diff options
Diffstat (limited to 'contrib/ntp/libntp/clocktime.c')
-rw-r--r-- | contrib/ntp/libntp/clocktime.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/contrib/ntp/libntp/clocktime.c b/contrib/ntp/libntp/clocktime.c new file mode 100644 index 000000000000..371859cda21c --- /dev/null +++ b/contrib/ntp/libntp/clocktime.c @@ -0,0 +1,132 @@ +/* + * clocktime - compute the NTP date from a day of year, hour, minute + * and second. + */ +#include "ntp_fp.h" +#include "ntp_unixtime.h" +#include "ntp_stdlib.h" + +/* + * Hacks to avoid excercising the multiplier. I have no pride. + */ +#define MULBY10(x) (((x)<<3) + ((x)<<1)) +#define MULBY60(x) (((x)<<6) - ((x)<<2)) /* watch overflow */ +#define MULBY24(x) (((x)<<4) + ((x)<<3)) + +/* + * Two days, in seconds. + */ +#define TWODAYS (2*24*60*60) + +/* + * We demand that the time be within CLOSETIME seconds of the receive + * time stamp. This is about 4 hours, which hopefully should be + * wide enough to collect most data, while close enough to keep things + * from getting confused. + */ +#define CLOSETIME (4*60*60) + + +int +clocktime( + int yday, + int hour, + int minute, + int second, + int tzoff, + u_long rec_ui, + u_long *yearstart, + u_int32 *ts_ui + ) +{ + register long tmp; + register u_long date; + register u_long yst; + + /* + * Compute the offset into the year in seconds. Note that + * this could come out to be a negative number. + */ + tmp = (long)(MULBY24((yday-1)) + hour + tzoff); + tmp = MULBY60(tmp) + (long)minute; + tmp = MULBY60(tmp) + (long)second; + + /* + * Initialize yearstart, if necessary. + */ + yst = *yearstart; + if (yst == 0) { + yst = calyearstart(rec_ui); + *yearstart = yst; + } + + /* + * Now the fun begins. We demand that the received clock time + * be within CLOSETIME of the receive timestamp, but + * there is uncertainty about the year the timestamp is in. + * Use the current year start for the first check, this should + * work most of the time. + */ + date = (u_long)(tmp + (long)yst); + if (date < (rec_ui + CLOSETIME) && + date > (rec_ui - CLOSETIME)) { + *ts_ui = date; + return 1; + } + + /* + * Trouble. Next check is to see if the year rolled over and, if + * so, try again with the new year's start. + */ + yst = calyearstart(rec_ui); + if (yst != *yearstart) { + date = (u_long)((long)yst + tmp); + *ts_ui = date; + if (date < (rec_ui + CLOSETIME) && + date > (rec_ui - CLOSETIME)) { + *yearstart = yst; + return 1; + } + } + + /* + * Here we know the year start matches the current system + * time. One remaining possibility is that the time code + * is in the year previous to that of the system time. This + * is only worth checking if the receive timestamp is less + * than a couple of days into the new year. + */ + if ((rec_ui - yst) < TWODAYS) { + yst = calyearstart(yst - TWODAYS); + if (yst != *yearstart) { + date = (u_long)(tmp + (long)yst); + if (date < (rec_ui + CLOSETIME) && + date > (rec_ui - CLOSETIME)) { + *yearstart = yst; + *ts_ui = date; + return 1; + } + } + } + + /* + * One last possibility is that the time stamp is in the year + * following the year the system is in. Try this one before + * giving up. + */ + yst = calyearstart(rec_ui + TWODAYS); + if (yst != *yearstart) { + date = (u_long)((long)yst + tmp); + if (date < (rec_ui + CLOSETIME) && + date > (rec_ui - CLOSETIME)) { + *yearstart = yst; + *ts_ui = date; + return 1; + } + } + + /* + * Give it up. + */ + return 0; +} |