Update allcall.py

pyModeS/decoder/allcall.py

@@ -1,87 +1,75 @@
+"""
+Decode all-call reply messages, with dowlink format 11
+"""
+
 from pyModeS import common
-"""
-Decoding all call replies DF=11
-"""
 
-def interrogator_code(msg):
-    if common.df(msg) == 11:  # check that the msg is DF11
-        '''Returns the IP code of the Mode S all-call reply (DF11)'''
-        binaryraw=common.hex2bin(msg)
-        PI=binaryraw[-24:]
-        DATA=binaryraw[:-24]
 
-        Gx='1111111111111010000001001000'
-        Mx=DATA[::-1].zfill(len(DATA)+24)[::-1]
-        initialdifference=len(Mx)-len(Gx)
-        Gx = Gx[::-1].zfill(len(Mx))[::-1]
-        while len(Mx)>initialdifference:
-            MSB=Mx[0]
-            if MSB=='1':
-                result=int(Mx,2)^int(Gx,2)
-                Mx = str(bin(result)[2:])
-                Gx = Gx.rstrip('0')[::-1].zfill(len(Mx))[::-1]
+def _checkdf(func):
+    """Ensure downlink format is 11."""
 
-            else: #If the Mx starts with a 0
-                Mx=Mx[1:]
-                Gx=Gx[:-1]
+    def wrapper(msg):
+        df = common.df(msg)
+        if df != 11:
+            raise RuntimeError(
+                "Incorrect downlink format, expect 11, got {}".format(df)
+            )
+        return func(msg)
 
-        SIcode=bin(int(Mx,2)^int(PI,2)).zfill(7) #Mx is the parity sequence and PI is the last field of the DF11.
-        if int(SIcode[0:3],2)>0:
-            return str("SI" + str(int(SIcode[3:],2)))
-        else:
-            return str("II" + str(int(SIcode,2)))
-    else:
-        raise RuntimeError("Incorrect or inconsistent message types")
+    return wrapper
 
-def flight_status(msg):
-    '''returns the flight status'''
-    if common.df(msg) == 11:  # check that the msg is DF11
-        binaryraw=common.hex2bin(msg)
-        CA = (int(binaryraw[5:8],2))
-        if CA in [0, 1, 2, 3, 6, 7]: #reserved
-            return None
-        if CA == 4:#level 2 transponder, ability to set CA to 7 and on ground
-            return "on ground"
-        if CA == 5:#level 2 transponder, ability to set CA to 7 and airborn
-            return "airborne"
-    else:
-        raise RuntimeError("Incorrect or inconsistent message types")
 
-def transponder_level(msg):
-    '''returns the transponder level'''
-    if common.df(msg) == 11:#check that the msg is DF11
-        binaryraw=common.hex2bin(msg)
-        CA = (int(binaryraw[5:8],2))
-        if CA in [1, 2, 3, 4, 5, 6, 7]: #reserved
-            return 2
-        if CA == 0:
-            return 1
-    else:
-        raise RuntimeError("Incorrect or inconsistent message types")
+@_checkdf
+def icao(msg):
+    """Decode transponder code (ICAO address).
 
+    Args:
+        msg (str): 14 hexdigits string
+    Returns:
+        string: ICAO address
+
+    """
+    return common.icao(msg)
+
+
+@_checkdf
+def interrogator(msg):
+    """Decode interrogator identifier code.
+
+    Args:
+        msg (str): 14 hexdigits string
+    Returns:
+        int: interrogator identifier code
+
+    """
+    # simply the CRC reminder
+    return common.crc(msg)
+
+
+@_checkdf
 def capability(msg):
-    '''return the capability code'''
-    if common.df(msg) == 11:#check that the msg is DF11
-        binaryraw=common.hex2bin(msg)
-        CA = (int(binaryraw[5:8],2))
-        if CA == 0: #level 1 transponder
-            return 0
-        if CA in [1, 2,  3]: #reserved
-            return None
-        if CA == 4:#level 2 transponder, ability to set CA to 7 and on ground
-            return 4
-        if CA == 5:#level 2 transponder, ability to set CA to 7 and airborn
-            return 5
-        if CA == 6:#level 2 transponder, ability to set CA to 7 and either airborn on ground
-            return 6
-        if CA == 7:# (either DR field is 0 or FS field is 2,3,4 or 5), and either airborn on ground
-            return 7
-    else:
-        raise RuntimeError("Incorrect or inconsistent message types")
+    """Decode transponder capability.
 
-def AA(msg):
-    '''returns the icao code of the aircraft'''
-    if common.df(msg) == 11:  # check that the msg is DF11
-        return (msg[2:8])
+    Args:
+        msg (str): 14 hexdigits string
+    Returns:
+        int, str: transponder capability, description
+
+    """
+    msgbin = common.hex2bin(msg)
+    ca = common.bin2int(msgbin[5:8])
+
+    if ca == 0:
+        text = "level 1 transponder"
+    elif ca == 4:
+        text = "level 2 transponder, ability to set CA to 7, on ground"
+    elif ca == 5:
+        text = "level 2 transponder, ability to set CA to 7, airborne"
+    elif ca == 6:
+        text = "evel 2 transponder, ability to set CA to 7, either airborne or ground"
+    elif ca == 7:
+        text = "Downlink Request value is 0,or the Flight Status is 2, 3, 4 or 5, either airborne or on the ground"
     else:
-        raise RuntimeError("Incorrect or inconsistent message types")
+        text = None
+
+    return ca, text