refactor aprs stuff

owrx/aprs/kiss.py

@@ -0,0 +1,59 @@
+import socket
+import time
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+FEND = 0xC0
+FESC = 0xDB
+TFEND = 0xDC
+TFESC = 0xDD
+
+
+class KissClient(object):
+    def __init__(self, port):
+        delay = 0.5
+        retries = 0
+        while True:
+            try:
+                self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                self.socket.connect(("localhost", port))
+                break
+            except ConnectionError:
+                if retries > 20:
+                    logger.error("maximum number of connection attempts reached. did direwolf start up correctly?")
+                    raise
+                retries += 1
+            time.sleep(delay)
+
+    def read(self):
+        return self.socket.recv(1)
+
+
+class KissDeframer(object):
+    def __init__(self):
+        self.escaped = False
+        self.buf = bytearray()
+
+    def parse(self, input):
+        frames = []
+        for b in input:
+            if b == FESC:
+                self.escaped = True
+            elif self.escaped:
+                if b == TFEND:
+                    self.buf.append(FEND)
+                elif b == TFESC:
+                    self.buf.append(FESC)
+                else:
+                    logger.warning("invalid escape char: %s", str(input[0]))
+                self.escaped = False
+            elif input[0] == FEND:
+                # data frames start with 0x00
+                if len(self.buf) > 1 and self.buf[0] == 0x00:
+                    frames += [self.buf[1:]]
+                self.buf = bytearray()
+            else:
+                self.buf.append(b)
+        return frames