/* * 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; }