[ECOS] RedBoot gets() implimentation question

[Gary Thomas]

On 18-Jan-2001 Grant Edwards wrote:
> 
> If you don't mind, I've got a couple questions about the
> implimentation of gets() in RedBoot:
> 
> ========================================================================
> gets(char *buf, int buflen, int timeout)
> {
> [...]
> 
>     while (true) {
>#ifdef CYGSEM_REDBOOT_FLASH_CONFIG
>         if (script && *script) {
>             c = *script++;
>         } else
>#endif
>         if ((timeout > 0) && (ptr == buf)) {
>             mon_set_read_char_timeout(50);
>             while (timeout > 0) {
>                 res = mon_read_char_with_timeout(&c);
>                 if (res) {
>                     // Got a character
>                     break;
>                 }
>                 timeout -= 50;
>             }
>             if (res == false) {
>                 return _GETS_TIMEOUT;  // Input timed out
>             }
>         } else {
>             mon_read_char(&c);
>         }
>         *ptr = '\0';
>         switch (c) {
> [...]        
> ========================================================================
> 
> The test ((timeout > 0) && (ptr == buf)) means that the timeout
> only applies for the first character, and once we've received
> that first character we use blocking reads until we see an
> end-of-line?
> 
> That means that network polling stops and TCP sockets (and
> associated timers) go dead between between the time the first
> character is received and the newline is received?  [I don't
> think that's a problem, but it's something to keep in mind.]
> 

Correct.  This was a design choice - avoid the overhead of polling
for potential new TCP connections (all that's really going on here)
once data starts coming in.

> 
> I'm also curious about the inner loop:
> 
>             mon_set_read_char_timeout(50);
>             while (timeout > 0) {
>                 res = mon_read_char_with_timeout(&c);
>                 if (res) {
>                     // Got a character
>                     break;
>                 }
>                 timeout -= 50;
>             }
> 
> Would the following be equivalent?
> 
>             mon_set_read_char_timeout(timeout);
>             res = mon_read_char_with_timeout(&c);
> 

Yes and no.  Yes - the overall timeout would be the same.  No since
we want to go back and check for new TCP connections as often as is
reasonable.