MOO-cows Mailing List Archive
[Subject Prev][Subject Next][Thread Prev][Thread Next][Subject Index][Thread Index]

MOOcode level race condition with read() and force_input()

If I have a loop that prompts the user (via $command_utils:yes_or_no) as to
if a certain command should be executed for them (which will happen via
force_input(), but I don't explictly say that in the prompt)... well, this
would best be explained with a code example:

for cmd in (commands)
  ok = $command_utils:yes_or_no("Execute ", command, "?");
  ok && force_input(player, cmd);
endfor

(The enclosing loop in actually in a different (enclosing) verb)

Now, :yes_or_no uses read() (is there another way?) which reads the input
buffer, which force_input() feeds.  Unfortunately, this doesn't work, since
the force_input()'ed command in response to the first question becomes the
answer to the second.  With an odd number of elements in "commands", the
last one will be executed, but with an even number of elements/iterations,
of course, you only have to answer (er, type in) half the responses, the
submitted command gets interpreted as a negative response to the next
:yes_or_no, and in general, nothing worthwhile happens (worthwhile here
being a command you answered 'yes' to being executed).

I considered using suspend() after force_input()ing the command, thereby
giving the server a chance to do network I/O and creating a new command
task for it, but that means I can't use :yes_or_no (er, read()) on
subsiquent iterations.  What I first thought of doing was doing a suspend()
with no args (to suspend indefinately), but force_input()ing two lines,
instead, one which was the command to execute, and other which would end up
resuming the task which is indefinately suspended (but this has the same
problem, what with not being able to read() from suspended tasks()).

Note that there actually is the case where the code could suspend(), but
because of the read(), which restores ticks/seconds limit, it never does
suspend().

Any way around this, short of buffering all the commands to force_input at
the end of the loop?
Follow-Ups:
Home | Subject Index | Thread Index