github.com/vmware/govmomi@v0.37.1/govc/device/model/tree.go

/*
Copyright (c) 2023-2023 VMware, Inc. All Rights Reserved.

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 model

import (
	"context"
	"flag"
	"fmt"
	"reflect"
	"sort"
	"unsafe"

	"github.com/xlab/treeprint"

	"github.com/vmware/govmomi/govc/cli"
	"github.com/vmware/govmomi/vim25/types"
)

type tree struct {
	backings bool
}

func init() {
	cli.Register("device.model.tree", &tree{})
}

func (cmd *tree) Register(ctx context.Context, f *flag.FlagSet) {
	f.BoolVar(&cmd.backings, "backings", false, "Print the devices backings")
}

func (cmd *tree) Description() string {
	return `Print the device model as a tree.

Examples:
  govc device.model.tree
  govc device.model.tree VirtualEthernetCard
  govc device.model.tree -backings
  govc device.model.tree -backings VirtualDiskRawDiskVer2BackingInfo`
}

func (cmd *tree) Process(ctx context.Context) error {
	return nil
}

func (cmd *tree) Run(ctx context.Context, f *flag.FlagSet) error {

	typeName := f.Arg(0)

	var node treeprint.Tree
	if cmd.backings {
		node = getTree[
			types.BaseVirtualDeviceBackingInfo,
			types.VirtualDeviceBackingInfo,
		]()
	} else {
		node = getTree[
			types.BaseVirtualDevice,
			types.VirtualDevice,
		]()
	}

	if typeName != "" {
		var found treeprint.Tree
		node.VisitAll(func(n *treeprint.Node) {
			if n.Value == typeName {
				found = n
			}
		})
		if found == nil {
			return fmt.Errorf("%q not found", typeName)
		}
		node = found
		node = node.Branch()
	}

	fmt.Print(node.String())

	return nil
}

//go:linkname typelinks reflect.typelinks
func typelinks() (sections []unsafe.Pointer, offset [][]int32)

//go:linkname add reflect.add
func add(p unsafe.Pointer, x uintptr, whySafe string) unsafe.Pointer

// typeEmbeds returns true if a embeds any of the b's.
func typeEmbeds(a reflect.Type, b ...reflect.Type) bool {
	for i := range b {
		if _, ok := a.FieldByName(b[i].Name()); ok {
			return true
		}
	}
	return false
}

// typeEmbeddedBy returns true if a is embedded by any of the b's.
func typeEmbeddedBy(a reflect.Type, b ...reflect.Type) bool {
	for i := range b {
		if _, ok := b[i].FieldByName(a.Name()); ok {
			return true
		}
	}
	return false
}

func getTree[T, K any]() treeprint.Tree {
	var (
		rootObj       K
		rootType      = reflect.TypeOf(rootObj)
		allTypes      = []reflect.Type{}
		embedsTypeMap = map[reflect.Type][]reflect.Type{}
		rootIfaceType = reflect.TypeOf((*T)(nil)).Elem()
	)

	sections, offsets := typelinks()
	for i := range sections {
		base := sections[i]
		for _, offset := range offsets[i] {
			typeAddr := add(base, uintptr(offset), "")
			typ3 := reflect.TypeOf(*(*any)(unsafe.Pointer(&typeAddr)))
			if typ3.Implements(rootIfaceType) {
				realType := reflect.Zero(typ3.Elem()).Type()
				allTypes = append(allTypes, realType)
				embedsTypeMap[realType] = []reflect.Type{}
			}
		}
	}

	// Create the child->parents map.
	for i := range allTypes {
		a := allTypes[i]
		for b := range embedsTypeMap {
			if typeEmbeds(a, b) {
				embedsTypeMap[a] = append(embedsTypeMap[a], b)
			}
		}
	}

	// Each child should have a single parent.
	for child, parents := range embedsTypeMap {
		notAncestors := []reflect.Type{}
		for i := range parents {
			p := parents[i]
			if !typeEmbeddedBy(p, parents...) {
				notAncestors = append(notAncestors, p)
			}
		}
		embedsTypeMap[child] = notAncestors
	}

	// Create the parent->children map.
	typeMap := map[string][]string{}
	for child, parents := range embedsTypeMap {
		for i := range parents {
			p := parents[i]
			typeMap[p.Name()] = append(typeMap[p.Name()], child.Name())
		}
	}

	// Sort the children for each parent by name.
	for _, children := range typeMap {
		sort.Strings(children)
	}

	var buildTree func(parent string, tree treeprint.Tree) treeprint.Tree
	buildTree = func(parent string, tree treeprint.Tree) treeprint.Tree {
		children := typeMap[parent]
		for i := range children {
			child := children[i]
			if _, childIsParentToo := typeMap[child]; childIsParentToo {
				buildTree(child, tree.AddBranch(child))
			} else {
				tree.AddNode(child)
			}
		}
		return tree
	}

	return buildTree(rootType.Name(), treeprint.NewWithRoot(rootType.Name()))
}