154359Sroberto/* 254359Sroberto * clocktime - compute the NTP date from a day of year, hour, minute 354359Sroberto * and second. 454359Sroberto */ 5280849Scy#include <config.h> 654359Sroberto#include "ntp_fp.h" 754359Sroberto#include "ntp_unixtime.h" 854359Sroberto#include "ntp_stdlib.h" 9280849Scy#include "ntp_calendar.h" 1054359Sroberto 1154359Sroberto/* 12280849Scy * We check that the time be within CLOSETIME seconds of the receive 13280849Scy * time stamp. This is about 4 hours, which hopefully should be wide 14280849Scy * enough to collect most data, while close enough to keep things from 15280849Scy * getting confused. 1654359Sroberto */ 17280849Scy#define CLOSETIME (4u*60u*60u) 1854359Sroberto 1954359Sroberto/* 20280849Scy * Since we try to match years, the result of a full search will not 21280849Scy * change when we are already less than a half year from the receive 22280849Scy * time stamp. Since the length of a year is variable we use a 23280849Scy * slightly narrower limit; this might require a full evaluation near 24280849Scy * the edge, but will make sure we always get the correct result. 2554359Sroberto */ 26280849Scy#define NEARTIME (182u * SECSPERDAY) 2754359Sroberto 2854359Sroberto/* 29280849Scy * local calendar helpers 3054359Sroberto */ 31280849Scystatic int32 ntp_to_year(u_int32); 32280849Scystatic u_int32 year_to_ntp(int32); 3354359Sroberto 34280849Scy/* 35280849Scy * Take a time spec given as day-of-year, hour, minute and second as 36280849Scy * well as a GMT offset in hours and convert it to a NTP time stamp in 37280849Scy * '*ts_ui'. The value will be in the range (rec_ui-0.5yrs) to 38280849Scy * (rec_ui+0.5yrs). A hint for the current start-of-year will be 39280849Scy * read from '*yearstart'. 40280849Scy * 41280849Scy * On return '*ts_ui' will always the best matching solution, and 42280849Scy * '*yearstart' will receive the associated start-of-year. 43280849Scy * 44280849Scy * The function will tell if the result in 'ts_ui' is in CLOSETIME 45280849Scy * (+/-4hrs) around the receive time by returning a non-zero value. 46280849Scy * 47280849Scy * Note: The function puts no constraints on the value ranges for the 48280849Scy * time specification, but evaluates the effective seconds in 49280849Scy * 32-bit arithmetic. 50280849Scy */ 5154359Srobertoint 5254359Srobertoclocktime( 53280849Scy int yday , /* day-of-year */ 54280849Scy int hour , /* hour of day */ 55280849Scy int minute , /* minute of hour */ 56280849Scy int second , /* second of minute */ 57280849Scy int tzoff , /* hours west of GMT */ 58280849Scy u_int32 rec_ui , /* pivot value */ 59280849Scy u_long *yearstart, /* cached start-of-year, should be fixed to u_int32 */ 60280849Scy u_int32 *ts_ui ) /* effective time stamp */ 6154359Sroberto{ 62280849Scy u_int32 ystt[3]; /* year start */ 63280849Scy u_int32 test[3]; /* result time stamp */ 64280849Scy u_int32 diff[3]; /* abs difference to receive */ 65280849Scy int32 y, tmp, idx, min; 66280849Scy 6754359Sroberto /* 68280849Scy * Compute the offset into the year in seconds. Note that 6954359Sroberto * this could come out to be a negative number. 7054359Sroberto */ 71280849Scy tmp = ((int32)second + 72280849Scy SECSPERMIN * ((int32)minute + 73280849Scy MINSPERHR * ((int32)hour + (int32)tzoff + 74280849Scy HRSPERDAY * ((int32)yday - 1)))); 7554359Sroberto /* 76280849Scy * Based on the cached year start, do a first attempt. Be 77280849Scy * happy and return if this gets us better than NEARTIME to 78280849Scy * the receive time stamp. Do this only if the cached year 79280849Scy * start is not zero, which will not happen after 1900 for the 80280849Scy * next few thousand years. 8154359Sroberto */ 82280849Scy if (*yearstart) { 83280849Scy /* -- get time stamp of potential solution */ 84280849Scy test[0] = (u_int32)(*yearstart) + tmp; 85280849Scy /* -- calc absolute difference to receive time */ 86280849Scy diff[0] = test[0] - rec_ui; 87280849Scy if (diff[0] >= 0x80000000u) 88280849Scy diff[0] = ~diff[0] + 1; 89280849Scy /* -- can't get closer if diff < NEARTIME */ 90280849Scy if (diff[0] < NEARTIME) { 91280849Scy *ts_ui = test[0]; 92280849Scy return diff[0] < CLOSETIME; 93280849Scy } 9454359Sroberto } 9554359Sroberto 9654359Sroberto /* 97280849Scy * Now the dance begins. Based on the receive time stamp and 98280849Scy * the seconds offset in 'tmp', we make an educated guess 99280849Scy * about the year to start with. This takes us on the spot 100280849Scy * with a fuzz of +/-1 year. 101280849Scy * 102280849Scy * We calculate the effective timestamps for the three years 103280849Scy * around the guess and select the entry with the minimum 104280849Scy * absolute difference to the receive time stamp. 10554359Sroberto */ 106280849Scy y = ntp_to_year(rec_ui - tmp); 107280849Scy for (idx = 0; idx < 3; idx++) { 108280849Scy /* -- get year start of potential solution */ 109280849Scy ystt[idx] = year_to_ntp(y + idx - 1); 110280849Scy /* -- get time stamp of potential solution */ 111280849Scy test[idx] = ystt[idx] + tmp; 112280849Scy /* -- calc absolute difference to receive time */ 113280849Scy diff[idx] = test[idx] - rec_ui; 114280849Scy if (diff[idx] >= 0x80000000u) 115280849Scy diff[idx] = ~diff[idx] + 1; 11654359Sroberto } 117280849Scy /* -*- assume current year fits best, then search best fit */ 118280849Scy for (min = 1, idx = 0; idx < 3; idx++) 119280849Scy if (diff[idx] < diff[min]) 120280849Scy min = idx; 121280849Scy /* -*- store results and update year start */ 122280849Scy *ts_ui = test[min]; 123280849Scy *yearstart = ystt[min]; 12454359Sroberto 125280849Scy /* -*- tell if we could get into CLOSETIME*/ 126280849Scy return diff[min] < CLOSETIME; 127280849Scy} 12854359Sroberto 129280849Scystatic int32 130280849Scyntp_to_year( 131280849Scy u_int32 ntp) 132280849Scy{ 133280849Scy vint64 t; 134280849Scy ntpcal_split s; 13554359Sroberto 136280849Scy t = ntpcal_ntp_to_ntp(ntp, NULL); 137280849Scy s = ntpcal_daysplit(&t); 138280849Scy s = ntpcal_split_eradays(s.hi + DAY_NTP_STARTS - 1, NULL); 139280849Scy return s.hi + 1; 140280849Scy} 14154359Sroberto 142280849Scystatic u_int32 143280849Scyyear_to_ntp( 144280849Scy int32 year) 145280849Scy{ 146280849Scy u_int32 days; 147280849Scy days = ntpcal_days_in_years(year-1) - DAY_NTP_STARTS + 1; 148280849Scy return days * SECSPERDAY; 14954359Sroberto} 150