Enhancements for civil time conversions

CODEOWNERS

@@ -270,6 +270,7 @@
 /kernel/                                  @andrewboie @andyross
 /lib/gui/                                 @vanwinkeljan
 /lib/libc/                                @nashif
+/lib/misc/                                @pabigot
 /lib/os/                                  @andrewboie @andyross
 /lib/posix/                               @pfalcon
 /lib/cmsis_rtos_v2/                       @nashif

include/misc/civiltime.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2019, Peter Bigot Consulting, LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Utilities for converting between civil time and UNIX time
+ */
+
+#ifndef ZEPHYR_INCLUDE_MISC_CIVILTIME_H_
+#define ZEPHYR_INCLUDE_MISC_CIVILTIME_H_
+
+#include <zephyr/types.h>
+#include <time.h>
+
+/** @brief Convert a civil (proleptic Gregorian) date to days relative to
+ * 1970-01-01.
+ *
+ * @param y the calendar year
+ * @param m the calendar month, in the range [1, 12]
+ * @param d the day of the month, in the range [1, last_day_of_month(y, m)]
+ *
+ * @return the signed number of days between 1970-01-01 and the
+ * specified day.  Negative days are before 1970-01-01.
+ */
+s64_t time_days_from_civil(s64_t y,
+			   unsigned int m,
+			   unsigned int d);
+
+/** @brief Convert civil time to UNIX time.
+ *
+ * @param tvp pointer to a civil time structure.  @c tm_year, @c
+ * tm_mon, @c tm_mday, @c tm_hour, @c tm_min, and @c tm_sec must be
+ * valid.  All other fields are ignored.
+ *
+ * @return the signed number of seconds between 1970-01-01T00:00:00
+ * and the specified time, ignoring leap seconds and DST offsets.
+ */
+time_t time_unix_from_civil(const struct tm *tvp);
+
+/** @brief Convert days relative to 1970-01-01 to date information
+ *
+ * This converts signed days relative to 1970-01-01 to the POSIX
+ * standard civil time structure assuming a proleptic Gregorian
+ * calendar.
+ *
+ * @param days the time represented as days.
+ *
+ * @return the time information for corresponding to the provided
+ * instant.  The @c tm_year, @c tm_mon@, @c tm_mday, @c tm_wday, and
+ * @c tm_yday fields are set; all other fields are zero.
+ */
+struct tm time_civil_from_days(s64_t days);
+
+/** @brief Convert a UNIX time to civil time.
+ *
+ * This converts integral seconds since (before) 1970-01-01T00:00:00 to the
+ * POSIX standard civil time representation.  Any adjustments due to time zone,
+ * leap seconds, or a different epoch must be applied to @p time before
+ * invoking this function.
+ *
+ * @note On systems where @c time_t has only 32 bits the range of
+ * supported conversions is restricted to 1901-12-14T20:45:51 to
+ * 2038-01-19T03:14:07.
+ *
+ * @param time the time represented as seconds.
+ *
+ * @return the time information for corresponding to the provided instant.
+ */
+struct tm time_civil_from_unix(time_t time);
+
+#endif /* ZEPHYR_INCLUDE_MISC_CIVILTIME_H_ */

lib/CMakeLists.txt

@@ -7,5 +7,6 @@ add_subdirectory_ifdef(CONFIG_POSIX_API            posix)
 add_subdirectory_ifdef(CONFIG_CMSIS_RTOS_V1        cmsis_rtos_v1)
 add_subdirectory_ifdef(CONFIG_CMSIS_RTOS_V2        cmsis_rtos_v2)
 add_subdirectory(gui)
+add_subdirectory(misc)
 add_subdirectory(os)
 add_subdirectory_ifdef(CONFIG_UPDATEHUB            updatehub)

lib/libc/minimal/include/time.h

@@ -4,7 +4,41 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#ifndef ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_TIME_H_
+#define ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_TIME_H_
+
+#include <stdint.h>
 
