11 releases
0.3.0 | Sep 11, 2024 |
---|---|
0.3.0-pre1 | Nov 4, 2023 |
0.3.0-alpha.3 | Aug 11, 2024 |
0.3.0-alpha.2 | Mar 30, 2024 |
0.1.2 | Mar 17, 2021 |
#124 in #rfc
1,506,825 downloads per month
Used in 855 crates
(via ptr_meta)
10KB
156 lines
ptr_meta
A radioactive stabilization of the ptr_meta
RFC.
Documentation
- ptr_meta, the core library
- ptr_meta_derive, proc macros for
implementing
Pointee
for structs and trait objects
Example
// 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"
}
Dependencies
~230–670KB
~16K SLoC