Struct abi_stable::sabi_types::MovePtr [−][src]
#[repr(transparent)]pub struct MovePtr<'a, T> { /* fields omitted */ }
Expand description
A move pointer, which allows moving the value from the reference, consuming it in the process.
If MovePtr::into_inner
isn’t called, this drops the referenced value when it’s dropped
Safety
This is unsafe to construct since the user must ensure that the original owner of the value never accesses it again.
Motivation
MovePtr
was created as a way to pass self
by value to ffi-safe trait object methods,
since one can’t simply pass self
by value(because the type is erased).
Examples
Using OwnedPointer::in_move_ptr
This is how one can use MovePtr without unsafe
.
This simply moves the contents of an RBox<T>
into a Box<T>
.
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
fn move_rbox_to_box<T>(rbox: RBox<T>) -> Box<T> {
rbox.in_move_ptr(|move_ptr| MovePtr::into_box(move_ptr))
}
assert_eq!(move_rbox_to_box(RBox::new(99)), Box::new(99));
assert_eq!(move_rbox_to_box(RBox::new(())), Box::new(()));
assert_eq!(
move_rbox_to_box(RBox::new(String::from("SHIT"))),
Box::new(String::from("SHIT"))
);
Using the (unsafe) MovePtr::new
This is (sort of) how RBox<T>
implements moving the T
it owns out of its allocation
This is basically what OwnedPointer::{with_move_ptr,in_move_ptr}
do.
use abi_stable::{
pointer_trait::{AsMutPtr, OwnedPointer},
sabi_types::MovePtr,
std_types::RBox,
};
use std::mem::ManuallyDrop;
let rbox = RBox::new(0x100);
let second_rbox;
unsafe {
let mut rbox = ManuallyDrop::new(rbox);
let move_ptr = unsafe { MovePtr::from_rmut(rbox.as_rmut()) };
second_rbox = RBox::from_move_ptr(move_ptr);
OwnedPointer::drop_allocation(&mut rbox);
}
assert_eq!(second_rbox, RBox::new(0x100));
Implementations
Constructs this move pointer from a mutable reference, moving the value out of the reference.
Safety
Callers must ensure that the original owner of the value won’t access the moved-out value anymore.
Example
use abi_stable::sabi_types::MovePtr;
use std::mem::ManuallyDrop;
let mut manual = ManuallyDrop::new(String::from("hello"));
let moveptr = unsafe { MovePtr::new(&mut *manual) };
drop(moveptr); // moveptr drops the String here.
Constructs this move pointer from an RMut
,
moving the value out of the reference.
Safety
Callers must ensure that the original owner of the value won’t access the moved-out value anymore.
Example
use abi_stable::{
pointer_trait::AsMutPtr, sabi_types::MovePtr, std_types::RString,
utils::manuallydrop_as_rmut,
};
use std::mem::ManuallyDrop;
let mut mdrop = ManuallyDrop::new(RString::from("hello"));
// safety: `mdrop` is never accessed again
let moveptr = unsafe { MovePtr::from_rmut(manuallydrop_as_rmut(&mut mdrop)) };
assert_eq!(*moveptr, "hello");
let string: RString = MovePtr::into_inner(moveptr);
assert_eq!(string, "hello");
Constructs this move pointer from a raw pointer, moving the value out of it.
Safety
Callers must ensure that the original owner of the value won’t access the moved-out value anymore.
Because this takes a mutable pointer, the lifetime of this MovePtr
is unbounded.
You must ensure that it’s not used for longer than the lifetime of the
pointed-to value.
Example
use abi_stable::{
pointer_trait::AsMutPtr, rvec, sabi_types::MovePtr, std_types::RVec,
utils::manuallydrop_as_raw_mut,
};
use std::mem::ManuallyDrop;
let mut mdrop = ManuallyDrop::new(rvec![3, 5, 8]);
// safety: `mdrop` is never accessed again
let moveptr = unsafe { MovePtr::from_raw(manuallydrop_as_raw_mut(&mut mdrop)) };
assert_eq!(moveptr[..], [3, 5, 8]);
let vector: RVec<u8> = MovePtr::into_inner(moveptr);
assert_eq!(vector[..], [3, 5, 8]);
Gets a raw pointer to the value being moved.
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("NOPE"));
let address_rbox = &*rbox as *const String as usize;
rbox.in_move_ptr(|move_ptr| {
assert_eq!(address_rbox, MovePtr::as_ptr(&move_ptr) as usize);
});
Gets a raw pointer to the value being moved.
