Improve ClassCondition performance (danfickle#8)

fixes danfickle#1

---------

Co-authored-by: Zachary Siegel <[email protected]>

openhtmltopdf-core/src/main/java/com/openhtmltopdf/css/newmatch/Condition.java

@@ -371,10 +371,10 @@ void toCSS(StringBuilder sb) {
 
     private static class ClassCondition extends Condition {
 
-        private String _paddedClassName;
+        private String _className;
 
         ClassCondition(String className) {
-            _paddedClassName = " " + className + " ";
+            _className = className;
         }
 
         @Override
@@ -383,20 +383,28 @@ boolean matches(Object e, AttributeResolver attRes, TreeResolver treeRes) {
                 return false;
             }
             String c = attRes.getClass(e);
-            if (c == null) {
+            if (c == null || c.length() < _className.length()) {
                 return false;
             }
 
             // This is much faster than calling `split()` and comparing individual values in a loop.
             // NOTE: In jQuery, for example, the attribute value first has whitespace normalized to spaces. But
             // in an XML DOM, space normalization in attributes is supposed to have happened already.
-            return (" " + c + " ").indexOf(_paddedClassName) != -1;
+            int idx = c.indexOf(_className);
+            if (idx == -1){
+                return false;
+            }
+            int beforeMatch = idx - 1;
+            int afterMatch = idx + _className.length();
+            boolean delimitedBefore = beforeMatch < 0 || Character.isWhitespace(c.charAt(beforeMatch));
+            boolean delimitedAfter = afterMatch == c.length() || Character.isWhitespace(c.charAt(afterMatch));
+            return delimitedBefore && delimitedAfter;
         }
 
         @Override
         public void toCSS(StringBuilder sb) {
             sb.append('.');
-            sb.append(_paddedClassName.substring(1, _paddedClassName.length() - 1));
+            sb.append(_className);
         }
     }