Refactor emit.

src/formatting_layer.rs

@@ -216,7 +216,7 @@ impl<W: for<'a> MakeWriter<'a> + 'static> BunyanFormattingLayer<W> {
     /// If we write directly to the writer returned by self.make_writer in more than one go
     /// we can end up with broken/incoherent bits and pieces of those records when
     /// running multi-threaded/concurrent programs.
-    fn emit(&self, mut buffer: Vec<u8>) -> Result<(), std::io::Error> {
+    fn emit(&self, mut buffer: &mut [u8]) -> Result<(), std::io::Error> {
         buffer.write_all(b"\n")?;
         self.make_writer.make_writer().write_all(&buffer)
     }
@@ -351,22 +351,22 @@ impl<S, W> Layer<S> for BunyanFormattingLayer<W>
         };
 
         let result: std::io::Result<Vec<u8>> = format();
-        if let Ok(formatted) = result {
-            let _ = self.emit(formatted);
+        if let Ok(mut formatted) = result {
+            let _ = self.emit(&mut formatted);
         }
     }
 
     fn on_new_span(&self, _attrs: &Attributes, id: &Id, ctx: Context<'_, S>) {
         let span = ctx.span(id).expect("Span not found, this is a bug");
-        if let Ok(serialized) = self.serialize_span(&span, Type::EnterSpan) {
-            let _ = self.emit(serialized);
+        if let Ok(mut serialized) = self.serialize_span(&span, Type::EnterSpan) {
+            let _ = self.emit(&mut serialized);
         }
     }
 
     fn on_close(&self, id: Id, ctx: Context<'_, S>) {
         let span = ctx.span(&id).expect("Span not found, this is a bug");
-        if let Ok(serialized) = self.serialize_span(&span, Type::ExitSpan) {
-            let _ = self.emit(serialized);
+        if let Ok(mut serialized) = self.serialize_span(&span, Type::ExitSpan) {
+            let _ = self.emit(&mut serialized);
         }
     }
 }