tg-rcore-tutorial-user 0.4.10

User-space apps for rCore Tutorial chapters (subset for ch2).
Documentation 
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#![no_std]
#![no_main]

#[macro_use]
extern crate user_lib;

use user_lib::{close, fstat, link, open, read, unlink, write, OpenFlags, Stat};

// 教学目标：
// 覆盖硬链接创建/删除语义，并验证 inode/dev 一致与 nlink 变化。
/// 测试 link/unlink，输出 Test link OK! 就算正确。

#[unsafe(no_mangle)]
extern "C" fn main() -> i32 {
    let test_str = "Hello, world!";
    let fname = "fname2\0";
    let (lname0, lname1, lname2) = ("linkname0\0", "linkname1\0", "linkname2\0");
    let fd = open(fname, OpenFlags::CREATE | OpenFlags::WRONLY) as usize;
    link(fname, lname0);
    let mut stat = Stat::new();
    fstat(fd, &mut stat);
    assert_eq!(stat.nlink, 2);
    link(fname, lname1);
    link(fname, lname2);
    fstat(fd, &mut stat);
    assert_eq!(stat.nlink, 4);
    write(fd, test_str.as_bytes());
    close(fd);

    unlink(fname);
    let fd = open(lname0, OpenFlags::RDONLY) as usize;
    let mut stat2 = Stat::new();
    let mut buf = [0u8; 100];
    let read_len = read(fd, &mut buf) as usize;
    assert_eq!(test_str, core::str::from_utf8(&buf[..read_len]).unwrap());
    fstat(fd, &mut stat2);
    assert_eq!(stat2.dev, stat.dev);
    assert_eq!(stat2.ino, stat.ino);
    assert_eq!(stat2.nlink, 3);
    unlink(lname1);
    unlink(lname2);
    fstat(fd, &mut stat2);
    assert_eq!(stat2.nlink, 1);
    close(fd);
    unlink(lname0);
    println!("Test link OK!");
    0
}