Merge pull request #134 from junzis/pr_flarm

FLARM decoder
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Xavier Olive 2022-12-04 23:41:18 +01:00 committed by GitHub
commit 5a703a0d3c
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 368 additions and 4 deletions

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from typing import TypedDict
from .decode import flarm as flarm_decode
__all__ = ["DecodedMessage", "flarm"]
class DecodedMessage(TypedDict):
timestamp: int
icao24: str
latitude: float
longitude: float
altitude: int
vertical_speed: float
groundspeed: int
track: int
type: str
sensorLatitude: float
sensorLongitude: float
isIcao24: bool
noTrack: bool
stealth: bool
flarm = flarm_decode

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#include "core.h"
/*
*
* https://pastebin.com/YK2f8bfm
*
* NEW ENCRYPTION
*
* Swiss glider anti-colission system moved to a new encryption scheme: XXTEA
* The algorithm encrypts all the packet after the header: total 20 bytes or 5 long int words of data
*
* XXTEA description and code are found here: http://en.wikipedia.org/wiki/XXTEA
* The system uses 6 iterations of the main loop.
*
* The system version 6 sends two type of packets: position and ... some unknown data
* The difference is made by bit 0 of byte 3 of the packet: for position data this bit is zero.
*
* For position data the key used depends on the time and transmitting device address.
* The key is as well obscured by a weird algorithm.
* The code to generate the key is:
*
* */
void make_key(int *key, long time, long address)
{
const long key1[4] = {0xe43276df, 0xdca83759, 0x9802b8ac, 0x4675a56b};
const long key1b[4] = {0xfc78ea65, 0x804b90ea, 0xb76542cd, 0x329dfa32};
const long *table = ((((time >> 23) & 255) & 0x01) != 0) ? key1b : key1;
for (int i = 0; i < 4; i++)
{
key[i] = obscure(table[i] ^ ((time >> 6) ^ address), 0x045D9F3B) ^ 0x87B562F4;
}
}
long obscure(long key, unsigned long seed)
{
unsigned int m1 = seed * (key ^ (key >> 16));
unsigned int m2 = seed * (m1 ^ (m1 >> 16));
return m2 ^ (m2 >> 16);
}
/*
* NEW PACKET FORMAT:
*
* Byte Bits
* 0 AAAA AAAA device address
* 1 AAAA AAAA
* 2 AAAA AAAA
* 3 00aa 0000 aa = 10 or 01
*
* 4 vvvv vvvv vertical speed
* 5 xxxx xxvv
* 6 gggg gggg GPS status
* 7 tttt gggg plane type
*
* 8 LLLL LLLL Latitude
* 9 LLLL LLLL
* 10 aaaa aLLL
* 11 aaaa aaaa Altitude
*
* 12 NNNN NNNN Longitude
* 13 NNNN NNNN
* 14 xxxx NNNN
* 15 FFxx xxxx multiplying factor
*
* 16 SSSS SSSS as in version 4
* 17 ssss ssss
* 18 KKKK KKKK
* 19 kkkk kkkk
*
* 20 EEEE EEEE
* 21 eeee eeee
* 22 PPPP PPPP
* 24 pppp pppp
* */
/*
* https://en.wikipedia.org/wiki/XXTEA
*/
void btea(uint32_t *v, int n, uint32_t const key[4])
{
uint32_t y, z, sum;
unsigned p, rounds, e;
if (n > 1)
{ /* Coding Part */
/* Unused, should remove? */
rounds = 6 + 52 / n;
sum = 0;
z = v[n - 1];
do
{
sum += DELTA;
e = (sum >> 2) & 3;
for (p = 0; p < (unsigned)n - 1; p++)
{
y = v[p + 1];
z = v[p] += MX;
}
y = v[0];
z = v[n - 1] += MX;
} while (--rounds);
}
else if (n < -1)
{ /* Decoding Part */
n = -n;
rounds = 6; // + 52 / n;
sum = rounds * DELTA;
y = v[0];
do
{
e = (sum >> 2) & 3;
for (p = n - 1; p > 0; p--)
{
z = v[p - 1];
y = v[p] -= MX;
}
z = v[n - 1];
y = v[0] -= MX;
sum -= DELTA;
} while (--rounds);
}
}

