From 7796b367cc779a001a42c7313bbdaf5f50c325b6 Mon Sep 17 00:00:00 2001
From: Aditya Borikar <adityaborikar2@gmail.com>
Date: Fri, 24 Jul 2020 06:30:53 +0530
Subject: [PATCH] Position parser at START_ELEMENT before parsing

This PR aims to provide parseXrdLinkReferencesFor() method the ability
to parse forward to the first START_ELEMENT tag.The HttpLookupMethodTest
tests the HttpLookupMethod class by parsing String. This makes use of
PacketParserUtils.getParserFor(String), which already does forward
winding to reach START_ELEMENT. However when fetching endpoints from a
remote host meta data, PacketParserUtils.getParserFor(InputStream) is
used which doesn't do winding in any form. And thus, even though
HttpLookupMethodTest tests pass, this implementation would crash while
parsing remote host-meta.
---
 .../smack/altconnections/HttpLookupMethod.java        |  2 ++
 .../jivesoftware/smack/util/PacketParserUtils.java    |  9 +--------
 .../java/org/jivesoftware/smack/util/ParserUtils.java | 11 +++++++++++
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/smack-core/src/main/java/org/jivesoftware/smack/altconnections/HttpLookupMethod.java b/smack-core/src/main/java/org/jivesoftware/smack/altconnections/HttpLookupMethod.java
index 75a4cf263..e30530be7 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/altconnections/HttpLookupMethod.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/altconnections/HttpLookupMethod.java
@@ -27,6 +27,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.jivesoftware.smack.util.PacketParserUtils;
+import org.jivesoftware.smack.util.ParserUtils;
 import org.jivesoftware.smack.xml.XmlPullParser;
 import org.jivesoftware.smack.xml.XmlPullParserException;
 
@@ -132,6 +133,7 @@ public final class HttpLookupMethod {
      * @throws URISyntaxException exception to indicate that a string could not be parsed as a URI reference
      */
     public static List<URI> parseXrdLinkReferencesFor(XmlPullParser parser, String relation) throws IOException, XmlPullParserException, URISyntaxException {
+        ParserUtils.forwardToStartElement(parser);
         List<URI> uriList = new ArrayList<>();
         int initialDepth = parser.getDepth();
 
diff --git a/smack-core/src/main/java/org/jivesoftware/smack/util/PacketParserUtils.java b/smack-core/src/main/java/org/jivesoftware/smack/util/PacketParserUtils.java
index 70861812b..67249b559 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/util/PacketParserUtils.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/util/PacketParserUtils.java
@@ -82,14 +82,7 @@ public class PacketParserUtils {
 
     public static XmlPullParser getParserFor(Reader reader) throws XmlPullParserException, IOException {
         XmlPullParser parser = SmackXmlParser.newXmlParser(reader);
-        // Wind the parser forward to the first start tag
-        XmlPullParser.Event event = parser.getEventType();
-        while (event != XmlPullParser.Event.START_ELEMENT) {
-            if (event == XmlPullParser.Event.END_DOCUMENT) {
-                throw new IllegalArgumentException("Document contains no start tag");
-            }
-            event = parser.next();
-        }
+        ParserUtils.forwardToStartElement(parser);
         return parser;
     }
 
diff --git a/smack-core/src/main/java/org/jivesoftware/smack/util/ParserUtils.java b/smack-core/src/main/java/org/jivesoftware/smack/util/ParserUtils.java
index 3486b372d..4b038cf8f 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/util/ParserUtils.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/util/ParserUtils.java
@@ -63,6 +63,17 @@ public class ParserUtils {
         assert parser.getEventType() == XmlPullParser.Event.END_ELEMENT;
     }
 
+    public static void forwardToStartElement(XmlPullParser parser) throws XmlPullParserException, IOException {
+         // Wind the parser forward to the first start tag
+        XmlPullParser.Event event = parser.getEventType();
+        while (event != XmlPullParser.Event.START_ELEMENT) {
+            if (event == XmlPullParser.Event.END_DOCUMENT) {
+                throw new IllegalArgumentException("Document contains no start tag");
+            }
+            event = parser.next();
+        }
+    }
+
     public static void forwardToEndTagOfDepth(XmlPullParser parser, int depth)
                     throws XmlPullParserException, IOException {
         XmlPullParser.Event event = parser.getEventType();