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+/****************************************************************************
+ * lib/time/lib_gmtimer.c
+ *
+ * Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ * used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdbool.h>
+#include <time.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/time.h>
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+#define SEC_PER_MIN ((time_t)60)
+#define SEC_PER_HOUR ((time_t)60 * SEC_PER_MIN)
+#define SEC_PER_DAY ((time_t)24 * SEC_PER_HOUR)
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Calendar/UTC conversion routines */
+
+static void clock_utc2calendar(time_t utc, int *year, int *month, int *day);
+#ifdef CONFIG_GREGORIAN_TIME
+static void clock_utc2gregorian (time_t jdn, int *year, int *month, int *day);
+
+#ifdef CONFIG_JULIAN_TIME
+static void clock_utc2julian(time_t jdn, int *year, int *month, int *day);
+#endif /* CONFIG_JULIAN_TIME */
+#endif /* CONFIG_GREGORIAN_TIME */
+
+/**************************************************************************
+ * Public Constant Data
+ **************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/**************************************************************************
+ * Private Variables
+ **************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function: clock_calendar2utc, clock_gregorian2utc,
+ * and clock_julian2utc
+ *
+ * Description:
+ * Calendar to UTC conversion routines. These conversions
+ * are based on algorithms from p. 604 of Seidelman, P. K.
+ * 1992. Explanatory Supplement to the Astronomical
+ * Almanac. University Science Books, Mill Valley.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_GREGORIAN_TIME
+static void clock_utc2calendar(time_t utc, int *year, int *month, int *day)
+{
+#ifdef CONFIG_JULIAN_TIME
+
+ if (utc >= GREG_DUTC)
+ {
+ clock_utc2gregorian(utc + JD_OF_EPOCH, year, month, day);
+ }
+ else
+ {
+ clock_utc2julian (utc + JD_OF_EPOCH, year, month, day);
+ }
+
+#else /* CONFIG_JULIAN_TIME */
+
+ clock_utc2gregorian(utc + JD_OF_EPOCH, year, month, day);
+
+#endif /* CONFIG_JULIAN_TIME */
+}
+
+static void clock_utc2gregorian(time_t jd, int *year, int *month, int *day)
+{
+ long l, n, i, j, d, m, y;
+
+ l = jd + 68569;
+ n = (4*l) / 146097;
+ l = l - (146097*n + 3)/4;
+ i = (4000*(l+1))/1461001;
+ l = l - (1461*i)/4 + 31;
+ j = (80*l)/2447;
+ d = l - (2447*j)/80;
+ l = j/11;
+ m = j + 2 - 12*l;
+ y = 100*(n-49) + i + l;
+
+ *year = y;
+ *month = m;
+ *day = d;
+}
+
+#ifdef CONFIG_JULIAN_TIME
+
+static void clock_utc2julian(time_t jd, int *year, int *month, int *day)
+{
+ long j, k, l, n, d, i, m, y;
+
+ j = jd + 1402;
+ k = (j-1)/1461;
+ l = j - 1461*k;
+ n = (l-1)/365 - l/1461;
+ i = l - 365*n + 30;
+ j = (80*i)/2447;
+ d = i - (2447*j)/80;
+ i = j/11;
+ m = j + 2 - 12*i;
+ y = 4*k + n + i - 4716;
+
+ *year = y;
+ *month = m;
+ *day = d;
+}
+
+#endif /* CONFIG_JULIAN_TIME */
+#else/* CONFIG_GREGORIAN_TIME */
+
+/* Only handles dates since Jan 1, 1970 */
+
+static void clock_utc2calendar(time_t days, int *year, int *month, int *day)
+{
+ int value;
+ int min;
+ int max;
+ int tmp;
+ bool leapyear;
+
+ /* There is one leap year every four years, so we can get close with the
+ * following:
+ */
+
+ value = days / (4*365 + 1); /* Number of 4-years periods since the epoch*/
+ days -= value * (4*365 + 1); /* Remaining days */
+ value <<= 2; /* Years since the epoch */
+
+ /* Then we will brute force the next 0-3 years */
+
+ for (;;)
+ {
+ /* Is this year a leap year (we'll need this later too) */
+
+ leapyear = clock_isleapyear(value + 1970);
+
+ /* Get the number of days in the year */
+
+ tmp = (leapyear ? 366 : 365);
+
+ /* Do we have that many days? */
+
+ if (days >= tmp)
+ {
+ /* Yes.. bump up the year */
+
+ value++;
+ days -= tmp;
+ }
+ else
+ {
+ /* Nope... then go handle months */
+
+ break;
+ }
+ }
+
+ /* At this point, value has the year and days has number days into this year */
+
+ *year = 1970 + value;
+
+ /* Handle the month (zero based) */
+
+ min = 0;
+ max = 11;
+
+ do
+ {
+ /* Get the midpoint */
+
+ value = (min + max) >> 1;
+
+ /* Get the number of days that occurred before the beginning of the month
+ * following the midpoint.
