68 lines
1.9 KiB
Python
68 lines
1.9 KiB
Python
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"""
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kvsimple - simple key-value message class for example applications
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Author: Min RK <benjaminrk@gmail.com>
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"""
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import struct # for packing integers
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import sys
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import zmq
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class KVMsg(object):
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"""
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Message is formatted on wire as 3 frames:
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frame 0: key (0MQ string)
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frame 1: sequence (8 bytes, network order)
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frame 2: body (blob)
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"""
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key = None # key (string)
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sequence = 0 # int
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body = None # blob
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def __init__(self, sequence, key=None, body=None):
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assert isinstance(sequence, int)
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self.sequence = sequence
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self.key = key
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self.body = body
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def store(self, dikt):
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"""Store me in a dict if I have anything to store"""
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# this seems weird to check, but it's what the C example does
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if self.key is not None and self.body is not None:
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dikt[self.key] = self
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def send(self, socket):
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"""Send key-value message to socket; any empty frames are sent as such."""
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key = b'' if self.key is None else self.key.encode()
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seq_s = struct.pack('!l', self.sequence)
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body = b'' if self.body is None else self.body.encode()
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socket.send_multipart([ key, seq_s, body ])
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@classmethod
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def recv(cls, socket):
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"""Reads key-value message from socket, returns new kvmsg instance."""
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key, seq_s, body = socket.recv_multipart(zmq.NOBLOCK)
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key = key.decode() if key else None
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seq = struct.unpack('!l',seq_s)[0]
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body = body.decode() if body else None
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return cls(seq, key=key, body=body)
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def dump(self):
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if self.body is None:
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size = 0
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data='NULL'
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else:
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size = len(self.body)
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data=repr(self.body)
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print >> sys.stderr, "[seq:{seq}][key:{key}][size:{size}] {data}".format(
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seq=self.sequence,
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key=self.key,
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size=size,
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data=data,
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)
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