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-# Coroutine implementation using Python threads.
-#
-# Combines ideas from Guido's Generator module, and from the coroutine
-# features of Icon and Simula 67.
-#
-# To run a collection of functions as coroutines, you need to create
-# a Coroutine object to control them:
-# co = Coroutine()
-# and then 'create' a subsidiary object for each function in the
-# collection:
-# cof1 = co.create(f1 [, arg1, arg2, ...]) # [] means optional,
-# cof2 = co.create(f2 [, arg1, arg2, ...]) #... not list
-# cof3 = co.create(f3 [, arg1, arg2, ...])
-# etc. The functions need not be distinct; 'create'ing the same
-# function multiple times gives you independent instances of the
-# function.
-#
-# To start the coroutines running, use co.tran on one of the create'd
-# functions; e.g., co.tran(cof2). The routine that first executes
-# co.tran is called the "main coroutine". It's special in several
-# respects: it existed before you created the Coroutine object; if any of
-# the create'd coroutines exits (does a return, or suffers an unhandled
-# exception), EarlyExit error is raised in the main coroutine; and the
-# co.detach() method transfers control directly to the main coroutine
-# (you can't use co.tran() for this because the main coroutine doesn't
-# have a name ...).
-#
-# Coroutine objects support these methods:
-#
-# handle = .create(func [, arg1, arg2, ...])
-# Creates a coroutine for an invocation of func(arg1, arg2, ...),
-# and returns a handle ("name") for the coroutine so created. The
-# handle can be used as the target in a subsequent .tran().
-#
-# .tran(target, data=None)
-# Transfer control to the create'd coroutine "target", optionally
-# passing it an arbitrary piece of data. To the coroutine A that does
-# the .tran, .tran acts like an ordinary function call: another
-# coroutine B can .tran back to it later, and if it does A's .tran
-# returns the 'data' argument passed to B's tran. E.g.,
-#
-# in coroutine coA in coroutine coC in coroutine coB
-# x = co.tran(coC) co.tran(coB) co.tran(coA,12)
-# print x # 12
-#
-# The data-passing feature is taken from Icon, and greatly cuts
-# the need to use global variables for inter-coroutine communication.
-#
-# .back( data=None )
-# The same as .tran(invoker, data=None), where 'invoker' is the
-# coroutine that most recently .tran'ed control to the coroutine
-# doing the .back. This is akin to Icon's "&source".
-#
-# .detach( data=None )
-# The same as .tran(main, data=None), where 'main' is the
-# (unnameable!) coroutine that started it all. 'main' has all the
-# rights of any other coroutine: upon receiving control, it can
-# .tran to an arbitrary coroutine of its choosing, go .back to
-# the .detach'er, or .kill the whole thing.
-#
-# .kill()
-# Destroy all the coroutines, and return control to the main
-# coroutine. None of the create'ed coroutines can be resumed after a
-# .kill(). An EarlyExit exception does a .kill() automatically. It's
-# a good idea to .kill() coroutines you're done with, since the
-# current implementation consumes a thread for each coroutine that
-# may be resumed.
-
-import _thread as thread
-import sync
-
-class _CoEvent:
- def __init__(self, func):
- self.f = func
- self.e = sync.event()
-
- def __repr__(self):
- if self.f is None:
- return 'main coroutine'
- else:
- return 'coroutine for func ' + self.f.__name__
-
- def __hash__(self):
- return id(self)
-
- def __cmp__(x,y):
- return cmp(id(x), id(y))
-
- def resume(self):
- self.e.post()
-
- def wait(self):
- self.e.wait()
- self.e.clear()
-
-class Killed(Exception): pass
-class EarlyExit(Exception): pass
-
-class Coroutine:
- def __init__(self):
- self.active = self.main = _CoEvent(None)
- self.invokedby = {self.main: None}
- self.killed = 0
- self.value = None
- self.terminated_by = None
-
- def create(self, func, *args):
- me = _CoEvent(func)
- self.invokedby[me] = None
- thread.start_new_thread(self._start, (me,) + args)
- return me
-
- def _start(self, me, *args):
- me.wait()
- if not self.killed:
- try:
- try:
- me.f(*args)
- except Killed:
- pass
- finally:
- if not self.killed:
- self.terminated_by = me
- self.kill()
-
- def kill(self):
- if self.killed:
- raise TypeError('kill() called on dead coroutines')
- self.killed = 1
- for coroutine in self.invokedby.keys():
- coroutine.resume()
-
- def back(self, data=None):
- return self.tran( self.invokedby[self.active], data )
-
- def detach(self, data=None):
- return self.tran( self.main, data )
-
- def tran(self, target, data=None):
- if target not in self.invokedby:
- raise TypeError('.tran target %r is not an active coroutine' % (target,))
- if self.killed:
- raise TypeError('.tran target %r is killed' % (target,))
- self.value = data
- me = self.active
- self.invokedby[target] = me
- self.active = target
- target.resume()
-
- me.wait()
- if self.killed:
- if self.main is not me:
- raise Killed
- if self.terminated_by is not None:
- raise EarlyExit('%r terminated early' % (self.terminated_by,))
-
- return self.value
-
-# end of module