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/*
* (c) Copyright 2016 Mopria Alliance, Inc.
* (c) Copyright 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.printservicestubs.servicediscovery.mdns;
import android.util.Log;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
class DnsSdParser {
private static final String TAG = DnsSdParser.class.getSimpleName();
private static final char SEPARATOR = '=';
private DnsPacket packet;
public DnsService[] parse(DnsPacket aPacket) throws DnsException {
this.packet = aPacket;
return this.parseServices();
}
private DnsService[] parseServices() throws DnsException {
ArrayList<DnsService> serviceList = new ArrayList<>();
for (DnsPacket.Entry answerEntry : this.packet.getAnswers()) {
if (DnsPacket.ResourceType.PTR == answerEntry.getType()) {
DnsPacket.Ptr ptr = (DnsPacket.Ptr) answerEntry;
try {
serviceList.add(this.buildService(ptr));
} catch (DnsSdException ignore) {
}
}
}
return serviceList.toArray(new DnsService[serviceList.size()]);
}
private DnsService buildService(DnsPacket.Ptr ptr) throws DnsSdException {
DnsPacket.Name serviceNameSuffix = ptr.getName();
DnsPacket.Name serviceName = ptr.getPointedName();
DnsPacket.Srv srvEntry = this.findSrv(serviceName);
DnsPacket.Txt txtEntry = this.findTxt(serviceName);
DnsPacket.Name hostname = srvEntry.getTarget();
DnsPacket.Address[] addressEntries = this.findAddresses(hostname);
int port = srvEntry.getPort();
Map<String, byte[]> attributes = parseAttributes(txtEntry.getText());
byte[][] addresses = new byte[addressEntries.length][];
for (int i = 0; i < addressEntries.length; i++) {
addresses[i] = addressEntries[i].getAddress();
}
return new DnsService(serviceName, serviceNameSuffix, hostname, addresses, port, attributes);
}
private DnsPacket.Srv findSrv(DnsPacket.Name serviceName) throws DnsSdException {
for (DnsPacket.Entry additionalEntry : this.packet.getAdditionals()) {
if (DnsPacket.ResourceType.SRV == additionalEntry.getType()) {
DnsPacket.Srv srv = (DnsPacket.Srv) additionalEntry;
if (srv.getName().equals(serviceName)) {
return srv;
}
}
}
throw new DnsSdException("Service does not contain correspondent srv entry.");
}
private DnsPacket.Txt findTxt(DnsPacket.Name serviceName) throws DnsSdException {
for (DnsPacket.Entry additionalEntry : this.packet.getAdditionals()) {
if (DnsPacket.ResourceType.TXT == additionalEntry.getType()) {
DnsPacket.Txt txt = (DnsPacket.Txt) additionalEntry;
if (txt.getName().equals(serviceName)) {
return txt;
}
}
}
throw new DnsSdException("Service does not contain correspondent txt entry.");
}
private DnsPacket.Address[] findAddresses(DnsPacket.Name hostname) throws DnsSdException {
ArrayList<DnsPacket.Address> addressEntries = new ArrayList<>();
for (DnsPacket.Entry additionalEntry : this.packet.getAdditionals()) {
if ((DnsPacket.ResourceType.A == additionalEntry.getType())
|| (DnsPacket.ResourceType.AAAA == additionalEntry.getType())) {
DnsPacket.Address address = (DnsPacket.Address) additionalEntry;
if (address.getName().equals(hostname)) {
addressEntries.add(address);
}
}
}
if (addressEntries.isEmpty()) {
throw new DnsSdException("Service does not contain correspondent address entry.");
}
return addressEntries.toArray(new DnsPacket.Address[addressEntries.size()]);
}
private static Map<String, byte[]> parseAttributes(byte[] txtData) {
Map<String, byte[]> attributes = new HashMap<>();
int offset = 0;
while (offset < txtData.length) {
int attrLength = txtData[offset++];
if (attrLength < 0) {
attrLength += 256;
}
int sepIndex;
int keyLength;
String key;
byte[] value = null;
if ((attrLength < 0) || ((offset + attrLength) > txtData.length)) {
return attributes;
}
sepIndex = findSeparator(txtData, offset, attrLength);
keyLength = (sepIndex > 0) ? (sepIndex - offset) : attrLength;
if (keyLength == 0) {
return attributes;
}
try {
key = new String(txtData, offset, keyLength, "US-ASCII");
} catch (Exception e) {
Log.e(TAG, "Exception: parsing attribute: " + e);
e.printStackTrace();
continue;
}
if (sepIndex > 0) {
int valueLength = (attrLength - keyLength - 1);
value = new byte[valueLength];
System.arraycopy(txtData, sepIndex + 1, value, 0, valueLength);
}
attributes.put(key, value);
offset += attrLength;
}
return attributes;
}
private static int findSeparator(byte[] txtData, int offset, int length) {
for (int i = offset; i < (offset + length); i++) {
if (txtData[i] == (byte) SEPARATOR) {
return i;
}
}
return -1;
}
}
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