Rust 指针

unsafe解引用原始指针

fn test() {
    let a = vec![1, 2]; // 声明一个固定容量的不可修改向量a
    println!("{}", a.capacity()); // 容量是2
    let p = &a as *const _ as *mut Vec<i32>; // 借用a，转换为原始指针。通过*const _可以强转为任意指针，不过解释指针是不安全的，需要unsafe方法或代码块
    unsafe  {
        let mut_a: &mut Vec<i32> = &mut *p; // 解引用，不安全操作
        mut_a.push(3);
        println!("{:?}", mut_a);
    }
}

//
2
[1, 2, 3]

String

fn test() {
    let mut a = String::with_capacity(1024);
    a.push_str("你好");
    bincode(&a as *const _ as *const u8, 24);
    println!("{:018p} :", a.as_ptr());
    bincode(a.as_ptr(), 7);
    println!("{}", a);
}

fn bincode(p: *const u8, le: i8) {
    unsafe {
        for i in 0..le {
            let a = p.offset(i as isize);
            print!("{:02x} ", *a);
        }
        println!();
    }
}

//
00 05 d4 f2 aa 55 00 00 00 04 00 00 00 00 00 00 06 00 00 00 00 00 00 00 
0x000055aaf2d40500 :
e4 bd a0 e5 a5 bd 00 
你好

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