feat(server-framework): add Server trait, Encode/Decode, async executor, syscall wrappers, and mock arch for host testing

crates/server-framework/src/codec/mod.rs

@@ -0,0 +1,10 @@
+#[cfg(test)]
+mod tests;
+
+pub trait Encode {
+    fn encode(&self) -> [usize; 4];
+}
+
+pub trait Decode: Sized {
+    fn decode(words: [usize; 4]) -> Option<Self>;
+}

crates/server-framework/src/codec/tests.rs

@@ -0,0 +1,72 @@
+use super::*;
+
+#[derive(Debug, PartialEq)]
+enum TestRequest {
+    Ping,
+    Add(u32, u32),
+}
+
+impl Encode for TestRequest {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            TestRequest::Ping => [0, 0, 0, 0],
+            TestRequest::Add(a, b) => [1, *a as usize, *b as usize, 0],
+        }
+    }
+}
+
+impl Decode for TestRequest {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => Some(TestRequest::Ping),
+            1 => Some(TestRequest::Add(words[1] as u32, words[2] as u32)),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+enum TestResponse {
+    Pong,
+    Sum(u32),
+}
+
+impl Encode for TestResponse {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            TestResponse::Pong => [0, 0, 0, 0],
+            TestResponse::Sum(v) => [1, *v as usize, 0, 0],
+        }
+    }
+}
+
+impl Decode for TestResponse {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => Some(TestResponse::Pong),
+            1 => Some(TestResponse::Sum(words[1] as u32)),
+            _ => None,
+        }
+    }
+}
+
+#[test]
+fn encode_decode_roundtrip() {
+    let req = TestRequest::Add(3, 7);
+    let words = req.encode();
+    let decoded = TestRequest::decode(words).unwrap();
+    assert_eq!(decoded, TestRequest::Add(3, 7));
+}
+
+#[test]
+fn decode_invalid_returns_none() {
+    assert!(TestRequest::decode([99, 0, 0, 0]).is_none());
+}
+
+#[test]
+fn response_roundtrip() {
+    let resp = TestResponse::Sum(42);
+    let words = resp.encode();
+    let decoded = TestResponse::decode(words).unwrap();
+    assert_eq!(decoded, TestResponse::Sum(42));
+}