From bc6c7377c3e5537c16f11fcdde815298b1ea5c99 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 30 Apr 2025 10:14:44 +0930
Subject: [PATCH] time: flesh out more timemono functions.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 ccan/time/test/run-monotonic.c |  7 ++++--
 ccan/time/time.h               | 40 ++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/ccan/time/test/run-monotonic.c b/ccan/time/test/run-monotonic.c
index 2da492d4..878d6249 100644
--- a/ccan/time/test/run-monotonic.c
+++ b/ccan/time/test/run-monotonic.c
@@ -7,13 +7,13 @@ int main(void)
 	struct timemono t1, t2;
 	struct timerel t3;
 
-	plan_tests(5);
+	plan_tests(7);
 
 	/* Test time_mono */
 	t1 = time_mono();
 	t2 = time_mono();
 
-	ok1(!time_less_(t2.ts, t1.ts));
+	ok1(!timemono_before(t2, t1));
 
 	t3.ts.tv_sec = 1;
 	t3.ts.tv_nsec = 0;
@@ -24,5 +24,8 @@ int main(void)
 	ok1(timemono_add(t1, t3).ts.tv_sec == t1.ts.tv_sec + 1);
 	ok1(timemono_add(t2, t3).ts.tv_nsec == t2.ts.tv_nsec);
 
+	ok1(timemono_sub(timemono_add(t1, t3), t3).ts.tv_sec == t1.ts.tv_sec);
+	ok1(timemono_sub(timemono_add(t1, t3), t3).ts.tv_nsec == t1.ts.tv_nsec);
+	
 	return exit_status();
 }
diff --git a/ccan/time/time.h b/ccan/time/time.h
index 2fc8161e..48b8d1d2 100644
--- a/ccan/time/time.h
+++ b/ccan/time/time.h
@@ -220,6 +220,23 @@ static inline bool time_before(struct timeabs a, struct timeabs b)
 	return time_less_(a.ts, b.ts);
 }
 
+/**
+ * timemono_before - is a before b?
+ * @a: one monotonic time.
+ * @b: another monotonic time.
+ *
+ * Example:
+ *	static bool still_valid(const struct timemono *start)
+ *	{
+ *	#define TIMEOUT time_from_msec(1000)
+ *		return timemono_before(time_mono(), timemono_add(*start, TIMEOUT));
+ *	}
+ */
+static inline bool timemono_before(struct timemono a, struct timemono b)
+{
+	return time_less_(a.ts, b.ts);
+}
+
 /**
  * time_less - is a before b?
  * @a: one relative time.
@@ -404,6 +421,29 @@ static inline struct timeabs timeabs_sub(struct timeabs abs, struct timerel rel)
 	return t;
 }
 
+/**
+ * timemono_sub - subtract a relative time from a monotonic time
+ * @mono: the monotonic time.
+ * @rel: the relative time.
+ *
+ * This returns a well formed struct timemono of @mono - @rel.
+ *
+ * Example:
+ *	// We do one every second.
+ *	static struct timemono previous_time(void)
+ *	{
+ *		return timemono_sub(time_mono(), time_from_msec(1000));
+ *	}
+ */
+static inline struct timemono timemono_sub(struct timemono mono, struct timerel rel)
+{
+	struct timemono t;
+
+	t.ts = time_sub_(mono.ts, rel.ts);
+	return t;
+}
+
+
 static inline struct timespec time_add_(struct timespec a, struct timespec b)
 {
 	struct timespec sum;
-- 
2.39.5