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# -*- coding: utf-8 -*-
__docformat__ = 'restructuredtext'
from category import Category
from pattern import Pattern
import setcross
class StateMachine:
"""
The state machine contains a list of dependencies between states, and a list
of states which are "up."
"""
def __init__(self):
"""
Create a new state machine
"""
self.up = set()
self.wanted = set()
self.deps = []
self.event_triggers = []
def emit(self, event):
"""
Emit an event.
"""
retval = False
for evpat, cat in self.event_triggers:
if event.subset_of(evpat):
retval |= self.bring_up(cat.intersect_args(**event.args))
return retval
def bring_up(self, cat, wanted=True):
"""
Move states in the given Category `cat` from down to up.
"""
found = None
for (match, dependency) in self.get_applicable_deps(cat):
res = self.get_satisfied_states(match, dependency)
if len(res) == 0:
return False
if found == None:
found = [res]
else:
found.append(res)
if found == None:
self.add_hold(cat, wanted)
sm.emit(Category("ε"))
return True
to_add = self.cat_cross(found)
for x in to_add:
self.add_hold(x, wanted)
sm.emit(Category("ε"))
return True
def cat_cross(self, found):
"""
Given a list of sets, where each set contains Category objects, return a
set of all categories that can be made by intersecting one element from
each set.
"""
to_add = set()
for tup in setcross.cross(*found):
orig = tup
while len(tup) > 1:
newtup = (tup[0].intersect(tup[1]),)
if newtup[0] == None:
tup = ()
break
tup = newtup + tup[2:len(tup)]
if len(tup) == 0 or tup[0] == None:
continue
to_add.add(tup[0])
return to_add
def add_hold(self, cat, wanted):
"""
Add a hold to a state. Does not check dependencies.
"""
for x in self.up:
if cat.subset_of(x):
return
if x.subset_of(cat):
self.up.remove(x)
self.up.add(cat)
return
self.up.add(cat)
if wanted: self.wanted.add(cat)
def bring_down(self, cat, rec=False):
"""
Bring a currently "up" state down.
"""
to_drop = set([ x for x in self.up if x.subset_of(cat) ])
if None in to_drop: to_drop.remove(None)
if len(to_drop) == 0: return False
for (dependent, dependency) in self.deps:
match = set([dependency.intersect(x) for x in to_drop])
if None in match: match.remove(None)
if match != None:
for item in match:
self.bring_down(dependent.fill(item.args), rec=True)
self.up -= to_drop
self.wanted -= to_drop
if not rec: self.cleanup_states()
def cleanup_states(self):
"""
Remove unwanted states
"""
new_up = self.wanted.copy()
addition = set([1])
while len(addition):
addition = set()
for s in addition:
for x in self.get_applicable_deps(s):
for y in self.up:
if y.subset_of(x):
addition.add(y)
new_up |= addition
self.up = new_up
def get_satisfied_states(self, dependents, dependencies):
"""
Given that states in `dependents` depend on states in `dependencies`,
return a new Category that contains only the states in `dependents` that
could match states in `dependencies`.
"""
retval = []
for cat in self.up:
if dependencies.superset_of(cat):
retval.append(dependents.intersect_args(**cat.args))
return set(retval) | dependents.inverse_set()
def get_applicable_deps(self, cat):
"""
Find dependencies that might apply to members of `cat`
"""
retval = []
for (x, y) in self.deps:
un = cat.intersect(x)
if un != None:
retval.append((un, y.fill(un.args)))
return retval
def __str__(self):
return "\n".join(["%s" % k for k in self.up])
def __repr__(self):
return str(self)
def m(*args): return Pattern(True, *args) # The "m" reads "match", so m("foo", "bar") reads 'match foo and bar'
def nm(*args): return Pattern(False, *args) # Reads as "don't match." See above
def any(): return nm() # Match anything. Implementation reads "don't match nothing"
if __name__ == "__main__":
sm = StateMachine()
sm.deps.append((Category("mounted", type=m("nfs")), Category("network_up")))
sm.deps.append((Category("mounted", type=nm("nfs")), Category("found_disk")))
sm.deps.append((Category("mounted"), Category("vol_conf")))
sm.event_triggers.append((Category("fstab_line"), Category("vol_conf", src=m("fstabd"))))
sm.bring_up(Category("network_up"))
sm.bring_up(Category("found_disk", uuid=m("d3adb3ef"), devname=m("/dev/sda"), label=m("myroot")))
sm.bring_up(Category("mounted", devname=any(), mountpoint=any()))
print sm
print "--"
sm.emit(Category("fstab_line", label=m("myroot"), type=m("ext3"), mountpoint=m("/")))
sm.emit(Category("fstab_line", devname=m("foosrv.com:/vol/home"), type=m("nfs"), mountpoint=m("/home")))
sm.emit(Category("fstab_line", devname=m("foosrv.com:/vol/beefs"), type=m("nfs"), mountpoint=m("/beefs")))
sm.bring_up(Category("mounted", devname=any(), mountpoint=any()))
print sm
print "--"
sm.bring_down(Category("network_up"))
print sm
|