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@ -0,0 +1,13 @@
#ifndef __CORE_H__
#define __CORE_H__
#include <stdint.h>
#define DELTA 0x9e3779b9
#define MX (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)))
void make_key(int *key, long time, long address);
long obscure(long key, unsigned long seed);
void btea(uint32_t *v, int n, uint32_t const key[4]);
#endif

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@ -0,0 +1,4 @@
cdef extern from "core.h":
void make_key(int*, long time, long address)
void btea(int*, int, int*)

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@ -0,0 +1,14 @@
from typing import Any
from . import DecodedMessage
AIRCRAFT_TYPES: list[str]
def flarm(
timestamp: int,
msg: str,
refLat: float,
refLon: float,
**kwargs: Any,
) -> DecodedMessage: ...

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@ -0,0 +1,145 @@
from core cimport make_key as c_make_key, btea as c_btea
from cpython cimport array
import array
import math
from ctypes import c_byte
from textwrap import wrap
AIRCRAFT_TYPES = [
"Unknown", # 0
"Glider", # 1
"Tow-Plane", # 2
"Helicopter", # 3
"Parachute", # 4
"Parachute Drop-Plane", # 5
"Hangglider", # 6
"Paraglider", # 7
"Aircraft", # 8
"Jet", # 9
"UFO", # 10
"Balloon", # 11
"Airship", # 12
"UAV", # 13
"Reserved", # 14
"Static Obstacle", # 15
]
cdef long bytearray2int(str icao24):
return (
(int(icao24[4:6], 16) & 0xFF)
| ((int(icao24[2:4], 16) & 0xFF) << 8)
| ((int(icao24[:2], 16) & 0xFF) << 16)
)
cpdef array.array make_key(long timestamp, str icao24):
cdef long addr = bytearray2int(icao24)
cdef array.array a = array.array('i', [0, 0, 0, 0])
c_make_key(a.data.as_ints, timestamp, (addr << 8) & 0xffffff)
return a
cpdef array.array btea(long timestamp, str msg):
cdef int p
cdef str icao24 = msg[4:6] + msg[2:4] + msg[:2]
cdef array.array key = make_key(timestamp, icao24)
pieces = wrap(msg[8:], 8)
cdef array.array toDecode = array.array('i', len(pieces) * [0])
for i, piece in enumerate(pieces):
p = 0
for elt in wrap(piece, 2)[::-1]:
p = (p << 8) + int(elt, 16)
toDecode[i] = p
c_btea(toDecode.data.as_ints, -5, key.data.as_ints)
return toDecode
cdef float velocity(int ns, int ew):
return math.hypot(ew / 4, ns / 4)
def heading(ns, ew, velocity):
if velocity < 1e-6:
velocity = 1
return (math.atan2(ew / velocity / 4, ns / velocity / 4) / 0.01745) % 360
def turningRate(a1, a2):
return ((((a2 - a1)) + 540) % 360) - 180
def flarm(long timestamp, str msg, float refLat, float refLon, **kwargs):
"""Decode a FLARM message.
Args:
timestamp (int)
msg (str)
refLat (float): the receiver's location
refLon (float): the receiver's location
Returns:
a dictionary with all decoded fields. Any extra keyword argument passed
is included in the output dictionary.
"""
cdef str icao24 = msg[4:6] + msg[2:4] + msg[:2]
cdef int magic = int(msg[6:8], 16)
if magic != 0x10 and magic != 0x20:
return None
cdef array.array decoded = btea(timestamp, msg)
cdef int aircraft_type = (decoded[0] >> 28) & 0xF
cdef int gps = (decoded[0] >> 16) & 0xFFF
cdef int raw_vs = c_byte(decoded[0] & 0x3FF).value
noTrack = ((decoded[0] >> 14) & 0x1) == 1
stealth = ((decoded[0] >> 13) & 0x1) == 1
cdef int altitude = (decoded[1] >> 19) & 0x1FFF
cdef int lat = decoded[1] & 0x7FFFF
cdef int mult_factor = 1 << ((decoded[2] >> 30) & 0x3)
cdef int lon = decoded[2] & 0xFFFFF
ns = list(
c_byte((decoded[3] >> (i * 8)) & 0xFF).value * mult_factor
for i in range(4)
)
ew = list(
c_byte((decoded[4] >> (i * 8)) & 0xFF).value * mult_factor
for i in range(4)
)
cdef int roundLat = int(refLat * 1e7) >> 7
lat = (lat - roundLat) % 0x080000
if lat >= 0x040000:
lat -= 0x080000
lat = (((lat + roundLat) << 7) + 0x40)
roundLon = int(refLon * 1e7) >> 7
lon = (lon - roundLon) % 0x100000
if lon >= 0x080000:
lon -= 0x100000
lon = (((lon + roundLon) << 7) + 0x40)
speed = sum(velocity(n, e) for n, e in zip(ns, ew)) / 4
heading4 = heading(ns[0], ew[0], speed)
heading8 = heading(ns[1], ew[1], speed)
return dict(
timestamp=timestamp,
icao24=icao24,
latitude=round(lat * 1e-7, 6),
longitude=round(lon * 1e-7, 6),
geoaltitude=altitude,
vertical_speed=raw_vs * mult_factor / 10,
groundspeed=round(speed),
track=round(heading4 - 4 * turningRate(heading4, heading8) / 4),
type=AIRCRAFT_TYPES[aircraft_type],
sensorLatitude=refLat,
sensorLongitude=refLon,
isIcao24=magic==0x10,
noTrack=noTrack,
stealth=stealth,
**kwargs
)

