Am 23.01.2012 22:48, schrieb M.Pekala:
I think that regex is too slow for this operation, but I'm uncertain
of another method in python that could be faster. A little help would
be appreciated.
Regardless of the outcome here, I would say that your code is still a
bit wonky on the handling of partial data and gaps due to buffer
overflows in the serial port buffers.
I'd start with something like this:
import unittest
class SensorReader(object):
def __init__(self):
pass
def parse(self, buffer):
"""store and parse given input"""
pass
def get_sample(self):
"""retrieve a single sample parsed from input data
This returns a tuple containing the sensor name and the
value. In case some input data was not parseable, it
returns a tuple with an empty string and the unrecognized
data.
"""
pass
class Test(unittest.TestCase):
def setUp(self):
self.handler = SensorReader()
def test_empty_buffer(self):
self.handler.parse(buffer='')
r = self.handler.get_sample()
self.assertEqual(r, None)
def test_input_1(self):
self.handler.parse(buffer='$A1234$')
r = self.handler.get_sample()
self.assertEqual(r, ('A', 1234))
def test_input_2(self):
self.handler.parse(buffer='$A1234$$B5678$')
r = self.handler.get_sample()
self.assertEqual(r, ('A', 1234))
r = self.handler.get_sample()
self.assertEqual(r, ('B', 5678))
def test_invalid_input(self):
self.handler.parse(buffer='234$$B5678$')
r = self.handler.get_sample()
self.assertEqual(r, ('', '234$'))
r = self.handler.get_sample()
self.assertEqual(r, ('B', 5678))
def test_partial_input(self):
self.handler.parse(buffer='$B56')
r = self.handler.get_sample()
self.assertEqual(r, None)
self.handler.parse(buffer='78$$C90')
r = self.handler.get_sample()
self.assertEqual(r, ('B', 5678))
Concerning the parsing itself, there is a "find" function in the str
class which you can use. Just search for dollar signs and take the data
in between. If it's empty, the first one is the end and the second one
the start of the next sample, so you can discard the content. Having
tests as above will make it a breeze for you to figure out actual
implementation. You could also start off with regexes and then switch to
linear scanning for speed.
Uli
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