Generational indices+get/free entity+free list

entity/entity.go

@@ -1,5 +1,19 @@
 package entity
 
+type EntityFlag byte
+
+const (
+	EntityFlag_Unknown EntityFlag = 0
+	EntityFlag_Dead    EntityFlag = 1 << (iota - 1)
+	EntityFlag_Alive
+)
+
+const (
+	GenerationShiftBits = 64 - 8
+	FlagsShiftBits      = 64 - 16
+	IndexBitMask        = 0x00_00_FFFF_FFFF_FFFF
+)
+
 type Entity struct {
 
 	// Byte 1: Generation; Byte 2: Flags; Bytes 3-8: Index
@@ -7,6 +21,26 @@ type Entity struct {
 	Comps []Comp
 }
 
+func GetGeneration(id uint64) byte {
+	return byte(id >> GenerationShiftBits)
+}
+
+func GetFlags(id uint64) byte {
+	return byte(id >> FlagsShiftBits)
+}
+
+func GetIndex(id uint64) uint64 {
+	return id & IndexBitMask
+}
+
+func (e *Entity) HasFlag(ef EntityFlag) bool {
+	return GetFlags(e.ID)&byte(ef) > 0
+}
+
+func NewEntityId(generation, flags byte, index uint64) uint64 {
+	return index | (uint64(generation) << GenerationShiftBits) | (uint64(flags) << FlagsShiftBits)
+}
+
 type Comp interface {
 	Name() string
 }

entity/registry.go

@@ -1,30 +1,89 @@
 package entity
 
-import "github.com/bloeys/nmage/assert"
+import (
+	"github.com/bloeys/nmage/assert"
+)
+
+type freeListitem struct {
+	EntityIndex uint64
+	nextFree    *freeListitem
+}
 
 type Registry struct {
 	EntityCount uint64
 	Entities    []Entity
+	FreeList    *freeListitem
 }
 
 func (r *Registry) NewEntity() *Entity {
 
 	assert.T(r.EntityCount < uint64(len(r.Entities)), "Can not add more entities to registry because it is full")
 
+	entityToUseIndex := uint64(0)
+	var entityToUse *Entity = nil
+
+	if r.FreeList != nil {
+
+		entityToUseIndex = r.FreeList.EntityIndex
+		entityToUse = &r.Entities[entityToUseIndex]
+		r.FreeList = r.FreeList.nextFree
+	} else {
+
 		for i := 0; i < len(r.Entities); i++ {
 
-		// @TODO: Implement generational indices
 			e := &r.Entities[i]
-		if e.ID == 0 {
-			r.EntityCount++
-			e.ID = uint64(i) + 1
+			if GetFlags(e.ID) != byte(EntityFlag_Unknown) && !e.HasFlag(EntityFlag_Dead) {
+				continue
+			}
+
+			entityToUse = e
+			entityToUseIndex = uint64(i)
+			break
+		}
+	}
+
+	if entityToUse == nil {
+		panic("failed to create new entity because we did not find a free spot in the registry. Why did the assert not go off?")
+	}
+
+	r.EntityCount++
+	entityToUse.ID = NewEntityId(GetGeneration(entityToUse.ID)+1, byte(EntityFlag_Alive), entityToUseIndex)
+	assert.T(entityToUse.ID != 0, "Entity ID must not be zero")
+	return entityToUse
+}
+
+func (r *Registry) GetEntity(id uint64) *Entity {
+
+	index := GetIndex(id)
+	gen := GetGeneration(id)
+
+	e := &r.Entities[index]
+	eGen := GetGeneration(e.ID)
+
+	if gen != eGen {
+		return nil
+	}
 
-			assert.T(e.ID != 0, "Entity ID must not be zero")
 	return e
 }
+
+func (r *Registry) FreeEntity(id uint64) {
+
+	e := r.GetEntity(id)
+	if e == nil {
+		return
 	}
 
