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60 lines
2.0 KiB
60 lines
2.0 KiB
class PriorityQueue(object):
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"""A priority queue implemented using multiple internal queues (typically,
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FIFO queues). The internal queue must implement the following methods:
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* push(obj)
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* pop()
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* close()
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* __len__()
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The constructor receives a qfactory argument, which is a callable used to
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instantiate a new (internal) queue when a new priority is allocated. The
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qfactory function is called with the priority number as first and only
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argument.
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Only integer priorities should be used. Lower numbers are higher
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priorities.
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startprios is a sequence of priorities to start with. If the queue was
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previously closed leaving some priority buckets non-empty, those priorities
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should be passed in startprios.
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"""
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def __init__(self, qfactory, startprios=()):
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self.queues = {}
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self.qfactory = qfactory
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for p in startprios:
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self.queues[p] = self.qfactory(p)
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self.curprio = min(startprios) if startprios else None
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def push(self, obj, priority=0):
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if priority not in self.queues:
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self.queues[priority] = self.qfactory(priority)
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q = self.queues[priority]
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q.push(obj) # this may fail (eg. serialization error)
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if self.curprio is None or priority < self.curprio:
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self.curprio = priority
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def pop(self):
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if self.curprio is None:
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return
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q = self.queues[self.curprio]
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m = q.pop()
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if len(q) == 0:
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del self.queues[self.curprio]
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q.close()
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prios = [p for p, q in self.queues.items() if len(q) > 0]
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self.curprio = min(prios) if prios else None
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return m
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def close(self):
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active = []
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for p, q in self.queues.items():
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if len(q):
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active.append(p)
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q.close()
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return active
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def __len__(self):
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return sum(len(x) for x in self.queues.values()) if self.queues else 0
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