eventlet.GreenPile ported to gevent.py

# not actually tested

from gevent.queue import Queue
from gevent.pool import Pool

class GreenPile(object):

    def __init__(self, size_or_pool=1000):
        if isinstance(size_or_pool, Pool):
            self.pool = size_or_pool
        else:
            self.pool = Pool(size_or_pool)
        self.waiters = Queue()
        self.used = False
        self.counter = 0

    def spawn(self, func, *args, **kw):
        self.used =  True
        self.counter += 1
        try:
            gt = self.pool.spawn(func, *args, **kw)
            self.waiters.put(gt)
        except:
            self.counter -= 1
            raise

    def __iter__(self):
        return self

    def next(self):
        if self.counter == 0 and self.used:
            raise StopIteration()
        try:
            return self.waiters.get().get()
        finally:
            self.counter -= 1