diff --git a/src/lib.rs b/src/lib.rs
index 88e3cf5..36909df 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,7 +7,6 @@ use std::{
     io::{self, Write, Error, ErrorKind},
     path::{Path, PathBuf},
     process::Command,
-    time::SystemTime,
 };
 
 pub const DEFAULT_BUF_SIZE: usize = 8 * 1024;
@@ -17,30 +16,13 @@ pub const SIZE_GB: i64 = SIZE_MB * SIZE_KB;
 pub const SIZE_PB: i64 = SIZE_GB * SIZE_KB;
 pub const SIZE_TB: i64 = SIZE_PB * SIZE_KB;
 
+pub mod util_io;
+pub mod util_os;
+
 pub type XResult<T> = Result<T, Box<dyn std::error::Error>>;
 
-pub fn is_macos() -> bool {
-    if cfg!(target_os = "macos") {
-        true
-    } else {
-        false
-    }
-}
-
-pub fn is_linux() -> bool {
-    if cfg!(target_os = "linux") {
-        true
-    } else {
-        false
-    }
-}
-
-pub fn is_macos_or_linux() -> bool {
-    is_macos() || is_linux()
-}
-
 pub fn get_home_str() -> Option<String> {
-    match is_macos_or_linux() {
+    match util_os::is_macos_or_linux() {
         true => env::var("HOME").ok(),
         false => None,
     }
@@ -264,49 +246,3 @@ pub fn extract_package_and_wait(dir: &str, file_name: &str) -> io::Result<()> {
     cmd.arg(file_name).current_dir(dir);
     run_command_and_wait(&mut cmd)
 }
-
-pub fn copy_io<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W, total: i64) -> io::Result<u64>
-        where R: io::Read, W: io::Write {
-    //let written_cell = RefCell::new(0u64);
-    let start = SystemTime::now();
-    let written = copy_io_callback(reader, writer, total, &|total, written, _len| {
-        //written_cell.replace_with(|&mut w| w + len as u64);
-        //let written = *written_cell.borrow();
-        let cost = SystemTime::now().duration_since(start.clone()).unwrap().as_secs();
-        let mut download_speed = "-".to_string();
-        if cost > 0 {
-            download_speed = format!("{}/s", get_display_size((written / cost) as i64));
-        }
-        if total > 0 {
-            print_lastline(&format!("Downloading, Total: {}, Downloaded: {}, Speed: {}", 
-                get_display_size(total),
-                get_display_size(written as i64),
-                download_speed));
-        } else {
-            print_lastline(&format!("Downloading, Downloaded: {}, Speed: {}", 
-                get_display_size(written as i64),
-                download_speed));
-        }
-    });
-    println!();
-    written
-}
-
-pub fn copy_io_callback<R: ?Sized, W: ?Sized, FCallback>(reader: &mut R, writer: &mut W, total: i64, callback: &FCallback) -> io::Result<u64>
-        where R: io::Read,
-              W: io::Write,
-              FCallback: Fn(i64, u64, usize) -> () {
-    let mut written = 0u64;
-    let mut buf: [u8; DEFAULT_BUF_SIZE] = [0u8; DEFAULT_BUF_SIZE];
-    loop {
-        let len = match reader.read(&mut buf) {
-            Ok(0) => return Ok(written),
-            Ok(len) => len,
-            Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
-            Err(e) => return Err(e),
-        };
-        writer.write_all(&buf[..len])?;
-        written += len as u64;
-        callback(total, written, len);
-    }
-}
diff --git a/src/util_io.rs b/src/util_io.rs
new file mode 100644
index 0000000..e1246c7
--- /dev/null
+++ b/src/util_io.rs
@@ -0,0 +1,61 @@
+
+use std::{
+    io::{self, ErrorKind},
+    time::SystemTime,
+};
+
+use super::get_display_size;
+use super::print_lastline;
+
+pub const DEFAULT_BUF_SIZE: usize = 8 * 1024;
+pub const SIZE_KB: i64 = 1024;
+pub const SIZE_MB: i64 = SIZE_KB * SIZE_KB;
+pub const SIZE_GB: i64 = SIZE_MB * SIZE_KB;
+pub const SIZE_PB: i64 = SIZE_GB * SIZE_KB;
+pub const SIZE_TB: i64 = SIZE_PB * SIZE_KB;
+
+pub fn copy_io<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W, total: i64) -> io::Result<u64>
+        where R: io::Read, W: io::Write {
+    //let written_cell = RefCell::new(0u64);
+    let start = SystemTime::now();
+    let written = copy_io_callback(reader, writer, total, &|total, written, _len| {
+        //written_cell.replace_with(|&mut w| w + len as u64);
+        //let written = *written_cell.borrow();
+        let cost = SystemTime::now().duration_since(start.clone()).unwrap().as_secs();
+        let mut download_speed = "-".to_string();
+        if cost > 0 {
+            download_speed = format!("{}/s", get_display_size((written / cost) as i64));
+        }
+        if total > 0 {
+            print_lastline(&format!("Downloading, Total: {}, Downloaded: {}, Speed: {}", 
+                get_display_size(total),
+                get_display_size(written as i64),
+                download_speed));
+        } else {
+            print_lastline(&format!("Downloading, Downloaded: {}, Speed: {}", 
+                get_display_size(written as i64),
+                download_speed));
+        }
+    });
+    println!();
+    written
+}
+
+pub fn copy_io_callback<R: ?Sized, W: ?Sized, FCallback>(reader: &mut R, writer: &mut W, total: i64, callback: &FCallback) -> io::Result<u64>
+        where R: io::Read,
+              W: io::Write,
+              FCallback: Fn(i64, u64, usize) -> () {
+    let mut written = 0u64;
+    let mut buf: [u8; DEFAULT_BUF_SIZE] = [0u8; DEFAULT_BUF_SIZE];
+    loop {
+        let len = match reader.read(&mut buf) {
+            Ok(0) => return Ok(written),
+            Ok(len) => len,
+            Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+            Err(e) => return Err(e),
+        };
+        writer.write_all(&buf[..len])?;
+        written += len as u64;
+        callback(total, written, len);
+    }
+}
diff --git a/src/util_os.rs b/src/util_os.rs
new file mode 100644
index 0000000..03959d9
--- /dev/null
+++ b/src/util_os.rs
@@ -0,0 +1,20 @@
+
+pub fn is_macos() -> bool {
+    if cfg!(target_os = "macos") {
+        true
+    } else {
+        false
+    }
+}
+
+pub fn is_linux() -> bool {
+    if cfg!(target_os = "linux") {
+        true
+    } else {
+        false
+    }
+}
+
+pub fn is_macos_or_linux() -> bool {
+    is_macos() || is_linux()
+}