tagptr/imp/non_null.rs
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use core::{
cmp,
convert::TryFrom,
fmt,
hash::{Hash, Hasher},
marker::PhantomData,
mem,
ptr::NonNull,
};
use crate::{Null, TagNonNull, TagPtr};
/********** impl Clone ****************************************************************************/
impl<T, const N: usize> Clone for TagNonNull<T, N> {
impl_clone!();
}
/********** impl Copy *****************************************************************************/
impl<T, const N: usize> Copy for TagNonNull<T, N> {}
/********** impl inherent *************************************************************************/
impl<T, const N: usize> TagNonNull<T, N> {
doc_comment! {
doc_tag_bits!(),
pub const TAG_BITS: usize = N;
}
doc_comment! {
doc_tag_mask!(),
pub const TAG_MASK: usize = crate::mark_mask(Self::TAG_BITS);
}
doc_comment! {
doc_ptr_mask!(),
pub const POINTER_MASK: usize = !Self::TAG_MASK;
}
const COMPOSE_ERR_MSG: &'static str =
"argument `ptr` is mis-aligned for `N` tag bits and could be parsed as marked `null` \
pointer.";
/// Creates a new marked non-null pointer from `marked_ptr` without
/// checking if it is `null`.
///
/// # Safety
///
/// The caller has to ensure that `marked_ptr` is not `null`.
/// This includes `null` pointers with non-zero tag values.
#[inline]
pub const unsafe fn new_unchecked(marked_ptr: TagPtr<T, N>) -> Self {
Self { inner: NonNull::new_unchecked(marked_ptr.inner), _marker: PhantomData }
}
doc_comment! {
doc_from_usize!(),
#[inline]
pub const unsafe fn from_usize(val: usize) -> Self {
Self { inner: NonNull::new_unchecked(val as *mut _), _marker: PhantomData }
}
}
doc_comment! {
doc_into_raw!(),
#[inline]
pub const fn into_raw(self) -> NonNull<T> {
self.inner
}
}
doc_comment! {
doc_cast!(),
pub const fn cast<U>(self) -> TagNonNull<U, N> {
TagNonNull { inner: self.inner.cast(), _marker: PhantomData }
}
}
doc_comment! {
doc_into_usize!(),
#[inline]
pub fn into_usize(self) -> usize {
self.inner.as_ptr() as _
}
}
/// Converts `self` into a (nullable) marked pointer.
#[inline]
pub const fn into_marked_ptr(self) -> TagPtr<T, N> {
TagPtr::new(self.inner.as_ptr())
}
/// Creates a new non-null pointer from `marked_ptr`.
///
/// # Errors
///
/// Fails if `marked_ptr` is `null`, in which case a [`Null`] instance is
/// returned containing argument pointer's tag value.
#[inline]
pub fn new(marked_ptr: TagPtr<T, N>) -> Result<Self, Null> {
Self::try_from(marked_ptr)
}
/// Creates a new pointer that is dangling but well aligned.
#[inline]
pub const fn dangling() -> Self {
let alignment = mem::align_of::<T>();
let val = if alignment >= Self::TAG_MASK + 1 { alignment } else { Self::TAG_MASK + 1 };
// SAFETY: a type's alignment is never 0, so val is always non-zero
unsafe { Self::from_usize(val) }
}
doc_comment! {
doc_compose!(),
/// # Panics
///
/// Panics if `ptr` is mis-aligned for `N` tag bits and contains only
/// zero bits in the upper bits, i.e., it would be parsed as a marked
/// `null` pointer.
#[inline]
pub fn compose(ptr: NonNull<T>, tag: usize) -> Self {
Self::try_compose(ptr, tag).expect(Self::COMPOSE_ERR_MSG)
}
}
/// Attempts to compose a new marked pointer from a raw (non-null) `ptr` and
/// a `tag` value.
///
/// # Errors
///
/// Fails if `ptr` is mis-aligned for `N` tag bits and contains only
/// zero bits in the upper bits, i.e., it would be parsed as a marked
/// `null` pointer.
/// In this case a [`Null`] instance is returned containing the argument
/// pointer's tag value.
#[inline]
pub fn try_compose(ptr: NonNull<T>, tag: usize) -> Result<Self, Null> {
Self::try_compose_inner(ptr.as_ptr(), tag)
}
/// Composes a new marked pointer from a raw (non-null) `ptr` and a `tag`
/// value without checking if `ptr` is valid.
