libc: Add mktime and gmtime_r

Both the FSP RTC and the upcoming IPMI RTC implementation need to
manipulate time in various ways. Rather than re-implementing slightly
different versions of the calculations twice lets implement some
standard library functions (with tests) and use those.

This patch adds mktime and gmtime_r to the libc.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

5 files changed, 250 insertions, 3 deletions

diff --git a/libc/Makefile.inc b/libc/Makefile.inc
index 7503f092..66ce4ab0 100644
--- a/libc/Makefile.inc
+++ b/libc/Makefile.inc
@@ -1,7 +1,7 @@
 LIBCDIR = libc
 
 SUBDIRS += $(LIBCDIR)
-LIBC = $(LIBCDIR)/built-in.o
+LIBC = $(LIBCDIR)/built-in.o $(LIBCDIR)/time.o
 
 include $(SRC)/$(LIBCDIR)/string/Makefile.inc
 include $(SRC)/$(LIBCDIR)/ctype/Makefile.inc
@@ -9,4 +9,3 @@ include $(SRC)/$(LIBCDIR)/stdlib/Makefile.inc
 include $(SRC)/$(LIBCDIR)/stdio/Makefile.inc
 
 $(LIBC): $(STRING) $(CTYPE) $(STDLIB) $(STDIO)
-
diff --git a/libc/include/time.h b/libc/include/time.h
index 807023b0..517f596f 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -33,10 +33,12 @@ struct timespec {
 	long   tv_nsec;       /* nanoseconds */
 };
 
+struct tm *gmtime_r(const time_t *timep, struct tm *result);
+time_t mktime(struct tm *tm);
+
 /* Not implemented by libc but by hosting environment, however
  * this is where the prototype is expected
  */
 int nanosleep(const struct timespec *req, struct timespec *rem);
 
