In-memory object tree size

tree.go

package tree

import (
  "reflect"
	"unsafe"
)

// Cost calculates the memory size of an object tree.
func Cost(v interface{}) uint64 {
	return cost(reflect.ValueOf(v))
}

func cost(v reflect.Value) uint64 {
	size := uint64(unsafe.Sizeof(v.Interface()))
	switch v.Kind() {
	case reflect.Array, reflect.Slice, reflect.String:
		for i := 0; i < v.Len(); i++ {
			size += cost(v.Index(i))
		}
	case reflect.Map:
		for _, key := range v.MapKeys() {
			size += cost(v.MapIndex(key))
		}
	case reflect.Ptr:
		size += cost(v.Elem())
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			size += cost(v.Field(i))
		}
	}
	return size
}