directly write to file

src/lib.rs

@@ -1,5 +1,6 @@
 use std::{
     collections::HashMap,
+    fs::File,
     io::Write,
     sync::{Mutex, atomic::AtomicU64},
     thread::ThreadId,
@@ -33,15 +34,25 @@ struct SpanInfo {
 }
 
 struct InnerPerfettoSubscriber {
-    buffer: Vec<perfetto::TracePacket>,
+    file: File,
     spans: HashMap<u64, SpanInfo>,
     threads: HashMap<ThreadId, u64>,
 }
 
 impl InnerPerfettoSubscriber {
     fn new(buffer: Vec<perfetto::TracePacket>) -> Self {
+        let mut file = File::options()
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open("out.trace")
+            .unwrap();
+
+        let trace = perfetto::Trace { packet: buffer };
+
+        file.write(&trace.encode_to_vec()).unwrap();
         Self {
-            buffer,
+            file,
             spans: HashMap::new(),
             threads: HashMap::new(),
         }
@@ -55,7 +66,7 @@ impl InnerPerfettoSubscriber {
             std::collections::hash_map::Entry::Vacant(vacant_entry) => {
                 vacant_entry.insert(nextfree);
 
-                self.buffer.push(perfetto::TracePacket {
+                self.push(perfetto::TracePacket {
                     timestamp: None,
                     data: Some(perfetto::trace_packet::Data::TrackDescriptor(
                         perfetto::TrackDescriptor {
@@ -83,23 +94,11 @@ impl InnerPerfettoSubscriber {
     }
 
     fn push(&mut self, packet: perfetto::TracePacket) {
-        self.buffer.push(packet);
-
-        self.flush();
-    }
-
-    fn flush(&mut self) {
         let trace = perfetto::Trace {
-            packet: std::mem::take(&mut self.buffer),
+            packet: vec![packet],
         };
-        let buf = trace.encode_to_vec();
 
-        let mut file = std::fs::File::options()
-            .append(true)
-            .open("out.trace")
-            .unwrap();
-
-        let _ = file.write(&buf);
+        self.file.write(&trace.encode_to_vec()).unwrap();
     }
 }