fragmentation.py
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32 
33 from rosbridge_library.capability import Capability
34 import math
35 
36 
38  """ The Fragmentation capability doesn't define any incoming operation
39  handlers, but provides methods to fragment outgoing messages """
40 
41  fragmentation_seed = 0
42 
43  def __init__(self, protocol):
44  # Call superclass constructor
45  Capability.__init__(self, protocol)
46 
47  def fragment(self, message, fragment_size, mid=None):
48  """ Serializes the provided message, then splits the serialized
49  message according to fragment_size, then sends the fragments.
50 
51  If the size of the message is less than the fragment size, then
52  the original message is returned rather than a single fragment
53 
54  Since fragmentation is typically only used for very large messages,
55  this method returns a generator for fragments rather than a list
56 
57  Keyword Arguments
58  message -- the message dict object to be fragmented
59  fragment_size -- the max size for the fragments
60  mid -- (optional) if provided, the fragment messages
61  will be given this id. Otherwise an id will be auto-generated.
62 
63  Returns a generator of message dict objects representing the fragments
64  """
65  # All fragmented messages need an ID so they can be reconstructed
66  if mid is None:
67  mid = self.fragmentation_seed
69 
70  serialized = self.protocol.serialize(message, mid)
71 
72  if serialized is None:
73  return []
74 
75  message_length = len(serialized)
76  if message_length <= fragment_size:
77  return [message]
78 
79  msg_id = message.get("id", None)
80 
81  expected_duration = int(math.ceil(math.ceil(message_length / float(fragment_size))) * self.protocol.delay_between_messages)
82 
83  log_msg = "sending " + str(int(math.ceil(message_length / float(fragment_size)))) + " parts [fragment size: " + str(fragment_size) +"; expected duration: ~" + str(expected_duration) + "s]"
84  self.protocol.log("info", log_msg)
85 
86  return self._fragment_generator(serialized, fragment_size, mid)
87 
88  def _fragment_generator(self, msg, size, mid):
89  """ Returns a generator of fragment messages """
90  total = ((len(msg)-1) / size) + 1
91  n = 0
92  for i in range(0, len(msg), size):
93  fragment = msg[i:i+size]
94  yield self._create_fragment(fragment, n, total, mid)
95  n = n + 1
96 
97  def _create_fragment(self, fragment, num, total, mid):
98  """ Given a string fragment of the original message, creates
99  the appropriate fragment message """
100  return {
101  "op": "fragment",
102  "id": mid,
103  "data": fragment,
104  "num": num,
105  "total": total
106  }
def fragment(self, message, fragment_size, mid=None)
def _create_fragment(self, fragment, num, total, mid)


rosbridge_library
Author(s): Jonathan Mace
autogenerated on Wed Jun 3 2020 03:55:14