From c62c1c8b441b51b31a23db0a04163afc20343f5c Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin@nitrokey.com>
Date: Tue, 7 Feb 2023 23:32:43 +0100
Subject: [PATCH] Add assertions for interchange size
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This patch adds assertions on the size of the Request, Reply and
TrussedInterchange types so that we don’t accidentally increase it.
---
 src/pipe.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/pipe.rs b/src/pipe.rs
index 8e0b3a2c09a..9dfe9875897 100644
--- a/src/pipe.rs
+++ b/src/pipe.rs
@@ -39,3 +39,36 @@ pub struct ServiceEndpoint<I: 'static, C> {
 }
 
 // pub type ClientEndpoint = Requester<TrussedInterchange>;
+
+#[cfg(test)]
+mod tests {
+    use super::TrussedInterchange;
+    use crate::api::{Reply, Request};
+    use core::mem;
+
+    // The following checks are used to ensure that we don’t accidentally increase the interchange
+    // size.  Bumping the size is not a breaking change but should only be done if really
+    // necessary.
+
+    const MAX_SIZE: usize = 2416;
+
+    fn assert_size<T>() {
+        let size = mem::size_of::<T>();
+        assert!(size <= MAX_SIZE, "{size}");
+    }
+
+    #[test]
+    fn test_request_size() {
+        assert_size::<Request>();
+    }
+
+    #[test]
+    fn test_reply_size() {
+        assert_size::<Reply>();
+    }
+
+    #[test]
+    fn test_interchange_size() {
+        assert_size::<TrussedInterchange>();
+    }
+}