Write stream implementation (#19)

Defines a WriteStream structure for buffering writes, similar to the existing ReadStream. WriteStreams can be created on OutEndpoints by using ep.NewStream().

endpoint_stream_test.go

@@ -27,10 +27,11 @@ func TestEndpointReadStream(t *testing.T) {
 	}()
 
 	goodTransfers := 7
+	done := make(chan struct{})
 	go func() {
 		var num int
 		for {
-			xfr := lib.waitForSubmitted()
+			xfr := lib.waitForSubmitted(done)
 			if xfr == nil {
 				return
 			}
@@ -83,4 +84,80 @@ func TestEndpointReadStream(t *testing.T) {
 	if got != want {
 		t.Errorf("stream.Read(): read %d bytes, want %d", got, want)
 	}
+	close(done)
+}
+
+func TestEndpointWriteStream(t *testing.T) {
+	t.Parallel()
+	lib := newFakeLibusb()
+	ctx := newContextWithImpl(lib)
+	defer func() {
+		if err := ctx.Close(); err != nil {
+			t.Errorf("Context.Close: %v", err)
+		}
+	}()
+
+	done := make(chan struct{})
+	total := 0
+	num := 0
+	go func() {
+		for {
+			xfr := lib.waitForSubmitted(done)
+			if xfr == nil {
+				return
+			}
+			xfr.length = len(xfr.buf)
+			xfr.status = TransferCompleted
+			xfr.done <- struct{}{}
+			num++
+			total += xfr.length
+		}
+	}()
+
+	dev, err := ctx.OpenDeviceWithVIDPID(0x9999, 0x0001)
+	if err != nil {
+		t.Fatalf("OpenDeviceWithVIDPID(9999, 0001): %v", err)
+	}
+	defer dev.Close()
+	cfg, err := dev.Config(1)
+	if err != nil {
+		t.Fatalf("%s.Config(1): %v", dev, err)
+	}
+	defer cfg.Close()
+	intf, err := cfg.Interface(0, 0)
+	if err != nil {
+		t.Fatalf("%s.Interface(0, 0): %v", cfg, err)
+	}
+	defer intf.Close()
+	ep, err := intf.OutEndpoint(1)
+	if err != nil {
+		t.Fatalf("%s.Endpoint(1): %v", intf, err)
+	}
+	pktSize := 1024
+	stream, err := ep.NewStream(pktSize, 5)
+	if err != nil {
+		t.Fatalf("%s.NewStream(%d, 5): %v", ep, pktSize, err)
+	}
+	defer stream.Close()
+	for i := 0; i < 5; i++ {
+		if n, err := stream.Write(make([]byte, pktSize*2)); err != nil {
+			t.Fatalf("stream.Write: got error %v", err)
+		} else if n != pktSize*2 {
+			t.Fatalf("stream.Write: %d, want %d", n, pktSize*2)
+		}
+	}
+	want := pktSize * 10
+	if err := stream.Close(); err != nil {
+		t.Fatalf("stream.Close: got error %v", err)
+	}
+	if got := stream.Written(); got != want {
+		t.Errorf("stream.Written: got %d, want %d", got, want)
+	}
+	done <- struct{}{}
+	if num != 10 {
+		t.Errorf("received transfers: got %d, want %d", num, 10)
+	}
+	if total != want {
+		t.Errorf("received data: got %d, want %d", total, want)
+	}
 }