server: Bind port before messing with log files as a lock

[tattlekey] / server / src / main.rs

diff --git a/server/src/main.rs b/server/src/main.rs
index a186abd58ec1b0e8045b0e29881fbcd7ecd76229..e7351db4ffa17f70a8c3ad9617b23155b09894b1 100644 (file)
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -20,6 +20,7 @@ use std::net::UdpSocket;
 use std::time::{Duration, SystemTime};
 
 const MESSAGE_SIZE: usize = 12;
+const LOGFILENAME: &str = "log.csv";
 
 #[derive(Eq, Debug, Hash, PartialEq, Serialize)]
 struct MessageKey {
@@ -79,15 +80,22 @@ impl Range {
     }
 }
 
-fn main() {
+fn open_log_for_writing() -> csv::Writer<std::fs::File> {
+    let log_file_exists = std::path::Path::new(LOGFILENAME).exists();
     let logfile = std::fs::OpenOptions::new()
-        .create(true)
+        .create_new(!log_file_exists)
         .append(true)
-        .open("log.csv")
+        .open(LOGFILENAME)
         .expect("Coudln't open log file");
-    let mut log = csv::Writer::from_writer(logfile);
-    let mut presses = HashMap::<MessageKey, Range>::new();
+    csv::WriterBuilder::new()
+        .has_headers(!log_file_exists)
+        .from_writer(logfile)
+}
+
+fn main() {
     let socket = UdpSocket::bind("0.0.0.0:29803").expect("couldn't bind to address");
+    let mut presses = HashMap::<MessageKey, Range>::new();
+    let mut log = open_log_for_writing();
     loop {
         let mut buf = [0; MESSAGE_SIZE];
         match socket.recv_from(&mut buf) {