Add function to get length of Map

Signed-off-by: m-murad <[email protected]>

map.go

@@ -30,12 +30,13 @@ func New() *Map {
 // The ok result indicates whether value was found in the map.
 func (m *Map) Get(key interface{}) (interface{}, bool) {
 	m.mu.RLock()
+	defer m.mu.RUnlock()
+
 	v, ok := m.mp[key]
 	if !ok {
-		m.mu.RUnlock()
 		return nil, false
 	}
-	m.mu.RUnlock()
+
 	me := v.Value.(mapElement)
 	return me.value, ok
 }
@@ -45,27 +46,28 @@ func (m *Map) Get(key interface{}) (interface{}, bool) {
 // even if the values are same.
 func (m *Map) Put(key interface{}, val interface{}) {
 	m.mu.Lock()
+	defer m.mu.Unlock()
+
 	if e, ok := m.mp[key]; !ok {
 		m.mp[key] = m.dll.PushFront(mapElement{key: key, value: val})
 	} else {
 		e.Value = mapElement{key: key, value: val}
 	}
-	m.mu.Unlock()
 }
 
 // Delete deletes the value for a key.
 // It returns a boolean indicating weather the key existed and it was deleted.
 func (m *Map) Delete(key interface{}) bool {
 	m.mu.Lock()
+	defer m.mu.Unlock()
+
 	e, ok := m.mp[key]
 	if !ok {
-		m.mu.Unlock()
 		return false
 	}
 
 	m.dll.Remove(e)
 	delete(m.mp, key)
-	m.mu.Unlock()
 	return true
 }
 
@@ -75,10 +77,11 @@ func (m *Map) Delete(key interface{}) bool {
 // It will cause a deadlock
 func (m *Map) UnorderedRange(f func(key interface{}, value interface{})) {
 	m.mu.RLock()
+	defer m.mu.RUnlock()
+
 	for k, v := range m.mp {
 		f(k, v.Value.(mapElement).value)
 	}
-	m.mu.RUnlock()
 }
 
 // OrderedRange will range over the map in ab ordered sequence.
@@ -89,11 +92,20 @@ func (m *Map) UnorderedRange(f func(key interface{}, value interface{})) {
 // It will cause a deadlock
 func (m *Map) OrderedRange(f func(key interface{}, value interface{})) {
 	m.mu.RLock()
+	defer m.mu.RUnlock()
+
 	cur := m.dll.Back()
 	for cur != nil {
 		me := cur.Value.(mapElement)
 		f(me.key, me.value)
 		cur = cur.Prev()
 	}
-	m.mu.RUnlock()
+}
+
+// Length will return the length of Map
+func (m *Map) Length() int {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	return m.dll.Len()
 }

map_test.go

@@ -119,3 +119,47 @@ func TestOrderedRange(t *testing.T) {
 	}
 	m.OrderedRange(rangeFunc)
 }
+
+func TestLength(t *testing.T) {
+	m := initMap()
+
+	m.Put("a", 1)
+	m.Put("b", 2)
+	if m.Length() != 2 {
+		t.FailNow()
+	}
+
+	m.Put("c", 2)
+	m.Put("d", 2)
+	m.Put("e", 2)
+	if m.Length() != 5 {
+		t.FailNow()
+	}
+
+	m.Put("e", 3)
+	if m.Length() != 5 {
+		t.FailNow()
+	}
+
+	m.Delete("a")
+	if m.Length() != 4 {
+		t.FailNow()
+	}
+
+	m.Delete("does_not_exist")
+	if m.Length() != 4 {
+		t.FailNow()
+	}
+
+	m.Delete("b")
+	m.Delete("c")
+	m.Delete("d")
+	if m.Length() != 1 {
+		t.FailNow()
+	}
+
+	m.Delete("e")
+	if m.Length() != 0 {
+		t.FailNow()
+	}
+}

readme.md

@@ -38,5 +38,8 @@ func main() {
     m.OrderedRange(func(key interface{}, val interface{}) {
         log.Println("Key - %v, Value - %v", key, val)
     })
+
+    // Length will return the length of the Map.
+    m.Length()
 }
 ```