[rialto] Move request processing to a separate module

To keep the RKP VM payload execution code isolated from the
rest of the code.

Bug: 291732060
Test: atest rialto_test
Change-Id: Ia242c5050e3d681116c3871533b1baf2ff14d37b
diff --git a/rialto/src/requests/api.rs b/rialto/src/requests/api.rs
new file mode 100644
index 0000000..11fdde4
--- /dev/null
+++ b/rialto/src/requests/api.rs
@@ -0,0 +1,31 @@
+// Copyright 2023, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! This module contains the main API for the request processing module.
+
+use alloc::vec::Vec;
+use service_vm_comm::{Request, Response};
+
+/// Processes a request and returns the corresponding response.
+/// This function serves as the entry point for the request processing
+/// module.
+pub fn process_request(request: Request) -> Response {
+    match request {
+        Request::Reverse(v) => Response::Reverse(reverse(v)),
+    }
+}
+
+fn reverse(payload: Vec<u8>) -> Vec<u8> {
+    payload.into_iter().rev().collect()
+}