rust 读写文件

代码：

//#![windows_subsystem = "windows"]

use std::{io::Read,io::Write};
use std::fs::{File, OpenOptions};

static  _NETDISK:&str = "\\192.168.3.2\共享文件\";
static  LOCALDISK:&str = "D:\临时文件夹\";

fn main() {  
  let buf = b"not allow zh-CN";
  write_file(LOCALDISK.to_owned() + "a.txt",buf).unwrap();
  println!("{:?}",read_file(LOCALDISK.to_owned() + "a.txt"));
}

fn read_file(fname:String) -> Option<String>{
    let mut contents = String::new();    
    let mut file= match std::fs::File::open(fname ){
        Ok(f) => f,
        Err(_) => return None,  
    };    
    match file.read_to_string(&mut contents){
        Ok(_) => return Some(contents),        
        Err(_) => return None,   
    };   
}

pub fn write_file(fname:String,buf:&[u8]) -> Result<(),std::io::Error> {   
        let fo = OpenOptions::new()    
        .create(true) // 新建，若文件存在则打开这个文件
        .write(true)
        //.append(true) // 追加内容        
        .open(fname);          
    let mut f:File = match fo {
        Ok(f)=>f,
        Err(e)=>return Err(e),
    };
    match f.write_all(buf){
      Ok(_)=>Ok(()),
      Err(e)=>return Err(e),
    }
         
 }