Capnproto serialize/deserialize loop running!

tests/capnp.rs

@@ -0,0 +1,50 @@
+use alloc_counter::{AllocCounterSystem, count_alloc, deny_alloc};
+
+use md_shootout::marketdata_capnp::multi_message;
+
+#[global_allocator]
+static A: AllocCounterSystem = AllocCounterSystem;
+
+#[test]
+fn reinit_memory_check() {
+    // Setting up the builder doesn't reserve any heap memory
+    let mut msg_block = deny_alloc(|| {
+        capnp::message::Builder::new_default()
+    });
+
+    // Setting up the root object, however, does reserve a first segment
+    let (stats, result) = count_alloc(|| {
+        let multimsg = msg_block.init_root::<multi_message::Builder>();
+        multimsg.init_messages(32);
+    });
+
+    assert_eq!(stats.0, 4);
+    assert_eq!(stats.1, 0);
+    assert_eq!(stats.2, 0);
+
+    // If we reinitialize an object on that original builder, we re-use memory
+    deny_alloc(|| {
+        let multimsg = msg_block.init_root::<multi_message::Builder>();
+        multimsg.init_messages(32);
+
+        // Even if we down-size and up-size the message list size, we don't need
+        // to re-allocate
+        let multimsg = msg_block.init_root::<multi_message::Builder>();
+        multimsg.init_messages(16);
+
+        let multimsg = msg_block.init_root::<multi_message::Builder>();
+        multimsg.init_messages(32);
+    });
+
+    // It's only when we init a larger message count that a fresh allocation occurs
+    let (stats, _) = count_alloc(|| {
+        let multimsg = msg_block.init_root::<multi_message::Builder>();
+        // Note: calling `init_messages(33)` doesn't force allocation because
+        // the Capnproto builder reserved extra memory the first time around
+        multimsg.init_messages(256);
+    });
+
+    assert_eq!(stats.0, 1);
+    assert_eq!(stats.1, 3);
+    assert_eq!(stats.2, 0);
+}