Fix reading empty files

Author: yoshuawuyts

src/body.rs

@@ -467,9 +467,12 @@ impl BufRead for Body {
 /// This is used for various binary formats such as images and videos.
 #[cfg(feature = "async_std")]
 async fn peek_mime(file: &mut async_std::fs::File) -> io::Result<Option<Mime>> {
+    // Reading the first 8 bytes should be enough to sniff the mime type.
     let mut buf = [0_u8; 8];
-    file.read_exact(&mut buf).await?;
+    file.read(&mut buf).await?;
     let mime = Mime::sniff(&buf).ok();
+
+    // Reset the file cursor back to the start.
     file.seek(io::SeekFrom::Start(0)).await?;
     Ok(mime)
 }

tests/mime.rs

@@ -1,4 +1,5 @@
 use async_std::io;
+use async_std::fs;
 use http_types::{mime, Body, Response};
 
 #[async_std::test]
@@ -11,11 +12,16 @@ async fn guess_plain_text_mime() -> io::Result<()> {
 }
 
 #[async_std::test]
-async fn guess_binary_mime() -> io::Result<()> {
+async fn guess_binary_mime() -> http_types::Result<()> {
     let body = Body::from_file("tests/fixtures/nori.png").await?;
     let mut res = Response::new(200);
     res.set_body(body);
     assert_eq!(res.content_type(), Some(mime::PNG));
+
+    // Assert the file is correctly reset after we've peeked the bytes
+    let left = fs::read("tests/fixtures/nori.png").await?;
+    let right = res.body_bytes().await?;
+    assert_eq!(left, right);
     Ok(())
 }