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Re: RedBoot - Bug in _rb_gets()?


On Tue, 2001-10-16 at 02:16, Chris Zankel wrote:
> Gary,
> 
> Sounds reasonable. But wouldn't that imply that the inner
> loop is set to at maximum to 50 ms? Right now
> mon_set_read_char_timeout() sets the timeout to whatever
> you passed to it.
> So, what happens right now is, if you do a mon_read_char_with_timeout()
> with, for example, 1s timeout, that the inner-loop
> mon_read_char_with_timout() waits 1s and the outer loop
> loops 1000/50 = 20 times. The whole function waits 20s instead
> of the specified one second.
> 
> Wouldn't it make more sense to rewrite that part to:
> 
> mon_set_read_char_timeout(timeout > 50? 50:timeout);
> 
> while (timeout > 0) {
>   ...
> }

Indeed, it does look like it's wrong.  I agree with your analysis and
will make this change to the sources:

Index: redboot/current/src/io.c
===================================================================
RCS file: /home/cvs/ecc/ecc/redboot/current/src/io.c,v
retrieving revision 1.36
diff -u -5 -p -r1.36 io.c
--- redboot/current/src/io.c	23 Aug 2001 21:27:13 -0000	1.36
+++ redboot/current/src/io.c	15 Oct 2001 23:24:00 -0000
@@ -295,19 +295,20 @@ _rb_gets(char *buf, int buflen, int time
         if (getc_script(&c))
             do_idle(false);
         else
 #endif
         if ((timeout > 0) && (ptr == buf)) {
-            mon_set_read_char_timeout(timeout);
+#define MIN_TIMEOUT 50
+            mon_set_read_char_timeout(timeout > MIN_TIMEOUT ? MIN_TIMEOUT : timeout);
             while (timeout > 0) {
                 res = mon_read_char_with_timeout(&c);
                 if (res) {
                     // Got a character
                     do_idle(false);
                     break;
                 }
-                timeout -= 50;
+                timeout -= MIN_TIMEOUT;
             }
             if (res == false) {
                 do_idle(true);
                 return _GETS_TIMEOUT;  // Input timed out
             }
> 
> 
> Thanks,
> Chris
> 
> Gary Thomas wrote:
> 
> >>Although the timeout value for the mon_read_char_with_timeout()
> >>function has already been set to a <timeout> value the while
> >>loop also loops over this <timeout> variable:
> >>
> >>...
> >>    mon_set_read_char_timeout(timeout);
> >>
> >>    while (timeout > 0) {
> >>       res = mon_read_char_with_timeout(&c);
> >>       if (res) {	...      }
> >>       timeout -= 50;
> >>    }
> >>...
> >>
> > 
> > There are two separate "timeout"s at work here.  The innermost one is
> > what is used by the read_char function to decide if a character has
> > arrived within some period of time.  The outermost is used by RedBoot
> > to allow it to do some things while waiting for characters to arrive
> > and will be much larger (orders of magnitude) than the innermost
> > timeout.  The idea is for RedBoot to see if a character has arrived
> > or wait at most the "innermost" time.  If no character has arrived, then
> > RedBoot can take on some "background" processing, e.g. checking for
> > any arriving network connections, blanking LCD screens, etc.
> > 
> 



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