1 files changed, 79 insertions, 0 deletions
diff --git a/src/lib/utc-mktime.c b/src/lib/utc-mktime.c
new file mode 100644
index 0000000..e67c687
--- /dev/null
+++ b/src/lib/utc-mktime.c
@@ -0,0 +1,79 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "utc-mktime.h"
+
+static int tm_cmp(const struct tm *tm1, const struct tm *tm2)
+{
+	int diff;
+
+	if ((diff = tm1->tm_year - tm2->tm_year) != 0)
+		return diff;
+	if ((diff = tm1->tm_mon - tm2->tm_mon) != 0)
+		return diff;
+	if ((diff = tm1->tm_mday - tm2->tm_mday) != 0)
+		return diff;
+	if ((diff = tm1->tm_hour - tm2->tm_hour) != 0)
+		return diff;
+	if ((diff = tm1->tm_min - tm2->tm_min) != 0)
+		return diff;
+	return tm1->tm_sec - tm2->tm_sec;
+}
+
+static inline void adjust_leap_second(struct tm *tm)
+{
+	if (tm->tm_sec == 60)
+		tm->tm_sec = 59;
+}
+
+#ifdef HAVE_TIMEGM
+/* Normalization done by timegm is considered a failure here, since it means
+ * the timestamp is not valid as-is. Leap second 60 is adjusted to 59 before
+ * this though. */
+time_t utc_mktime(const struct tm *tm)
+{
+	struct tm leap_adj_tm = *tm;
+	adjust_leap_second(&leap_adj_tm);
+	struct tm tmp = leap_adj_tm;
+	time_t t;
+
+	t = timegm(&tmp);
+	if (tm_cmp(&leap_adj_tm, &tmp) != 0)
+		return (time_t)-1;
+	return t;
+}
+#else
+time_t utc_mktime(const struct tm *tm)
+{
+	struct tm leap_adj_tm = *tm;
+	adjust_leap_second(&leap_adj_tm);
+	const struct tm *try_tm;
+	time_t t;
+	int bits, dir;
+
+	/* we'll do a binary search across the entire valid time_t range.
+	   when gmtime()'s output matches the tm parameter, we've found the
+	   correct time_t value. this also means that if tm contains invalid
+	   values, -1 is returned. */
+#ifdef TIME_T_SIGNED
+	t = 0;
+#else
+	t = (time_t)1 << (TIME_T_MAX_BITS - 1);
+#endif
+	for (bits = TIME_T_MAX_BITS - 2;; bits--) {
+		try_tm = gmtime(&t);
+		dir = tm_cmp(&leap_adj_tm, try_tm);
+		if (dir == 0)
+			return t;
+		if (bits < 0)
+			break;
+
+		if (dir < 0)
+			t -= (time_t)1 << bits;
+		else
+			t += (time_t)1 << bits;
+	}
+
+	return (time_t)-1;
+}
+#endif