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Fix overflow in calculate_offset #25

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merged 3 commits into from
Aug 17, 2024
Merged

Fix overflow in calculate_offset #25

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d26daeb
Fix overflow
robertbastian Jul 22, 2024
609f805
fmt
Aug 9, 2024
b6f4a47
lib.rs: Switch from wrapping to saturating add
vpetrigo Aug 17, 2024
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24 changes: 18 additions & 6 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -84,9 +84,9 @@
//! socket
//! .set_read_timeout(Some(Duration::from_secs(2)))
//! .expect("Unable to set UDP socket read timeout");
//! # #[cfg(all(feature = "std", feature = "sup"))]
//! # #[cfg(all(feature = "std"))]
//! let result = sntpc::simple_get_time("time.google.com:123", socket);
//! # #[cfg(all(feature = "std", feature = "sup"))]
//! # #[cfg(all(feature = "std"))]
//! match result {
//! Ok(time) => {
//! println!("Got time: {}.{}", time.sec(), sntpc::fraction_to_milliseconds(time.sec_fraction()));
Expand Down Expand Up @@ -604,7 +604,7 @@ fn roundtrip_calculate(
t4: u64,
units: Units,
) -> u64 {
let delta = t4.wrapping_sub(t1).wrapping_sub(t3.wrapping_sub(t2));
let delta = t4.wrapping_sub(t1).saturating_sub(t3.wrapping_sub(t2));
let delta_sec = (delta & SECONDS_MASK) >> 32;
let delta_sec_fraction = delta & SECONDS_FRAC_MASK;

Expand All @@ -619,9 +619,8 @@ fn roundtrip_calculate(
}

fn offset_calculate(t1: u64, t2: u64, t3: u64, t4: u64, units: Units) -> i64 {
let theta = (t2.wrapping_sub(t1) as i64)
.wrapping_add(t3.wrapping_sub(t4) as i64)
/ 2;
let theta = ((t2.wrapping_sub(t1) / 2) as i64)
.saturating_add((t3.wrapping_sub(t4) / 2) as i64);
let theta_sec = (theta.unsigned_abs() & SECONDS_MASK) >> 32;
let theta_sec_fraction = theta.unsigned_abs() & SECONDS_FRAC_MASK;

Expand All @@ -639,6 +638,19 @@ fn offset_calculate(t1: u64, t2: u64, t3: u64, t4: u64, units: Units) -> i64 {
}
}

#[test]
fn test_offset_calculate() {
let t1 = 9487534663484046772u64;
let t2 = 16882120099581835046u64;
let t3 = 16882120099583884144u64;
let t4 = 9487534663651464597u64;

assert_eq!(
offset_calculate(t1, t2, t3, t4, Units::Microseconds),
1721686086620926
);
}

#[cfg(feature = "log")]
fn debug_ntp_packet(packet: &NtpPacket, _recv_timestamp: u64) {
let mode = shifter(packet.li_vn_mode, MODE_MASK, MODE_SHIFT);
Expand Down
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