Add timeout for invokeGuestFunction; use base64 for losslessly encoding byte sequence in cache

core/src/main/java/io/roastedroot/quickjs4j/core/Runner.java

@@ -60,7 +60,10 @@ public void compileAndExec(String code) {
 
     public Object invokeGuestFunction(
             String moduleName, String name, List<Object> args, String libraryCode) {
-        return engine.invokeGuestFunction(moduleName, name, args, libraryCode);
+        return submitWithTimeout(
+                () -> engine.invokeGuestFunction(moduleName, name, args, libraryCode),
+                this.timeoutMs,
+                "Timeout while invoking guest function");
     }
 
     public String stdout() {
@@ -98,17 +101,17 @@ private <T> T submitWithTimeout(Callable<T> task, int timeout, String timeoutMes
             throw new RuntimeException("Thread interrupted", e);
         } catch (ExecutionException e) {
             if (e.getCause() != null) {
-                if (e.getCause() instanceof RuntimeException) {
-                    throw (RuntimeException) e.getCause();
-                } else {
-                    throw new RuntimeException(e.getCause());
-                }
-            } else {
-                throw new RuntimeException(e);
+                sneakyThrow(e.getCause());
             }
+            throw new RuntimeException(e);
         }
     }
 
+    @SuppressWarnings("unchecked")
+    private static <E extends Throwable> void sneakyThrow(Throwable e) throws E {
+        throw (E) e;
+    }
+
     public static Builder builder() {
         return new Builder();
     }

core/src/test/java/io/roastedroot/quickjs4j/core/RunnerTest.java

@@ -339,6 +339,43 @@ public void compileTimeout() throws Exception {
         runner.close();
     }
 
+    @Test
+    public void invokeGuestFunctionTimeout() throws Exception {
+        var invokables =
+                Invokables.builder("from_js")
+                        .add(new GuestFunction("hang", List.of(), Integer.class))
+                        .build();
+
+        var libraryCode = "function hang() { while(true) {} return 1; };";
+
+        var es = Executors.newSingleThreadExecutor();
+        var jsEngine = Engine.builder().addInvokables(invokables).build();
+        var runner =
+                Runner.builder()
+                        .withEngine(jsEngine)
+                        .withTimeoutMs(500)
+                        .withExecutorService(es)
+                        .build();
+
+        var ex =
+                assertThrows(
+                        RuntimeException.class,
+                        () ->
+                                runner.invokeGuestFunction(
+                                        "from_js", "hang", List.of(), libraryCode));
+
+        assertTrue(ex.getCause() instanceof TimeoutException);
+        assertTrue(
+                ex.getMessage().contains("Timeout while invoking guest function"),
+                "Expected execution timeout, got: " + ex.getMessage());
+
+        // Verify the executor thread is free after timeout
+        var probe = es.submit(() -> "ok");
+        assertEquals("ok", probe.get(5, java.util.concurrent.TimeUnit.SECONDS));
+
+        runner.close();
+    }
+
     @Test
     public void handleExceptionsThrownInJava() {
         var builtins =