154359Sroberto/* 254359Sroberto * clocktime - compute the NTP date from a day of year, hour, minute 354359Sroberto * and second. 454359Sroberto */ 5290000Sglebius#include <config.h> 654359Sroberto#include "ntp_fp.h" 754359Sroberto#include "ntp_unixtime.h" 854359Sroberto#include "ntp_stdlib.h" 9290000Sglebius#include "ntp_calendar.h" 1054359Sroberto 1154359Sroberto/* 12290000Sglebius * We check that the time be within CLOSETIME seconds of the receive 13290000Sglebius * time stamp. This is about 4 hours, which hopefully should be wide 14290000Sglebius * enough to collect most data, while close enough to keep things from 15290000Sglebius * getting confused. 1654359Sroberto */ 17290000Sglebius#define CLOSETIME (4u*60u*60u) 1854359Sroberto 1954359Sroberto/* 20290000Sglebius * Since we try to match years, the result of a full search will not 21290000Sglebius * change when we are already less than a half year from the receive 22290000Sglebius * time stamp. Since the length of a year is variable we use a 23290000Sglebius * slightly narrower limit; this might require a full evaluation near 24290000Sglebius * the edge, but will make sure we always get the correct result. 2554359Sroberto */ 26290000Sglebius#define NEARTIME (182u * SECSPERDAY) 2754359Sroberto 2854359Sroberto/* 29290000Sglebius * local calendar helpers 3054359Sroberto */ 31290000Sglebiusstatic int32 ntp_to_year(u_int32); 32290000Sglebiusstatic u_int32 year_to_ntp(int32); 3354359Sroberto 34290000Sglebius/* 35290000Sglebius * Take a time spec given as day-of-year, hour, minute and second as 36290000Sglebius * well as a GMT offset in hours and convert it to a NTP time stamp in 37290000Sglebius * '*ts_ui'. The value will be in the range (rec_ui-0.5yrs) to 38290000Sglebius * (rec_ui+0.5yrs). A hint for the current start-of-year will be 39290000Sglebius * read from '*yearstart'. 40290000Sglebius * 41290000Sglebius * On return '*ts_ui' will always the best matching solution, and 42290000Sglebius * '*yearstart' will receive the associated start-of-year. 43290000Sglebius * 44290000Sglebius * The function will tell if the result in 'ts_ui' is in CLOSETIME 45290000Sglebius * (+/-4hrs) around the receive time by returning a non-zero value. 46290000Sglebius * 47290000Sglebius * Note: The function puts no constraints on the value ranges for the 48290000Sglebius * time specification, but evaluates the effective seconds in 49290000Sglebius * 32-bit arithmetic. 50290000Sglebius */ 5154359Srobertoint 5254359Srobertoclocktime( 53290000Sglebius int yday , /* day-of-year */ 54290000Sglebius int hour , /* hour of day */ 55290000Sglebius int minute , /* minute of hour */ 56290000Sglebius int second , /* second of minute */ 57290000Sglebius int tzoff , /* hours west of GMT */ 58290000Sglebius u_int32 rec_ui , /* pivot value */ 59290000Sglebius u_long *yearstart, /* cached start-of-year, should be fixed to u_int32 */ 60290000Sglebius u_int32 *ts_ui ) /* effective time stamp */ 6154359Sroberto{ 62290000Sglebius u_int32 ystt[3]; /* year start */ 63290000Sglebius u_int32 test[3]; /* result time stamp */ 64290000Sglebius u_int32 diff[3]; /* abs difference to receive */ 65290000Sglebius int32 y, tmp, idx, min; 66290000Sglebius 6754359Sroberto /* 68290000Sglebius * Compute the offset into the year in seconds. Note that 6954359Sroberto * this could come out to be a negative number. 