# HG changeset patch
# User John W. Eaton <jwe@octave.org>
# Date 1440619549 14400
# Node ID 44eb1102f8a8d3afba12e7a0ffeca490d67f5be3
# Parent  7fbba8c8efd5d919be9a7f05e7d7de78bd958fcf
don't recycle scanf format string if all conversions are done (bug #45808)

* oct-stream.cc, oct-stream.h (scanf_format_elt::special_conversion):
New enum value, no_conversion.
(scanf_format_list::next): If not cycling through the list, return
dummy scanf_format_elt after list has been exhausted.
(octave_base_stream::do_scanf): Only cycle through the format list
more than once if there are conversions to make and the limit on the
number of values to convert has not been reached.

diff -r 7fbba8c8efd5 -r 44eb1102f8a8 libinterp/corefcn/oct-stream.cc
--- a/libinterp/corefcn/oct-stream.cc	Wed Aug 26 22:51:59 2015 +0200
+++ b/libinterp/corefcn/oct-stream.cc	Wed Aug 26 16:05:49 2015 -0400
@@ -1603,11 +1603,19 @@
 
           if (elt)
             {
-              if (! (elt->type == scanf_format_elt::whitespace_conversion
-                     || elt->type == scanf_format_elt::literal_conversion
-                     || elt->type == '%')
-                  && max_conv > 0 && conversion_count == max_conv)
+              if (elt->type == scanf_format_elt::null
+                  || (! (elt->type == scanf_format_elt::whitespace_conversion
+                        || elt->type == scanf_format_elt::literal_conversion
+                        || elt->type == '%')
+                      && max_conv > 0 && conversion_count == max_conv))
                 {
+                  // We are done, either because we have reached the end
+                  // of the format string and are not cycling through
+                  // the format again or because we've converted all the
+                  // values that have been requested and the next format
+                  // element is a conversion.  Determine final array
+                  // size and exit.
+
                   if (all_char_conv && one_elt_size_spec)
                     {
                       final_nr = 1;
@@ -1859,7 +1867,16 @@
               break;
             }
           else
-            elt = fmt_list.next (nconv > 0);
+            {
+              // Cycle through the format list more than once if we have
+              // some conversions to make and we haven't reached the
+              // limit on the number of values to convert (possibly
+              // because there is no specified limit).
+
+              elt = fmt_list.next (nconv > 0
+                                   && (max_conv == 0
+                                       || conversion_count < max_conv));
+            }
         }
     }
 
diff -r 7fbba8c8efd5 -r 44eb1102f8a8 libinterp/corefcn/oct-stream.h
--- a/libinterp/corefcn/oct-stream.h	Wed Aug 26 22:51:59 2015 +0200
+++ b/libinterp/corefcn/oct-stream.h	Wed Aug 26 16:05:49 2015 -0400
@@ -49,7 +49,8 @@
   enum special_conversion
   {
     whitespace_conversion = 1,
-    literal_conversion = 2
+    literal_conversion = 2,
+    null = 3
   };
 
   scanf_format_elt (const char *txt = 0, int w = 0, bool d = false,
@@ -129,6 +130,9 @@
 
   const scanf_format_elt *next (bool cycle = true)
   {
+    static scanf_format_elt dummy
+      (0, 0, false, scanf_format_elt::null, '\0', "");
+
     curr_idx++;
 
     if (curr_idx >= list.numel ())
@@ -136,8 +140,9 @@
         if (cycle)
           curr_idx = 0;
         else
-          return 0;
+          return &dummy;
       }
+
     return current ();
   }