-	panic("failed to create new entity because we did not find a free spot in the registry. Why did the assert not go off?")
+	r.EntityCount--
+	eIndex := GetIndex(e.ID)
+
+	e.Comps = []Comp{}
+	e.ID = NewEntityId(GetGeneration(e.ID), byte(EntityFlag_Dead), eIndex)
+
+	r.FreeList = &freeListitem{
+		EntityIndex: eIndex,
+		nextFree:    r.FreeList,
+	}
 }
 
 func NewRegistry(size uint32) *Registry {

main.go

@@ -8,7 +8,9 @@ import (
 	"github.com/bloeys/nmage/assets"
 	"github.com/bloeys/nmage/camera"
 	"github.com/bloeys/nmage/engine"
+	"github.com/bloeys/nmage/entity"
 	"github.com/bloeys/nmage/input"
+	"github.com/bloeys/nmage/level"
 	"github.com/bloeys/nmage/logging"
 	"github.com/bloeys/nmage/materials"
 	"github.com/bloeys/nmage/meshes"
@@ -52,45 +54,45 @@ type OurGame struct {
 	ImGUIInfo nmageimgui.ImguiInfo
 }
 
-// type TransformComp struct {
-// 	Pos   *gglm.Vec3
-// 	Rot   *gglm.Quat
-// 	Scale *gglm.Vec3
-// }
+type TransformComp struct {
+	Pos   *gglm.Vec3
+	Rot   *gglm.Quat
+	Scale *gglm.Vec3
+}
 
-// func (t TransformComp) Name() string {
-// 	return "Transform Component"
-// }
+func (t TransformComp) Name() string {
+	return "Transform Component"
+}
 
-// func Test() {
+func Test() {
 
-// 	lvl := level.NewLevel("test level", 1000)
-// 	e := lvl.Registry.NewEntity()
+	lvl := level.NewLevel("test level", 1000)
+	e1 := lvl.Registry.NewEntity()
 
-// 	trComp := entity.GetComp[*TransformComp](e)
-// 	fmt.Println("Got comp 1:", trComp)
+	trComp := entity.GetComp[*TransformComp](e1)
+	fmt.Println("Got comp 1:", trComp)
 
-// 	e.Comps = append(e.Comps, &TransformComp{
-// 		Pos:   gglm.NewVec3(0, 0, 0),
-// 		Rot:   gglm.NewQuatEulerXYZ(0, 0, 0),
-// 		Scale: gglm.NewVec3(0, 0, 0),
-// 	}, &TransformComp{
-// 		Pos:   gglm.NewVec3(0, 0, 0),
-// 		Rot:   gglm.NewQuatEulerXYZ(0, 0, 0),
-// 		Scale: gglm.NewVec3(1, 1, 1),
-// 	})
+	e1.Comps = append(e1.Comps, &TransformComp{
+		Pos:   gglm.NewVec3(0, 0, 0),
+		Rot:   gglm.NewQuatEulerXYZ(0, 0, 0),
+		Scale: gglm.NewVec3(0, 0, 0),
+	}, &TransformComp{
+		Pos:   gglm.NewVec3(0, 0, 0),
+		Rot:   gglm.NewQuatEulerXYZ(0, 0, 0),
+		Scale: gglm.NewVec3(1, 1, 1),
+	})
 
-// 	trComp = entity.GetComp[*TransformComp](e)
-// 	fmt.Println("Got comp 2:", trComp)
+	trComp = entity.GetComp[*TransformComp](e1)
+	fmt.Println("Got comp 2:", trComp)
 
-// 	trComps := entity.GetAllCompOfType[*TransformComp](e)
-// 	fmt.Printf("Got comp 3: %+v, %+v\n", trComps[0], trComps[1])
+	trComps := entity.GetAllCompOfType[*TransformComp](e1)
+	fmt.Printf("Got comp 3: %+v, %+v\n", trComps[0], trComps[1])
 
-// 	fmt.Printf("Entity: %+v\n", e)
-// 	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
-// 	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
-// 	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
-// }
+	fmt.Printf("Entity: %+v\n", e1)
+	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
+	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
+	fmt.Printf("Entity: %+v\n", lvl.Registry.NewEntity())
+}
 
 func main() {