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| author | Gary E. Miller <gem@rellim.com> | 2015-02-02 13:50:48 -0800 |
|---|---|---|
| committer | Gary E. Miller <gem@rellim.com> | 2015-02-02 13:50:48 -0800 |
| commit | 61a37a2f3a8b47513f5d2e4a7dee0b3a4a581aed (patch) | |
| tree | 6468c9907b658b704fd82deb8ff3cc2a6914bddb /gpsd_json.c | |
| parent | 8c0106875fe6c4792b5cc0781b1aba109a9e75f7 (diff) | |
| download | gpsd-61a37a2f3a8b47513f5d2e4a7dee0b3a4a581aed.tar.gz | |
Fix loss of precision in PPS json message.
PPS time is 63 bits of precision
A doulbe is only 53 bits of preccision
PPS time does not fit in a double without loss of precision
Diffstat (limited to 'gpsd_json.c')
| -rw-r--r-- | gpsd_json.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/gpsd_json.c b/gpsd_json.c index 9962a809..48c63664 100644 --- a/gpsd_json.c +++ b/gpsd_json.c @@ -187,9 +187,12 @@ void json_tpv_dump(const struct gps_device_t *session, #ifdef PPS_ENABLE /*@-type -formattype@*/ /* splint is confused about struct timespec */ if (session->ppscount) + /* you can not use a double here as you will lose 11 bits + * of precision */ str_appendf(reply, replylen, - "\"pps\":%.9f,", - session->ppslast.clock.tv_sec + session->ppslast.clock.tv_nsec / 1e9); + "\"pps\":%ld.$09ld,", + session->ppslast.clock.tv_sec, + session->ppslast.clock.tv_nsec); /*@+type +formattype@*/ #endif /* PPS_ENABLE */ str_appendf(reply, replylen, |