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rename extra to other

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this is a breaking change
This commit is contained in:
nora 2022-04-06 20:04:49 +02:00
parent 299e1613ff
commit bde74a68ba
4 changed files with 167 additions and 160 deletions
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200
src/lib.rs
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@ -13,10 +13,10 @@
//!
//! [`StuffedPtr`] is the main type of this crate. You it's a type whose size depends on the
//! choice of [`Backend`] (defaults to `usize`, `u64` and `u128` are also possible). It can store a
//! pointer or some extra data.
//! pointer or some `other` data.
//!
//! You can choose any arbitrary bitstuffing depending on the [`StuffingStrategy`], an unsafe trait that governs
//! how the extra data (or the pointer itself) will be packed into the backend. While this trait is still unsafe,
//! how the `other` data (or the pointer itself) will be packed into the backend. While this trait is still unsafe,
//! it's a lot safer than doing everything by hand.
//!
//! # Example: NaN-Boxing
@ -35,21 +35,23 @@
//! // Create a unit struct for our strategy
//! struct NanBoxStrategy;
//!
//! const QNAN: u64 = 0x7ffc000000000000; // implementation detail of NaN boxing, a quiet NaN mask
//! const SIGN_BIT: u64 = 0x8000000000000000; // implementation detail of NaN boxing, the sign bit of an f64
//! // implementation detail of NaN boxing, a quiet NaN mask
//! const QNAN: u64 = 0x7ffc000000000000;
//! // implementation detail of NaN boxing, the sign bit of an f64
//! const SIGN_BIT: u64 = 0x8000000000000000;
//!
//! unsafe impl StuffingStrategy<u64> for NanBoxStrategy {
//! type Extra = f64;
//! type Other = f64;
//!
//! fn is_extra(data: u64) -> bool {
//! fn is_other(data: u64) -> bool {
//! (data & QNAN) != QNAN
//! }
//!
//! fn stuff_extra(inner: Self::Extra) -> u64 {
//! fn stuff_other(inner: Self::Other) -> u64 {
//! unsafe { std::mem::transmute(inner) } // both are 64 bit POD's
//! }
//!
//! unsafe fn extract_extra(data: u64) -> Self::Extra {
//! unsafe fn extract_other(data: u64) -> Self::Other {
//! std::mem::transmute(data) // both are 64 bit POD's
//! }
//!
@ -64,12 +66,14 @@
//! }
//! }
//!
//! type Object = HashMap<String, u32>; // a very, very crude representation of an object
//! // a very, very crude representation of an object
//! type Object = HashMap<String, u32>;
//!
//! type Value = StuffedPtr<Object, NanBoxStrategy, u64>; // our value type
//! // our value type
//! type Value = StuffedPtr<Object, NanBoxStrategy, u64>;
//!
//! let float: Value = StuffedPtr::new_extra(123.5);
//! assert_eq!(float.copy_extra(), Some(123.5));
//! let float: Value = StuffedPtr::new_other(123.5);
//! assert_eq!(float.copy_other(), Some(123.5));
//!
//! let object: Object = HashMap::from([("a".to_owned(), 457)]);
//! let boxed = Box::new(object);
@ -80,7 +84,7 @@
//!
//! drop(unsafe { Box::from_raw(ptr.get_ptr().unwrap()) });
//!
//! // `ptr` is a dangling pointer now!
//! // be careful, `ptr` is a dangling pointer now!
//! ```
#[cfg(test)]
@ -101,7 +105,7 @@ use sptr::Strict;
pub use crate::{backend::Backend, strategy::StuffingStrategy};
/// A union of a pointer or some extra data, bitpacked into a value with the size depending on
/// A union of a pointer or some `other` data, bitpacked into a value with the size depending on
/// `B`. It defaults to `usize`, meaning pointer sized, but `u64` and `u128` are also provided
/// by this crate. You can also provide your own [`Backend`] implementation
///
@ -111,9 +115,9 @@ pub use crate::{backend::Backend, strategy::StuffingStrategy};
///
/// For a usage example, view the crate level documentation.
///
/// This pointer does *not* drop extra data, [`StuffedPtr::into_extra`] can be used if that is required.
/// This pointer does *not* drop `other` data, [`StuffedPtr::into_other`] can be used if that is required.
