Trait repr_offset::ext::ROExtRawAcc
source · pub unsafe trait ROExtRawAcc: PointerTarget {
// Required method
unsafe fn f_raw_get<F, A>(
self,
offset: FieldOffset<Self::Target, F, A>
) -> *const F;
}Expand description
Extension trait for raw pointers to access fields generically,
where the field is determined by a FieldOffset parameter.
Safety
This trait must not to be implemented outside the repr_offset crate.
Example
This example shows how you can get references to known aligned fields from a raw pointer to a partially initialized value..
use repr_offset::{
for_examples::ReprC,
off,
ROExtRawAcc, ROExtRawMutOps,
};
use std::mem::MaybeUninit;
type This = ReprC<u8, Option<usize>, &'static [u16], &'static str>;
let mut uninit = MaybeUninit::<This>::uninit();
unsafe {
let ptr = uninit.as_mut_ptr();
ptr.f_write(off!(a), 3);
ptr.f_write(off!(b), Some(5));
let (a, b) = get_init_refs(&uninit);
assert_eq!(*a, 3);
assert_eq!(*b, Some(5));
}
/// # Safety
///
/// The fields up to and including `b` must be initialized.
unsafe fn get_init_refs(this: &MaybeUninit<This>) -> (&u8, &Option<usize>) {
let this = this.as_ptr();
(
&*this.f_raw_get(off!(a)),
&*this.f_raw_get(off!(b)),
)
}
Required Methods§
sourceunsafe fn f_raw_get<F, A>(
self,
offset: FieldOffset<Self::Target, F, A>
) -> *const F
unsafe fn f_raw_get<F, A>( self, offset: FieldOffset<Self::Target, F, A> ) -> *const F
Gets a raw pointer to a field (determined by offset) from this raw pointer.
Safety
self must point to some allocated object,
allocated at least up to the field (inclusive).
Example
use repr_offset::{
for_examples::{ReprC, ReprPacked},
tstr::TS,
GetPubFieldOffset, FieldType,
ROExtRawAcc,
pub_off,
};
use std::cmp::Ordering;
let value = ReprPacked {
a: 3,
b: Some(5),
c: Ordering::Less,
d: ReprC {
a: 8,
b: "bar",
c: 13,
d: 21,
},
};
unsafe {
assert_eq!(copy_fields(&value), (3, 13));
}
/// Copies the `a` and `d.c` fields in this.
///
/// # Safety
///
/// The `a` and `d.c` fields in this must be initialized
unsafe fn copy_fields<T, O, U>(
this: *const T,
) -> (O, U)
where
T: GetPubFieldOffset<TS!(a), Type = O>,
T: GetPubFieldOffset<TS!(d,c), Type = U>,
O: Copy,
U: Copy,
{
(
this.f_raw_get(pub_off!(a)).read_unaligned(),
this.f_raw_get(pub_off!(d.c)).read_unaligned(),
)
}