1 files changed, 30 insertions, 4 deletions

diff --git a/src/version.rs b/src/version.rs
index c1dcee5..adc2a8d 100644
--- a/src/version.rs
+++ b/src/version.rs
@@ -5,6 +5,7 @@
 //! accepted until the server has answered it.
 
 use std::env;
+use std::time::{SystemTime, UNIX_EPOCH};
 
 /// Version this build reports. The client and the server share it.
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
@@ -73,9 +74,9 @@ pub fn is_newer(latest: &str, current: &str) -> bool {
     }
 }
 
-/// The server line that accepts a handshake.
-pub fn hello_line(version: &str, latest: &str, url: &str) -> String {
-    format!("HELLO {version} latest={latest} url={url}")
+/// The server line that accepts a handshake. `time` is Unix milliseconds.
+pub fn hello_line(version: &str, latest: &str, url: &str, time: u64) -> String {
+    format!("HELLO {version} latest={latest} url={url} time={time}")
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -83,9 +84,11 @@ pub struct HelloReply {
     pub version: String,
     pub latest: String,
     pub url: String,
+    /// Server clock at the moment the reply was built, Unix milliseconds.
+    pub time: u64,
 }
 
-/// Parse `HELLO <version> latest=<version> url=<url>`.
+/// Parse `HELLO <version> latest=<version> url=<url> time=<unix_ms>`.
 pub fn parse_hello(line: &str) -> Option<HelloReply> {
     let rest = line.trim().strip_prefix("HELLO ")?;
     let mut tokens = rest.split_whitespace();
@@ -93,11 +96,14 @@ pub fn parse_hello(line: &str) -> Option<HelloReply> {
 
     let mut latest = None;
     let mut url = None;
+    let mut time = None;
     for token in tokens {
         if let Some(value) = token.strip_prefix("latest=") {
             latest = Some(value.to_string());
         } else if let Some(value) = token.strip_prefix("url=") {
             url = Some(value.to_string());
+        } else if let Some(value) = token.strip_prefix("time=") {
+            time = value.parse().ok();
         }
     }
 
@@ -105,9 +111,29 @@ pub fn parse_hello(line: &str) -> Option<HelloReply> {
         version,
         latest: latest?,
         url: url?,
+        time: time?,
     })
 }
 
+/// The reply to `PING`: `PONG <unix_ms>`.
+pub fn pong_line(time: u64) -> String {
+    format!("PONG {time}")
+}
+
+/// Parse a `PONG` reply's server time.
+pub fn parse_pong(line: &str) -> Option<u64> {
+    line.trim().strip_prefix("PONG ")?.trim().parse().ok()
+}
+
+/// Current Unix time in milliseconds. Used for handshake timestamps and crash
+/// anchors; a system clock before the epoch reads as zero.
+pub fn unix_time_ms() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|duration| duration.as_millis().min(u128::from(u64::MAX)) as u64)
+        .unwrap_or(0)
+}
+
 /// Download page advertised by the server. `DOWNLOAD_URL` wins when set.
 pub fn download_url() -> String {
     env::var("DOWNLOAD_URL")