1 files changed, 65 insertions, 0 deletions
diff --git a/multimespec.c b/multimespec.c
new file mode 100644
index 0000000..2e1c2a9
--- /dev/null
+++ b/multimespec.c
@@ -0,0 +1,65 @@
+/* See LICENSE file for copyright and license details. */
+#include "libsimple.h"
+
+
+int
+libsimple_multimespec(struct timespec *prod, const struct timespec *multiplicand, int multiplier)
+{
+	time_t s = multiplicand->tv_sec;
+	long long int ns = (long long int)(multiplicand->tv_nsec);
+	long long int xs;
+	int neg = (s < 0) ^ (multiplier < 0);
+
+	if (multiplier == 0 || multiplier == 1) {
+		prod->tv_sec = multiplier * multiplicand->tv_sec;
+		prod->tv_nsec = multiplier * multiplicand->tv_nsec;
+		return 0;
+	}
+
+	if (s < 0) {
+		if (TIME_MIN != -TIME_MAX && s == TIME_MIN)
+			goto overflow;
+		s = -s;
+		if (ns)
+			ns = 1000000000L - ns;
+	}
+	if (multiplier < 0)
+		multiplier = -multiplier;
+
+	ns *= multiplier;
+	xs = ns / 1000000000L;
+	ns %= 1000000000L;
+
+	if (s > TIME_MAX / multiplier)
+		goto overflow;
+	s *= multiplier;
+
+	if (s > TIME_MAX - (time_t)xs)
+		goto overflow;
+	s += (time_t)xs;
+
+	if (neg) {
+		s = -s;
+		if (ns) {
+			if (s == TIME_MIN)
+				goto overflow;
+			ns = 1000000000L - ns;
+			s -= 1;
+		}
+	}
+
+	prod->tv_sec = s;
+	prod->tv_nsec = ns;
+	return 0;
+
+overflow:
+	if (neg) {
+		prod->tv_sec = TIME_MIN;
+		prod->tv_nsec = 0;
+	} else {
+		prod->tv_sec = TIME_MAX;
+		prod->tv_nsec = 999999999L;
+	}
+	errno = ERANGE;
+	return -1;
+}