 /* Dummy time.h to fulfill the requirements of certain libraries
- * i.e. mbedTLS
+ * i.e. mbedTLS and Zephyr civil time APIs
  */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct tm {
+	int tm_sec;
+	int tm_min;
+	int tm_hour;
+	int tm_mday;
+	int tm_mon;
+	int tm_year;
+	int tm_wday;
+	int tm_yday;
+	int tm_isdst;
+};
+
+typedef int64_t time_t;
+typedef int32_t suseconds_t;
+
+struct timespec {
+	time_t tv_sec;
+	long tv_nsec;
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_STDIO_H_ */

lib/misc/CMakeLists.txt

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_sources(
+  civiltime.c
+  )

lib/misc/civiltime.c

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2019, Peter Bigot Consulting, LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <misc/civiltime.h>
+
+/* http://howardhinnant.github.io/date_algorithms.html#days_from_civil */
+s64_t time_days_from_civil(s64_t y,
+			   unsigned int m,
+			   unsigned int d)
+{
+	y -= m <= 2;
+
+	s64_t era = (y >= 0 ? y : y - 399) / 400;
+	unsigned int yoe = y - era * 400;
+	unsigned int doy = (153U * (m + (m > 2 ? -3 : 9)) + 2U) / 5U + d;
+	unsigned int doe = yoe * 365U + yoe / 4U - yoe / 100U + doy;
+
+	return era * 146097 + (time_t)doe - 719468;
+}
+
+time_t time_unix_from_civil(const struct tm *tvp)
+{
+	s64_t y = 1900 + (s64_t)tvp->tm_year;
+	unsigned int m = tvp->tm_mon + 1;
+	unsigned int d = tvp->tm_mday - 1;
+	s64_t ndays = time_days_from_civil(y, m, d);
+
+	return (time_t)tvp->tm_sec
+	       + 60 * (tvp->tm_min + 60 * tvp->tm_hour)
+	       + 86400 * ndays;
+}
+
+/* http://howardhinnant.github.io/date_algorithms.html#civil_from_days */
+struct tm time_civil_from_days(s64_t z)
+{
+	struct tm tv = { 0 };
+
+	tv.tm_wday = (z >= -4) ? ((z + 4) % 7) : ((z + 5) % 7 + 6);
+	z += 719468;
+
+	s64_t era = ((z >= 0) ? z : (z - 146096)) / 146097;
+	unsigned int doe = (z - era * (s64_t)146097);
+	unsigned int yoe = (doe - doe / 1460U + doe / 36524U
+			    - doe / 146096U) / 365U;
+	s64_t y = (time_t)yoe + era * 400;
+	unsigned int doy = doe - (365U * yoe + yoe / 4U - yoe / 100U);
+	unsigned int mp = (5U * doy + 2U) / 153U;
+	unsigned int d = doy - (153U * mp + 2U) / 5U + 1U;
+	unsigned int m = mp + ((mp < 10) ? 3 : -9);
+
+	tv.tm_year = y + (m <= 2) - 1900;
+	tv.tm_mon = m - 1;
+	tv.tm_mday = d;
+
+	/* Everything above is explained on the date algorithms page,
+	 * but doy is relative to --03-01 and we need it relative to
+	 * --01-01.
+	 *
+	 * doy=306 corresponds to --01-01, doy=364 to --02-28, and
+	 * doy=365 to --02-29.  So we can just subtract 306 to handle
+	 * January and February.
+	 *
+	 * For doy<306 we have to add the number of days before
+	 * --03-01, which is 59 in a common year and 60 in a leap
+	 * year.  Note that the first year in the era is a leap
+	 * year.
+	 */
+	if (doy >= 306U) {
+		tv.tm_yday = doy - 306U;
+	} else {
+		tv.tm_yday = doy + 59U +
+			     (((yoe % 4U == 0U) && (yoe % 100U != 0U))
+			      || (yoe == 0U));
+	}
+
+	return tv;
+}
+
+struct tm time_civil_from_unix(time_t z)
+{
+	s64_t days = (z >= 0 ? z : z - 86399) / 86400;
+	struct tm tv = time_civil_from_days(days);
+	unsigned int rem = z - days * 86400;
+
+	tv.tm_hour = rem / 60U / 60U;
+	rem -= tv.tm_hour * 60 * 60;
+	tv.tm_min = rem / 60U;
+	tv.tm_sec = rem - tv.tm_min * 60;
+
+	return tv;
+}

