1 files changed, 50 insertions, 0 deletions
diff --git a/difftimespec.c b/difftimespec.c
new file mode 100644
index 0000000..4ea74a8
--- /dev/null
+++ b/difftimespec.c
@@ -0,0 +1,50 @@
+/* See LICENSE file for copyright and license details. */
+#include "libsimple.h"
+
+
+int
+libsimple_difftimespec(struct timespec *diff, const struct timespec *minuend, const struct timespec *subtrahend)
+{
+	long int ns = minuend->tv_nsec - subtrahend->tv_nsec;
+	time_t s;
+	int ret = 0;
+
+	s = minuend->tv_sec - subtrahend->tv_sec;
+	if ((minuend->tv_sec <= 0) != (subtrahend->tv_sec <= 0)) {
+		if (minuend->tv_sec < 0 && minuend->tv_sec < TIME_MIN + subtrahend->tv_sec) {
+			s = TIME_MIN;
+			ns = 0;
+			errno = ERANGE;
+			ret = -1;
+		} else if (minuend->tv_sec >= 0 && minuend->tv_sec > TIME_MAX + subtrahend->tv_sec) {
+			s = TIME_MAX;
+			ns = 999999999L;
+			errno = ERANGE;
+			ret = -1;
+		}
+	}
+
+	if (ns < 0) {
+		if (s == TIME_MIN) {
+			ns = 0L;
+			errno = ERANGE;
+			ret = -1;
+		} else {
+			s -= 1;
+			ns += 1000000000L;
+		}
+	} else if (ns >= 1000000000L) {
+		if (s == TIME_MAX) {
+			ns = 999999999L;
+			errno = ERANGE;
+			ret = -1;
+		} else {
+			s += 1;
+			ns -= 1000000000L;
+		}
+	}
+
+	diff->tv_sec = s;
+	diff->tv_nsec = ns;
+	return ret;
+}