mirror of
https://github.com/python/cpython.git
synced 2024-12-01 03:01:36 +01:00
100 lines
3.7 KiB
Python
100 lines
3.7 KiB
Python
# Module sched -- a generally useful event scheduler class
|
|
|
|
# Each instance of this class manages its own queue.
|
|
# No multi-threading is implied; you are supposed to hack that
|
|
# yourself, or use a single instance per application.
|
|
#
|
|
# Each instance is parametrized with two functions, one that is
|
|
# supposed to return the current time, one that is supposed to
|
|
# implement a delay. You can implement real-time scheduling by
|
|
# substituting time and sleep from built-in module time, or you can
|
|
# implement simulated time by writing your own functions. This can
|
|
# also be used to integrate scheduling with STDWIN events; the delay
|
|
# function is allowed to modify the queue. Time can be expressed as
|
|
# integers or floating point numbers, as long as it is consistent.
|
|
|
|
# Events are specified by tuples (time, priority, action, argument).
|
|
# As in UNIX, lower priority numbers mean higher priority; in this
|
|
# way the queue can be maintained fully sorted. Execution of the
|
|
# event means calling the action function, passing it the argument.
|
|
# Remember that in Python, multiple function arguments can be packed
|
|
# in a tuple. The action function may be an instance method so it
|
|
# has another way to reference private data (besides global variables).
|
|
# Parameterless functions or methods cannot be used, however.
|
|
|
|
# XXX The timefunc and delayfunc should have been defined as methods
|
|
# XXX so you can define new kinds of schedulers using subclassing
|
|
# XXX instead of having to define a module or class just to hold
|
|
# XXX the global state of your particular time and delay functtions.
|
|
|
|
import bisect
|
|
|
|
class scheduler:
|
|
#
|
|
# Initialize a new instance, passing the time and delay functions
|
|
#
|
|
def __init__(self, timefunc, delayfunc):
|
|
self.queue = []
|
|
self.timefunc = timefunc
|
|
self.delayfunc = delayfunc
|
|
#
|
|
# Enter a new event in the queue at an absolute time.
|
|
# Returns an ID for the event which can be used
|
|
# to remove it, if necessary.
|
|
#
|
|
def enterabs(self, time, priority, action, argument):
|
|
event = time, priority, action, argument
|
|
bisect.insort(self.queue, event)
|
|
return event # The ID
|
|
#
|
|
# A variant that specifies the time as a relative time.
|
|
# This is actually the more commonly used interface.
|
|
#
|
|
def enter(self, delay, priority, action, argument):
|
|
time = self.timefunc() + delay
|
|
return self.enterabs(time, priority, action, argument)
|
|
#
|
|
# Remove an event from the queue.
|
|
# This must be presented the ID as returned by enter().
|
|
# If the event is not in the queue, this raises RuntimeError.
|
|
#
|
|
def cancel(self, event):
|
|
self.queue.remove(event)
|
|
#
|
|
# Check whether the queue is empty.
|
|
#
|
|
def empty(self):
|
|
return len(self.queue) == 0
|
|
#
|
|
# Run: execute events until the queue is empty.
|
|
#
|
|
# When there is a positive delay until the first event, the
|
|
# delay function is called and the event is left in the queue;
|
|
# otherwise, the event is removed from the queue and executed
|
|
# (its action function is called, passing it the argument).
|
|
# If the delay function returns prematurely, it is simply
|
|
# restarted.
|
|
#
|
|
# It is legal for both the delay function and the action
|
|
# function to to modify the queue or to raise an exception;
|
|
# exceptions are not caught but the scheduler's state
|
|
# remains well-defined so run() may be called again.
|
|
#
|
|
# A questionably hack is added to allow other threads to run:
|
|
# just after an event is executed, a delay of 0 is executed,
|
|
# to avoid monopolizing the CPU when other threads are also
|
|
# runnable.
|
|
#
|
|
def run(self):
|
|
q = self.queue
|
|
while q:
|
|
time, priority, action, argument = q[0]
|
|
now = self.timefunc()
|
|
if now < time:
|
|
self.delayfunc(time - now)
|
|
else:
|
|
del q[0]
|
|
void = apply(action, argument)
|
|
self.delayfunc(0) # Let other threads run
|
|
#
|