Add some oneoff tools for comm-b decoding testing

Makefile

@@ -70,3 +70,6 @@ benchmarks: convert_benchmark
 
 oneoff/convert_benchmark: oneoff/convert_benchmark.o convert.o util.o
 	$(CC) $(CPPFLAGS) $(CFLAGS) -g -o $@ $^ -lm
+
+oneoff/decode_comm_b: oneoff/decode_comm_b.o comm_b.o ais_charset.o
+	$(CC) $(CPPFLAGS) $(CFLAGS) -g -o $@ $^ -lm

oneoff/decode_comm_b.c

@@ -0,0 +1,172 @@
+#include <stdio.h>
+
+#include "../dump1090.h"
+#include "../comm_b.h"
+
+char last_callsign[8];
+double last_callsign_ts = 0;
+double last_track = -1;
+double last_track_ts = 0;
+double last_magnetic = -1;
+double last_magnetic_ts = 0;
+double last_gs = -1;
+double last_gs_ts = 0;
+double last_ias = -1;
+double last_ias_ts = 0;
+double last_tas = -1;
+double last_tas_ts = 0;
+double last_mach = -1;
+double last_mach_ts = 0;
+
+double angle_difference(double h1, double h2)
+{
+    float delta = fabs(h1 - h2);
+    if (delta > 180.0)
+        delta = 360.0 - delta;
+    return delta;
+}
+
+void process(double timestamp, const char *line, struct modesMessage *mm)
+{
+    decodeCommB(mm);
+
+    printf("line\t%s\tformat\t", line);
+
+    switch (mm->commb_format) {
+#define EMIT(x) case COMMB_ ## x: printf("%s", #x); break
+        EMIT(UNKNOWN);
+        EMIT(AMBIGUOUS);
+        EMIT(EMPTY_RESPONSE);
+        EMIT(DATALINK_CAPS);
+        EMIT(GICB_CAPS);
+        EMIT(AIRCRAFT_IDENT);
+        EMIT(ACAS_RA);
+        EMIT(VERTICAL_INTENT);
+        EMIT(TRACK_TURN);
+        EMIT(HEADING_SPEED);
+#undef EMIT
+    default:
+        printf("%s", "UNHANDLED"); break;
+    }
+
+    int suspicious = 0;
+    
+    if (mm->callsign_valid) {
+        printf("\tcallsign\t%s", mm->callsign);
+        if ((timestamp - last_callsign_ts) < 30.0 && strcmp(last_callsign, mm->callsign)) {
+            suspicious = 1;
+        }
+        memcpy(last_callsign, mm->callsign, sizeof(last_callsign));
+        last_callsign_ts = timestamp;
+    }
+    if (mm->heading_valid && mm->heading_type == HEADING_GROUND_TRACK) {
+        printf("\ttrack\t%.1f", mm->heading);
+        if ((timestamp - last_track_ts) < 10.0 && angle_difference(last_track, mm->heading) > 45) {
+            suspicious = 1;
+        }
+        if ((timestamp - last_magnetic_ts) < 10.0 && angle_difference(last_magnetic, mm->heading) > 45) {
+            suspicious = 1;
+        }
+        last_track = mm->heading;
+        last_track_ts = timestamp;
+    } 
+    if (mm->heading_valid && mm->heading_type == HEADING_MAGNETIC) {
+        printf("\tmagnetic\t%.1f", mm->heading);
+        if ((timestamp - last_magnetic_ts) < 10.0 && angle_difference(last_magnetic, mm->heading) > 45) {
+            suspicious = 1;
+        }
+        if ((timestamp - last_track_ts) < 10.0 && angle_difference(last_track, mm->heading) > 45) {
+            suspicious = 1;
+        }
+        last_magnetic = mm->heading;
+        last_magnetic_ts = timestamp;
+    } 
+    if (mm->track_rate_valid) {
+        printf("\ttrack_rate\t%.2f", mm->track_rate);
+    }
+    if (mm->roll_valid) {
+        printf("\troll\t%.1f", mm->roll);
+    }
+    if (mm->gs_valid) {
+        printf("\tgs\t%.1f", mm->gs.selected);
+        if ((timestamp - last_gs_ts) < 10.0 && fabs(last_gs - mm->gs.selected) > 50) {
+            suspicious = 1;
+        }
+        last_gs = mm->gs.selected;
+        last_gs_ts = timestamp;
+    }
+    if (mm->ias_valid) {
+        printf("\tias\t%d", mm->ias);
+        if ((timestamp - last_ias_ts) < 10.0 && abs(last_ias - mm->ias) > 50) {
+            suspicious = 1;
+        }
+        last_ias = mm->ias;
+        last_ias_ts = timestamp;
+    }
+    if (mm->tas_valid) {
+        printf("\ttas\t%d", mm->tas);
+        if ((timestamp - last_tas_ts) < 10.0 && abs(last_tas - mm->tas) > 50) {
+            suspicious = 1;
+        }
+        last_tas = mm->tas;
+        last_tas_ts = timestamp;
+    }
+    if (mm->mach_valid) {
+        printf("\tmach\t%.3f", mm->mach);
+        if ((timestamp - last_mach_ts) < 10.0 && abs(last_mach - mm->mach) > 0.1) {
+            suspicious = 1;
+        }
+        last_mach = mm->mach;
+        last_mach_ts = timestamp;
+    }
+
+    if (suspicious) {
+        printf("\tsuspicious\tyes!");
+    }
+
+    printf("\n");
+}
+
+int main(int argc, char **argv)
+{
+    /* unused */ (void)argc;
+    /* unused */ (void)argv;
+    
+    char line[1024];
+
+    while (fgets(line, sizeof(line), stdin)) {
+        if (line[strlen(line)-1] == '\n') {
+            line[strlen(line)-1] = '\0';
+        }
+
+        double timestamp = 0;
+        int index = 0;
+        if (sscanf(line, "%lf %n", &timestamp, &index) < 1) {
+            goto bad;
+        }
+
+        char *hex = line + index;
+
+        static struct modesMessage mmZero;
+        struct modesMessage mm = mmZero;
+        for (unsigned i = 0; i < sizeof(mm.MB); ++i) {
+            if (!isxdigit(hex[i*2]) || !isxdigit(hex[i*2 + 1])) {
+                goto bad;
+            }
+
+            unsigned xvalue = 0;
+            if (sscanf(hex + i*2, "%2x", &xvalue) < 1) {
+                goto bad;
+            }
+
+            mm.MB[i] = xvalue;
+        }
+
+        process(timestamp, line, &mm);
+        continue;
+
+    bad:
+        fprintf(stderr, "failed to scan line: %s", line);
+        continue;
+    }
+}

oneoff/extract-comm-b.py

@@ -0,0 +1,17 @@
+#!/usr/bin/env python3
+
+# Run me like this:
+#  view1090 --no-interactive | ./extract-comm-b.py
+
+import re, sys, time
+from contextlib import closing
+
+commb_match = re.compile(r'^DF:\d+ addr:([a-zA-Z0-9]{6}) FS:\d+ DR:\d+ UM:\d+ (?:ID|AC):\d+ MB:([a-zA-Z0-9]{14})$')
+
+for line in sys.stdin:
+    match = commb_match.match(line)
+    if match:
+        addr, mb = match.groups()
+
+        with closing(open('commb/' + addr.upper() + '.txt', 'a')) as f:
+            print('%.3f %s' % (time.time(), mb), file=f)