7054359Sroberto */ 71290000Sglebius tmp = ((int32)second + 72290000Sglebius SECSPERMIN * ((int32)minute + 73290000Sglebius MINSPERHR * ((int32)hour + (int32)tzoff + 74290000Sglebius HRSPERDAY * ((int32)yday - 1)))); 7554359Sroberto /* 76290000Sglebius * Based on the cached year start, do a first attempt. Be 77290000Sglebius * happy and return if this gets us better than NEARTIME to 78290000Sglebius * the receive time stamp. Do this only if the cached year 79290000Sglebius * start is not zero, which will not happen after 1900 for the 80290000Sglebius * next few thousand years. 8154359Sroberto */ 82290000Sglebius if (*yearstart) { 83290000Sglebius /* -- get time stamp of potential solution */ 84290000Sglebius test[0] = (u_int32)(*yearstart) + tmp; 85290000Sglebius /* -- calc absolute difference to receive time */ 86290000Sglebius diff[0] = test[0] - rec_ui; 87290000Sglebius if (diff[0] >= 0x80000000u) 88290000Sglebius diff[0] = ~diff[0] + 1; 89290000Sglebius /* -- can't get closer if diff < NEARTIME */ 90290000Sglebius if (diff[0] < NEARTIME) { 91290000Sglebius *ts_ui = test[0]; 92290000Sglebius return diff[0] < CLOSETIME; 93290000Sglebius } 9454359Sroberto } 9554359Sroberto 9654359Sroberto /* 97290000Sglebius * Now the dance begins. Based on the receive time stamp and 98290000Sglebius * the seconds offset in 'tmp', we make an educated guess 99290000Sglebius * about the year to start with. This takes us on the spot 100290000Sglebius * with a fuzz of +/-1 year. 101290000Sglebius * 102290000Sglebius * We calculate the effective timestamps for the three years 103290000Sglebius * around the guess and select the entry with the minimum 104290000Sglebius * absolute difference to the receive time stamp. 10554359Sroberto */ 106290000Sglebius y = ntp_to_year(rec_ui - tmp); 107290000Sglebius for (idx = 0; idx < 3; idx++) { 108290000Sglebius /* -- get year start of potential solution */ 109290000Sglebius ystt[idx] = year_to_ntp(y + idx - 1); 110290000Sglebius /* -- get time stamp of potential solution */ 111290000Sglebius test[idx] = ystt[idx] + tmp; 112290000Sglebius /* -- calc absolute difference to receive time */ 113290000Sglebius diff[idx] = test[idx] - rec_ui; 114290000Sglebius if (diff[idx] >= 0x80000000u) 115290000Sglebius diff[idx] = ~diff[idx] + 1; 11654359Sroberto } 117290000Sglebius /* -*- assume current year fits best, then search best fit */ 118290000Sglebius for (min = 1, idx = 0; idx < 3; idx++) 119290000Sglebius if (diff[idx] < diff[min]) 120290000Sglebius min = idx; 121290000Sglebius /* -*- store results and update year start */ 122290000Sglebius *ts_ui = test[min]; 123290000Sglebius *yearstart = ystt[min]; 12454359Sroberto 125290000Sglebius /* -*- tell if we could get into CLOSETIME*/ 126290000Sglebius return diff[min] < CLOSETIME; 127290000Sglebius} 12854359Sroberto 129290000Sglebiusstatic int32 130290000Sglebiusntp_to_year( 131290000Sglebius u_int32 ntp) 132290000Sglebius{ 133290000Sglebius vint64 t; 134290000Sglebius ntpcal_split s; 13554359Sroberto 136290000Sglebius t = ntpcal_ntp_to_ntp(ntp, NULL); 137290000Sglebius s = ntpcal_daysplit(&t); 138290000Sglebius s = ntpcal_split_eradays(s.hi + DAY_NTP_STARTS - 1, NULL); 139290000Sglebius return s.hi + 1; 140290000Sglebius} 14154359Sroberto 142290000Sglebiusstatic u_int32 143290000Sglebiusyear_to_ntp( 144290000Sglebius int32 year) 145290000Sglebius{ 146290000Sglebius u_int32 days; 147290000Sglebius days = ntpcal_days_in_years(year-1) - DAY_NTP_STARTS + 1; 148290000Sglebius return days * SECSPERDAY; 14954359Sroberto} 150