core: add Parser.Close() to fix memory leak (#216) [backport] (#224)

Parser.Close() will call msgDispatcher.RemoveAllQueues() to terminate the goroutine handling net-messages.
It needs to be called by the user before discarding the Parser.

Author: markus-wa

README.md

@@ -52,6 +52,7 @@ func main() {
 	defer f.Close()
 
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	// Register handler on kill events
 	p.RegisterEventHandler(func(e events.Kill) {

examples/entities/entities.go

@@ -18,6 +18,7 @@ func main() {
 	defer f.Close()
 
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	p.RegisterEventHandler(func(events.DataTablesParsed) {
 		p.ServerClasses().FindByName("CWeaponAWP").OnEntityCreated(func(ent *st.Entity) {

examples/heatmap/heatmap.go

@@ -34,6 +34,7 @@ func main() {
 	defer f.Close()
 
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	// Parse header (contains map-name etc.)
 	header, err := p.ParseHeader()

examples/nade-trajectories/nade_trajectories.go

@@ -46,6 +46,7 @@ func main() {
 	defer f.Close()
 
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	header, err := p.ParseHeader()
 	checkError(err)

examples/net-messages/netmessages.go

@@ -26,6 +26,7 @@ func main() {
 	}
 
 	p := dem.NewParserWithConfig(f, cfg)
+	defer p.Close()
 
 	// Register handler for BSPDecal messages
 	p.RegisterNetMessageHandler(func(m *msg.CSVCMsg_BSPDecal) {

examples/print-events/print_events.go

@@ -13,10 +13,12 @@ import (
 // Run like this: go run print_events.go -demo /path/to/demo.dem
 func main() {
 	f, err := os.Open(ex.DemoPathFromArgs())
-	defer f.Close()
 	checkError(err)
 
+	defer f.Close()
+
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	// Parse header
 	header, err := p.ParseHeader()

examples_test.go

@@ -18,20 +18,24 @@ func ExampleParser() {
 	if err != nil {
 		panic(err)
 	}
+
 	defer f.Close()
 
 	p := dem.NewParser(f)
+	defer p.Close()
 
 	// Register handler on kill events
 	p.RegisterEventHandler(func(e events.Kill) {
 		var hs string
 		if e.IsHeadshot {
 			hs = " (HS)"
 		}
+
 		var wallBang string
 		if e.PenetratedObjects > 0 {
 			wallBang = " (WB)"
 		}
+
 		fmt.Printf("%s <%v%s%s> %s\n", e.Killer, e.Weapon, hs, wallBang, e.Victim)
 	})
 
@@ -46,5 +50,6 @@ func TestExamplesWithoutOutput(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping long running test")
 	}
+
 	ExampleParser()
 }

fake/parser.go

@@ -227,3 +227,9 @@ func max(numbers map[int][]interface{}) (maxNumber int) {
 func (p *Parser) Cancel() {
 	p.Called()
 }
+
+// Close is a mock-implementation of Parser.Close().
+// NOP implementation.
+func (p *Parser) Close() {
+	p.Called()
+}

parser.go

@@ -31,6 +31,7 @@ Example (without error handling):
 
 	f, _ := os.Open("/path/to/demo.dem")
 	p := dem.NewParser(f)
+	defer p.Close()
 	header := p.ParseHeader()
 	fmt.Println("Map:", header.MapName)
 	p.RegisterEventHandler(func(e events.BombExplode) {
@@ -203,6 +204,12 @@ func (p *Parser) UnregisterNetMessageHandler(identifier dp.HandlerIdentifier) {
 	p.msgDispatcher.UnregisterHandler(identifier)
 }
 
+// Close closes any open resources used by the Parser (go routines, file handles).
+// This must be called before discarding the Parser to avoid memory leaks.
+func (p *Parser) Close() {
+	p.msgDispatcher.RemoveAllQueues()
+}
+
 func (p *Parser) error() (err error) {
 	p.errLock.Lock()
 	err = p.err

parser_interface.go

@@ -24,6 +24,7 @@ import (
 //
 // 	f, _ := os.Open("/path/to/demo.dem")
 // 	p := dem.NewParser(f)
+// 	defer p.Close()
 // 	header := p.ParseHeader()
 // 	fmt.Println("Map:", header.MapName)
 // 	p.RegisterEventHandler(func(e events.BombExplode) {
@@ -92,6 +93,9 @@ type IParser interface {
 	//
 	// The identifier is returned at registration by RegisterNetMessageHandler().
 	UnregisterNetMessageHandler(identifier dp.HandlerIdentifier)
+	// Close closes any open resources used by the Parser (go routines, file handles).
+	// This must be called before discarding the Parser to avoid memory leaks.
+	Close()
 	// ParseHeader attempts to parse the header of the demo and returns it.
 	// If not done manually this will be called by Parser.ParseNextFrame() or Parser.ParseToEnd().
 	//