///
/// # Safety
///
/// The caller has to ensure that `ptr` is non-null even after considering
/// its `N` lower bits as tag bits.
#[inline]
pub unsafe fn compose_unchecked(ptr: NonNull<T>, tag: usize) -> Self {
Self::new_unchecked(TagPtr::compose(ptr.as_ptr(), tag))
}
doc_comment! {
doc_clear_tag!(),
#[inline]
pub fn clear_tag(self) -> Self {
Self { inner: self.decompose_non_null(), _marker: PhantomData }
}
}
doc_comment! {
doc_split_tag!(),
#[inline]
pub fn split_tag(self) -> (Self, usize) {
let (inner, tag) = self.decompose();
(Self { inner, _marker: PhantomData }, tag)
}
}
doc_comment! {
doc_set_tag!(),
#[inline]
pub fn set_tag(self, tag: usize) -> Self {
let ptr = self.decompose_non_null();
// SAFETY: ptr was decomposed from a valid marked non-nullable pointer
unsafe { Self::compose_unchecked(ptr, tag) }
}
}
doc_comment! {
doc_update_tag!(),
#[inline]
pub fn update_tag(self, func: impl FnOnce(usize) -> usize) -> Self {
let (ptr, tag) = self.decompose();
// SAFETY: ptr was decomposed from a valid marked non-nullable pointer
unsafe { Self::compose_unchecked(ptr, func(tag)) }
}
}
doc_comment! {
doc_add_tag!(),
/// # Safety
///
/// The caller has to ensure that the resulting pointer is not
/// `null` (neither marked nor unmarked).
#[inline]
pub unsafe fn add_tag(self, value: usize) -> Self {
Self::from_usize(self.into_usize().wrapping_add(value))
}
}
doc_comment! {
doc_sub_tag!(),
/// # Safety
///
/// The caller has to ensure that the resulting pointer is not
/// `null` (neither marked nor unmarked).
#[inline]
pub unsafe fn sub_tag(self, value: usize) -> Self {
Self::from_usize(self.into_usize().wrapping_sub(value))
}
}
doc_comment! {
doc_decompose!(),
#[inline]
pub fn decompose(self) -> (NonNull<T>, usize) {
(self.decompose_non_null(), self.decompose_tag())
}
}
doc_comment! {
doc_decompose_ptr!(),
#[inline]
pub fn decompose_ptr(self) -> *mut T {
crate::decompose_ptr(self.inner.as_ptr() as usize, Self::TAG_BITS)
}
}
doc_comment! {
doc_decompose_non_null!(),
#[inline]
pub fn decompose_non_null(self) -> NonNull<T> {
// SAFETY: every valid TagNonNull is also a valid NonNull
unsafe { NonNull::new_unchecked(self.decompose_ptr()) }
}
}
doc_comment! {
doc_decompose_tag!(),
#[inline]
pub fn decompose_tag(self) -> usize {
crate::decompose_tag::<T>(self.inner.as_ptr() as usize, Self::TAG_BITS)
}
}
doc_comment! {
doc_as_ref!("non-nullable"),
#[inline]
pub unsafe fn as_ref(&self) -> &T {
&*self.decompose_non_null().as_ptr()
}
}
doc_comment! {
doc_as_mut!("non-nullable", TagNonNull),
#[inline]
pub unsafe fn as_mut(&mut self) -> &mut T {
&mut *self.decompose_non_null().as_ptr()
}
}
/// Decomposes the marked pointer, returning a reference and the separated
/// tag.
///
/// # Safety
///
/// The same safety caveats as with [`as_ref`][TagNonNull::as_ref] apply.
#[inline]
pub unsafe fn decompose_ref(&self) -> (&T, usize) {
let (ptr, tag) = self.decompose();
(&*ptr.as_ptr(), tag)
}
/// Decomposes the marked pointer, returning a *mutable* reference and the
/// separated tag.
///
/// # Safety
///
/// The same safety caveats as with [`as_mut`][TagNonNull::as_mut] apply.
