package runtime

import (
	"reflect"
	"unsafe"
)

var (
	offsetGoid  uintptr
	offsetSched uintptr
)

func init() {
	pg, err := TypeByString("*runtime.g")
	if err != nil {
		return
	}
	if pg.Kind() != reflect.Ptr {
		return
	}
	g := pg.Elem()
	if g.Kind() != reflect.Struct {
		return
	}
	goid, ok := g.FieldByName("goid")
	if !ok {
		return
	}
	sched, ok := g.FieldByName("sched")
	if !ok {
		return
	}
	offsetGoid = goid.Offset
	offsetSched = sched.Offset
}

//go:linkname mcall runtime.mcall
//go:nosplit
func mcall(func(uintptr))

//go:linkname gogo runtime.gogo
//go:nosplit
func gogo(uintptr)



func GOID() (goid int64) {
	mcall(func(g uintptr) {
		id := unsafe.Pointer(g + offsetGoid)
		goid = *(*int64)(id)
		sched := g + offsetSched
		gogo(sched)
	})
	return
}