Complete first alpha version

database/iterator/iterator.go

@@ -1,6 +1,10 @@
 package iterator
 
 import (
+	"sync"
+
+	"github.com/tevino/abool"
+
 	"github.com/Safing/portbase/database/record"
 )
 
@@ -8,19 +12,43 @@ import (
 type Iterator struct {
 	Next chan record.Record
 	Done chan struct{}
-	Err  error
+
+	errLock    sync.Mutex
+	err        error
+	doneClosed *abool.AtomicBool
 }
 
 // New creates a new Iterator.
 func New() *Iterator {
 	return &Iterator{
-		Next: make(chan record.Record, 10),
-		Done: make(chan struct{}),
+		Next:       make(chan record.Record, 10),
+		Done:       make(chan struct{}),
+		doneClosed: abool.NewBool(false),
 	}
 }
 
+// Finish is called be the storage to signal the end of the query results.
 func (it *Iterator) Finish(err error) {
 	close(it.Next)
-	close(it.Done)
-	it.Err = err
+	if it.doneClosed.SetToIf(false, true) {
+		close(it.Done)
+	}
+
+	it.errLock.Lock()
+	defer it.errLock.Unlock()
+	it.err = err
+}
+
+// Cancel is called by the iteration consumer to cancel the running query.
+func (it *Iterator) Cancel() {
+	if it.doneClosed.SetToIf(false, true) {
+		close(it.Done)
+	}
+}
+
+// Err returns the iterator error, if exists.
+func (it *Iterator) Err() error {
+	it.errLock.Lock()
+	defer it.errLock.Unlock()
+	return it.err
 }