#[inline]
pub unsafe fn decompose_mut(&mut self) -> (&mut T, usize) {
let (ptr, tag) = self.decompose();
(&mut *ptr.as_ptr(), tag)
}
#[inline]
fn try_compose_inner(ptr: *mut T, tag: usize) -> Result<Self, Null> {
match ptr as usize & Self::POINTER_MASK {
0 => Err(Null(ptr as usize)),
// SAFETY: the pointer's upper bits are non-zero,
_ => Ok(unsafe { Self::new_unchecked(TagPtr::compose(ptr, tag)) }),
}
}
}
/********** impl Debug ****************************************************************************/
impl<T, const N: usize> fmt::Debug for TagNonNull<T, N> {
impl_debug!("TagNonNull");
}
/********** impl Pointer **************************************************************************/
impl<T, const N: usize> fmt::Pointer for TagNonNull<T, N> {
impl_pointer!();
}
/********** impl From (&T) ************************************************************************/
impl<T, const N: usize> From<&T> for TagNonNull<T, N> {
#[inline]
fn from(reference: &T) -> Self {
Self { inner: NonNull::from(reference), _marker: PhantomData }
}
}
/********** impl From (&mut T) ********************************************************************/
impl<T, const N: usize> From<&mut T> for TagNonNull<T, N> {
#[inline]
fn from(reference: &mut T) -> Self {
Self { inner: NonNull::from(reference), _marker: PhantomData }
}
}
/********** impl PartialEq ************************************************************************/
impl<T, const N: usize> PartialEq for TagNonNull<T, N> {
impl_partial_eq!();
}
/********** impl PartialOrd ***********************************************************************/
impl<T, const N: usize> PartialOrd for TagNonNull<T, N> {
impl_partial_ord!();
}
/********** impl Eq *******************************************************************************/
impl<T, const N: usize> Eq for TagNonNull<T, N> {}
/********** impl Ord ******************************************************************************/
impl<T, const N: usize> Ord for TagNonNull<T, N> {
impl_ord!();
}
/********** impl Hash *****************************************************************************/
impl<T, const N: usize> Hash for TagNonNull<T, N> {
impl_hash!();
}
/********** impl TryFrom (*mut T) *****************************************************************/
impl<T, const N: usize> TryFrom<*mut T> for TagNonNull<T, N> {
type Error = Null;
#[inline]
fn try_from(ptr: *mut T) -> Result<Self, Self::Error> {
Self::try_compose_inner(ptr, 0)
}
}
/********** impl TryFrom (*const T) ***************************************************************/
impl<T, const N: usize> TryFrom<*const T> for TagNonNull<T, N> {
type Error = Null;
#[inline]
fn try_from(ptr: *const T) -> Result<Self, Self::Error> {
Self::try_from(ptr as *mut _)
}
}
/********** impl TryFrom (TagPtr) **************************************************************/
impl<T, const N: usize> TryFrom<TagPtr<T, N>> for TagNonNull<T, N> {
type Error = Null;
#[inline]
fn try_from(ptr: TagPtr<T, N>) -> Result<Self, Self::Error> {
Self::try_from(ptr.into_raw())
}
}
/********** impl TryFrom (NonNull) ****************************************************************/
impl<T, const N: usize> TryFrom<NonNull<T>> for TagNonNull<T, N> {
type Error = Null;
#[inline]
fn try_from(ptr: NonNull<T>) -> Result<Self, Self::Error> {
Self::try_from(ptr.as_ptr())
}
}
#[cfg(test)]
mod tests {
use core::ptr::NonNull;
use crate::Null;
type TagNonNull = crate::TagNonNull<i32, 2>;
#[test]
fn test_dangling() {
assert_eq!(TagNonNull::dangling().into_raw(), NonNull::dangling());
#[repr(align(64))]
struct Alignment64;
assert_eq!(crate::TagNonNull::<Alignment64, 0>::dangling().into_usize(), 64);
}
#[test]
fn test_try_compose() {
let reference = &1;
let ptr = NonNull::from(reference);
let res = TagNonNull::try_compose(ptr, 0b11).map(|ptr| ptr.decompose());
assert_eq!(res, Ok((ptr, 0b11)));
let dangling = NonNull::dangling();
let res = TagNonNull::try_compose(dangling, 0).map(|ptr| ptr.decompose());
assert_eq!(res, Ok((dangling, 0)));
let ptr = NonNull::new(0b11 as *mut i32).unwrap();
let res = TagNonNull::try_compose(ptr, 0b11);
assert_eq!(res, Err(Null(0b11)));
}
}