Decrement value when end is in open range. (#2072)

* Decrement value when end is in open range.

Not an error when end is in open range.

* change API call

pkg/sfu/rtpmunger.go

@@ -297,9 +297,7 @@ func (r *RTPMunger) UpdateAndGetPaddingSnTs(num int, clockRate uint32, frameRate
 
 	r.extSecondLastSN = extLastSN - 1
 	r.extLastSN = extLastSN
-	if err := r.snRangeMap.CloseRangeAndDecValue(r.extHighestIncomingSN, uint64(num)); err != nil {
-		r.logger.Errorw("could not close range", err, "sn", r.extHighestIncomingSN)
-	}
+	r.snRangeMap.DecValue(r.extHighestIncomingSN, uint64(num))
 	r.updateSnOffset("pad")
 
 	r.tsOffset -= extLastTS - r.extLastTS

pkg/sfu/utils/rangemap.go

@@ -16,6 +16,7 @@ package utils
 
 import (
 	"errors"
+	"fmt"
 	"math"
 	"unsafe"
 )
@@ -66,13 +67,15 @@ func (r *RangeMap[RT, VT]) ClearAndResetValue(val VT) {
 	r.initRanges(val)
 }
 
-func (r *RangeMap[RT, VT]) CloseRangeAndDecValue(end RT, dec VT) error {
-	// close open range
+func (r *RangeMap[RT, VT]) DecValue(end RT, dec VT) {
 	lr := &r.ranges[len(r.ranges)-1]
 	if lr.start > end {
-		// start of open range is after given end
-		return errReversedOrder
+		// modify existing value if end is in open range
+		lr.value -= dec
+		return
 	}
+
+	// close open range
 	lr.end = end
 
 	// start a new open one with decremented value
@@ -82,7 +85,6 @@ func (r *RangeMap[RT, VT]) CloseRangeAndDecValue(end RT, dec VT) error {
 		value: lr.value - dec,
 	})
 	r.prune()
-	return nil
 }
 
 func (r *RangeMap[RT, VT]) initRanges(val VT) {
@@ -97,13 +99,13 @@ func (r *RangeMap[RT, VT]) initRanges(val VT) {
 
 func (r *RangeMap[RT, VT]) ExcludeRange(startInclusive RT, endExclusive RT) error {
 	if endExclusive == startInclusive || endExclusive-startInclusive > r.halfRange {
-		return errReversedOrder
+		return fmt.Errorf("%w, start %d, end %d", errReversedOrder, startInclusive, endExclusive)
 	}
 
 	lr := &r.ranges[len(r.ranges)-1]
 	if lr.start > startInclusive {
 		// start of open range is after start of exclusion range, cannot close the open range
-		return errReversedOrder
+		return fmt.Errorf("%w, existingStart %d, newStart %d", errReversedOrder, lr.start, startInclusive)
 	}
 
 	newValue := lr.value + VT(endExclusive-startInclusive)

pkg/sfu/utils/rangemap_test.go

@@ -234,8 +234,7 @@ func TestRangeMapUint32(t *testing.T) {
 	require.Equal(t, uint32(23), value)
 
 	// decrement value and ensure that any key returns that value
-	err = r.CloseRangeAndDecValue(34, 12)
-	require.NoError(t, err)
+	r.DecValue(34, 12)
 
 	expectedRanges = []rangeVal[uint32, uint32]{
 		{
@@ -293,8 +292,7 @@ func TestRangeMapUint32(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, uint32(16), value)
 
-	err = r.CloseRangeAndDecValue(66, 6)
-	require.NoError(t, err)
+	r.DecValue(66, 6)
 
 	expectedRanges = []rangeVal[uint32, uint32]{
 		{
@@ -315,9 +313,6 @@ func TestRangeMapUint32(t *testing.T) {
 	}
 	require.Equal(t, expectedRanges, r.ranges)
 
-	err = r.CloseRangeAndDecValue(66, 6)
-	require.ErrorIs(t, err, errReversedOrder)
-
 	// aged out range access
 	value, err = r.GetValue(5)
 	require.ErrorIs(t, err, errKeyTooOld)
@@ -331,4 +326,31 @@ func TestRangeMapUint32(t *testing.T) {
 	value, err = r.GetValue(67)
 	require.NoError(t, err)
 	require.Equal(t, uint32(10), value)
+
+	// decrement with old end and check that open range gets decremented
+	r.DecValue(66, 6)
+
+	expectedRanges = []rangeVal[uint32, uint32]{
+		{
+			start: 35,
+			end:   39,
+			value: 11,
+		},
+		{
+			start: 45,
+			end:   66,
+			value: 16,
+		},
+		{
+			start: 67,
+			end:   0,
+			value: 4,
+		},
+	}
+	require.Equal(t, expectedRanges, r.ranges)
+
+	// open range access should get decremented value
+	value, err = r.GetValue(67)
+	require.NoError(t, err)
+	require.Equal(t, uint32(4), value)
 }