From 99055e5cae599c8521b549e56ba6dd23d5104f00 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Fri, 15 Apr 2022 03:35:34 +0200
Subject: [PATCH] Make duration functions work with negative values.

---
 estimator/estimator.go  |  6 ++++--
 rtpconn/rtpstats.go     |  2 +-
 rtpconn/rtpwriter.go    |  2 +-
 rtptime/rtptime.go      | 19 +++++++++++++------
 rtptime/rtptime_test.go | 16 +++++++++++++---
 5 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/estimator/estimator.go b/estimator/estimator.go
index 58acb21..44349c0 100644
--- a/estimator/estimator.go
+++ b/estimator/estimator.go
@@ -23,8 +23,10 @@ type Estimator struct {
 // New creates a new estimator that estimates rate over the last interval.
 func New(interval time.Duration) *Estimator {
 	return &Estimator{
-		interval: rtptime.FromDuration(interval, rtptime.JiffiesPerSec),
-		time:     rtptime.Now(rtptime.JiffiesPerSec),
+		interval: uint64(
+			rtptime.FromDuration(interval, rtptime.JiffiesPerSec),
+		),
+		time: rtptime.Now(rtptime.JiffiesPerSec),
 	}
 }
 
diff --git a/rtpconn/rtpstats.go b/rtpconn/rtpstats.go
index 0fcde0d..882904e 100644
--- a/rtpconn/rtpstats.go
+++ b/rtpconn/rtpstats.go
@@ -57,7 +57,7 @@ func (c *webClient) GetStats() *stats.Client {
 			maxTid := layer.maxTid
 			rate, _ := t.rate.Estimate()
 			maxRate, _, _ := t.GetMaxBitrate()
-			rtt := rtptime.ToDuration(t.getRTT(),
+			rtt := rtptime.ToDuration(int64(t.getRTT()),
 				rtptime.JiffiesPerSec)
 			loss, jitter := t.stats.Get(jiffies)
 			j := time.Duration(jitter) * time.Second /
diff --git a/rtpconn/rtpwriter.go b/rtpconn/rtpwriter.go
index 6161fb5..f5e6dbc 100644
--- a/rtpconn/rtpwriter.go
+++ b/rtpconn/rtpwriter.go
@@ -138,7 +138,7 @@ func (wp *rtpWriterPool) write(seqno uint16, index uint16, delay uint32, isvideo
 			// audio, try again with a delay
 			d := delay / uint32(2*len(wp.writers))
 			timer := time.NewTimer(rtptime.ToDuration(
-				uint64(d), rtptime.JiffiesPerSec,
+				int64(d), rtptime.JiffiesPerSec,
 			))
 
 			select {
diff --git a/rtptime/rtptime.go b/rtptime/rtptime.go
index 7feef33..45aacec 100644
--- a/rtptime/rtptime.go
+++ b/rtptime/rtptime.go
@@ -9,18 +9,25 @@ import (
 var epoch = time.Now()
 
 // FromDuration converts a time.Duration into units of 1/hz.
-func FromDuration(d time.Duration, hz uint32) uint64 {
-	return uint64(d) * uint64(hz) / uint64(time.Second)
+func FromDuration(d time.Duration, hz uint32) int64 {
+	return int64(d) * int64(hz) / int64(time.Second)
 }
 
 // ToDuration converts units of 1/hz into a time.Duration.
-func ToDuration(tm uint64, hz uint32) time.Duration {
-	return time.Duration(tm * uint64(time.Second) / uint64(hz))
+func ToDuration(tm int64, hz uint32) time.Duration {
+	return time.Duration(tm * int64(time.Second) / int64(hz))
+}
+
+func sat(a int64) uint64 {
+	if a < 0 {
+		return 0
+	}
+	return uint64(a)
 }
 
 // Now returns the current time in units of 1/hz from an arbitrary origin.
 func Now(hz uint32) uint64 {
-	return FromDuration(time.Since(epoch), hz)
+	return sat(FromDuration(time.Since(epoch), hz))
 }
 
 // Microseconds is like Now, but uses microseconds.
@@ -39,7 +46,7 @@ func Jiffies() uint64 {
 
 // TimeToJiffies converts a time.Time into jiffies.
 func TimeToJiffies(tm time.Time) uint64 {
-	return FromDuration(tm.Sub(epoch), JiffiesPerSec)
+	return sat(FromDuration(tm.Sub(epoch), JiffiesPerSec))
 }
 
 // The origin of NTP time.
diff --git a/rtptime/rtptime_test.go b/rtptime/rtptime_test.go
index 9f8b01a..0b7e447 100644
--- a/rtptime/rtptime_test.go
+++ b/rtptime/rtptime_test.go
@@ -11,9 +11,19 @@ func TestDuration(t *testing.T) {
 		t.Errorf("Expected 48000, got %v", a)
 	}
 
-	b := ToDuration(48000, 48000)
-	if b != time.Second {
-		t.Errorf("Expected %v, got %v", time.Second, b)
+	b := FromDuration(-time.Second, 48000)
+	if b != -48000 {
+		t.Errorf("Expected -48000, got %v", b)
+	}
+
+	c := ToDuration(48000, 48000)
+	if c != time.Second {
+		t.Errorf("Expected %v, got %v", time.Second, c)
+	}
+
+	d := ToDuration(-48000, 48000)
+	if d != -time.Second {
+		t.Errorf("Expected %v, got %v", -time.Second, d)
 	}
 }