From 7b1c0353d854a0c29a29423536cd8513042a72c2 Mon Sep 17 00:00:00 2001
From: Stefan `Sec` Zehl <sec@42.org>
Date: Fri, 31 May 2024 20:19:44 +0200
Subject: [PATCH] [reassembler] nal 10-byte position report

---
 iridiumtk/reassembler/sbd_nal.py | 70 ++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100755 iridiumtk/reassembler/sbd_nal.py

diff --git a/iridiumtk/reassembler/sbd_nal.py b/iridiumtk/reassembler/sbd_nal.py
new file mode 100755
index 0000000..704a248
--- /dev/null
+++ b/iridiumtk/reassembler/sbd_nal.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+# vim: set ts=4 sw=4 tw=0 et pm=:
+
+import sys
+import re
+from util import to_ascii
+
+from .base import *
+from .sbd import ReassembleIDASBD
+from ..config import config, outfile
+
+class ReassembleIDASBDNal(ReassembleIDASBD):
+    def consume_l2(self,q):
+#        print(repr(q.__dict__))
+        typ=q.typ
+        time=q.time
+        prehdr=q.prehdr
+        data=q.data
+
+        if len(data)!=10:
+            return
+
+        lat_raw = _extract_bits(data, 4, 25)
+        long_raw = _extract_bits(data, 29, 25)
+        seconds = _extract_bits(data, 55, 17)
+        pdop_index = _extract_bits(data, 72, 4)
+        bits = _extract_bits(data, 76, 4)
+
+        if lat_raw > 18000000:
+            print("NALException: Invalid latitude value", file=sys.stderr)
+            return
+        if long_raw > 36000000:
+            print("NALException: Invalid longitude value", file=sys.stderr)
+            return
+        if seconds >= 86400:
+            print("NALException: Invalid seconds value", file=sys.stderr)
+            return
+        if pdop_index >= 8:
+            print("NALException: Invalid PDOP value", file=sys.stderr)
+            return
+
+        lat = (lat_raw - 9000000) / 100000
+        lon = (long_raw - 18000000) / 100000
+
+        #minutes, seconds = divmod(seconds, 60)
+        #hours, minutes = divmod(minutes, 60)
+
+        pdop = [1, 2, 5, 10, 20, 40, 70, 100][pdop_index]
+
+        fix = bool(bits & 0b0001)
+        emergency = bool(bits & 0b0010)
+        emergency_acknowledged = bool(bits & 0b0100)
+        motion = bool(bits & 0b1000)
+
+
+        bcd=["%x"%(x>>s&0xf) for x in prehdr[5:13] for s in (0,4)]
+
+        print("".join(bcd[1:]),f"lat=%.6f lon=%.6f, pdop={pdop}, emerg/ack: {emergency}/{emergency_acknowledged}, motion: {motion}, fix: {fix}, time: %02d:%02d:%02d"%(lat,lon,seconds//3600,(seconds//60)%60,seconds%60), file=outfile)
+
+def _extract_bits(data: bytes, start: int, amount: int) -> int:
+    value = 0
+    num = start + amount
+    for index in range(start, num):
+        if (data[index // 8] & (1 << (index % 8))) != 0:
+            value += (1 << (index - start))
+    return value
+
+modes=[
+["nal10",        ReassembleIDASBDNal, ],
+]