///
/// `StuffedPtr` implements most traits like `Clone`, `PartialEq` or `Copy` if the extra type does.
/// `StuffedPtr` implements most traits like `Clone`, `PartialEq` or `Copy` if the `other` type does.
///
/// This type is guaranteed to be `#[repr(transparent)]` to a `B::Stored`.
#[repr(transparent)]
@ -134,20 +138,20 @@ where
StuffedPtr(B::set_ptr(ptr, stuffed), PhantomData)
}
/// Create a new `StuffPtr` from extra data
pub fn new_extra(extra: S::Extra) -> Self {
/// Create a new `StuffPtr` from `other` data
pub fn new_other(other: S::Other) -> Self {
// this doesn't have any provenance, which is ok, since it's never a pointer anyways.
// if the user calls `set_ptr` it will use the new provenance from that ptr
let ptr = core::ptr::null_mut();
let extra = S::stuff_extra(extra);
StuffedPtr(B::set_ptr(ptr, extra), PhantomData)
let other = S::stuff_other(other);
StuffedPtr(B::set_ptr(ptr, other), PhantomData)
}
/// Get the pointer data, or `None` if it contains extra data
/// Get the pointer data, or `None` if it contains `other` data
pub fn get_ptr(&self) -> Option<*mut T> {
match self.is_extra().not() {
match self.is_other().not() {
true => {
// SAFETY: We have done a check that it's not extra
// SAFETY: We have done a check that it's not other
unsafe { Some(self.get_ptr_unchecked()) }
}
false => None,
@ -158,103 +162,103 @@ where
/// contains pointer data.
///
/// # Safety
/// `StuffedPtr` must contain pointer data and not extra data
/// `StuffedPtr` must contain pointer data and not `other` data
pub unsafe fn get_ptr_unchecked(&self) -> *mut T {
let (provenance, addr) = B::get_ptr(self.0);
let addr = S::extract_ptr(addr);
Strict::with_addr(provenance, addr)
}
/// Get owned extra data from this, or `None` if it contains pointer data
pub fn into_extra(self) -> Option<S::Extra> {
match self.is_extra() {
/// Get owned `other` data from this, or `None` if it contains pointer data
pub fn into_other(self) -> Option<S::Other> {
match self.is_other() {
true => {
// SAFETY: We checked that it contains an extra above
unsafe { Some(self.into_extra_unchecked()) }
// SAFETY: We checked that it contains an other above
unsafe { Some(self.into_other_unchecked()) }
}
false => None,
}
}
/// Turn this pointer into extra data.
/// Turn this pointer into `other` data.
/// # Safety
/// `StuffedPtr` must contain extra data and not pointer
pub unsafe fn into_extra_unchecked(self) -> S::Extra {
/// `StuffedPtr` must contain `other` data and not pointer
pub unsafe fn into_other_unchecked(self) -> S::Other {
// SAFETY: `self` is consumed and forgotten after this call
let extra = self.get_extra_unchecked();
let other = self.get_other_unchecked();
mem::forget(self);
extra
other
}
/// Get extra data from this, or `None` if it contains pointer data
/// Get `other` data from this, or `None` if it contains pointer data
/// # Safety
/// The caller must guarantee that only ever on `Extra` exists if `Extra: !Copy`
pub unsafe fn get_extra(&self) -> Option<S::Extra> {
match self.is_extra() {
/// The caller must guarantee that only ever on `Other` exists if `Other: !Copy`
pub unsafe fn get_other(&self) -> Option<S::Other> {
match self.is_other() {
true => {
// SAFETY: We checked that it contains extra above, the caller guarantees the rest
Some(self.get_extra_unchecked())
// SAFETY: We checked that it contains other above, the caller guarantees the rest
Some(self.get_other_unchecked())
}
false => None,
}
}
/// Get extra data from this
/// Get `other` data from this
/// # Safety
/// Must contain extra data and not pointer data,
/// and the caller must guarantee that only ever on `Extra` exists if `Extra: !Copy`
pub unsafe fn get_extra_unchecked(&self) -> S::Extra {
/// Must contain `other` data and not pointer data,
/// and the caller must guarantee that only ever on `Other` exists if `Other: !Copy`
pub unsafe fn get_other_unchecked(&self) -> S::Other {
let data = self.addr();
S::extract_extra(data)
S::extract_other(data)
}
fn addr(&self) -> B {
B::get_int(self.0)
}
fn is_extra(&self) -> bool {
S::is_extra(self.addr())
fn is_other(&self) -> bool {
S::is_other(self.addr())
}
}
/// Extra implementations if the extra type is `Copy`
/// Extra implementations if the `other` type is `Copy`
