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//! Single-threaded reference-counting persistent pointers
//!
//! [`Prc`] is a persistent pointer sharing the underlying data between multiple
//! owners. To create a new strong reference, you may use [`pclone`] function.
//! When the last owner of data goes out of scope, the strong reference count
//! becomes zero, and the owner drops the allocation.
//!
//! # Cyclic References
//! If there is a cycle in the chain of references, dropping the link may yield
//! a memory leak. For example, assume that we have three nodes of `A`, `B`, and
//! `C`, which are connected together like figure (a) below:
//!
//! ```text
//! Strong Refs: 1 2 1 1 1 1 1 1 1
//! A -▷ B -▷ C A B -▷ C A -▷ B -▷ C
//! △ │ △ │ △ ┆
//! └────┘ └────┘ └----┘
//! (a) (b) (c)
//! ```
//!
//! In this topology, `B` has two strong references: `A` and `C`. Therefore,
//! when the `A -▷ B` link drops, it loses only one strong references allowing
//! the other strong reference to keep the cycle it in memory while the nodes
//! are unreachable. The resulting network is shown in figure (b).
//!
//! [`Weak`] is provided to fix this issue. Although it is not enforced, the
//! programmer can take benefits out of it. A weak link does not increment the
//! strong reference counter. Making `C -▷ B` weak, which is shown in figure (c),
//! resolves this problem. Since `B`'s strong reference counter is 1, dropping
//! `A -▷ B` makes it zero and `B`'s drop function gets called.
//!
//! # Example
//!
//! The following example does not use a weak pointer leading to a memory leak.
//! It creates the following links: `A -> B`, `B -> C`, and `C -> B`. The last
//! two links create a cycle. Therefore, when `A` goes of scope, it cannot drop
//! `B` and `C` because the strong reference count for both of them is non-zero.
//! Nodes `B` and `C` remain in memory forever.
//!
//! ```
//! use corundum::default::*;
//! type P = Allocator;
//!
//! struct Node {
//! val: char,
//! link: PRefCell<Option<Prc<Node>>>
//! }
//!
//! impl Node {
//! fn new(val: char) -> Self {
//! println!("{} is created", val);
//! Self { val, link: PRefCell::new(None) }
//! }
//! }
//!
//! impl Drop for Node {
//! fn drop(&mut self) {
//! println!("{} is dropped", self.val);
//! }
//! }
//!
//! let _pool = P::open_no_root("net.pool", O_CF).unwrap();
//!
//! transaction(|j| {
//! let A = Prc::new(Node::new('A'), j);
//! let B = Prc::new(Node::new('B'), j);
//! let C = Prc::new(Node::new('C'), j);
//! let mut a_link = A.link.borrow_mut(j);
//! let mut b_link = B.link.borrow_mut(j);
//! let mut c_link = C.link.borrow_mut(j);
//! *a_link = Some(B.pclone(j));
//! *b_link = Some(C.pclone(j));
//! *c_link = Some(B.pclone(j));
//! }).unwrap();
//! ```
//!
//! The output of the example above is as follows (`B` and `C` do not drop the
//! allocation):
//!
//! ```text
//! A is created
//! B is created
//! C is created
//! A is dropped
//! ```
//!
//! To prevent the memory leak, we can use a weak link. The following example
//! shows how to manually prevent cycles. The `C -> B` link is weak, so the
//! strong reference counter becomes zero when `A -> B` is eliminated.
//!
//! ```
//! use corundum::default::*;
//! type P = Allocator;
//!
//! enum Link<T: PSafe> {
//! Strong(Prc<T>),
//! Weak(prc::PWeak<T>),
//! Null
//! }
//!
//! struct Node {
//! val: char,
//! link: PRefCell<Link<Node>>
//! }
//!
//! impl Node {
//! fn new(val: char) -> Self {
//! println!("{} is created", val);
//! Self { val, link: PRefCell::new(Null) }
//! }
//! }
//!
//! impl Drop for Node {
//! fn drop(&mut self) {
//! println!("{} is dropped", self.val);
//! }
//! }
//! # use Link::*;
//!
//! let _pool = P::open_no_root("net.pool", O_CF).unwrap();
//!
