diff options
| -rwxr-xr-x | devtools/ais.py | 13 | ||||
| -rw-r--r-- | driver_aivdm.c | 12 | ||||
| -rw-r--r-- | gpsdecode.c | 2 | ||||
| -rw-r--r-- | www/AIVDM.txt | 12 |
4 files changed, 30 insertions, 9 deletions
diff --git a/devtools/ais.py b/devtools/ais.py index 6f63a097..0f67beac 100755 --- a/devtools/ais.py +++ b/devtools/ais.py @@ -758,8 +758,17 @@ def aivdm_unpack(data, offset, values, instructions): value = data.sbits(offset, inst.width) elif inst.type == 'string': value = '' - for i in range(inst.width/6): - value += "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^- !\"#$%&`()*+,-./0123456789:;<=>?"[data.ubits(offset + 6*i, 6)] + # The try/catch error here is in case we run off the end + # of a variable-length string field, as in messages 12 and 14 + try: + for i in range(inst.width/6): + newchar = "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^- !\"#$%&`()*+,-./0123456789:;<=>?"[data.ubits(offset + 6*i, 6)] + if newchar == '@': + break + else: + value += newchar + except IndexError: + pass value = value.replace("@", " ").rstrip() elif inst.type == 'raw': value = BitVector(data.bits[offset/8:], len(data)-offset) diff --git a/driver_aivdm.c b/driver_aivdm.c index c09f9eb2..674566f4 100644 --- a/driver_aivdm.c +++ b/driver_aivdm.c @@ -36,11 +36,17 @@ static void from_sixbit(char *bitvec, uint start, int count, char *to) const char sixchr[64] = "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^- !\"#$%&`()*+,-./0123456789:;<=>?"; #endif /* S_SPLINT_S */ int i; + char newchar; /* six-bit to ASCII */ - for (i = 0; i < count-1; i++) - to[i] = sixchr[ubits(bitvec, start + 6*i, 6U)]; - to[count-1] = '\0'; + for (i = 0; i < count-1; i++) { + newchar = sixchr[ubits(bitvec, start + 6*i, 6U)]; + if (newchar == '@') + break; + else + to[i] = newchar; + } + to[i] = '\0'; /* trim spaces on right end */ for (i = count-2; i >= 0; i--) if (to[i] == ' ' || to[i] == '@') diff --git a/gpsdecode.c b/gpsdecode.c index 113e65c7..d566f5a8 100644 --- a/gpsdecode.c +++ b/gpsdecode.c @@ -365,6 +365,8 @@ static void decode(FILE *fpin, FILE *fpout) rtcm3_dump(&rtcm3, stdout); } else if (lexer.type == AIVDM_PACKET) { + if (verbose >=1 ) + (void)fputs((char *)lexer.outbuffer, stdout); /*@ -uniondef */ if (aivdm_decode((char *)lexer.outbuffer, lexer.outbuflen, &aivdm, &ais)) { if (!json) diff --git a/www/AIVDM.txt b/www/AIVDM.txt index d1ef3957..79969a82 100644 --- a/www/AIVDM.txt +++ b/www/AIVDM.txt @@ -1,6 +1,6 @@ = AIVDM/AIVDO protocol decoding = Eric S. Raymond <esr@thyrsus.com> -v1.16, Nov 2009 +v1.17, Nov 2009 This document is mastered in asciidoc format. If you are reading it in HTML, you can find the original at http://gpsd.berlios.de/AIVDM.txt[] @@ -299,9 +299,11 @@ brackets, pipe bar, tilde and DEL cannot be encoded. ----------------------------------------------------------------------------- According to the standard, trailing unused characters in six-bit -fields will be represented by "@" (six-bit zero). It is common to -space-fill the fields instead, so a decoder should strip trailing -spaces well as at-signs. +fields will be represented by "@" (six-bit zero). The terminating "@" +should not be considered part of the text, and any non-"@" characters +adter it should be discarded. It is common to space-fill the fields +instead, so a decoder should strip trailing spaces well as at-signs +and garbage after them. == AIVDM/AIVDO Payload Interpretation == @@ -1548,3 +1550,5 @@ corrected it because it confused someone working on a Python decoder. Version 1.16 incorporated various minor fixes and corrections from Neal Arundale. One 'standard' fieldname changed, in message type 21: type -> aid_type. + +Version 1.17 clatfies the role of @ as a terminator in 6-bit text. |