Make Reader event notification asynchronous

Instead of notifying the event coordinator (EventBox) whenever a new
line is arrived, start a background goroutine that periodically does the
task. Atomic.StoreInt32 is much cheaper than mutex synchronization
that happens during EventBox update.

src/reader_test.go

@@ -2,6 +2,7 @@ package fzf
 
 import (
 	"testing"
+	"time"
 
 	"github.com/junegunn/fzf/src/util"
 )
@@ -11,7 +12,10 @@ func TestReadFromCommand(t *testing.T) {
 	eb := util.NewEventBox()
 	reader := Reader{
 		pusher:   func(s []byte) bool { strs = append(strs, string(s)); return true },
-		eventBox: eb}
+		eventBox: eb,
+		event:    int32(EvtReady)}
+
+	reader.startEventPoller()
 
 	// Check EventBox
 	if eb.Peek(EvtReadNew) {
@@ -19,21 +23,16 @@ func TestReadFromCommand(t *testing.T) {
 	}
 
 	// Normal command
-	reader.readFromCommand(`echo abc && echo def`)
+	reader.fin(reader.readFromCommand(`echo abc && echo def`))
 	if len(strs) != 2 || strs[0] != "abc" || strs[1] != "def" {
 		t.Errorf("%s", strs)
 	}
 
 	// Check EventBox again
-	if !eb.Peek(EvtReadNew) {
-		t.Error("EvtReadNew should be set yet")
-	}
+	eb.WaitFor(EvtReadFin)
 
 	// Wait should return immediately
 	eb.Wait(func(events *util.Events) {
-		if _, found := (*events)[EvtReadNew]; !found {
-			t.Errorf("%s", events)
-		}
 		events.Clear()
 	})
 
@@ -42,8 +41,14 @@ func TestReadFromCommand(t *testing.T) {
 		t.Error("EvtReadNew should not be set yet")
 	}
 
+	// Make sure that event poller is finished
+	time.Sleep(readerPollIntervalMax)
+
+	// Restart event poller
+	reader.startEventPoller()
+
 	// Failing command
-	reader.readFromCommand(`no-such-command`)
+	reader.fin(reader.readFromCommand(`no-such-command`))
 	strs = []string{}
 	if len(strs) > 0 {
 		t.Errorf("%s", strs)
@@ -51,6 +56,9 @@ func TestReadFromCommand(t *testing.T) {
 
 	// Check EventBox again
 	if eb.Peek(EvtReadNew) {
-		t.Error("Command failed. EvtReadNew should be set")
+		t.Error("Command failed. EvtReadNew should not be set")
+	}
+	if !eb.Peek(EvtReadFin) {
+		t.Error("EvtReadFin should be set")
 	}
 }