1 files changed, 150 insertions, 0 deletions
diff --git a/src/ck_ec_timeutil.h b/src/ck_ec_timeutil.h
new file mode 100644
index 0000000..50cfb67
--- /dev/null
+++ b/src/ck_ec_timeutil.h
@@ -0,0 +1,150 @@
+#ifndef CK_EC_TIMEUTIL_H
+#define CK_EC_TIMEUTIL_H
+#include <ck_cc.h>
+#include <ck_ec.h>
+#include <ck_limits.h>
+#include <ck_stdint.h>
+#include <sys/time.h>
+
+#define TIME_MAX ((time_t)((1ULL << ((sizeof(time_t) * CHAR_BIT) - 1)) - 1))
+#define NSEC_MAX ((1000L * 1000 * 1000) - 1)
+
+/*
+ * Approximates (nsec * multiplier) >> shift. Clamps to UINT32_MAX on
+ * overflow.
+ */
+CK_CC_UNUSED static uint32_t
+wait_time_scale(uint32_t nsec,
+		uint32_t multiplier,
+		unsigned int shift)
+{
+	uint64_t temp = (uint64_t)nsec * multiplier;
+	uint64_t max = (uint64_t)UINT32_MAX << shift;
+
+	if (temp >= max) {
+		return UINT32_MAX;
+	}
+
+	return temp >> shift;
+}
+
+
+/*
+ * Returns ts + ns. ns is clamped to at most 1 second. Clamps the
+ * return value to TIME_MAX, NSEC_MAX on overflow.
+ *
+ */
+CK_CC_UNUSED static struct timespec timespec_add_ns(const struct timespec ts,
+						    uint32_t ns)
+{
+	struct timespec ret = {
+		.tv_sec = TIME_MAX,
+		.tv_nsec = NSEC_MAX
+	};
+	time_t sec;
+	uint32_t sum_ns;
+
+	if (ns > (uint32_t)NSEC_MAX) {
+		if (ts.tv_sec >= TIME_MAX) {
+			return ret;
+		}
+
+		ret.tv_sec = ts.tv_sec + 1;
+		ret.tv_nsec = ts.tv_nsec;
+		return ret;
+	}
+
+	sec = ts.tv_sec;
+	sum_ns = ns + ts.tv_nsec;
+	if (sum_ns > NSEC_MAX) {
+		if (sec >= TIME_MAX) {
+			return ret;
+		}
+
+		sec++;
+		sum_ns -= (NSEC_MAX + 1);
+	}
+
+	ret.tv_sec = sec;
+	ret.tv_nsec = sum_ns;
+	return ret;
+}
+
+
+/*
+ * Returns ts + inc. If inc is negative, it is normalized to 0.
+ * Clamps the return value to TIME_MAX, NSEC_MAX on overflow.
+ */
+CK_CC_UNUSED static struct timespec timespec_add(const struct timespec ts,
+						 const struct timespec inc)
+{
+	/* Initial return value is clamped to infinite future. */
+	struct timespec ret = {
+		.tv_sec = TIME_MAX,
+		.tv_nsec = NSEC_MAX
+	};
+	time_t sec;
+	unsigned long nsec;
+
+	/* Non-positive delta is a no-op. Invalid nsec is another no-op. */
+	if (inc.tv_sec < 0 || inc.tv_nsec < 0 || inc.tv_nsec > NSEC_MAX) {
+		return ts;
+	}
+
+	/* Detect overflow early. */
+	if (inc.tv_sec > TIME_MAX - ts.tv_sec) {
+		return ret;
+	}
+
+	sec = ts.tv_sec + inc.tv_sec;
+	/* This sum can't overflow if the inputs are valid.*/
+	nsec = (unsigned long)ts.tv_nsec + inc.tv_nsec;
+
+	if (nsec > NSEC_MAX) {
+		if (sec >= TIME_MAX) {
+			return ret;
+		}
+
+		sec++;
+		nsec -= (NSEC_MAX + 1);
+	}
+
+	ret.tv_sec = sec;
+	ret.tv_nsec = nsec;
+	return ret;
+}
+
+/* Compares two timespecs. Returns -1 if x < y, 0 if x == y, and 1 if x > y. */
+CK_CC_UNUSED static int timespec_cmp(const struct timespec x,
+				     const struct timespec y)
+{
+	if (x.tv_sec != y.tv_sec) {
+		return (x.tv_sec < y.tv_sec) ? -1 : 1;
+	}
+
+	if (x.tv_nsec != y.tv_nsec) {
+		return (x.tv_nsec < y.tv_nsec) ? -1 : 1;
+	}
+
+	return 0;
+}
+
+/*
+ * Overwrites now with the current CLOCK_MONOTONIC time, and returns
+ * true if the current time is greater than or equal to the deadline,
+ * or the clock is somehow broken.
+ */
+CK_CC_UNUSED static bool check_deadline(struct timespec *now,
+					const struct ck_ec_ops *ops,
+					const struct timespec deadline)
+{
+	int r;
+
+	r = ops->gettime(ops, now);
+	if (r != 0) {
+		return true;
+	}
+
+	return timespec_cmp(*now, deadline) >= 0;
+}
+#endif /* !CK_EC_TIMEUTIL_H */