fix RingBuffer.IsFull

pingcap · Aug 16, 2024 · be4f25c · be4f25c
1 parent 44a2349
commit be4f25c
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Showing 2 changed files with 186 additions and 1 deletion.
diff --git a/utils/ringbuffer/ring_buffer.go b/utils/ringbuffer/ring_buffer.go
@@ -82,6 +82,12 @@ func (rb *RingBuffer[T]) PushBack(item T) {
 
 // Push to front
 func (rb *RingBuffer[T]) PushFront(item T) {
+	// equivalent to
+	// if rb.front == 0 {
+	//     rb.front = rb.capacity
+	// } else {
+	//     rb.front--
+	// }
 	rb.front = (rb.front + rb.capacity) % (rb.capacity + 1)
 	rb.buffer[rb.front] = item
 
@@ -117,7 +123,7 @@ func (rb *RingBuffer[T]) PopBack() (T, bool) {
 }
 
 func (rb *RingBuffer[T]) IsFull() bool {
-	return (rb.back+1)%rb.capacity == rb.front
+	return (rb.back+1)%(rb.capacity+1) == rb.front
 }
 
 func (rb *RingBuffer[T]) IsEmpty() bool {

diff --git a/utils/ringbuffer/ring_buffer_test.go b/utils/ringbuffer/ring_buffer_test.go
@@ -184,3 +184,182 @@ func TestRingBuffer(t *testing.T) {
 		assert.Equal(t, []int{3, 6, 7}, items)
 	}
 }
+
+func TestRingBufferReverse(t *testing.T) {
+	rb := NewRingBuffer[int](3)
+
+	rb.PushFront(1)
+	rb.PushFront(2)
+	rb.PushFront(3)
+
+	{
+		item, ok := rb.Back()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 1, item)
+	}
+
+	rb.PushFront(4)
+
+	{
+		item, ok := rb.Back()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 2, item)
+	}
+
+	{
+		item, ok := rb.Front()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 4, item)
+	}
+
+	rb.PushFront(5)
+	rb.PushFront(6)
+	rb.PushFront(7)
+	rb.PushFront(8)
+
+	assert.Equal(t, true, rb.IsFull())
+	{
+		item, ok := rb.Back()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 6, item)
+	}
+
+	{
+		item, ok := rb.Front()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 8, item)
+	}
+
+	{
+		item, ok := rb.PopBack()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 6, item)
+	}
+	{
+		item, ok := rb.PopBack()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 7, item)
+	}
+	{
+		item, ok := rb.PopBack()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 8, item)
+	}
+	{
+		item, ok := rb.PopBack()
+		assert.Equal(t, false, ok)
+		assert.Equal(t, 0, item)
+	}
+	assert.Equal(t, true, rb.IsEmpty())
+
+	rb.PushFront(1)
+	rb.PushFront(2)
+	assert.Equal(t, 2, rb.Length())
+
+	rb.PushFront(3)
+
+	assert.Equal(t, 3, rb.Length())
+
+	{
+		item, ok := rb.Back()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 1, item)
+	}
+
+	rb.PushFront(4)
+
+	{
+		item, ok := rb.Back()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 2, item)
+	}
+
+	{
+		item, ok := rb.Front()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 4, item)
+	}
+
+	{
+		itr := rb.BackwardIterator()
+		items := make([]int, 0)
+		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
+			items = append(items, item)
+		}
+		assert.Equal(t, []int{2, 3, 4}, items)
+	}
+
+	{
+		itr := rb.ForwardIterator()
+		items := make([]int, 0)
+		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
+			items = append(items, item)
+		}
+		assert.Equal(t, []int{4, 3, 2}, items)
+	}
+
+	{
+		item, ok := rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 4, item)
+		item, ok = rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 3, item)
+		item, ok = rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 2, item)
+		_, ok = rb.PopFront()
+		assert.Equal(t, false, ok)
+	}
+
+	{
+		rb.PushFront(1)
+		rb.PushFront(2)
+
+		rb.PushFront(3)
+		rb.PushFront(4)
+		rb.PushFront(5)
+
+		item, ok := rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 5, item)
+		item, ok = rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 4, item)
+		item, ok = rb.PopFront()
+		assert.Equal(t, true, ok)
+		assert.Equal(t, 3, item)
+		_, ok = rb.PopFront()
+		assert.Equal(t, false, ok)
+	}
+
+	{
+		rb.PushFront(1)
+		rb.PushFront(2)
+
+		rb.PushFront(3)
+		rb.PushFront(4)
+		rb.PushFront(5)
+
+		rb.PushBack(6)
+		rb.PushBack(7)
+	}
+
+	{
+		itr := rb.BackwardIterator()
+		items := make([]int, 0)
+		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
+			items = append(items, item)
+		}
+		assert.Equal(t, []int{7, 6, 3}, items)
+	}
+
+	{
+		itr := rb.ForwardIterator()
+		items := make([]int, 0)
+		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
+			items = append(items, item)
+		}
+		assert.Equal(t, []int{3, 6, 7}, items)
+	}
+}