impl<T, S, B> StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: Copy,
S::Other: Copy,
B: Backend<T>,
{
/// Get extra data from this, or `None` if it's pointer data
pub fn copy_extra(&self) -> Option<S::Extra> {
// SAFETY: `S::Extra: Copy`
unsafe { self.get_extra() }
/// Get `other` data from this, or `None` if it's pointer data
pub fn copy_other(&self) -> Option<S::Other> {
// SAFETY: `S::Other: Copy`
unsafe { self.get_other() }
}
/// Get extra data from this
/// Get `other` data from this
/// # Safety
/// Must contain extra data and not pointer data,
pub unsafe fn copy_extra_unchecked(&self) -> S::Extra {
// SAFETY: `S::Extra: Copy`, and the caller guarantees that it's extra
self.get_extra_unchecked()
/// Must contain `other` data and not pointer data,
pub unsafe fn copy_other_unchecked(&self) -> S::Other {
// SAFETY: `S::Other: Copy`, and the caller guarantees that it's other
self.get_other_unchecked()
}
}
impl<T, S, B> Debug for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: Debug,
S::Other: Debug,
B: Backend<T>,
{
fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
// SAFETY:
// If S::Extra: !Copy, we can't just copy it out and call it a day
// If S::Other: !Copy, we can't just copy it out and call it a day
// For example, if it's a Box, not forgetting it here would lead to a double free
// So we just format it and forget it afterwards
if let Some(extra) = unsafe { self.get_extra() } {
f.debug_struct("StuffedPtr::Extra")
.field("extra", &extra)
if let Some(other) = unsafe { self.get_other() } {
f.debug_struct("StuffedPtr::Other")
.field("other", &other)
.finish()?;
mem::forget(extra);
mem::forget(other);
Ok(())
} else {
// SAFETY: Checked above
@ -269,15 +273,15 @@ where
impl<T, S, B> Clone for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: Clone,
S::Other: Clone,
B: Backend<T>,
{
fn clone(&self) -> Self {
// SAFETY: We forget that `extra` ever existed after taking the reference and cloning it
if let Some(extra) = unsafe { self.get_extra() } {
let cloned_extra = extra.clone();
mem::forget(extra);
Self::new_extra(cloned_extra)
// SAFETY: We forget that `other` ever existed after taking the reference and cloning it
if let Some(other) = unsafe { self.get_other() } {
let cloned_other = other.clone();
mem::forget(other);
Self::new_other(cloned_other)
} else {
// just copy the pointer
StuffedPtr(self.0, PhantomData)
@ -288,7 +292,7 @@ where
impl<T, S, B> Copy for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: Copy,
S::Other: Copy,
B: Backend<T>,
{
}
@ -296,17 +300,17 @@ where
impl<T, S, B> PartialEq for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: PartialEq,
S::Other: PartialEq,
B: Backend<T>,
{
fn eq(&self, other: &Self) -> bool {
// SAFETY: We forget them after
let extras = unsafe { (self.get_extra(), other.get_extra()) };
let others = unsafe { (self.get_other(), other.get_other()) };
let eq = match &extras {
(Some(extra1), Some(extra2)) => extra1.eq(extra2),
let eq = match &others {
(Some(other1), Some(other2)) => other1.eq(other2),
(None, None) => {
// SAFETY: `get_extra` returned `None`, so it must be a ptr
// SAFETY: `get_other` returned `None`, so it must be a ptr
unsafe {
let ptr1 = self.get_ptr_unchecked();
let ptr2 = self.get_ptr_unchecked();
@ -316,7 +320,7 @@ where
_ => false,
};
mem::forget(extras);
mem::forget(others);
eq
}
@ -325,7 +329,7 @@ where
impl<T, S, B> Eq for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: PartialEq + Eq,
S::Other: PartialEq + Eq,
B: Backend<T>,
{
}
@ -333,14 +337,14 @@ where
impl<T, S, B> Hash for StuffedPtr<T, S, B>
where
S: StuffingStrategy<B>,
S::Extra: Hash,
S::Other: Hash,
B: Backend<T>,
{
fn hash<H: Hasher>(&self, state: &mut H) {
// SAFETY: We forget that `extra` ever existed after taking the reference and cloning it
if let Some(extra) = unsafe { self.get_extra() } {
extra.hash(state);
mem::forget(extra);
// SAFETY: We forget that `other` ever existed after taking the reference and cloning it
if let Some(other) = unsafe { self.get_other() } {
other.hash(state);
mem::forget(other);
} else {
// SAFETY: Checked above
let ptr = unsafe { self.get_ptr_unchecked() };
@ -364,7 +368,7 @@ mod tests {
};
// note: the tests mostly use the `PanicsInDrop` type and strategy, to make sure that no
// extra is ever dropped accidentally.