tests/lib/misc/civiltime/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(civiltime)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/lib/misc/civiltime/prj.conf

@@ -0,0 +1 @@
+CONFIG_ZTEST=y

tests/lib/misc/civiltime/src/civiltime_test.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2019 Peter Bigot Consulting
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef CIVILTIME_TEST_H
+#define CIVILTIME_TEST_H
+
+#include <stdlib.h>
+#include <misc/civiltime.h>
+
+struct civiltime_test_data {
+	time_t unix;
+	const char *civil;
+	struct tm tm;
+};
+
+void civiltime_check(const struct civiltime_test_data *tp,
+		     size_t count);
+
+void test_s32(void);
+void test_s64(void);
+
+#endif /* CIVILTIME_TEST_H */

tests/lib/misc/civiltime/src/main.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2019 Peter Bigot Consulting
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <ztest.h>
+#include "civiltime_test.h"
+
+void civiltime_check(const struct civiltime_test_data *tp,
+		     size_t count)
+{
+	const struct civiltime_test_data *tpe = tp + count;
+
+	while (tp < tpe) {
+		struct tm tm = time_civil_from_unix(tp->unix);
+		time_t unix = time_unix_from_civil(&tm);
+
+		zassert_equal(tm.tm_year, tp->tm.tm_year,
+			      "datetime %s year %d != %d",
+			      tp->civil, tm.tm_year, tp->tm.tm_year);
+		zassert_equal(tm.tm_mon, tp->tm.tm_mon,
+			      "datetime %s mon %d != %d",
+			      tp->civil, tm.tm_mon, tp->tm.tm_mon);
+		zassert_equal(tm.tm_mday, tp->tm.tm_mday,
+			      "datetime %s mday %d != %d",
+			      tp->civil, tm.tm_mday, tp->tm.tm_mday);
+		zassert_equal(tm.tm_hour, tp->tm.tm_hour,
+			      "datetime %s hour %d != %d",
+			      tp->civil, tm.tm_hour, tp->tm.tm_hour);
+		zassert_equal(tm.tm_min, tp->tm.tm_min,
+			      "datetime %s min %d != %d",
+			      tp->civil, tm.tm_min, tp->tm.tm_min);
+		zassert_equal(tm.tm_sec, tp->tm.tm_sec,
+			      "datetime %s sec %d != %d",
+			      tp->civil, tm.tm_sec, tp->tm.tm_sec);
+		zassert_equal(tm.tm_wday, tp->tm.tm_wday,
+			      "datetime %s wday %d != %d",
+			      tp->civil, tm.tm_wday, tp->tm.tm_wday);
+		zassert_equal(tm.tm_yday, tp->tm.tm_yday,
+			      "datetime %s yday %d != %d",
+			      tp->civil, tm.tm_yday, tp->tm.tm_yday);
+		zassert_equal(tp->unix, unix,
+			      "datetime %s reverse != %ld",
+			      tp->civil, unix);
+
+		++tp;
+	}
+}
+
+/*test case main entry*/
+void test_main(void)
+{
+	ztest_test_suite(test_civiltime_api,
+			 ztest_unit_test(test_s32),
+			 ztest_unit_test(test_s64)
+			 );
+	ztest_run_test_suite(test_civiltime_api);
+}