+ */
+
+ tmp = clock_daysbeforemonth(value + 1, leapyear);
+
+ /* Does the number of days before this month that equal or exceed the
+ * number of days we have remaining?
+ */
+
+ if (tmp > days)
+ {
+ /* Yes.. then the month we want is somewhere from 'min' and to the
+ * midpoint, 'value'. Could it be the midpoint?
+ */
+
+ tmp = clock_daysbeforemonth(value, leapyear);
+ if (tmp > days)
+ {
+ /* No... The one we want is somewhere between min and value-1 */
+
+ max = value - 1;
+ }
+ else
+ {
+ /* Yes.. 'value' contains the month that we want */
+
+ break;
+ }
+ }
+ else
+ {
+ /* No... The one we want is somwhere between value+1 and max */
+
+ min = value + 1;
+ }
+
+ /* If we break out of the loop because min == max, then we want value
+ * to be equal to min == max.
+ */
+
+ value = min;
+ }
+ while (min < max);
+
+ /* The selected month number is in value. Subtract the number of days in the
+ * selected month
+ */
+
+ days -= clock_daysbeforemonth(value, leapyear);
+
+ /* At this point, value has the month into this year (zero based) and days has
+ * number of days into this month (zero based)
+ */
+
+ *month = value + 1; /* 1-based */
+ *day = days + 1; /* 1-based */
+}
+
+#endif /* CONFIG_GREGORIAN_TIME */
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function: gmtime_r
+ *
+ * Description:
+ * Time conversion (based on the POSIX API)
+ *
+ ****************************************************************************/
+
+FAR struct tm *gmtime_r(FAR const time_t *timer, FAR struct tm *result)
+{
+ time_t epoch;
+ time_t jdn;
+ int year;
+ int month;
+ int day;
+ int hour;
+ int min;
+ int sec;
+
+ /* Get the seconds since the EPOCH */
+
+ epoch = *timer;
+ sdbg("timer=%d\n", (int)epoch);
+
+ /* Convert to days, hours, minutes, and seconds since the EPOCH */
+
+ jdn = epoch / SEC_PER_DAY;
+ epoch -= SEC_PER_DAY * jdn;
+
+ hour = epoch / SEC_PER_HOUR;
+ epoch -= SEC_PER_HOUR * hour;
+
+ min = epoch / SEC_PER_MIN;
+ epoch -= SEC_PER_MIN * min;
+
+ sec = epoch;
+
+ sdbg("hour=%d min=%d sec=%d\n",
+ (int)hour, (int)min, (int)sec);
+
+ /* Convert the days since the EPOCH to calendar day */
+
+ clock_utc2calendar(jdn, &year, &month, &day);
+
+ sdbg("jdn=%d year=%d month=%d day=%d\n",
+ (int)jdn, (int)year, (int)month, (int)day);
+
+ /* Then return the struct tm contents */
+
+ result->tm_year = (int)year - 1900; /* Relative to 1900 */
+ result->tm_mon = (int)month - 1; /* zero-based */
+ result->tm_mday = (int)day; /* one-based */
+ result->tm_hour = (int)hour;
+ result->tm_min = (int)min;
+ result->tm_sec = (int)sec;
+
+ return result;
+}
+
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