106 lines
2.9 KiB
Python
106 lines
2.9 KiB
Python
import struct
|
|
import mapping
|
|
|
|
class NotImplementedException(Exception):
|
|
pass
|
|
|
|
class Transport(object):
|
|
def __init__(self, device, *args, **kwargs):
|
|
self.device = device
|
|
self.session_depth = 0
|
|
self._open()
|
|
|
|
def _open(self):
|
|
raise NotImplementedException("Not implemented")
|
|
|
|
def _close(self):
|
|
raise NotImplementedException("Not implemented")
|
|
|
|
def _write(self, msg):
|
|
raise NotImplementedException("Not implemented")
|
|
|
|
def _read(self):
|
|
raise NotImplementedException("Not implemented")
|
|
|
|
def _session_begin(self):
|
|
pass
|
|
|
|
def _session_end(self):
|
|
pass
|
|
|
|
def ready_to_read(self):
|
|
raise NotImplementedException("Not implemented")
|
|
|
|
def session_begin(self):
|
|
if self.session_depth == 0:
|
|
self._session_begin()
|
|
self.session_depth += 1
|
|
|
|
def session_end(self):
|
|
self.session_depth -= 1
|
|
self.session_depth = max(0, self.session_depth)
|
|
if self.session_depth == 0:
|
|
self._session_end()
|
|
|
|
def close(self):
|
|
self._close()
|
|
|
|
def write(self, msg):
|
|
ser = msg.SerializeToString()
|
|
header = struct.pack(">HL", mapping.get_type(msg), len(ser))
|
|
self._write("##%s%s" % (header, ser))
|
|
|
|
def read(self):
|
|
if not self.ready_to_read():
|
|
return None
|
|
|
|
data = self._read()
|
|
if data == None:
|
|
return None
|
|
|
|
return self._parse_message(data)
|
|
|
|
def read_blocking(self):
|
|
while True:
|
|
data = self._read()
|
|
if data != None:
|
|
break
|
|
|
|
return self._parse_message(data)
|
|
|
|
def _parse_message(self, data):
|
|
(msg_type, data) = data
|
|
inst = mapping.get_class(msg_type)()
|
|
inst.ParseFromString(data)
|
|
return inst
|
|
|
|
def _read_headers(self, read_f):
|
|
# Try to read headers until some sane value are detected
|
|
is_ok = False
|
|
while not is_ok:
|
|
|
|
# Align cursor to the beginning of the header ("##")
|
|
c = read_f.read(1)
|
|
i = 0
|
|
while c != '#':
|
|
i += 1
|
|
if i >= 64:
|
|
# timeout
|
|
raise Exception("Timed out while waiting for the magic character")
|
|
#print "Aligning to magic characters"
|
|
c = read_f.read(1)
|
|
|
|
if read_f.read(1) != "#":
|
|
# Second character must be # to be valid header
|
|
raise Exception("Second magic character is broken")
|
|
|
|
# Now we're most likely on the beginning of the header
|
|
try:
|
|
headerlen = struct.calcsize(">HL")
|
|
(msg_type, datalen) = struct.unpack(">HL", read_f.read(headerlen))
|
|
break
|
|
except:
|
|
raise Exception("Cannot parse header length")
|
|
|
|
return (msg_type, datalen)
|