audio: remove locks from (*Player).Position

audio/player.go

@@ -18,6 +18,7 @@ import (
 	"io"
 	"runtime"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -73,10 +74,10 @@ type playerImpl struct {
 	initBufferSize int
 	bytesPerSample int
 
-	// adjustedPosition is the player's more accurate position.
+	// adjustedPosition is the player's more accurate position as time.Duration.
 	// The underlying buffer might not be changed even if the player is playing.
 	// adjustedPosition is adjusted by the time duration during the player position doesn't change while its playing.
-	adjustedPosition time.Duration
+	adjustedPosition atomic.Int64
 
 	// lastSamples is the last value of the number of samples.
 	// When lastSamples is a negative number, this value is not initialized yet.
@@ -269,9 +270,7 @@ func (p *playerImpl) Close() error {
 }
 
 func (p *playerImpl) Position() time.Duration {
-	p.m.Lock()
-	defer p.m.Unlock()
-	return p.adjustedPosition
+	return time.Duration(p.adjustedPosition.Load())
 }
 
 func (p *playerImpl) Rewind() error {
@@ -283,7 +282,7 @@ func (p *playerImpl) SetPosition(offset time.Duration) error {
 	defer p.m.Unlock()
 
 	if offset == 0 && p.player == nil {
-		p.adjustedPosition = 0
+		p.adjustedPosition.Store(0)
 		return nil
 	}
 
@@ -297,7 +296,7 @@ func (p *playerImpl) SetPosition(offset time.Duration) error {
 	}
 	p.lastSamples = -1
 	// Just after setting a position, the buffer size should be 0 as no data is sent.
-	p.adjustedPosition = p.stream.positionInTimeDuration()
+	p.adjustedPosition.Store(int64(p.stream.positionInTimeDuration()))
 	p.stopwatch.reset()
 	if p.isPlaying() {
 		p.stopwatch.start()
@@ -359,11 +358,11 @@ func (p *playerImpl) updatePosition() {
 	defer p.m.Unlock()
 
 	if p.player == nil {
-		p.adjustedPosition = 0
+		p.adjustedPosition.Store(0)
 		return
 	}
 	if !p.context.IsReady() {
-		p.adjustedPosition = 0
+		p.adjustedPosition.Store(0)
 		return
 	}
 
@@ -383,7 +382,7 @@ func (p *playerImpl) updatePosition() {
 	}
 
 	// Update the adjusted position every tick. This is necessary to keep the position accurate.
-	p.adjustedPosition = time.Duration(samples)*time.Second/time.Duration(p.factory.sampleRate) + adjustingTime
+	p.adjustedPosition.Store(int64(time.Duration(samples)*time.Second/time.Duration(p.factory.sampleRate) + adjustingTime))
 }
 
 type timeStream struct {