/**
* Compress DNS data.
*
* <p>see E.3 of the Wi-Fi Direct technical specification for the detail.
*
* @param dnsName dns name
* @return compressed dns name
*/
private static String compressDnsName(String dnsName) {
StringBuffer sb = new StringBuffer();
// The domain name is replaced with a pointer to a prior
// occurrence of the same name in virtual memory packet.
while (true) {
String data = sVmPacket.get(dnsName);
if (data != null) {
sb.append(data);
break;
}
int i = dnsName.indexOf('.');
if (i == -1) {
if (dnsName.length() > 0) {
sb.append(String.format(Locale.US, "%02x", dnsName.length()));
sb.append(WifiP2pServiceInfo.bin2HexStr(dnsName.getBytes()));
}
// for a sequence of labels ending in a zero octet
sb.append("00");
break;
}
String name = dnsName.substring(0, i);
dnsName = dnsName.substring(i + 1);
sb.append(String.format(Locale.US, "%02x", name.length()));
sb.append(WifiP2pServiceInfo.bin2HexStr(name.getBytes()));
}
return sb.toString();
}
/**
* Create wpa_supplicant service query for PTR record.
*
* @param instanceName instance name.<br>
* e.g) "MyPrinter"
* @param serviceType service type.<br>
* e.g) "_ipp._tcp"
* @return wpa_supplicant service query.
*/
private static String createPtrServiceQuery(String instanceName, String serviceType) {
StringBuffer sb = new StringBuffer();
sb.append("bonjour ");
sb.append(createRequest(serviceType + ".local.", DNS_TYPE_PTR, VERSION_1));
sb.append(" ");
byte[] data = instanceName.getBytes();
sb.append(String.format(Locale.US, "%02x", data.length));
sb.append(WifiP2pServiceInfo.bin2HexStr(data));
// This is the start point of this response.
// Therefore, it indicates the request domain name.
sb.append("c027");
return sb.toString();
}
