Struct const_field_offset::FieldOffset

#[repr(transparent)]
pub struct FieldOffset<T, U, PinFlag = NotPinned>(_, _);

Represents a pointer to a field of type U within the type T

The PinFlag parameter can be set to AllowPin to enable the projection from Pin<&T> to Pin<&U>

Implementations

impl<T, U> FieldOffset<T, U, NotPinned>

pub unsafe fn new<F>(f: F) -> FieldOffset<T, U, NotPinned> where
    F: FnOnce(*const T) -> *const U, 

Construct a field offset via a lambda which returns a reference to the field in question.

Safety

The lambda must not dereference the provided pointer or access the inner value in any way as it may point to uninitialized memory.

For the returned FieldOffset to be safe to use, the returned pointer must be valid for any instance of T. For example, returning a pointer to a field from an enum with multiple variants will produce a FieldOffset which is unsafe to use.

pub const unsafe fn new_from_offset(
    offset: usize
) -> FieldOffset<T, U, NotPinned>

Construct a field offset directly from a byte offset.

Safety

For the returned FieldOffset to be safe to use, the field offset must be valid for any instance of T. For example, returning the offset to a field from an enum with multiple variants will produce a FieldOffset which is unsafe to use.

impl<T, U, PinFlag> FieldOffset<T, U, PinFlag>

pub fn apply_ptr(self, x: *const T) -> *const U

Apply the field offset to a native pointer.

pub fn apply_ptr_mut(self, x: *mut T) -> *mut U

Apply the field offset to a native mutable pointer.

pub fn apply(self, x: &'a T) -> &'a U

Apply the field offset to a reference.

pub fn apply_mut(self, x: &'a mut T) -> &'a mut U

Apply the field offset to a mutable reference.

pub const fn get_byte_offset(self) -> usize

Get the raw byte offset for this field offset.

pub unsafe fn unapply_ptr(self, x: *const U) -> *const T

Unapply the field offset to a native pointer.

Safety

Warning: very unsafe!

This applies a negative offset to a pointer. If the safety implications of this are not already clear to you, then do not use this method. Also be aware that Rust has stronger aliasing rules than other languages, so it may be UB to dereference the resulting pointer even if it points to a valid location, due to the presence of other live references.

pub unsafe fn unapply_ptr_mut(self, x: *mut U) -> *mut T

Unapply the field offset to a native mutable pointer.

Safety

Warning: very unsafe!

This applies a negative offset to a pointer. If the safety implications of this are not already clear to you, then do not use this method. Also be aware that Rust has stronger aliasing rules than other languages, so it may be UB to dereference the resulting pointer even if it points to a valid location, due to the presence of other live references.

pub unsafe fn unapply(self, x: &'a U) -> &'a T

Unapply the field offset to a reference.

Safety

Warning: very unsafe!

This applies a negative offset to a reference. If the safety implications of this are not already clear to you, then do not use this method. Also be aware that Rust has stronger aliasing rules than other languages, so this method may cause UB even if the resulting reference points to a valid location, due to the presence of other live references.

pub unsafe fn unapply_mut(self, x: &'a mut U) -> &'a mut T

Unapply the field offset to a mutable reference.

Safety

Warning: very unsafe!

This applies a negative offset to a reference. If the safety implications of this are not already clear to you, then do not use this method. Also be aware that Rust has stronger aliasing rules than other languages, so this method may cause UB even if the resulting reference points to a valid location, due to the presence of other live references.

pub const unsafe fn as_pinned_projection(self) -> FieldOffset<T, U, AllowPin>

Convert this offset to an offset that is allowed to go from Pin<&T> to Pin<&U>

Safety

The Pin safety rules for projection must be respected. These rules are explained in the Pin documentation

pub const fn as_unpinned_projection(self) -> FieldOffset<T, U, NotPinned>

Remove the AllowPin flag

impl<T, U> FieldOffset<T, U, AllowPin>

pub const unsafe fn new_from_offset_pinned(
    offset: usize
) -> FieldOffset<T, U, AllowPin>

Construct a field offset directly from a byte offset, which can be projected from a pinned.

Safety

In addition to the safety rules of FieldOffset::new_from_offset, the projection from Pin<&T> to Pin<&U> must also be allowed. The rules are explained in the Pin documentation

pub fn apply_pin(self, x: Pin<&'a T>) -> Pin<&'a U>

Apply the field offset to a pinned reference and return a pinned reference to the field

pub fn apply_pin_mut(self, x: Pin<&'a mut T>) -> Pin<&'a mut U>

Apply the field offset to a pinned mutable reference and return a pinned mutable reference to the field

Trait Implementations

impl<T, U, V> Add<FieldOffset<U, V, AllowPin>> for FieldOffset<T, U, NotPinned>

type Output = FieldOffset<T, V, NotPinned>

The resulting type after applying the + operator.

pub fn add(
    self,
    other: FieldOffset<U, V, AllowPin>
) -> FieldOffset<T, V, NotPinned>

Performs the + operation.

impl<T, U, V> Add<FieldOffset<U, V, AllowPin>> for FieldOffset<T, U, AllowPin>

type Output = FieldOffset<T, V, AllowPin>

The resulting type after applying the + operator.

pub fn add(
    self,
    other: FieldOffset<U, V, AllowPin>
) -> FieldOffset<T, V, AllowPin>

Performs the + operation.

impl<T, U, V> Add<FieldOffset<U, V, NotPinned>> for FieldOffset<T, U, NotPinned>

Allow chaining pointer-to-members.

Applying the resulting field offset is equivalent to applying the first field offset, then applying the second field offset.

The requirements on the generic type parameters ensure this is a safe operation.

type Output = FieldOffset<T, V, NotPinned>

The resulting type after applying the + operator.

pub fn add(
    self,
    other: FieldOffset<U, V, NotPinned>
) -> FieldOffset<T, V, NotPinned>

Performs the + operation.

impl<T, U, V> Add<FieldOffset<U, V, NotPinned>> for FieldOffset<T, U, AllowPin>

type Output = FieldOffset<T, V, NotPinned>

The resulting type after applying the + operator.

pub fn add(
    self,
    other: FieldOffset<U, V, NotPinned>
) -> FieldOffset<T, V, NotPinned>

Performs the + operation.

impl<T, U, Flag> Clone for FieldOffset<T, U, Flag>

pub fn clone(&self) -> FieldOffset<T, U, Flag>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, U, Flag> Debug for FieldOffset<T, U, Flag>

The debug implementation prints the byte offset of the field in hexadecimal.

pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T, U> From<FieldOffset<T, U, AllowPin>> for FieldOffset<T, U, NotPinned>

pub fn from(other: FieldOffset<T, U, AllowPin>) -> FieldOffset<T, U, NotPinned>

Performs the conversion.

impl<T, U, Flag> Copy for FieldOffset<T, U, Flag>