refactor io dir to be same with std

src/io/buf_reader.rs

@@ -4,11 +4,9 @@ use std::{cmp, fmt};
 
 use pin_project_lite::pin_project;
 
-use crate::io::{self, BufRead, Read, Seek, SeekFrom};
+use crate::io::{self, BufRead, Read, Seek, SeekFrom, DEFAULT_BUF_SIZE};
 use crate::task::{Context, Poll};
 
-const DEFAULT_CAPACITY: usize = 8 * 1024;
-
 pin_project! {
     /// Adds buffering to any reader.
     ///
@@ -72,7 +70,7 @@ impl<R: io::Read> BufReader<R> {
     /// # Ok(()) }) }
     /// ```
     pub fn new(inner: R) -> BufReader<R> {
-        BufReader::with_capacity(DEFAULT_CAPACITY, inner)
+        BufReader::with_capacity(DEFAULT_BUF_SIZE, inner)
     }
 
     /// Creates a new buffered reader with the specified capacity.

src/io/buf_writer.rs

@@ -4,11 +4,9 @@ use std::pin::Pin;
 use pin_project_lite::pin_project;
 
 use crate::io::write::WriteExt;
-use crate::io::{self, Seek, SeekFrom, Write};
+use crate::io::{self, Seek, SeekFrom, Write, DEFAULT_BUF_SIZE};
 use crate::task::{Context, Poll, ready};
 
-const DEFAULT_CAPACITY: usize = 8 * 1024;
-
 pin_project! {
     /// Wraps a writer and buffers its output.
     ///
@@ -107,7 +105,7 @@ impl<W: Write> BufWriter<W> {
     /// # Ok(()) }) }
     /// ```
     pub fn new(inner: W) -> BufWriter<W> {
-        BufWriter::with_capacity(DEFAULT_CAPACITY, inner)
+        BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
     }
 
     /// Creates a new `BufWriter` with the specified buffer capacity.

src/io/mod.rs

@@ -269,6 +269,8 @@
 //! [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
 //! [`.unwrap()`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap
 
+const DEFAULT_BUF_SIZE: usize = 8 * 1024;
+
 cfg_std! {
     #[doc(inline)]
     pub use std::io::{Error, ErrorKind, IoSlice, IoSliceMut, Result, SeekFrom};