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|
package socket
import (
"errors"
"unsafe"
)
func controlHeaderLen() int {
return roundup(sizeofCmsghdr)
}
func controlMessageLen(dataLen int) int {
return roundup(sizeofCmsghdr) + dataLen
}
// returns the whole length of control message.
func ControlMessageSpace(dataLen int) int {
return roundup(sizeofCmsghdr) + roundup(dataLen)
}
// A ControlMessage represents the head message in a stream of control
// messages.
//
// A control message comprises of a header, data and a few padding
// fields to conform to the interface to the kernel.
//
// See RFC 3542 for further information.
type ControlMessage []byte
// Data returns the data field of the control message at the head.
func (m ControlMessage) Data(dataLen int) []byte {
l := controlHeaderLen()
if len(m) < l || len(m) < l+dataLen {
return nil
}
return m[l : l+dataLen]
}
// ParseHeader parses and returns the header fields of the control
// message at the head.
func (m ControlMessage) ParseHeader() (lvl, typ, dataLen int, err error) {
l := controlHeaderLen()
if len(m) < l {
return 0, 0, 0, errors.New("short message")
}
h := (*cmsghdr)(unsafe.Pointer(&m[0]))
return h.lvl(), h.typ(), int(uint64(h.len()) - uint64(l)), nil
}
// Next returns the control message at the next.
func (m ControlMessage) Next(dataLen int) ControlMessage {
l := ControlMessageSpace(dataLen)
if len(m) < l {
return nil
}
return m[l:]
}
// MarshalHeader marshals the header fields of the control message at
// the head.
func (m ControlMessage) MarshalHeader(lvl, typ, dataLen int) error {
if len(m) < controlHeaderLen() {
return errors.New("short message")
}
h := (*cmsghdr)(unsafe.Pointer(&m[0]))
h.set(controlMessageLen(dataLen), lvl, typ)
return nil
}
// Marshal marshals the control message at the head, and returns the next
// control message.
func (m ControlMessage) Marshal(lvl, typ int, data []byte) (ControlMessage, error) {
l := len(data)
if len(m) < ControlMessageSpace(l) {
return nil, errors.New("short message")
}
h := (*cmsghdr)(unsafe.Pointer(&m[0]))
h.set(controlMessageLen(l), lvl, typ)
if l > 0 {
copy(m.Data(l), data)
}
return m.Next(l), nil
}
// Parse parses as a single or multiple control messages.
func (m ControlMessage) Parse() ([]ControlMessage, error) {
var ms []ControlMessage
for len(m) >= controlHeaderLen() {
h := (*cmsghdr)(unsafe.Pointer(&m[0]))
l := h.len()
if l <= 0 {
return nil, errors.New("invalid header length")
}
if uint64(l) < uint64(controlHeaderLen()) {
return nil, errors.New("invalid message length")
}
if uint64(l) > uint64(len(m)) {
return nil, errors.New("short buffer")
}
ms = append(ms, ControlMessage(m[:l]))
ll := l - controlHeaderLen()
if len(m) >= ControlMessageSpace(ll) {
m = m[ControlMessageSpace(ll):]
} else {
m = m[controlMessageLen(ll):]
}
}
return ms, nil
}
// NewControlMessage returns a new stream of control messages.
func NewControlMessage(dataLen []int) ControlMessage {
var l int
for i := range dataLen {
l += ControlMessageSpace(dataLen[i])
}
return make([]byte, l)
}
|
