(back_comment): Simplify string-parity counting (with

the added benefit of handling multiple string-styles as long as
they are not nested).
Jump to the slow code as soon as a comment starter is found in
a "string_lossage" position.  Fixes the case:  " /* " /* " */.

diff --git a/src/ChangeLog b/src/ChangeLog
index cc1d665..2bd068d 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2000-06-21  Stefan Monnier  <monnier@cs.yale.edu>
+
+       * syntax.c (back_comment): Simplify string-parity counting (with
+       the added benefit of handling multiple string-styles as long as
+       they are not intertwined).
+       Jump to the slow code as soon as a comment starter is found in
+       a "string_lossage" position.  Fixes the case:  " /* " /* " */.
+
 2000-06-21  Dave Love  <fx@gnu.org>
 
        * Makefile.in: Use GETLOADAVG_LIBS.

diff --git a/src/syntax.c b/src/syntax.c
index 656d567..fcc6dc6 100644 (file)
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -467,8 +467,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
      OFROM[I] is position of the earliest comment-starter seen
      which is I+2X quotes from the comment-end.
      PARITY is current parity of quotes from the comment end.  */
-  int parity = 0;
-  int my_stringend = 0;
+  int string_style = -1;       /* Presumed outside of any string. */
   int string_lossage = 0;
   int comment_end = from;
   int comment_end_byte = from_byte;
@@ -476,7 +475,6 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
   int comstart_byte;
   /* Value that PARITY had, when we reached the position
      in COMSTART_POS.  */
-  int comstart_parity = 0;
   int scanstart = from - 1;
   /* Place where the containing defun starts,
      or 0 if we didn't come across it yet.  */
@@ -530,34 +528,33 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
        continue;
 
       /* Track parity of quotes.  */
-      if (code == Sstring)
+      switch (code)
        {
-         parity ^= 1;
-         if (my_stringend == 0)
-           my_stringend = c;
-         /* If we have two kinds of string delimiters.
-            There's no way to grok this scanning backwards.  */
-         else if (my_stringend != c)
-           string_lossage = 1;
-       }
-
-      if (code == Sstring_fence || code == Scomment_fence)
-       {
-         parity ^= 1;
-         if (my_stringend == 0)
-           my_stringend
-             = code == Sstring_fence ? ST_STRING_STYLE : ST_COMMENT_STYLE;
-         /* If we have two kinds of string delimiters.
-            There's no way to grok this scanning backwards.  */
-         else if (my_stringend != (code == Sstring_fence 
-                                   ? ST_STRING_STYLE : ST_COMMENT_STYLE))
+       case Sstring_fence:
+       case Scomment_fence:
+         c = (code == Sstring_fence ? ST_STRING_STYLE : ST_COMMENT_STYLE);
+       case Sstring:
+         /* Track parity of quotes.  */
+         if (string_style == -1)
+           /* Entering a string.  */
+           string_style = c;
+         else if (string_style == c)
+           /* Leaving the string.  */
+           string_style = -1;
+         else
+           /* If we have two kinds of string delimiters.
+              There's no way to grok this scanning backwards.  */
            string_lossage = 1;
-       }
+         break;
+         
+       case Scomment:
+         /* We've already checked that it is the relevant comstyle.  */
+         if (string_style != -1 || string_lossage)
+           /* There are odd string quotes involved, so let's be careful.
+              Test case in Pascal: " { " a { " } */
+           goto lossage;
 
-      if (code == Scomment)
-       /* We've already checked that it is the relevant comstyle.  */
-       {
-         if (comnested && --nesting <= 0 && parity == 0 && !string_lossage)
+         if (comnested && --nesting <= 0)
            /* nested comments have to be balanced, so we don't need to
               keep looking for earlier ones.  We use here the same (slightly
               incorrect) reasoning as below:  since it is followed by uniform
@@ -567,9 +564,12 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
 
          /* Record comment-starters according to that
             quote-parity to the comment-end.  */
-         comstart_parity = parity;
          comstart_pos = from;
          comstart_byte = from_byte;
+         break;
+
+       default:
+         ;
        }
 
       /* If we find another earlier comment-ender,
@@ -607,7 +607,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
      we know it can't be inside a string
      since if it were then the comment ender would be inside one.
      So it does start a comment.  Skip back to it.  */
-  else if (!comnested && comstart_parity == 0 && !string_lossage) 
+  else if (!comnested)
     {
       from = comstart_pos;
       from_byte = comstart_byte;
@@ -615,12 +615,13 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
     }
   else
     {
+      struct lisp_parse_state state;
+    lossage:
       /* We had two kinds of string delimiters mixed up
         together.  Decode this going forwards.
         Scan fwd from the previous comment ender
         to the one in question; this records where we
         last passed a comment starter.  */
-      struct lisp_parse_state state;
       /* If we did not already find the defun start, find it now.  */
       if (defun_start == 0)
        {