server/compression: Don't wrap HashReader output stream in BufReader

Now it implements AsyncBufRead if the inner stream also implements
it.

server/src/compression.rs

@@ -2,7 +2,7 @@ use std::sync::Arc;
 
 use digest::Output as DigestOutput;
 use sha2::{Digest, Sha256};
-use tokio::io::{AsyncBufRead, AsyncRead, BufReader};
+use tokio::io::{AsyncBufRead, AsyncRead};
 use tokio::sync::OnceCell;
 
 use attic::io::HashReader;
@@ -38,7 +38,7 @@ pub struct CompressionStream {
 
 impl CompressionStream {
     /// Creates a new compression stream.
-    pub fn new<R>(stream: R, compressor: CompressorFn<BufReader<HashReader<R, Sha256>>>) -> Self
+    pub fn new<R>(stream: R, compressor: CompressorFn<HashReader<R, Sha256>>) -> Self
     where
         R: AsyncBufRead + Unpin + Send + 'static,
     {
@@ -46,7 +46,7 @@ impl CompressionStream {
         let (stream, nar_compute) = HashReader::new(stream, Sha256::new());
 
         // compress NAR
-        let stream = compressor(BufReader::new(stream));
+        let stream = compressor(stream);
 
         // compute file hash and size
         let (stream, file_compute) = HashReader::new(stream, Sha256::new());