 #endif /* _TIME_H */
-
diff --git a/libc/test/Makefile.check b/libc/test/Makefile.check
new file mode 100644
index 00000000..188b6b1f
--- /dev/null
+++ b/libc/test/Makefile.check
@@ -0,0 +1,22 @@
+# -*-Makefile-*-
+LIBC_TEST := libc/test/run-time
+
+check: $(LIBC_TEST:%=%-check)
+
+$(LIBC_TEST:%=%-check) : %-check: %
+	$(VALGRIND) $<
+
+$(LIBC_TEST) : % : %.c
+	$(HOSTCC) $(HOSTCFLAGS) -O0 -g -I include -I . -I libfdt -I libc/include -o $@ $<
+
+$(LIBC_TEST): % : %.d
+
+libc/test/%.d: libc/test/%.c
+	$(HOSTCC) $(HOSTCFLAGS) -I include -I . -I libfdt -I libc/include -M $< > $@
+
+-include libc/test/*.d
+
+clean: libc-test-clean
+
+libc-test-clean:
+	$(RM) -f libc/test/*.[od] $(LIBC_TEST)
diff --git a/libc/test/run-time.c b/libc/test/run-time.c
new file mode 100644
index 00000000..95662f40
--- /dev/null
+++ b/libc/test/run-time.c
@@ -0,0 +1,82 @@
+#include "/usr/include/assert.h"
+#include <stdio.h>
+#include <time.h>
+
+#include "../time.c"
+
+#define MKTIME_TEST(Y,M,D,h,m,s,t) \
+	tm.tm_year = Y; \
+	tm.tm_mon = M; \
+	tm.tm_mday = D; \
+	tm.tm_hour = h; \
+	tm.tm_min = m; \
+	tm.tm_sec = s; \
+	assert(mktime(&tm) == t); \
+	assert(tm.tm_year == Y); \
+	assert(tm.tm_mon == M); \
+	assert(tm.tm_mday == D); \
+	assert(tm.tm_hour == h); \
+	assert(tm.tm_min == m); \
+	assert(tm.tm_sec == s)
+
+#define GMTIME_TEST(Y,M,D,h,m,s,tv) \
+	t = tv; \
+	gmtime_r(&t, &tm); \
+	assert(tm.tm_year == Y); \
+	assert(tm.tm_mon == M); \
+	assert(tm.tm_mday == D); \
+	assert(tm.tm_hour == h); \
+	assert(tm.tm_min == m); \
+	assert(tm.tm_sec == s)
+
+#define TIME_TEST(Y,M,D,h,m,s,tv) \
+	MKTIME_TEST(Y,M,D,h,m,s,tv);		\
+	GMTIME_TEST(Y,M,D,h,m,s,tv)
+
+int main(void)
+{
+	struct tm tm;
+	time_t t = 0;
+	uint32_t time;
+
+	TIME_TEST(1970, 0, 1, 0, 0, 0, 0);
+	TIME_TEST(1971, 0, 1, 0, 0, 0, 365*SECS_PER_DAY);
+	TIME_TEST(1972, 0, 1, 0, 0, 0, 2*365*SECS_PER_DAY);
+	TIME_TEST(1972, 11, 31, 0, 0, 0, 3*365*SECS_PER_DAY);
+	TIME_TEST(1973, 0, 1, 0, 0, 0, (3*365+1)*SECS_PER_DAY);
+	TIME_TEST(2000, 11, 31, 0, 0, 0, 978220800);
+	TIME_TEST(2001, 0, 1, 0, 0, 0, 978307200);
+	TIME_TEST(2003, 11, 31, 0, 0, 0, 1072828800);
+	TIME_TEST(2004, 0, 1, 0, 0, 0, 1072828800+SECS_PER_DAY);
+	TIME_TEST(2004, 11, 29, 0, 0, 0, 1072828800+364*SECS_PER_DAY);
+	TIME_TEST(2004, 11, 30, 0, 0, 0, 1072828800+365*SECS_PER_DAY);
+	TIME_TEST(2004, 11, 31, 0, 0, 0, 1072828800+366*SECS_PER_DAY);
+	TIME_TEST(2004, 11, 31, 23, 59, 59, 1072828800+367*SECS_PER_DAY-1);
+	TIME_TEST(2100, 11, 31, 0, 0, 0, 4133894400);
+	TIME_TEST(2101, 0, 1, 0, 0, 0, 4133980800);
+
+	/* Test the normalisation functionality of mktime */
+	tm.tm_year = 2000;
+	tm.tm_mon = 1;
+	tm.tm_mday = 10;
+	tm.tm_hour = 5;
+	tm.tm_min = 32;
+	tm.tm_sec = 105;
+	mktime(&tm);
+	assert(tm.tm_year == 2000);
+	assert(tm.tm_mon == 1);
+	assert(tm.tm_mday == 10);
+	assert(tm.tm_hour == 5);
+	assert(tm.tm_min == 33);
+	assert(tm.tm_sec == 45);
+	tm.tm_sec += 366*24*60*60;
+	mktime(&tm);
+	assert(tm.tm_year == 2001);
+	assert(tm.tm_mon == 1);
+	assert(tm.tm_mday == 10);
+	assert(tm.tm_hour == 5);
+	assert(tm.tm_min == 33);
+	assert(tm.tm_sec == 45);
+
+	return 0;
+}
diff --git a/libc/time.c b/libc/time.c
new file mode 100644
index 00000000..9be6e11e
--- /dev/null
+++ b/libc/time.c
@@ -0,0 +1,142 @@
+#include <stdbool.h>
+#include <time.h>
