feat(bin/client): use BufWriter when writing to file (#1756)

* feat: Use `std::io::BufWriter` with a 64KB buffer for dumping data

Let's see if this makes things faster.

* Flush `BufWriter` on FIN

* Update neqo-bin/src/bin/client/http3.rs

Co-authored-by: Max Inden <mail@max-inden.de>
Signed-off-by: Lars Eggert <lars@eggert.org>

* Fix

* Also for h09

* Move BufWriter construction into get_output_file

---------

Signed-off-by: Lars Eggert <lars@eggert.org>
Co-authored-by: Lars Eggert <lars@eggert.org>

neqo-bin/src/bin/client/http09.rs

@@ -10,7 +10,7 @@ use std::{
     cell::RefCell,
     collections::{HashMap, VecDeque},
     fs::File,
-    io::Write,
+    io::{BufWriter, Write},
     net::SocketAddr,
     path::PathBuf,
     rc::Rc,
@@ -29,7 +29,7 @@ use super::{get_output_file, Args, KeyUpdateState, Res};
 use crate::qlog_new;
 
 pub struct Handler<'a> {
-    streams: HashMap<StreamId, Option<File>>,
+    streams: HashMap<StreamId, Option<BufWriter<File>>>,
     url_queue: VecDeque<Url>,
     all_paths: Vec<PathBuf>,
     args: &'a Args,
@@ -219,7 +219,7 @@ impl<'b> Handler<'b> {
         client: &mut Connection,
         stream_id: StreamId,
         output_read_data: bool,
-        maybe_out_file: &mut Option<File>,
+        maybe_out_file: &mut Option<BufWriter<File>>,
     ) -> Res<bool> {
         let mut data = vec![0; 4096];
         loop {
@@ -246,8 +246,7 @@ impl<'b> Handler<'b> {
     }
 
     fn read(&mut self, client: &mut Connection, stream_id: StreamId) -> Res<()> {
-        let mut maybe_maybe_out_file = self.streams.get_mut(&stream_id);
-        match &mut maybe_maybe_out_file {
+        match self.streams.get_mut(&stream_id) {
             None => {
                 println!("Data on unexpected stream: {stream_id}");
                 return Ok(());
@@ -261,7 +260,9 @@ impl<'b> Handler<'b> {
                 )?;
 
                 if fin_recvd {
-                    if maybe_out_file.is_none() {
+                    if let Some(mut out_file) = maybe_out_file.take() {
+                        out_file.flush()?;
+                    } else {
                         println!("<FIN[{stream_id}]>");
                     }
                     self.streams.remove(&stream_id);

neqo-bin/src/bin/client/http3.rs

@@ -11,7 +11,7 @@ use std::{
     collections::{HashMap, VecDeque},
     fmt::Display,
     fs::File,
-    io::Write,
+    io::{BufWriter, Write},
     net::SocketAddr,
     path::PathBuf,
     rc::Rc,
@@ -269,7 +269,7 @@ impl StreamHandlerType {
 }
 
 struct DownloadStreamHandler {
-    out_file: Option<File>,
+    out_file: Option<BufWriter<File>>,
 }
 
 impl StreamHandler for DownloadStreamHandler {
@@ -300,8 +300,12 @@ impl StreamHandler for DownloadStreamHandler {
             println!("READ[{}]: 0x{}", stream_id, hex(&data));
         }
 
-        if fin && self.out_file.is_none() {
-            println!("<FIN[{stream_id}]>");
+        if fin {
+            if let Some(mut out_file) = self.out_file.take() {
+                out_file.flush()?;
+            } else {
+                println!("<FIN[{stream_id}]>");
+            }
         }
 
         Ok(true)

neqo-bin/src/bin/client/main.rs

@@ -8,7 +8,7 @@ use std::{
     collections::{HashMap, VecDeque},
     fmt::{self, Display},
     fs::{create_dir_all, File, OpenOptions},
-    io,
+    io::{self, BufWriter},
     net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, ToSocketAddrs},
     path::PathBuf,
     pin::Pin,
@@ -36,6 +36,8 @@ use url::{Origin, Url};
 mod http09;
 mod http3;
 
+const BUFWRITER_BUFFER_SIZE: usize = 64 * 1024;
+
 #[derive(Debug)]
 pub enum ClientError {
     ArgumentError(&'static str),
@@ -252,7 +254,7 @@ fn get_output_file(
     url: &Url,
     output_dir: &Option<PathBuf>,
     all_paths: &mut Vec<PathBuf>,
-) -> Option<File> {
+) -> Option<BufWriter<File>> {
     if let Some(ref dir) = output_dir {
         let mut out_path = dir.clone();
 
@@ -284,7 +286,7 @@ fn get_output_file(
             .ok()?;
 
         all_paths.push(out_path);
-        Some(f)
+        Some(BufWriter::with_capacity(BUFWRITER_BUFFER_SIZE, f))
     } else {
         None
     }