From 1ac7fe4f9c0726c70102e83fe4e3a93901d9872c Mon Sep 17 00:00:00 2001
From: Greg Wilkins <gregw@webtide.com>
Date: Mon, 11 May 2020 14:00:04 +0200
Subject: [PATCH] Issue #4860 NPE from HttpFields

 + Fix bug with list iterator nextIndex
 + List iterator cannot inject null fields
 + minor cleanups

Signed-off-by: Greg Wilkins <gregw@webtide.com>
---
 .../org/eclipse/jetty/http/HttpFields.java    | 32 +++++++++++++------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
index 316ea07245a..3787fc627f8 100644
--- a/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
+++ b/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java
@@ -303,14 +303,18 @@ public class HttpFields implements Iterable<HttpField>
      */
     public List<String> getValuesList(String name)
     {
-        final List<String> list = new ArrayList<>();
+        List<String> list = null;
         for (int i = 0; i < _size; i++)
         {
             HttpField f = _fields[i];
             if (f.getName().equalsIgnoreCase(name))
+            {
+                if (list == null)
+                    list = new ArrayList<>(size() - i);
                 list.add(f.getValue());
+            }
         }
-        return list;
+        return list == null ? Collections.emptyList() : list;
     }
 
     /**
@@ -711,7 +715,8 @@ public class HttpFields implements Iterable<HttpField>
 
     public void add(HttpHeader header, HttpHeaderValue value)
     {
-        add(header, value.toString());
+        if (value != null)
+            add(header, value.toString());
     }
 
     /**
@@ -966,8 +971,11 @@ public class HttpFields implements Iterable<HttpField>
      *
      * @param fields the fields to add
      */
+    @Deprecated
     public void add(HttpFields fields)
     {
+        // TODO this implementation doesn't do what the javadoc says and is really the same
+        // as addAll, which is renamed to add anyway in 10.
         if (fields == null)
             return;
 
@@ -1185,7 +1193,7 @@ public class HttpFields implements Iterable<HttpField>
         @Override
         public int nextIndex()
         {
-            return _cursor + 1;
+            return _cursor;
         }
 
         @Override
@@ -1199,16 +1207,22 @@ public class HttpFields implements Iterable<HttpField>
         {
             if (_current < 0)
                 throw new IllegalStateException();
-            _fields[_current] = field;
+            if (field == null)
+                remove();
+            else
+                _fields[_current] = field;
         }
 
         @Override
         public void add(HttpField field)
         {
-            _fields = Arrays.copyOf(_fields, _fields.length + 1);
-            System.arraycopy(_fields, _cursor, _fields, _cursor + 1, _size++);
-            _fields[_cursor++] = field;
-            _current = -1;
+            if (field != null)
+            {
+                _fields = Arrays.copyOf(_fields, _fields.length + 1);
+                System.arraycopy(_fields, _cursor, _fields, _cursor + 1, _size++);
+                _fields[_cursor++] = field;
+                _current = -1;
+            }
         }
     }
 }