marketdata-shootout/tests/capnp.rs

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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);
}