sync: Made doc comment on Gate.Close make more sense

sync/gate.go

@@ -1,6 +1,6 @@
 package usync
 
-import "sync"
+import "sync/atomic"
 
 // Error defines errors that this package can produce
 type Error string; const (
@@ -12,83 +12,74 @@ func (err Error) Error () string {
 	return string(err)
 }
 
+// if you know of a better way, i'd like to hear of it. otherwise, STFU!!!!
+
 // Gate wraps a channel and allows the receiver to abruptly stop receiving
 // messages without causing the sender to lock up.
 type Gate[T any] struct {
-	channel    chan T
-	lock       sync.RWMutex
-	open       bool
+	channel    atomic.Value
 	bufferSize int
 }
 
 // NewGate creates a new gate with no buffer.
 func NewGate[T any] () Gate[T] {
-	return Gate[T] {
-		channel: make(chan T),
-		open:    true,
-	}
+	return NewBufferedGate[T](0)
 }
 
 // NewBufferedGate creates a new gate with a buffer.
 func NewBufferedGate[T any] (buffer int) Gate[T] {
-	return Gate[T] {
-		channel:    make(chan T, buffer),
-		open:       true,
+	gate := Gate[T] {
 		bufferSize: buffer,
 	}
+	gate.channel.Store(make(chan T, buffer))
+	return gate
 }
 
 // Send sends and item to the channel, returning whether the item was sent.
-func (this *Gate[T]) Send (item T) bool {
-	this.lock.RLock()
-	defer this.lock.RUnlock()
-	if !this.open { return false }
-	this.channel <- item
+func (this *Gate[T]) Send (item T) (ok bool) {
+	channel := this.load()
+	if channel == nil { return false }
+	// if the channel send panics, "return true" never gets run so it just
+	// returns false after recovering
+	defer func() { recover() }()
+	channel <- item
 	return true
 }
 
 // Receive returns a receive-only channel that can be used to receive items.
 func (this *Gate[T]) Receive () <- chan T {
-	this.lock.RLock()
-	defer this.lock.RUnlock()
-	return this.channel
+	return this.load()
 }
 
-// Close closes the gate, drains all remaining messages, and closes the channel.
+// Close closes the gate, unblocking any send or receive operations.
 func (this *Gate[T]) Close () error {
-	this.lock.Lock()
-	if !this.open { return ErrAlreadyClosed }
-	this.open = false
-	this.lock.Unlock()
-	for len(this.channel) > 0 { <- this.channel }
-	close(this.channel)
+	channel := this.channel.Swap((chan T)(nil)).(chan T)
+	if channel == nil { return ErrAlreadyClosed }
+	close(channel)
 	return nil
 }
 
 // Reset re-opens the gate if it is closed, and creates a new channel.
 func (this *Gate[T]) Reset () error {
-	this.lock.Lock()
-	defer this.lock.Unlock()
-	this.open = true
-	if this.channel != nil { close(this.channel) }
-	this.channel = make(chan T, this.bufferSize)
+	this.channel.Store(make(chan T, this.bufferSize))
 	return nil
 }
 
 // Open returns whether the gate is open.
 func (this *Gate[T]) Open () bool {
-	this.lock.RLock()
-	defer this.lock.RUnlock()
-	return this.open
+	return this.load() != nil
 }
 
 // Len returns the amount of items in the channel.
 func (this *Gate[T]) Len () int {
-	return len(this.channel)
+	return len(this.load())
 }
 
 // Cap returns the amount of items the channel can hold.
 func (this *Gate[T]) Cap () int {
-	return cap(this.channel)
+	return cap(this.load())
 }
 
+func (this *Gate[T]) load() chan T {
+	return this.channel.Load().(chan T)
+}

sync/gate_test.go

@@ -0,0 +1,63 @@
+package usync
+
+import "time"
+import "errors"
+import "testing"
+
+func TestGate(test *testing.T) {
+	gate := NewGate[int]()
+	go func() {
+		for number := range 21 {
+			test.Log("send", number)
+			gate.Send(number)
+		}
+		test.Log("send done")
+	}()
+	for correct := range 21 {
+		got := <- gate.Receive()
+		test.Log("RECV", correct, got)
+		if correct != got {
+			test.Fatal("RECV not equal")
+		}
+	}
+	test.Log("RECV done")
+}
+
+func TestGateCloseEarly(test *testing.T) {
+	gate := NewGate[int]()
+	sendDone := make(chan struct { })
+	go func() {
+		for number := range 21 {
+			test.Log("send", number)
+			gate.Send(number)
+		}
+		test.Log("send done")
+		close(sendDone)
+	}()
+	for correct := range 15 {
+		got := <- gate.Receive()
+		test.Log("RECV", correct, got)
+		if correct != got {
+			test.Fatal("RECV not equal")
+		}
+	}
+	test.Log("RECV done, closing gate... DOOR STUCK!! PLS I BEG OF YOU!!")
+	gate.Close()
+	test.Log("RECV closed gate yay :)))")
+	timeout := time.NewTimer(time.Second * 4)
+	select {
+	case <- sendDone:
+	case <- timeout.C:
+		test.Fatal("timed out waiting for sender goroutine to stop")
+	}
+}
+
+func TestGateCloseIdempotent(test *testing.T) {
+	gate := NewGate[int]()
+	err := gate.Close()
+	if err != nil { test.Fatal(err) }
+	err = gate.Close()
+	if !errors.Is(err, ErrAlreadyClosed) {
+		test.Fatal("wrong error: ", err)
+	}
+}