from __future__ import absolute_import
import six
class Masker(object):
"""
Data sent from the server must be masked to prevent malicious clients
from sending data over the wire in predictable patterns.
Servers do not have to mask data they send to the client.
https://tools.ietf.org/html/rfc6455#section-5.3
"""
def __init__(self, key):
self.key = key
self.offset = 0
def mask(self, offset, data):
result = bytearray(data)
for i in range(len(data)):
if six.PY2:
result[i] ^= ord(self.key[offset % 4])
else:
result[i] ^= self.key[offset % 4]
offset += 1
result = bytes(result)
return result
def __call__(self, data):
ret = self.mask(self.offset, data)
self.offset += len(ret)
return ret
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