ebiten/internal/bsp/bsp.go
2018-02-25 21:26:12 +09:00

149 lines
3.0 KiB
Go

// Copyright 2018 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package bsp offers binary space partitioning algorithm.
package bsp
const (
MaxSize = 1024
minSize = 4
)
type Page struct {
root *Node
}
type Node struct {
x int
y int
width int
height int
used bool
parent *Node
child0 *Node
child1 *Node
}
func (n *Node) canFree() bool {
if n.used {
return false
}
if n.child0 == nil && n.child1 == nil {
return true
}
return n.child0.canFree() && n.child1.canFree()
}
func (n *Node) Region() (x, y, width, height int) {
return n.x, n.y, n.width, n.height
}
func (n *Node) alloc(width, height int) *Node {
if n.width < width || n.height < height {
return nil
}
if n.used {
return nil
}
if n.child0 == nil && n.child1 == nil {
if n.width == width && n.height == height {
n.used = true
return n
}
if n.height == height || (n.width != width && width <= height) {
// Split vertically
n.child0 = &Node{
x: n.x,
y: n.y,
width: width,
height: n.height,
parent: n,
}
n.child1 = &Node{
x: n.x + width,
y: n.y,
width: n.width - width,
height: n.height,
parent: n,
}
return n.child0.alloc(width, height)
} else {
// Split holizontally
n.child0 = &Node{
x: n.x,
y: n.y,
width: n.width,
height: height,
parent: n,
}
n.child1 = &Node{
x: n.x,
y: n.y + height,
width: n.width,
height: n.height - height,
parent: n,
}
return n.child0.alloc(width, height)
}
}
if n.child0 == nil || n.child1 == nil {
panic("not reached")
}
if node := n.child0.alloc(width, height); node != nil {
return node
}
if node := n.child1.alloc(width, height); node != nil {
return node
}
return nil
}
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: MaxSize,
height: MaxSize,
}
}
if width < minSize {
width = minSize
}
if height < minSize {
height = minSize
}
return p.root.alloc(width, height)
}
func (p *Page) Free(node *Node) {
if node.child0 != nil || node.child1 != nil {
panic("bsp: can't free the node including children")
}
node.used = false
if node.parent == nil {
return
}
if node.parent.child0 == nil || node.parent.child1 == nil {
panic("not reached")
}
if node.parent.child0.canFree() && node.parent.child1.canFree() {
node.parent.child0 = nil
node.parent.child1 = nil
p.Free(node.parent)
}
}