f Drop BufReader to just read to Vec directly

As we're always reading the files to their end anyways there is no
benefit to maintaining a separate buffer as `BufReader`. Here, we
therefore opt to read to our `Vec` directly.

Author: tnull

lightning-persister/src/fs_store.rs

@@ -4,7 +4,7 @@ use lightning::util::string::PrintableString;
 
 use std::collections::HashMap;
 use std::fs;
-use std::io::{BufReader, Read, Write};
+use std::io::{Read, Write};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
@@ -28,6 +28,9 @@ fn path_to_windows_str<T: AsRef<OsStr>>(path: T) -> Vec<u16> {
 	path.as_ref().encode_wide().chain(Some(0)).collect()
 }
 
+// We reuse std::io's DEFAULT_BUF_SIZE value of 8KB.
+const DEFAULT_BUF_SIZE: usize = 8 * 1024;
+
 /// A [`KVStore`] implementation that writes to and reads from the file system.
 pub struct FilesystemStore {
 	data_dir: PathBuf,
@@ -76,10 +79,9 @@ impl KVStore for FilesystemStore {
 		};
 		let _guard = inner_lock_ref.read().unwrap();
 
-		let mut buf = Vec::new();
-		let f = fs::File::open(dest_file_path.clone())?;
-		let mut reader = BufReader::new(f);
-		let nread = reader.read_to_end(&mut buf)?;
+		let mut buf = Vec::with_capacity(DEFAULT_BUF_SIZE);
+		let mut f = fs::File::open(dest_file_path.clone())?;
+		let nread = f.read_to_end(&mut buf)?;
 		debug_assert_ne!(nread, 0);
 
 		Ok(buf)