diff options
Diffstat (limited to 'driver_ais.c')
| -rw-r--r-- | driver_ais.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/driver_ais.c b/driver_ais.c index f000e01f..92f9d123 100644 --- a/driver_ais.c +++ b/driver_ais.c @@ -1029,20 +1029,16 @@ bool ais_binary_decode(const struct gpsd_errout_t *errout, ais->type25.dest_mmsi = UBITS(40, 30); if (ais->type25.structured) ais->type25.app_id = UBITS(40+ais->type25.addressed*30,16); - /* - * Not possible to do this right without machinery we - * don't yet have. The problem is that if the addressed - * bit is on, the bitfield start won't be on a byte - * boundary. Thus the formulas below (and in message type 26) - * will work perfectly for broadcast messages, but for addressed - * messages the retrieved data will be led by the 30 bits of - * the destination MMSI - */ ais->type25.bitcount = bitlen - 40 - 16*ais->type25.structured; /* bit 40 is exactly 5 bytes in; 2 bytes is 16 bits */ (void)memcpy(ais->type25.bitdata, (char *)bits+5 + 2 * ais->type25.structured, (ais->type25.bitcount + 7) / 8); + /* discard MMSI if addressed */ + if (ais->type25.addressed) { + shiftleft((unsigned char *)ais->type25.bitdata, ais->type25.bitcount, 30); + ais->type25.bitcount -= 30; + } break; case 26: /* Binary Message, Multiple Slot */ RANGE_CHECK(60, 1004); @@ -1059,8 +1055,13 @@ bool ais_binary_decode(const struct gpsd_errout_t *errout, ais->type26.app_id = UBITS(40+ais->type26.addressed*30,16); ais->type26.bitcount = bitlen - 60 - 16*ais->type26.structured; (void)memcpy(ais->type26.bitdata, - (char *)bits+5 + 2 * ais->type26.structured, + (unsigned char *)bits+5 + 2 * ais->type26.structured, (ais->type26.bitcount + 7) / 8); + /* discard MMSI if addressed */ + if (ais->type26.addressed) { + shiftleft((char *)ais->type26.bitdata, ais->type26.bitcount, 30); + ais->type26.bitcount -= 30; + } break; case 27: /* Long Range AIS Broadcast message */ if (bitlen != 96 && bitlen != 168) { |