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#!/usr/bin/env python |
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# -*- coding: utf-8 -*- |
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"""APRS KISS Class Definitions""" |
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# These imports are for python3 compatability inside python2 |
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from __future__ import absolute_import |
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from __future__ import division |
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from __future__ import print_function |
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import logging |
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import apex.kiss |
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__author__ = 'Jeffrey Phillips Freeman (WI2ARD)' |
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__maintainer__ = 'Jeffrey Phillips Freeman (WI2ARD)' |
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__email__ = '[email protected]' |
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__license__ = 'Apache License, Version 2.0' |
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__copyright__ = 'Copyright 2016, Syncleus, Inc. and contributors' |
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__credits__ = [] |
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class Aprs(object): |
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"""APRS interface.""" |
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def __init__(self, data_stream): |
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self.data_Stream = data_stream |
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@staticmethod |
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def __decode_frame(raw_frame): |
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""" |
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Decodes a KISS-encoded APRS frame. |
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:param raw_frame: KISS-encoded frame to decode. |
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:type raw_frame: str |
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:return: APRS frame-as-dict. |
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:rtype: dict |
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""" |
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logging.debug('raw_frame=%s', raw_frame) |
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frame = {} |
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frame_len = len(raw_frame) |
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if frame_len > 16: |
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for raw_slice in range(0, frame_len): |
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# Is address field length correct? |
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if raw_frame[raw_slice] & 0x01 and ((raw_slice + 1) % 7) == 0: |
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i = (raw_slice + 1) / 7 |
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# Less than 2 callsigns? |
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if 1 < i < 11: |
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if (raw_frame[raw_slice + 1] & 0x03 == 0x03 and raw_frame[raw_slice + 2] in [0xf0, 0xcf]): |
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frame['text'] = ''.join(map(chr, raw_frame[raw_slice + 3:])) |
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frame['destination'] = Aprs.__identity_as_string(Aprs.__extract_callsign(raw_frame)) |
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frame['source'] = Aprs.__identity_as_string(Aprs.__extract_callsign(raw_frame[7:])) |
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frame['path'] = Aprs.__extract_path(int(i), raw_frame) |
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return frame |
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logging.debug('frame=%s', frame) |
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return frame |
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@staticmethod |
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def __extract_path(start, raw_frame): |
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"""Extracts path from raw APRS KISS frame. |
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:param start: |
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:param raw_frame: Raw APRS frame from a KISS device. |
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:return: Full path from APRS frame. |
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:rtype: list |
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""" |
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full_path = [] |
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for i in range(2, start): |
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path = Aprs.__identity_as_string(Aprs.__extract_callsign(raw_frame[i * 7:])) |
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if path: |
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if raw_frame[i * 7 + 6] & 0x80: |
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full_path.append(''.join([path, '*'])) |
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else: |
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full_path.append(path) |
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return full_path |
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@staticmethod |
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def __extract_callsign(raw_frame): |
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""" |
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Extracts callsign from a raw KISS frame. |
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:param raw_frame: Raw KISS Frame to decode. |
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:returns: Dict of callsign and ssid. |
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:rtype: dict |
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""" |
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callsign = ''.join([chr(x >> 1) for x in raw_frame[:6]]).strip() |
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ssid = ((raw_frame[6]) >> 1) & 0x0f |
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return {'callsign': callsign, 'ssid': ssid} |
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@staticmethod |
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def __identity_as_string(identity): |
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""" |
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Returns a fully-formatted callsign (Callsign + SSID). |
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:param identity: Callsign Dictionary {'callsign': '', 'ssid': n} |
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:type callsign: dict |
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:returns: Callsign[-SSID]. |
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:rtype: str |
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""" |
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if identity['ssid'] > 0: |
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return '-'.join([identity['callsign'], str(identity['ssid'])]) |
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else: |
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return identity['callsign'] |
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@staticmethod |
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def __encode_frame(frame): |
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""" |
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Encodes an APRS frame-as-dict as a KISS frame. |
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:param frame: APRS frame-as-dict to encode. |
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:type frame: dict |
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:return: KISS-encoded APRS frame. |
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:rtype: list |
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""" |
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enc_frame = Aprs.__encode_callsign(Aprs.__parse_identity_string(frame['destination'])) + \ |
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Aprs.__encode_callsign(Aprs.__parse_identity_string(frame['source'])) |
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for p in frame['path']: |
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enc_frame += Aprs.__encode_callsign(Aprs.__parse_identity_string(p)) |
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return enc_frame[:-1] + [enc_frame[-1] | 0x01] + [apex.kiss.constants.SLOT_TIME] + [0xf0] + frame['text'] |
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@staticmethod |
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def __encode_callsign(callsign): |
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""" |
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Encodes a callsign-dict within a KISS frame. |
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:param callsign: Callsign-dict to encode. |
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:type callsign: dict |
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:return: KISS-encoded callsign. |
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:rtype: list |
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""" |
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call_sign = callsign['callsign'] |
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enc_ssid = (callsign['ssid'] << 1) | 0x60 |
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if '*' in call_sign: |
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call_sign = call_sign.replace('*', '') |
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enc_ssid |= 0x80 |
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while len(call_sign) < 6: |
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call_sign = ''.join([call_sign, ' ']) |
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encoded = [] |
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for p in call_sign: |
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encoded += [ord(p) << 1] |
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return encoded + [enc_ssid] |
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@staticmethod |
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def __parse_identity_string(identity_string): |
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""" |
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Creates callsign-as-dict from callsign-as-string. |
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:param identity_string: Callsign-as-string (with or without ssid). |
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:type raw_callsign: str |
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:return: Callsign-as-dict. |
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:rtype: dict |
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""" |
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# If we are parsing a spent token then first lets get rid of the astresick suffix. |
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if identity_string.endswith('*'): |
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identity_string = identity_string[:-1] |
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if '-' in identity_string: |
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call_sign, ssid = identity_string.split('-') |
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else: |
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call_sign = identity_string |
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ssid = 0 |
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return {'callsign': call_sign, 'ssid': int(ssid)} |
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def write(self, frame, port=0): |
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"""Writes APRS-encoded frame to KISS device. |
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:param frame: APRS frame to write to KISS device. |
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:type frame: dict |
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""" |
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encoded_frame = Aprs.__encode_frame(frame) |
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self.data_Stream.write(encoded_frame, port) |
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def read(self): |
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"""Reads APRS-encoded frame from KISS device. |
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""" |
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frame = self.data_Stream.read() |
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if frame is not None and len(frame): |
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return Aprs.__decode_frame(frame) |
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else: |
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return None |
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Syncleus /
apex