//! transaction(|j| {
//! let A = Prc::new(Node::new('A'), j);
//! let B = Prc::new(Node::new('B'), j);
//! let C = Prc::new(Node::new('C'), j);
//! let mut a_link = A.link.borrow_mut(j);
//! let mut b_link = B.link.borrow_mut(j);
//! let mut c_link = C.link.borrow_mut(j);
//! *a_link = Strong(B.pclone(j));
//! *b_link = Strong(C.pclone(j));
//! *c_link = Weak(Prc::downgrade(&B, j));
//! }).unwrap();
//! ```
//!
//! The output shows that no `Node` remains in memory.
//!
//! ```text
//! A is created
//! B is created
//! C is created
//! A is dropped
//! B is dropped
//! C is dropped
//! ```
//!
//! [`pclone`]: ./struct.Prc.html#method.pclone
//!
use std::panic::RefUnwindSafe;
use std::panic::UnwindSafe;
use crate::alloc::{MemPool, PmemUsage};
use crate::cell::VCell;
use crate::clone::*;
use crate::ptr::Ptr;
use crate::stm::*;
use crate::*;
use std::fmt::{self,Debug};
use std::cmp::Ordering;
use std::hash::Hash;
use std::hash::Hasher;
use std::marker::PhantomData;
use std::mem::MaybeUninit;
use std::ops::Deref;
use std::*;
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
use crate::cell::TCell;
struct Counter<A: MemPool> {
strong: usize,
weak: usize,
#[cfg(not(any(
feature = "no_log_rc",
feature = "use_pspd",
feature = "use_vspd"
)))]
has_log: u8,
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
temp: TCell<Option<*mut Self>, A>,
phantom: PhantomData<A>
}
unsafe impl<A: MemPool> PSafe for Counter<A> {}
unsafe impl<A: MemPool> TxInSafe for Counter<A> {}
impl<A: MemPool> Debug for Counter<A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
write!(f, "{{strong: {}, weak: {}}}", self.strong, self.weak)?;
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
write!(f, "(temp: {:?})", self.temp)?;
Ok(())
}
}
pub struct PrcBox<T: ?Sized, A: MemPool> {
counter: Counter<A>,
#[cfg(not(feature = "no_volatile_pointers"))]
vlist: VCell<VWeakList, A>,
dummy: [A; 0],
value: T,
}
unsafe impl<T: ?Sized, A: MemPool> PSafe for PrcBox<T, A> {}
unsafe impl<T: ?Sized, A: MemPool> TxInSafe for PrcBox<T, A> {}
impl<T: ?Sized, A: MemPool> UnwindSafe for PrcBox<T, A> {}
impl<T: ?Sized, A: MemPool> RefUnwindSafe for PrcBox<T, A> {}
impl<T: ?Sized, A: MemPool> !VSafe for PrcBox<T, A> {}
impl<T: ?Sized, A: MemPool> !PSend for PrcBox<T, A> {}
unsafe fn set_data_ptr<T: ?Sized, U>(mut ptr: *mut T, data: *mut U) -> *mut T {
std::ptr::write(&mut ptr as *mut _ as *mut *mut u8, data as *mut u8);
ptr
}
/// A single-thread reference-counting persistent pointer. 'Prc' stands for
/// 'Persistent Reference Counted'.
///
/// The main aspect of `Prc<T>` is that its counters are transactional which
/// means that functions [`pclone`], [`downgrade`], and [`upgrade`] require a
/// [`Journal`] to operate. In other words, you need to wrap them in a
/// [`transaction`].
///
/// `Prc` uses reference counting to manage memory. Although it provides a fast
/// solution for deallocation without scan, cyclic references yield a memory
/// leak. At this point, we have not provided a static solution to detect cyclic
/// references. However, following Rust's partial solution for that, you may use
/// [`Weak`] references for reference cycles.
