求教大神,在Golang Go语言中如果想学会怎么使用 unsafe 这个包...该怎么学...

求教大神,在Golang Go语言中如果想学会怎么使用 unsafe 这个包…该怎么学…
以下的代码说实在,看不懂…
import (
“unsafe”
“reflect”
)

func isChanClosed(ch interface{}) bool {
if reflect.TypeOf(ch).Kind() != reflect.Chan {
panic(“only channels!”)
}
cptr := *(*uintptr)(unsafe.Pointer(
unsafe.Pointer(uintptr(unsafe.Pointer(&ch)) + unsafe.Sizeof(uint(0))),
))

// this function will return true if chan.closed > 0
// see hchan on https://github.com/golang/go/blob/master/src/runtime/chan.go
// type hchan struct {
// qcount uint // total data in the queue
// dataqsiz uint // size of the circular queue
// buf unsafe.Pointer // points to an array of dataqsiz elements
// elemsize uint16
// closed uint32
// **

cptr += unsafe.Sizeof(uint(0))*2
cptr += unsafe.Sizeof(unsafe.Pointer(uintptr(0)))
cptr += unsafe.Sizeof(uint16(0))
return *(*uint32)(unsafe.Pointer(cptr)) > 0
}