Always return a valid index from Rfc822Tokenizer.findTokenEnd()

If an invalid input string ends with a backslash inside a comment
or quoted string, the returned index would be past the end of the
string. In one case this would lead to a runtime exception being
thrown from MultiAutoCompleteTextView.performValidation.

Change-Id: If629372b429716c25cdc25764f088e95d4812d57

Author: Mattias Niklewski

core/java/android/text/util/Rfc822Tokenizer.java

@@ -256,7 +256,7 @@ public int findTokenEnd(CharSequence text, int cursor) {
                     if (c == '"') {
                         i++;
                         break;
-                    } else if (c == '\\') {
+                    } else if (c == '\\' && i + 1 < len) {
                         i += 2;
                     } else {
                         i++;
@@ -275,7 +275,7 @@ public int findTokenEnd(CharSequence text, int cursor) {
                     } else if (c == '(') {
                         level++;
                         i++;
-                    } else if (c == '\\') {
+                    } else if (c == '\\' && i + 1 < len) {
                         i += 2;
                     } else {
                         i++;

core/tests/coretests/src/android/text/TextUtilsTest.java

@@ -255,6 +255,23 @@ public void testRfc822TokenizeItemWithError() {
         assertEquals("Foo Bar", tokens[0].getAddress());
     }
 
+    @SmallTest
+    public void testRfc822FindToken() {
+        Rfc822Tokenizer tokenizer = new Rfc822Tokenizer();
+        //                0           1         2           3         4
+        //                0 1234 56789012345678901234 5678 90123456789012345
+        String address = "\"Foo\" <foo@google.com>, \"Bar\" <bar@google.com>";
+        assertEquals(0, tokenizer.findTokenStart(address, 21));
+        assertEquals(22, tokenizer.findTokenEnd(address, 21));
+        assertEquals(24, tokenizer.findTokenStart(address, 25));
+        assertEquals(46, tokenizer.findTokenEnd(address, 25));
+    }
+
+    @SmallTest
+    public void testRfc822FindTokenWithError() {
+        assertEquals(9, new Rfc822Tokenizer().findTokenEnd("\"Foo Bar\\", 0));
+    }
+
     @LargeTest
     public void testEllipsize() {
         CharSequence s1 = "The quick brown fox jumps over \u00FEhe lazy dog.";