +2952,7 @@ window-start value is reasonable when this function is called.  */)
 	  Fset_buffer (w->buffer);
 	  /* This computation used to temporarily move point, but that
 	     can have unwanted side effects due to text properties.  */
-	  pos = *vmotion (startpos, -top, w);
+	  pos = *vmotion (startpos, startbyte, -top, w);
 
 	  set_marker_both (w->start, w->buffer, pos.bufpos, pos.bytepos);
 	  w->window_end_valid = 0;
@@ -4748,7 +4749,8 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
   register Lisp_Object tem;
   int lose;
   Lisp_Object bolp;
-  ptrdiff_t startpos;
+  ptrdiff_t startpos = marker_position (w->start);
+  ptrdiff_t startbyte = marker_byte_position (w->start);
   Lisp_Object original_pos = Qnil;
 
   /* If scrolling screen-fulls, compute the number of lines to
@@ -4756,8 +4758,6 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
   if (whole)
     n *= max (1, ht - next_screen_context_lines);
 
-  startpos = marker_position (w->start);
-
   if (!NILP (Vscroll_preserve_screen_position))
     {
       if (window_scroll_preserve_vpos <= 0
@@ -4765,10 +4765,8 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
 	  || NILP (Fget (KVAR (current_kboard, Vlast_command), Qscroll_command)))
 	{
 	  struct position posit
-	    = *compute_motion (startpos, 0, 0, 0,
-			       PT, ht, 0,
-			       -1, w->hscroll,
-			       0, w);
+	    = *compute_motion (startpos, startbyte, 0, 0, 0,
+			       PT, ht, 0, -1, w->hscroll, 0, w);
 	  window_scroll_preserve_vpos = posit.vpos;
 	  window_scroll_preserve_hpos = posit.hpos + w->hscroll;
 	}
@@ -4784,9 +4782,10 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
     {
       Fvertical_motion (make_number (- (ht / 2)), window);
       startpos = PT;
+      startbyte = PT_BYTE;
     }
 
-  SET_PT (startpos);
+  SET_PT_BOTH (startpos, startbyte);
   lose = n < 0 && PT == BEGV;
   Fvertical_motion (make_number (n), window);
   pos = PT;
@@ -5321,7 +5320,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
 
 	  iarg = max (iarg, this_scroll_margin);
 
-	  pos = *vmotion (PT, -iarg, w);
+	  pos = *vmotion (PT, PT_BYTE, -iarg, w);
 	  charpos = pos.bufpos;
 	  bytepos = pos.bytepos;
 	}
@@ -5340,7 +5339,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
       iarg = clip_to_bounds (this_scroll_margin, iarg,
 			     ht - this_scroll_margin - 1);
 
-      pos = *vmotion (PT, - iarg, w);
+      pos = *vmotion (PT, PT_BYTE, - iarg, w);
       charpos = pos.bufpos;
       bytepos = pos.bytepos;
     }