(Ffind_coding_systems_region_internal): Cache checked characters.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/coding.c b/src/coding.c
index e2a328fd908..3fc43df636b 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -8640,7 +8640,7 @@ DEFUN ("find-coding-systems-region-internal",
   EMACS_INT start_byte, end_byte;
   const unsigned char *p, *pbeg, *pend;
   int c;
-  Lisp_Object tail, elt;
+  Lisp_Object tail, elt, work_table;
 
   if (STRINGP (start))
     {
@@ -8698,6 +8698,7 @@ DEFUN ("find-coding-systems-region-internal",
   while (p < pend && ASCII_BYTE_P (*p)) p++;
   while (p < pend && ASCII_BYTE_P (*(pend - 1))) pend--;
 
+  work_table = Fmake_char_table (Qnil, Qnil);
   while (p < pend)
     {
       if (ASCII_BYTE_P (*p))
@@ -8705,6 +8706,9 @@ DEFUN ("find-coding-systems-region-internal",
       else
         {
           c = STRING_CHAR_ADVANCE (p);
+          if (!NILP (char_table_ref (work_table, c)))
+            /* This character was already checked.  Ignore it.  */
+            continue;
 
           charset_map_loaded = 0;
           for (tail = coding_attrs_list; CONSP (tail);)
@@ -8736,6 +8740,7 @@ DEFUN ("find-coding-systems-region-internal",
               p = pbeg + p_offset;
               pend = pbeg + pend_offset;
             }
+          char_table_set (work_table, c, Qt);
         }
     }