+
+/*
+ * Returns the number of leap years prior to the given year.
+ */
+static int leap_years(int year)
+{
+	return (year-1)/4 + (year-1)/400 - (year-1)/100;
+}
+
+static int is_leap_year(int year)
+{
+	return ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
+}
+
+static int days_in_month(int month, int year)
+{
+	static int month_days[] = {
+		31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+	};
+
+	/* we may need to update this in the year 4000, pending a
+	 * decision on whether or not it's a leap year */
+	if (month == 1)
+		return is_leap_year(year) ? 29 : 28;
+
+	return month_days[month];
+}
+
+static const int days_per_month[2][13] =
+	{{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
+	 {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}};
+
+#define SECS_PER_MIN 60
+#define SECS_PER_HOUR (SECS_PER_MIN*60)
+#define SECS_PER_DAY (24*SECS_PER_HOUR)
+#define DAYS_PER_YEAR 365
+struct tm *gmtime_r(const time_t *timep, struct tm *result)
+{
+	int i;
+	int Y;
+	int M;
+	int D;
+	int h;
+	int m;
+	int s;
+
+	D = *timep / SECS_PER_DAY;
+	s = *timep % SECS_PER_DAY;
+	m = s / 60;
+	h = m / 60;
+	m %= 60;
+	s %= 60;
+
+	/*
+	 * Work out the year. We subtract one day for every four years
+	 * and every 400 years after 1969. However as leap years don't
+	 * occur every 100 years we add one day back to counteract the
+	 * the substraction for every 4 years.
+	 */
+	Y = (D - (1+D/365)/4 + (69+D/365)/100 - (369+D/365)/400)/365;
+
+	/*
+	 * Remember we're doing integer arithmetic here so
+	 * leap_years(Y+1970) - leap_years(1970) != leap_years(Y)
+	 */
+	D = D - Y*365 - (leap_years(Y+1970) - leap_years(1970)) + 1;
+	Y += 1970;
+
+	M = 0;
+	for (i = 0; i < 13; i++)
+		if (D <= days_per_month[is_leap_year(Y) ? 1 : 0][i]) {
+			M = i;
+			break;
+		}
+
+	D -= days_per_month[is_leap_year(Y)][M-1];
+	result->tm_year = Y;
+	result->tm_mon = M - 1;
+	result->tm_mday = D;
+	result->tm_hour = h;
+	result->tm_min = m;
+	result->tm_sec = s;
+	return result;
+}
+
+time_t mktime(struct tm *tm)
+{
+	unsigned long year, month, mday, hour, minute, second, d;
+	static const unsigned long sec_in_400_years =
+		((3903ul * 365) + (97 * 366)) * 24 * 60 * 60;
+
+	second = tm->tm_sec;
+	minute = tm->tm_min;
+	hour = tm->tm_hour;
+	mday = tm->tm_mday;
+	month = tm->tm_mon;
+	year = tm->tm_year;
+
+	/* There are the same number of seconds in any 400-year block; this
+	 * limits the iterations in the loop below */
+	year += 400 * (second / sec_in_400_years);
+	second = second % sec_in_400_years;
+
+	if (second >= 60) {
+		minute += second / 60;
+		second = second % 60;
+	}
+
+	if (minute >= 60) {
+		hour += minute / 60;
+		minute = minute % 60;
+	}
+
+	if (hour >= 24) {
+		mday += hour / 24;
+		hour = hour % 24;
+	}
+
+	for (d = days_in_month(month, year); mday > d;
+			d = days_in_month(month, year)) {
+		month++;
+		if (month > 12) {
+			month = 0;
+			year++;
+		}
+		mday -= d;
+	}
+
+	tm->tm_year = year;
+	tm->tm_mon = month;
+	tm->tm_mday = mday;
+	tm->tm_hour = hour;
+	tm->tm_min = minute;
+	tm->tm_sec = second;
+
+	d = mday;
+	d += days_per_month[is_leap_year(year)][month];
+	d += (year-1970)*DAYS_PER_YEAR + leap_years(year) - leap_years(1970) - 1;
+	return d*SECS_PER_DAY + hour*SECS_PER_HOUR + minute*SECS_PER_MIN + second;
+}