added PositionReport object

CHANGES

@@ -3,6 +3,8 @@ CHANGES
 
 # 0.6.42
 
+- added util submodule containing various helper functions
+- added objects for creating packets (PositionReport, APRSPacket in packets submodule)
 - added DAO parsing
 - added parsing for invalid & user-defined formats
 - split parsing module into submodules

aprslib/packets/__init__.py

@@ -0,0 +1 @@
+from aprslib.packets.position import PositionReport

aprslib/packets/base.py

@@ -0,0 +1,31 @@
+
+
+class APRSPacket(object):
+    def __init__(self, fromcall, tocall, path=[]):
+        self.fromcall = fromcall
+        self.tocall = tocall
+        self.path = path
+
+    def __repr__(self):
+        return "<%s(%s)>" % (
+                    self.__class__.__name__,
+                    repr(str(self)),
+                    )
+
+    def _serialize_header(self):
+        header = "%s>%s" % (self.fromcall, self.tocall)
+
+        if self.path:
+            header += "," + ",".join(self.path)
+
+        return header
+
+    def _serialize_body(self):
+        return getattr(self, 'body', '')
+
+    def __str__(self):
+        return "%s:%s" % (
+            self._serialize_header(),
+            self._serialize_body(),
+            )
+

aprslib/packets/position.py

@@ -0,0 +1,38 @@
+from datetime import datetime
+from aprslib.packets.base import APRSPacket
+from aprslib.util import latitude_to_ddm, longitude_to_ddm, comment_altitude
+
+
+class PositionReport(APRSPacket):
+    latitude = 0
+    longitude = 0
+    symbol_table = '/'
+    symbol = 'l'
+    altitude = None
+    timestamp = None
+    comment = ''
+
+    def _serialize_body(self):
+
+        if self.timestamp is None:
+            timestamp = ''
+        elif isinstance(self.timestamp, str):
+            timestamp = self.timestamp
+        else:
+            timestamp = datetime.utcfromtimestamp(self.timestamp).strftime("%d%H%M") + 'z'
+
+        body = [
+            '/' if self.timestamp else '!',  # packet type
+            timestamp,
+            latitude_to_ddm(self.latitude),
+            self.symbol_table,
+            longitude_to_ddm(self.longitude),
+            self.symbol,
+            comment_altitude(self.altitude) if self.altitude is not None else '',
+            self.comment,
+        ]
+
+        return "".join(body)
+
+
+

aprslib/util/__init__.py

@@ -0,0 +1,36 @@
+from math import floor
+
+
+def degrees_to_ddm(dd):
+    degrees = int(floor(dd))
+    minutes = (dd - degrees) * 60
+    return (degrees, minutes)
+
+
+def latitude_to_ddm(dd):
+    direction = "S" if dd < 0 else "N"
+    degrees, minutes = degrees_to_ddm(abs(dd))
+
+    return "{0:02d}{1:05.2f}{2}".format(
+        degrees,
+        minutes,
+        direction,
+        )
+
+def longitude_to_ddm(dd):
+    direction = "W" if dd < 0 else "E"
+    degrees, minutes = degrees_to_ddm(abs(dd))
+
+    return "{0:03d}{1:05.2f}{2}".format(
+        degrees,
+        minutes,
+        direction,
+        )
+
+def comment_altitude(altitude):
+    altitude /= 0.3048  # to feet
+    altitude = min(999999, altitude)
+    altitude = max(-99999, altitude)
+    return "/A={0:06.0f}".format(altitude)
+
+