refactor: add Empty to dll

andy2046 · May 8, 2020 · 2de0ba8 · 2de0ba8
1 parent 2924ba8
commit 2de0ba8
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Showing 3 changed files with 90 additions and 7 deletions.
diff --git a/docs/dll.md b/docs/dll.md
@@ -16,6 +16,7 @@ Package dll provides a lock-free implementation of doubly linked list.
 * [type Element](#Element)
 * [type List](#List)
   * [func New() *List](#New)
+  * [func (l *List) Empty() bool](#List.Empty)
   * [func (l *List) Init() *List](#List.Init)
   * [func (l *List) Next(node *Element) *Element](#List.Next)
   * [func (l *List) PopLeft() interface{}](#List.PopLeft)
@@ -78,6 +79,15 @@ New returns an initialized list.
 
 
 
+### <a name="List.Empty">func</a> (\*List) [Empty](/src/target/dll.go?s=995:1022#L42)
+``` go
+func (l *List) Empty() bool
+```
+Empty returns true if list l is empty, false otherwise
+
+
+
+
 ### <a name="List.Init">func</a> (\*List) [Init](/src/target/dll.go?s=546:573#L25)
 ``` go
 func (l *List) Init() *List
@@ -87,7 +97,7 @@ Init initializes or clears list l.
 
 
 
-### <a name="List.Next">func</a> (\*List) [Next](/src/target/dll.go?s=5215:5258#L246)
+### <a name="List.Next">func</a> (\*List) [Next](/src/target/dll.go?s=5438:5481#L258)
 ``` go
 func (l *List) Next(node *Element) *Element
 ```
@@ -96,7 +106,7 @@ Next returns the next list element or nil.
 
 
 
-### <a name="List.PopLeft">func</a> (\*List) [PopLeft](/src/target/dll.go?s=2499:2535#L121)
+### <a name="List.PopLeft">func</a> (\*List) [PopLeft](/src/target/dll.go?s=2722:2758#L133)
 ``` go
 func (l *List) PopLeft() interface{}
 ```
@@ -105,7 +115,7 @@ PopLeft returns the first element of list l or nil if the list is empty.
 
 
 
-### <a name="List.PopRight">func</a> (\*List) [PopRight](/src/target/dll.go?s=3166:3203#L152)
+### <a name="List.PopRight">func</a> (\*List) [PopRight](/src/target/dll.go?s=3389:3426#L164)
 ``` go
 func (l *List) PopRight() interface{}
 ```
@@ -114,7 +124,7 @@ PopRight returns the last element of list l or nil if the list is empty.
 
 
 
-### <a name="List.Prev">func</a> (\*List) [Prev](/src/target/dll.go?s=5836:5879#L279)
+### <a name="List.Prev">func</a> (\*List) [Prev](/src/target/dll.go?s=6059:6102#L291)
 ``` go
 func (l *List) Prev(node *Element) *Element
 ```
@@ -123,7 +133,7 @@ Prev returns the previous list element or nil.
 
 
 
-### <a name="List.PushLeft">func</a> (\*List) [PushLeft](/src/target/dll.go?s=3698:3745#L177)
+### <a name="List.PushLeft">func</a> (\*List) [PushLeft](/src/target/dll.go?s=3921:3968#L189)
 ``` go
 func (l *List) PushLeft(v interface{}) *Element
 ```
@@ -132,7 +142,7 @@ PushLeft inserts a new element e with value v at the front of list l and returns
 
 
 
-### <a name="List.PushRight">func</a> (\*List) [PushRight](/src/target/dll.go?s=4255:4303#L202)
+### <a name="List.PushRight">func</a> (\*List) [PushRight](/src/target/dll.go?s=4478:4526#L214)
 ``` go
 func (l *List) PushRight(v interface{}) *Element
 ```
@@ -141,7 +151,7 @@ PushRight inserts a new element e with value v at the back of list l and returns
 
 
 
-### <a name="List.Remove">func</a> (\*List) [Remove](/src/target/dll.go?s=1060:1105#L43)
+### <a name="List.Remove">func</a> (\*List) [Remove](/src/target/dll.go?s=1283:1328#L55)
 ``` go
 func (l *List) Remove(e *Element) interface{}
 ```

diff --git a/pkg/dll/dll.go b/pkg/dll/dll.go
@@ -38,6 +38,18 @@ func (l *List) Init() *List {
 	return l
 }
 
+// Empty returns true if list l is empty, false otherwise
+func (l *List) Empty() bool {
+	t := l.head.next.getReference()
+	h := l.tail.prev.getReference()
+
+	if t == l.tail && h == l.head {
+		return true
+	}
+
+	return false
+}
+
 // Remove removes e from l if e is an element of list l.
 // It returns the element value e.Value if succeed, nil otherwise
 func (l *List) Remove(e *Element) interface{} {

diff --git a/pkg/dll/dll_test.go b/pkg/dll/dll_test.go
@@ -11,6 +11,51 @@ var (
 	lock sync.Mutex
 )
 
+func TestDListEmpty(t *testing.T) {
+	l := New()
+	if !l.Empty() {
+		t.Error("new list is empty")
+	}
+
+	var elm *Element
+
+	elm = l.PushLeft(1)
+	if l.Empty() {
+		t.Error("list is not empty")
+	}
+	l.Remove(elm)
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
+
+	elm = l.PushRight(2)
+	if l.Empty() {
+		t.Error("list is not empty")
+	}
+	l.Remove(elm)
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
+
+	elm = l.PushLeft(3)
+	if l.Empty() {
+		t.Error("list is not empty")
+	}
+	l.PopRight()
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
+
+	elm = l.PushRight(4)
+	if l.Empty() {
+		t.Error("list is not empty")
+	}
+	l.PopLeft()
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
+}
+
 func TestDListNext(t *testing.T) {
 	l := New()
 	start := make(chan struct{})
@@ -58,6 +103,10 @@ func TestDListNext(t *testing.T) {
 		}
 		fmt.Printf("%v.", v)
 	}
+
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
 }
 
 func TestDListPrev(t *testing.T) {
@@ -107,6 +156,10 @@ func TestDListPrev(t *testing.T) {
 		}
 		fmt.Printf("%v.", v)
 	}
+
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
 }
 
 func TestDListPL(t *testing.T) {
@@ -161,6 +214,10 @@ func TestDListPL(t *testing.T) {
 		}
 		fmt.Printf("%v.", v)
 	}
+
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
 }
 
 func TestDListPR(t *testing.T) {
@@ -215,6 +272,10 @@ func TestDListPR(t *testing.T) {
 		}
 		fmt.Printf("%v.", v)
 	}
+
+	if !l.Empty() {
+		t.Error("list is empty")
+	}
 }
 
 func record(t *testing.T, v int) {