Example
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("NOPE"));
let address_rbox = &*rbox as *const String as usize;
rbox.in_move_ptr(|mut move_ptr| {
assert_eq!(address_rbox, MovePtr::as_mut_ptr(&mut move_ptr) as usize);
});
Converts this MovePtr into a raw pointer, which must be moved from before the pointed to value is deallocated, otherwise the value will be leaked.
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("NOPE"));
let string =
rbox.in_move_ptr(|move_ptr| unsafe { MovePtr::into_raw(move_ptr).read() });
assert_eq!(string, String::from("NOPE"));
Moves the value into a new Box<T>
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("WHAT!!!"));
let boxed = rbox.in_move_ptr(|move_ptr| unsafe { MovePtr::into_box(move_ptr) });
assert_eq!(boxed, Box::new(String::from("WHAT!!!")));
Moves the value into a new RBox<T>
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("WHAT!!!"));
let boxed = rbox.in_move_ptr(|move_ptr| unsafe { MovePtr::into_rbox(move_ptr) });
assert_eq!(boxed, RBox::new(String::from("WHAT!!!")));
Moves the value out of the reference
Example
use abi_stable::{
pointer_trait::OwnedPointer, sabi_types::MovePtr, std_types::RBox,
};
let rbox = RBox::new(String::from("(The Wi)zard(of)oz"));
let string = rbox.in_move_ptr(|ptr| MovePtr::into_inner(ptr));
assert_eq!(string, String::from("(The Wi)zard(of)oz"));
Transmute this RMove<'a, T>
into a RMove<'a, U>
.
Safety
This has the safety requirements as
std::mem::transmute
,
as well as requiring that this MovePtr
is aligned for U
.
Example
use abi_stable::{
pointer_trait::OwnedPointer,
sabi_types::MovePtr,
std_types::{RBox, RString, RVec},
};
let rbox = RBox::new(RString::from("hello"));
let bytes = rbox.in_move_ptr(|ptr| unsafe {
MovePtr::into_inner(MovePtr::transmute::<RVec<u8>>(ptr))
});
assert_eq!(bytes.as_slice(), b"hello");
Trait Implementations
type StaticEquivalent = _static_MovePtr<'static, __GetStaticEquivalent<T>>
type Element = T
type Element = T
The type of the value this owns.
Unwraps this type into its owned value.
This method returns an ordering between self
and other
values if one exists. Read more
This method tests less than (for self
and other
) and is used by the <
operator. Read more
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
type IsNonZeroType = <NonNull<T> as __StableAbi>::IsNonZeroType
type IsNonZeroType = <NonNull<T> as __StableAbi>::IsNonZeroType
Whether this type has a single invalid bit-pattern. Read more
The layout of the type provided by implementors.
const
-equivalents of the associated types.
Auto Trait Implementations
impl<'a, T> RefUnwindSafe for MovePtr<'a, T> where
T: RefUnwindSafe,
impl<'a, T> !UnwindSafe for MovePtr<'a, T>
Blanket Implementations
Mutably borrows from an owned value. Read more
type ForSelf = WithMetadata_<T, T>
type ForSelf = WithMetadata_<T, T>
This is always WithMetadata_<Self, Self>
Compares the address of self
with the address of other
. Read more
Emulates the pipeline operator, allowing method syntax in more places. Read more
The same as piped
except that the function takes &Self
Useful for functions that take &Self
instead of Self
. Read more
The same as piped
, except that the function takes &mut Self
.
Useful for functions that take &mut Self
instead of Self
. Read more
Mutates self using a closure taking self by mutable reference, passing it along the method chain. Read more
Observes the value of self, passing it along unmodified. Useful in long method chains. Read more
Performs a conversion with Into
.
using the turbofish .into_::<_>()
syntax. Read more
Performs a reference to reference conversion with AsRef
,
using the turbofish .as_ref_::<_>()
syntax. Read more
Performs a mutable reference to mutable reference conversion with AsMut
,
using the turbofish .as_mut_::<_>()
syntax. Read more
unsafe fn transmute_element<T>(
self
) -> <Self as CanTransmuteElement<T>>::TransmutedPtr where
Self: CanTransmuteElement<T>,
unsafe fn transmute_element<T>(
self
) -> <Self as CanTransmuteElement<T>>::TransmutedPtr where
Self: CanTransmuteElement<T>,
Transmutes the element type of this pointer.. Read more
type Type = T
type Type = T
This is always Self
.
Converts a value back to the original type.
Converts a mutable reference back to the original type.
alloc
only.Converts a box back to the original type.
Converts a value back to the original type.
Converts a reference back to the original type.
Converts a mutable reference back to the original type.
alloc
only.Converts a box back to the original type.
alloc
only.Converts an Arc back to the original type.
alloc
only.Converts an Rc back to the original type.