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| author | Eric S. Raymond <esr@thyrsus.com> | 2014-08-29 01:43:06 -0400 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2014-08-29 01:43:06 -0400 |
| commit | 79c812ad6600872bb4d974aede78460eb0950341 (patch) | |
| tree | 3bb6d6961495f98966749db7bcedda0089f148f4 | |
| parent | c9024359e0808ad3867ddce9aab0b2d5ae557a5b (diff) | |
| download | gpsd-79c812ad6600872bb4d974aede78460eb0950341.tar.gz | |
Properly handle addressed versions of AIS Type 25 and 26. Untested, alas.
All regression tests pass.
| -rw-r--r-- | TODO | 4 | ||||
| -rw-r--r-- | driver_ais.c | 21 |
2 files changed, 11 insertions, 14 deletions
@@ -184,10 +184,6 @@ complete; the only missing cases are a handful of IMO 236 and IMO 289 message 6 and 8 subtypes - specifically, 6/23, 8/21, 8/22, 8/24, and 8/26. -**** Addressed case of AIS Types 25 and 26 is not handled. - -We'd need machinery to shift a byte array 30 bits left... - ** To do: *** Make subframe reports available in the C API. 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) { |