///
/// References to data can be strong (using [`pclone`]), weak (using [`downgrade`]),
/// or volatile weak (using [`demote`]). The first two generate NV-to-NV
/// pointers, while the last on is a V-to-NV pointer. Please see [`Weak`] and
/// [`VWeak`] for more details on their implementation and safety. Please also
/// visit the [module-level documentation](index.html) for the cyclic references
/// issue.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
/// use corundum::clone::PClone;
///
/// # #[allow(unused)]
/// P::transaction(|j| {
/// let p = Prc::<i32,P>::new(1, j);
///
/// // Create a new persistent strong reference
/// let s = p.pclone(j);
///
/// assert_eq!(*p, *s);
/// assert_eq!(2, Prc::strong_count(&p));
/// assert_eq!(0, Prc::weak_count(&p));
///
/// // Create a new persistent weak reference
/// let w = Prc::downgrade(&p, j);
/// assert_eq!(2, Prc::strong_count(&p));
/// assert_eq!(1, Prc::weak_count(&p));
///
/// // Create a new volatile weak reference
/// let v = Prc::demote(&p);
/// assert_eq!(2, Prc::strong_count(&p));
/// assert_eq!(1, Prc::weak_count(&p));
///
/// // Upgrade the persistent weak ref to a strong ref
/// let ws = w.upgrade(j).unwrap();
/// assert_eq!(3, Prc::strong_count(&p));
/// assert_eq!(1, Prc::weak_count(&p));
///
/// // Upgrade the volatile weak ref to a strong ref
/// let vs = w.upgrade(j).unwrap();
/// assert_eq!(4, Prc::strong_count(&p));
/// assert_eq!(1, Prc::weak_count(&p));
/// }).unwrap();
/// ```
///
/// [`pclone`]: #method.pclone
/// [`downgrade`]: #method.downgrade
/// [`demote`]: #method.demote
/// [`upgrade`]: ./struct.Weak.html#method.upgrade
/// [`promote`]: ./struct.Weak.html#method.promote
/// [`Journal`]: ../stm/journal/struct.Journal.html
/// [`transaction`]: ../stm/fn.transaction.html
pub struct Prc<T: PSafe + ?Sized, A: MemPool> {
ptr: Ptr<PrcBox<T, A>, A>,
phantom: PhantomData<T>,
}
impl<T: ?Sized, A: MemPool> !TxOutSafe for Prc<T, A> {}
impl<T: ?Sized, A: MemPool> !Send for Prc<T, A> {}
impl<T: ?Sized, A: MemPool> !Sync for Prc<T, A> {}
impl<T: ?Sized, A: MemPool> !VSafe for Prc<T, A> {}
impl<T: ?Sized, A: MemPool> !PSend for Prc<T, A> {}
impl<T: PSafe, A: MemPool> Prc<T, A> {
/// Constructs a new `Prc<T>`.
///
/// It also creates a `DropOnFailure` log to make sure that if the program
/// crashes, the allocation drops of recovery.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
/// }).unwrap();
/// ```
pub fn new(value: T, journal: &Journal<A>) -> Prc<T, A> {
unsafe {
let ptr = Ptr::new_unchecked(A::new(
PrcBox::<T, A> {
counter: Counter {
strong: 1,
weak: 1,
#[cfg(not(any(
feature = "no_log_rc",
feature = "use_pspd",
feature = "use_vspd"
)))]
has_log: 0,
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
temp: TCell::new_invalid(None),
phantom: PhantomData
},
#[cfg(not(feature = "no_volatile_pointers"))]
vlist: VCell::new(VWeakList::default()),
dummy: [],
value,
},
journal,
));
Self::from_inner(ptr)
}
}
/// Constructs a new `Prc` with uninitialized contents.
///
/// A `DropOnFailure` log is taken for the allocation.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let mut five = Prc::<u32,Heap>::new_uninit(j);
///
/// let five = unsafe {
/// // Deferred initialization:
/// Prc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
///
/// five.assume_init()
/// };
///
/// assert_eq!(*five, 5)
/// }).unwrap();
/// ```
pub fn new_uninit(journal: &Journal<A>) -> Prc<MaybeUninit<T>, A> {
unsafe {
Prc::from_inner(Ptr::from_mut(A::new(
PrcBox {
counter: Counter {
strong: 1,
weak: 1,
#[cfg(not(any(
feature = "no_log_rc",
feature = "use_pspd",
feature = "use_vspd"
)))]
has_log: 0,
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
temp: TCell::new_invalid(None),
phantom: PhantomData
},
#[cfg(not(feature = "no_volatile_pointers"))]
vlist: VCell::new(VWeakList::default()),
dummy: [],
value: MaybeUninit::<T>::uninit(),
},
journal,
)))
}
}
/// Constructs a new `Prc` with uninitialized contents, with the memory
/// being filled with `0` bytes.
