Rust引用借用 vs 原始指针

henreash2024-03-29 13:14

rust 复制代码

let v: i32 = 10;
let v1 = &v;
let a: *const i32 = &v;
println!("a={:p}", a);
let b = a as *mut i32;  //无法从&v直接转换成*mut i32，需要从*const i32过度
println!("b={:p}", b);
unsafe {
    *b+=1;
}
println!("v={}   v1={}", v, v1);

输出

复制代码

a=0xa7c8fb4d8
b=0xa7c8fb4d8
v=11   v1=11

rust 复制代码

    let mut mv: i32 = 10;
    let mut mv2 = &mut mv;
    *mv2 = *mv2 + 1;
    let p1 = mv2 as *const i32 as *mut i32;
    unsafe {
        *p1 += 1;
    }
    //let p2 = mv2 as *const i32;
    let mv3 = unsafe {
        let i: i32 = *p1;
        i
    };
    println!("mv2={}  mv3={}", mv2, mv3);

mv2=12 mv3=12

rust 复制代码

    use std::borrow::Cow;
    use std::os::raw::c_char;
    use std::ffi::CStr;
    let C: [u8; 11] = [116, 104, 97, 110, 107, 115, 102, 105, 115, 104, 0];
    let c_str: Cow<str>;
    unsafe{
        let c_ptr = &C as *const u8 as *const c_char;
        c_str = CStr::from_ptr(c_ptr).to_string_lossy();
    }
    println!("c_str is    {}", c_str);

c_str is thanksfish

原始指针和unsafe块配合，可以避过引用借用保护，但也失去了rust的优势。rust严谨也足够灵活...，除非必要原始指针慎用，用多了又变成c了...