feat: add file read and write function(but with directly statx) (#193)

monoio/src/fs/mod.rs

@@ -1,7 +1,39 @@
 //! Filesystem manipulation operations.
 
 mod file;
+use std::{io, path::Path};
+
 pub use file::File;
 
 mod open_options;
 pub use open_options::OpenOptions;
+
+use crate::buf::IoBuf;
+
+/// Read the entire contents of a file into a bytes vector.
+#[cfg(unix)]
+pub async fn read<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
+    use std::os::fd::{AsRawFd, FromRawFd, IntoRawFd};
+
+    use crate::buf::IoBufMut;
+
+    let file = File::open(path).await?;
+    let sys_file = unsafe { std::fs::File::from_raw_fd(file.as_raw_fd()) };
+    let size = sys_file.metadata()?.len() as usize;
+    let _ = sys_file.into_raw_fd();
+
+    let (res, buf) = file
+        .read_exact_at(Vec::with_capacity(size).slice_mut(0..size), 0)
+        .await;
+    res?;
+    Ok(buf.into_inner())
+}
+
+/// Write a buffer as the entire contents of a file.
+pub async fn write<P: AsRef<Path>, C: IoBuf>(path: P, contents: C) -> (io::Result<()>, C) {
+    let file = match File::create(path).await {
+        Ok(f) => f,
+        Err(e) => return (Err(e), contents),
+    };
+    file.write_all_at(contents, 0).await
+}