original files of m241

components/ip_net2-6.9/ipntp/src/libntp/clocktime.c

@@ -0,0 +1,149 @@
+/*
+ * clocktime - compute the NTP date from a day of year, hour, minute
+ *	       and second.
+ */
+#include <ipntp_config.h>
+#include "ntp_fp.h"
+#include "ntp_unixtime.h"
+#include "ntp_stdlib.h"
+#include "ntp_calendar.h"
+
+/*
+ * We check 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	(4u*60u*60u)
+
+/*
+ * Since we try to match years, the result of a full search will not
+ * change when we are already less than a half year from the receive
+ * time stamp.	Since the length of a year is variable we use a
+ * slightly narrower limit; this might require a full evaluation near
+ * the edge, but will make sure we always get the correct result.
+ */
+#define NEARTIME	(182u * SECSPERDAY)
+
+/*
+ * local calendar helpers
+ */
+static int32   ntp_to_year(u_int32);
+static u_int32 year_to_ntp(int32);
+
+/*
+ * Take a time spec given as day-of-year, hour, minute and second as
+ * well as a GMT offset in hours and convert it to a NTP time stamp in
+ * '*ts_ui'. The value will be in the range (rec_ui-0.5yrs) to
+ * (rec_ui+0.5yrs). A hint for the current start-of-year will be
+ * read from '*yearstart'.
+ *
+ * On return '*ts_ui' will always the best matching solution, and
+ * '*yearstart' will receive the associated start-of-year.
+ *
+ * The function will tell if the result in 'ts_ui' is in CLOSETIME
+ * (+/-4hrs) around the receive time by returning a non-zero value.
+ *
+ * Note: The function puts no constraints on the value ranges for the
+ * time specification, but evaluates the effective seconds in
+ * 32-bit arithmetic.
+ */
+int
+clocktime(
+	int	yday	 ,	/* day-of-year */
+	int	hour	 ,	/* hour of day */
+	int	minute	 ,	/* minute of hour */
+	int	second	 ,	/* second of minute */
+	int	tzoff	 ,	/* hours west of GMT */
+	u_int32 rec_ui	 ,	/* pivot value */
+	u_long *yearstart,	/* cached start-of-year, should be fixed to u_int32 */
+	u_int32 *ts_ui	 )	/* effective time stamp */
+{
+	u_int32 ystt[3];	/* year start */
+	u_int32 test[3];	/* result time stamp */
+	u_int32 diff[3];	/* abs difference to receive */
+	int32 y, tmp, idx, min;
+	
+	/*
+	 * Compute the offset into the year in seconds.	 Note that
+	 * this could come out to be a negative number.
+	 */
+	tmp = ((int32)second +
+	       SECSPERMIN * ((int32)minute +
+			     MINSPERHR * ((int32)hour + (int32)tzoff +
+					  HRSPERDAY * ((int32)yday - 1))));
+	/*
+	 * Based on the cached year start, do a first attempt. Be
+	 * happy and return if this gets us better than NEARTIME to
+	 * the receive time stamp. Do this only if the cached year
+	 * start is not zero, which will not happen after 1900 for the
+	 * next few thousand years.
+	 */
+	if (*yearstart) {
+		/* -- get time stamp of potential solution */
+		test[0] = (u_int32)(*yearstart) + tmp;
+		/* -- calc absolute difference to receive time */
+		diff[0] = test[0] - rec_ui;
+		if (diff[0] >= 0x80000000u)
+			diff[0] = ~diff[0] + 1;
+		/* -- can't get closer if diff < NEARTIME */
+		if (diff[0] < NEARTIME) {
+			*ts_ui = test[0];
+			return diff[0] < CLOSETIME;
+		}
+	}
+
+	/*
+	 * Now the dance begins. Based on the receive time stamp and
+	 * the seconds offset in 'tmp', we make an educated guess
+	 * about the year to start with. This takes us on the spot
+	 * with a fuzz of +/-1 year.
+	 *
+	 * We calculate the effective timestamps for the three years
+	 * around the guess and select the entry with the minimum
+	 * absolute difference to the receive time stamp.
+	 */
+	y = ntp_to_year(rec_ui - tmp);
+	for (idx = 0; idx < 3; idx++) {
+		/* -- get year start of potential solution */
+		ystt[idx] = year_to_ntp(y + idx - 1);
+		/* -- get time stamp of potential solution */
+		test[idx] = ystt[idx] + tmp;
+		/* -- calc absolute difference to receive time */
+		diff[idx] = test[idx] - rec_ui;
+		if (diff[idx] >= 0x80000000u)
+			diff[idx] = ~diff[idx] + 1;
+	}
+	/* -*- assume current year fits best, then search best fit */
+	for (min = 1, idx = 0; idx < 3; idx++)
+		if (diff[idx] < diff[min])
+			min = idx;
+	/* -*- store results and update year start */
+	*ts_ui	   = test[min];
+	*yearstart = ystt[min];
+
+	/* -*- tell if we could get into CLOSETIME*/
+	return diff[min] < CLOSETIME;
+}
+
+static int32
+ntp_to_year(
+	u_int32 ntp)
+{
+	vint64	     t;
+	ntpcal_split s;
+
+	t = ntpcal_ntp_to_ntp(ntp, NULL);
+	s = ntpcal_daysplit(&t);
+	s = ntpcal_split_eradays(s.hi + DAY_NTP_STARTS - 1, NULL);
+	return s.hi + 1;
+}
+
+static u_int32
+year_to_ntp(
+	int32 year)
+{
+	u_int32 days;
+	days = ntpcal_days_in_years(year-1) - DAY_NTP_STARTS + 1;
+	return days * SECSPERDAY;
+}