package rtcp

import (
	"encoding/binary"
	"errors"
)

// Timestamp gets the timestamp from a receiver report and returns as the most
// significant word, and the least significant word. If the given bytes do not
// represent a valid receiver report, an error is returned.
func Timestamp(buf []byte) (msw, lsw uint32, err error) {
	if len(buf) < 4 {
		return 0, 0, errors.New("bad RTCP packet, not of sufficient length")
	}
	if (buf[0] & 0xc0 >> 6) != 2 {
		return 0, 0, errors.New("incompatible RTCP version")
	}

	if buf[1] != typeSenderReport {
		return 0, 0, errors.New("RTCP packet is not of sender report type")
	}

	msw = binary.BigEndian.Uint32(buf[8:])
	lsw = binary.BigEndian.Uint32(buf[12:])

	return
}