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
END