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demo/insn: report start and end time as unsigned values

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Report the seconds and microseconds values from the INSN_GTOD
instructions as unsigned values to postpone the Y2038 problem to a Y2106
problem.  Be a bit more careful with the conversion to a signed
difference.  We wouldn't normally expect time to go backwards, but it is
possible if the system time is set to to an older time between the
instructions.

Also, in the description of INSN_GTOD in the Comedilib manual,
explicitly mention that the seconds and microseconds values are
unsigned.
This commit is contained in:
Ian Abbott 2016-06-20 11:09:55 +01:00
parent e0ee6039eb
commit a4dd004076
2 changed files with 16 additions and 5 deletions
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19
demo/insn.c
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@ -52,6 +52,7 @@ int main(int argc, char *argv[])
comedi_insnlist il;
lsampl_t t1[2], t2[2];
lsampl_t data[MAX_SAMPLES];
long diffus;
struct parsed_options options;
init_parsed_options(&options);
@ -102,14 +103,24 @@ int main(int argc, char *argv[])
exit(-1);
}
printf("initial time: %d.%06d\n", t1[0], t1[1]);
printf("initial time: %u.%06u\n", t1[0], t1[1]);
for(i = 0; i < options.n_scan; i++){
printf("%d\n", data[i]);
}
printf("final time: %d.%06d\n", t2[0], t2[1]);
printf("final time: %u.%06u\n", t2[0], t2[1]);
printf("difference (us): %ld\n",(long)(t2[0]-t1[0]) * 1000000 +
(t2[1] - t1[1]));
if (t2[0] >= t1[0]) {
diffus = (long)(t2[0] - t1[0]);
} else {
diffus = -(long)(t1[0] - t2[0]);
}
diffus *= 1000000;
if (t2[1] >= t1[1]) {
diffus += (long)(t2[1] - t1[1]);
} else {
diffus -= (long)(t1[1] - t2[1]);
}
printf("difference (us): %ld\n", diffus);
return 0;
}

2
doc/reference.xml
View file

@ -604,7 +604,7 @@ configure a subdevice
<listitem>
<para>
read a timestamp, identical to <function>gettimeofday</function> except the seconds
and microseconds values are of type <type><link linkend="ref-type-lsampl-t">lsampl_t</link></type>.
and microseconds values are unsigned values of type <type><link linkend="ref-type-lsampl-t">lsampl_t</link></type>.
</para>
</listitem>
</varlistentry>