// Checker allows to verify the checksum of a reader.
type Checker struct {
	c io.Closer
	r io.Reader
	h hash.Hash

	want []byte
}

// NewChecker ensures that content with the specified length is read from rc.
// Calling Close on this will close upstream.
func NewChecker(rc io.ReadCloser, h hash.Hash, wantSum []byte, length int64) *Checker {
	return &Checker{c: rc, r: ioutil.HardLimitReader(rc, length), h: h, want: wantSum}
}

pkg go/types, func MissingMethod(Type, *Interface, bool) (*Func, bool)
pkg go/types, func NewArray(Type, int64) *Array
pkg go/types, func NewChan(ChanDir, Type) *Chan
pkg go/types, func NewChecker(*Config, *token.FileSet, *Package, *Info) *Checker
pkg go/types, func NewConst(token.Pos, *Package, string, Type, constant.Value) *Const
pkg go/types, func NewField(token.Pos, *Package, string, Type, bool) *Var

		if err != nil {
			return false
		}
		r.Body = hash.NewChecker(r.Body, md5.New(), want, r.ContentLength)
		return true
	}
	cs, err := hash.GetContentChecksum(r.Header)
	if err != nil {
		return false
	}
	if cs == nil || !cs.Type.IsSet() {
		return false
	}
	if cs.Valid() && !cs.Type.Trailing() {
		r.Body = hash.NewChecker(r.Body, cs.Type.Hasher(), cs.Raw, r.ContentLength)
	}
	return true
}