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Calculate distance between u64 without overflow #9592

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merged 2 commits into from
Apr 20, 2020
Merged

Calculate distance between u64 without overflow #9592

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77c3b0f
fix overflow
aeyakovenko Apr 19, 2020
3ad3561
fixed num_live_peers overflow
aeyakovenko Apr 19, 2020
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21 changes: 20 additions & 1 deletion core/src/broadcast_stage.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -412,11 +412,19 @@ pub fn broadcast_shreds(
Ok(())
}

fn distance(a: u64, b: u64) -> u64 {
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Can we call this abs for absolute value? (same name as std::num crate)

if a > b {
a - b
} else {
b - a
}
}

fn num_live_peers(peers: &[ContactInfo]) -> i64 {
let mut num_live_peers = 1i64;
peers.iter().for_each(|p| {
// A peer is considered live if they generated their contact info recently
if timestamp() - p.wallclock <= CRDS_GOSSIP_PULL_CRDS_TIMEOUT_MS {
if distance(timestamp(), p.wallclock) <= CRDS_GOSSIP_PULL_CRDS_TIMEOUT_MS {
num_live_peers += 1;
}
});
Expand Down Expand Up @@ -506,6 +514,17 @@ pub mod test {
assert_eq!(num_expected_coding_shreds, coding_index);
}

#[test]
fn test_num_live_peers() {
let mut ci = ContactInfo::default();
ci.wallclock = std::u64::MAX;
assert_eq!(num_live_peers(&[ci.clone()]), 1);
ci.wallclock = timestamp() - 1;
assert_eq!(num_live_peers(&[ci.clone()]), 2);
ci.wallclock = timestamp() - CRDS_GOSSIP_PULL_CRDS_TIMEOUT_MS - 1;
assert_eq!(num_live_peers(&[ci]), 1);
}

#[test]
fn test_duplicate_retransmit_signal() {
// Setup
Expand Down