util: do not crash on jar: relative URIs of less than 4 characters,…

… avoid string creation

echosvg-util/src/main/java/io/sf/carte/echosvg/util/ParsedURLJarProtocolHandler.java

@@ -25,8 +25,10 @@
  * Protocol Handler for the 'jar' protocol. This appears to have the format:
  * jar:<URL for jar file>!<path in jar file>
  *
- * @author <a href="mailto:[email protected]">Thomas DeWeese</a>
- * @author For later modifications, see Git history.
+ * <p>
+ * Original author: <a href="mailto:[email protected]">Thomas DeWeese</a>
+ * For later modifications, see Git history.
+ * </p>
  * @version $Id$
  */
 public class ParsedURLJarProtocolHandler extends ParsedURLDefaultProtocolHandler {
@@ -42,10 +44,8 @@ public ParsedURLJarProtocolHandler() {
 	// is an absolute URL.
 	@Override
 	public ParsedURLData parseURL(ParsedURL baseURL, String urlStr) {
-		String start = urlStr.substring(0, JAR.length() + 1).toLowerCase();
-
-		// urlStr is absolute...
-		if (start.equals(JAR + ":"))
+		// Check whether urlStr is absolute...
+		if (startsWithJarColon(urlStr))
 			return parseURL(urlStr);
 
 		// It's relative so base it off baseURL.
@@ -58,4 +58,11 @@ public ParsedURLData parseURL(ParsedURL baseURL, String urlStr) {
 		}
 	}
 
+	private boolean startsWithJarColon(String url) {
+		char c;
+		return url.length() > 3 && ((c = url.charAt(0)) == 'j' || c == 'J')
+				&& ((c = url.charAt(1)) == 'a' || c == 'A')
+				&& ((c = url.charAt(2)) == 'r' || c == 'R') && url.charAt(3) == ':';
+	}
+
 }

echosvg-util/src/test/java/io/sf/carte/echosvg/util/ParsedURLTest.java

@@ -75,6 +75,14 @@ public void testJar() {
 				"jar:file:dir/file.jar!/p/a/t/c/h/new.svg");
 		runTest("jar:file:dir/file.jar!/p/a/t/h/init.svg", "../c/h/new.svg#foo",
 				"jar:file:dir/file.jar!/p/a/t/c/h/new.svg#foo");
+		runTest("jar:file:dir/file.jar!/p/a/t/h/init.svg", "#id",
+				"jar:file:dir/file.jar!/p/a/t/h/init.svg#id");
+		runTest("JAR:file:dir/file.jar!/p/a/t/h/init.svg", "#id",
+				"jar:file:dir/file.jar!/p/a/t/h/init.svg#id");
+		runTest("jaR:file:dir/file.jar!/p/a/t/h/init.svg", "#id",
+				"jar:file:dir/file.jar!/p/a/t/h/init.svg#id");
+		runTest("JAr:file:dir/file.jar!/p/a/t/h/init.svg", "#",
+				"jar:file:dir/file.jar!/p/a/t/h/init.svg");
 	}
 
 	@Test