Brian Oleksa skrev 2010-04-08 16:41:
Wiresharkers
I am trying to dissect the time in a particular packet. Here is it's format:
"The time is the source computer's system time in Greenwich Mean Time
(GMT)." The size is 32 bits or 4 bytes.
What is the best method to use to dissect this time..?? I tired
this...but did not have any luck:
nstime_t t;
guint64 msecs_since_the_epoch;
struct tm *tmp;
msecs_since_the_epoch = tvb_get_ntoh64(tvb, offset);
Well you are fetching 8 bytes not four...
t.secs = msecs_since_the_epoch / 1000;
t.nsecs = (msecs_since_the_epoch %
1000)*1000000; /* milliseconds to nanoseconds */
tmp = gmtime(&t.secs);
if (tmp != NULL)
{
proto_tree_add_time_format(time_sub_tree,
hf_helen_time, tvb, offset, 4,&t,
"Date: %s %2d, %d %02d:%02d:%02d UTC",
mon_names[tmp->tm_mon], tmp->tm_mday,
tmp->tm_year + 1900, tmp->tm_hour,
tmp->tm_min, tmp->tm_sec);
}
offset += 4
Also...I am trying to dissect longitude, latitude and altitude. Here is
it's format. The size is also 32 bits or 4 bytes.
The<latitude>,<longitude>, and<altitude> fields contain values
corresponding to GPS information for the MGEN source if it was
available. The<latitude> and<longitude> fields are encoded as follows:
<fieldValue> = (unsigned long)((<actualValue>+180.0)*60000.0)
The<altitude> field is the direct representation of the altitude value
available from the source's GPS system.
I tried this but had no luck:
longitude = tvb_get_ntoh64(tvb, offset);
Well you are fetching 8 bytes not four...
longitude = (longitude+180)*60000;
Assuming the field on the wire is encoded as:
<fieldValue> = (unsigned long)((<actualValue>+180.0)*60000.0)
shouldn't that be (double)actualValue= (longitude/60000.0)-180
proto_tree_add_uint_format(mgen_sub_tree, hf_helen_length,
tvb, offset, 4, 0,
"Longitude: %f", longitude);
offset += 4;
Thanks,
Brian
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