func (r *Reader) readHeader() error {
buf := make([]byte, 24)
if n, err := io.ReadFull(r.r, buf); err != nil {
return err
} else if n < 24 {
return errors.New("Not enough data for read")
}
if magic := binary.LittleEndian.Uint32(buf[0:4]); magic == magicNanoseconds {
r.byteOrder = binary.LittleEndian
r.nanoSecsFactor = 1
} else if magic == magicNanosecondsBigendian {
r.byteOrder = binary.BigEndian
r.nanoSecsFactor = 1
} else if magic == magicMicroseconds {
r.byteOrder = binary.LittleEndian
r.nanoSecsFactor = 1000
} else if magic == magicMicrosecondsBigendian {
r.byteOrder = binary.BigEndian
r.nanoSecsFactor = 1000
} else {
return errors.New(fmt.Sprintf("Unknown maigc %x", magic))
}
if r.versionMajor = r.byteOrder.Uint16(buf[4:6]); r.versionMajor != versionMajor {
return errors.New(fmt.Sprintf("Unknown major version %d", r.versionMajor))
}
if r.versionMinor = r.byteOrder.Uint16(buf[6:8]); r.versionMinor != versionMinor {
return errors.New(fmt.Sprintf("Unknown minor version %d", r.versionMinor))
}
// ignore timezone 8:12 and sigfigs 12:16
r.snaplen = r.byteOrder.Uint32(buf[16:20])
r.buf = make([]byte, r.snaplen+16)
r.linkType = layers.LinkType(r.byteOrder.Uint32(buf[20:24]))
return nil
}
// LinkType returns pcap_datalink, as a layers.LinkType.
func (p *Handle) LinkType() layers.LinkType {
return layers.LinkType(C.pcap_datalink(p.cptr))
}