// `other` is ever dropped accidentally.
fn from_box<T, S, B>(boxed: Box<T>) -> StuffedPtr<T, S, B>
where
@ -378,7 +382,7 @@ mod tests {
($backend:ident) => {
paste! {
#[test]
fn [<set_get_ptr_no_extra__ $backend>]() {
fn [<set_get_ptr_no_other__ $backend>]() {
unsafe {
let boxed = Box::new(1);
let stuffed_ptr: StuffedPtr<i32, (), $backend> = from_box(boxed);
@ -390,10 +394,10 @@ mod tests {
#[test]
fn [<get_extra__ $backend>]() {
let stuffed_ptr: StuffedPtr<(), EmptyInMax, $backend> = StuffedPtr::new_extra(EmptyInMax);
assert!(stuffed_ptr.is_extra());
assert!(matches!(stuffed_ptr.copy_extra(), Some(EmptyInMax)));
fn [<get_other__ $backend>]() {
let stuffed_ptr: StuffedPtr<(), EmptyInMax, $backend> = StuffedPtr::new_other(EmptyInMax);
assert!(stuffed_ptr.is_other());
assert!(matches!(stuffed_ptr.copy_other(), Some(EmptyInMax)));
}
#[test]
@ -404,11 +408,11 @@ mod tests {
drop(unsafe { Box::from_raw(stuffed_ptr.get_ptr().unwrap()) });
let extra = HasDebug;
let stuffed_ptr: StuffedPtr<i32, HasDebug, $backend> = StuffedPtr::new_extra(extra);
let other = HasDebug;
let stuffed_ptr: StuffedPtr<i32, HasDebug, $backend> = StuffedPtr::new_other(other);
assert_eq!(
format!("{stuffed_ptr:?}"),
"StuffedPtr::Extra { extra: hello! }"
"StuffedPtr::Other { other: hello! }"
);
}
@ -419,7 +423,7 @@ mod tests {
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_ptr(&mut unit);
let _ = stuffed_ptr1.clone();
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_extra(PanicsInDrop);
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_other(PanicsInDrop);
let stuffed_ptr2 = stuffed_ptr1.clone();
mem::forget((stuffed_ptr1, stuffed_ptr2));
@ -436,7 +440,7 @@ mod tests {
assert_eq!(stuffed_ptr1, stuffed_ptr2);
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_ptr(&mut unit);
let stuffed_ptr2: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_extra(PanicsInDrop);
let stuffed_ptr2: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_other(PanicsInDrop);
assert_ne!(stuffed_ptr1, stuffed_ptr2);
mem::forget(stuffed_ptr2);
@ -444,7 +448,7 @@ mod tests {
#[test]
fn [<dont_drop_extra_when_pointer__ $backend>]() {
fn [<dont_drop_other_when_pointer__ $backend>]() {
let mut unit = ();
let stuffed_ptr: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_ptr(&mut unit);
// the panicking drop needs not to be called here!
@ -454,10 +458,10 @@ mod tests {
#[test]
fn [<some_traits_dont_drop__ $backend>]() {
// make sure that extra is never dropped twice
// make sure that other is never dropped twice
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_extra(PanicsInDrop);
let stuffed_ptr2: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_extra(PanicsInDrop);
let stuffed_ptr1: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_other(PanicsInDrop);
let stuffed_ptr2: StuffedPtr<(), PanicsInDrop, $backend> = StuffedPtr::new_other(PanicsInDrop);
// PartialEq
assert_eq!(stuffed_ptr1, stuffed_ptr2);