Crates.io | ptr_meta_derive |
lib.rs | ptr_meta_derive |
version | 0.3.0 |
source | src |
created_at | 2021-02-03 17:57:18.080611 |
updated_at | 2024-09-11 05:38:27.112873 |
description | Proc macros for ptr_meta |
homepage | |
repository | https://github.com/rkyv/ptr_meta |
max_upload_size | |
id | 350167 |
size | 10,889 |
ptr_meta
A radioactive stabilization of the ptr_meta
RFC.
Pointee
for structs and trait objects// Get the associated metadata for pointers
let str = "hello world";
assert_eq!(ptr_meta::metadata(str), str.len());
let slice = &[1, 2, 3, 4, 5] as &[i32];
assert_eq!(ptr_meta::metadata(slice), slice.len());
// Make your own wide pointers from data pointers and metadata
let bytes = [b'h', b'e', b'l', b'l', b'o'];
let ptr = ptr_meta::from_raw_parts::<str>(bytes.as_ptr().cast(), 5);
println!("{} world!", unsafe { &*ptr }); // prints "hello world!"
// Derive Pointee on your own types
#[derive(ptr_meta::Pointee)]
#[repr(transparent)]
struct CoolStr {
inner: str,
}
impl CoolStr {
fn print_cool(&self) {
println!("😎 {} 😎", &self.inner);
}
}
let ptr = ptr_meta::from_raw_parts::<CoolStr>(bytes.as_ptr().cast(), 5);
let cool = unsafe { &*ptr };
cool.print_cool(); // prints "😎 hello 😎"
// Implement Pointee for trait objects
#[ptr_meta::pointee]
trait Printable {
fn print(&self);
}
impl Printable for i32 {
fn print(&self) {
println!("i32: {self}");
}
}
let i32_vtable = ptr_meta::metadata(&0i32 as &dyn Printable);
let one_hundred = 100i32;
let printable = ptr_meta::from_raw_parts::<dyn Printable>(
(&one_hundred as *const i32).cast(),
i32_vtable,
);
unsafe {
(*printable).print(); // prints "i32: 100"
}