packing: Add Extend

internal/packing/packing.go

@@ -15,17 +15,23 @@
 // Package packing offers a packing algorithm in 2D space.
 package packing
 
+import (
+	"errors"
+)
+
 const (
 	minSize = 1
 )
 
 type Page struct {
 	root    *Node
+	size    int
 	maxSize int
 }
 
-func NewPage(maxSize int) *Page {
+func NewPage(initSize int, maxSize int) *Page {
 	return &Page{
+		size:    initSize,
 		maxSize: maxSize,
 	}
 }
@@ -135,14 +141,18 @@ func (p *Page) alloc(n *Node, width, height int) *Node {
 	return nil
 }
 
+func (p *Page) Size() int {
+	return p.size
+}
+
 func (p *Page) Alloc(width, height int) *Node {
 	if width <= 0 || height <= 0 {
 		panic("bsp: width and height must > 0")
 	}
 	if p.root == nil {
 		p.root = &Node{
-			width:  p.maxSize,
-			height: p.maxSize,
+			width:  p.size,
+			height: p.size,
 		}
 	}
 	if width < minSize {
@@ -172,3 +182,89 @@ func (p *Page) Free(node *Node) {
 		p.Free(node.parent)
 	}
 }
+
+func walk(n *Node, f func(n *Node) error) error {
+	if err := f(n); err != nil {
+		return err
+	}
+	if n.child0 != nil {
+		if err := walk(n.child0, f); err != nil {
+			return err
+		}
+	}
+	if n.child1 != nil {
+		if err := walk(n.child1, f); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (p *Page) Extend() bool {
+	if p.size >= p.maxSize {
+		return false
+	}
+	newSize := p.size * 2
+	edgeNodes := []*Node{}
+	abort := errors.New("abort")
+	aborted := false
+	_ = walk(p.root, func(n *Node) error {
+		if n.x+n.width < p.size && n.y+n.height < p.size {
+			return nil
+		}
+		if n.used {
+			aborted = true
+			return abort
+		}
+		edgeNodes = append(edgeNodes, n)
+		return nil
+	})
+	if aborted {
+		leftUpper := p.root
+		leftLower := &Node{
+			x:      0,
+			y:      p.size,
+			width:  p.size,
+			height: newSize - p.size,
+		}
+		left := &Node{
+			x:      0,
+			y:      0,
+			width:  p.size,
+			height: p.size,
+			child0: leftUpper,
+			child1: leftLower,
+		}
+		leftUpper.parent = left
+		leftLower.parent = left
+
+		right := &Node{
+			x:      p.size,
+			y:      0,
+			width:  newSize - p.size,
+			height: newSize,
+		}
+		p.root = &Node{
+			x:      0,
+			y:      0,
+			width:  newSize,
+			height: newSize,
+			child0: left,
+			child1: right,
+		}
+		left.parent = p.root
+		right.parent = p.root
+	} else {
+		for _, n := range edgeNodes {
+			if n.x+n.width == p.size {
+				n.width += newSize - p.size
+			}
+			if n.y+n.height == p.size {
+				n.height += newSize - p.size
+			}
+		}
+	}
+
+	p.size = newSize
+	return true
+}

internal/packing/packing_test.go

@@ -211,7 +211,7 @@ func TestPage(t *testing.T) {
 	}
 
 	for _, c := range cases {
-		p := NewPage(1024)
+		p := NewPage(1024, 1024)
 		nodes := []*Node{}
 		nnodes := 0
 		for i, in := range c.In {
@@ -252,3 +252,46 @@ func TestPage(t *testing.T) {
 		}
 	}
 }
+
+func TestExtend(t *testing.T) {
+	p := NewPage(1024, 4096)
+	s := p.Size()
+	p.Alloc(s/2, s/2)
+	p.Extend()
+	if p.Size() != s*2 {
+		t.Errorf("p.Size(): got: %d, want: %d", p.Size(), s*2)
+	}
+	if p.Alloc(s*3/2, s*2) == nil {
+		t.Errorf("p.Alloc failed: width: %d, height: %d", s*3/2, s*2)
+	}
+	if p.Alloc(s/2, s*3/2) == nil {
+		t.Errorf("p.Alloc failed: width: %d, height: %d", s/2, s*3/2)
+	}
+	if p.Alloc(1, 1) != nil {
+		t.Errorf("p.Alloc must fail: width: %d, height: %d", 1, 1)
+	}
+}
+
+func TestExtend2(t *testing.T) {
+	p := NewPage(1024, 4096)
+	s := p.Size()
+	p.Alloc(s/2, s/2)
+	n1 := p.Alloc(s/2, s/2)
+	n2 := p.Alloc(s/2, s/2)
+	p.Alloc(s/2, s/2)
+	p.Free(n1)
+	p.Free(n2)
+	p.Extend()
+	if p.Size() != s*2 {
+		t.Errorf("p.Size(): got: %d, want: %d", p.Size(), s*2)
+	}
+	if p.Alloc(s, s*2) == nil {
+		t.Errorf("p.Alloc failed: width: %d, height: %d", s, s*2)
+	}
+	if p.Alloc(s, s) == nil {
+		t.Errorf("p.Alloc failed: width: %d, height: %d", s, s)
+	}
+	if p.Alloc(s, s) != nil {
+		t.Errorf("p.Alloc must fail: width: %d, height: %d", s, s)
+	}
+}

internal/shareable/shareable.go

@@ -201,7 +201,7 @@ func NewImage(width, height int) *Image {
 	}
 	s := &backend{
 		restorable: restorable.NewImage(maxSize, maxSize, false),
-		page:       packing.NewPage(maxSize),
+		page:       packing.NewPage(maxSize, maxSize), // TODO: Utilize 'Extend' page.
 	}
 	theBackends = append(theBackends, s)