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@ -11,6 +11,8 @@ Steps for deploying a new version:
4. twine upload dist/*
"""
import sys
# Always prefer setuptools over distutils
from setuptools import setup, find_packages
@ -46,17 +48,54 @@ details = dict(
# typing_extensions are no longer necessary after Python 3.8 (TypedDict)
install_requires=["numpy", "pyzmq", "typing_extensions"],
extras_require={"fast": ["Cython"]},
package_data={"pyModeS": ["*.pyx", "*.pxd", "py.typed"]},
package_data={
"pyModeS": ["*.pyx", "*.pxd", "py.typed"],
"pyModeS.decoder.flarm": ["*.pyx", "*.pxd", "*.pyi"],
},
scripts=["pyModeS/streamer/modeslive"],
)
try:
from setuptools.extension import Extension
from distutils.core import Extension
from Cython.Build import cythonize
extensions = [Extension("pyModeS.c_common", ["pyModeS/c_common.pyx"])]
compile_args = []
include_dirs = ["pyModeS/decoder/flarm"]
setup(**dict(details, ext_modules=cythonize(extensions)))
if sys.platform == "linux":
compile_args += [
"-march=native",
"-O3",
"-msse",
"-msse2",
"-mfma",
"-mfpmath=sse",
"-Wno-pointer-sign",
]
extensions = [
Extension("pyModeS.c_common", ["pyModeS/c_common.pyx"]),
Extension(
"pyModeS.decoder.flarm.decode",
[
"pyModeS/decoder/flarm/decode.pyx",
"pyModeS/decoder/flarm/core.c",
],
extra_compile_args=compile_args,
include_dirs=include_dirs,
),
]
setup(
**dict(
details,
ext_modules=cythonize(
extensions,
include_path=include_dirs,
compiler_directives={"binding": True, "language_level": 3},
),
)
)
except ImportError:
setup(**details)