Optimize isStdLibRubyOrCExtFile() check

Author: eregon

src/main/java/org/truffleruby/language/loader/FileLoader.java

@@ -11,7 +11,6 @@
 
 import java.io.File;
 import java.io.IOException;
-import java.util.Locale;
 
 import com.oracle.truffle.api.nodes.Node;
 import org.graalvm.collections.Pair;
@@ -57,7 +56,6 @@ public static void ensureReadable(RubyContext context, TruffleFile file, Node cu
         }
     }
 
-
     public Pair<Source, TStringWithEncoding> loadFile(String path) throws IOException {
         if (context.getOptions().LOG_LOAD) {
             RubyLanguage.LOGGER.info("loading " + path);
@@ -93,7 +91,7 @@ public static TruffleFile getSafeTruffleFile(RubyLanguage language, RubyContext
         }
 
         final TruffleFile home = language.getRubyHomeTruffleFile();
-        if (file.startsWith(home) && isStdLibRubyOrCExtFile(home.relativize(file))) {
+        if (file.startsWith(home.resolve("lib")) && isStdLibRubyOrCExtFile(file.getPath())) {
             return file;
         } else {
             try {
@@ -109,19 +107,8 @@ public static TruffleFile getSafeTruffleFile(RubyLanguage language, RubyContext
         }
     }
 
-    private static boolean isStdLibRubyOrCExtFile(TruffleFile relativePathFromHome) {
-        final String fileName = relativePathFromHome.getName();
-        if (fileName == null) {
-            return false;
-        }
-
-        final String lowerCaseFileName = fileName.toLowerCase(Locale.ROOT);
-        if (!lowerCaseFileName.endsWith(TruffleRuby.EXTENSION) &&
-                !lowerCaseFileName.endsWith(RubyLanguage.CEXT_EXTENSION)) {
-            return false;
-        }
-
-        return relativePathFromHome.startsWith("lib");
+    private static boolean isStdLibRubyOrCExtFile(String path) {
+        return path.endsWith(TruffleRuby.EXTENSION) || path.endsWith(RubyLanguage.CEXT_EXTENSION);
     }
 
     Source buildSource(TruffleFile file, String path, TStringWithEncoding sourceTStringWithEncoding, boolean internal,