///
/// See `MaybeUninit::zeroed` for examples of correct and incorrect usage of
/// this method.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let zero = Prc::<i32,P>::new_zeroed(j);
/// let zero = unsafe { zero.assume_init() };
///
/// assert_eq!(*zero, 0)
/// }).unwrap();
/// ```
///
pub fn new_zeroed(journal: &Journal<A>) -> Prc<mem::MaybeUninit<T>, A> {
unsafe {
let mut uninit = Self::new_uninit(journal);
std::ptr::write_bytes::<T>(Prc::get_mut_unchecked(&mut uninit).as_mut_ptr(), 0, 1);
uninit
}
}
/// Owns contents of `p` without cloning, leaving `p` untouched
pub fn from(p: Prc<T, A>) -> Self {
let res = Self::from_inner(p.ptr);
mem::forget(p);
res
}
}
impl<T: PSafe + ?Sized, A: MemPool> Prc<T, A> {
#[inline]
fn from_inner(ptr: Ptr<PrcBox<T, A>, A>) -> Self {
Prc {
ptr,
phantom: PhantomData,
}
}
#[inline(always)]
fn inner(&self) -> &PrcBox<T, A> {
self.ptr.as_ref()
}
#[allow(clippy::missing_safety_doc)]
unsafe fn from_ptr(ptr: *mut PrcBox<T, A>, j: &Journal<A>) -> Self {
let off = A::off_unchecked(ptr);
let res = Self::from_inner(Ptr::from_off_unchecked(off));
res.inc_strong(j);
res
}
}
impl<T: PSafe, A: MemPool> Prc<mem::MaybeUninit<T>, A> {
/// Converts to `Rc<T>`.
///
/// # Safety
///
/// As with [`MaybeUninit::assume_init`],
/// it is up to the caller to guarantee that the inner value
/// really is in an initialized state.
/// Calling this when the content is not yet fully initialized
/// causes immediate undefined behavior.
///
/// [`MaybeUninit::assume_init`]: ../../std/mem/union.MaybeUninit.html#method.assume_init
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// corundum::transaction(|j| {
/// let mut five = Prc::<u32,P>::new_uninit(j);
///
/// let five = unsafe {
/// // Deferred initialization:
/// Prc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
///
/// five.assume_init()
/// };
///
/// assert_eq!(*five, 5);
/// }).unwrap();
/// ```
#[inline]
pub unsafe fn assume_init(self) -> Prc<T, A> {
Prc::from_inner(mem::ManuallyDrop::new(self).ptr.cast())
}
}
impl<T: PSafe, A: MemPool> Prc<MaybeUninit<T>, A> {
#[inline]
/// Returns a mutable reference into the given `Prc`, if there are
/// no other `Prc` or `Weak` pointers to the same allocation.
///
/// Returns `None` otherwise, because it is not safe to mutate a shared
/// value. It only works for `Prc<MaybeUninit<T>>` to be able to defer the
/// initialization.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let mut five = Prc::<u32,P>::new_uninit(j);
///
/// let five = unsafe {
/// // Deferred initialization:
/// Prc::get_mut(&mut five).unwrap().as_mut_ptr().write(5);
///
/// five.assume_init()
/// };
///
/// assert_eq!(*five, 5)
/// }).unwrap();
/// ```
pub fn get_mut(this: &mut Self) -> Option<&mut MaybeUninit<T>> {
if Prc::is_unique(this) {
unsafe { Some(Prc::get_mut_unchecked(this)) }
} else {
None
}
}
#[inline]
/// Returns a mutable reference into the given `Prc`,
/// without any check.
///
/// It only works for `Prc<MaybeUninit<T>>` to be able to defer the
/// initialization.
///
/// # Safety
///
/// Any other `Prc` or `Weak` pointers to the same allocation must not be
/// dereferenced for the duration of the returned borrow.
/// This is trivially the case if no such pointers exist,
/// for example immediately after `Rc::new`.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let mut five = Prc::<i32,P>::new_uninit(j);
///
/// let five = unsafe {
/// // Deferred initialization:
/// Prc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
///
/// five.assume_init()
/// };
///
/// assert_eq!(*five, 5);
/// }).unwrap();
/// ```
pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut MaybeUninit<T> {
&mut this.ptr.value
}
}
impl<T: PSafe + ?Sized, A: MemPool> Prc<T, A> {
/// Creates a new `Weak` persistent pointer to this allocation.
///
/// The `Weak` pointer can later be [`upgrade`]d to a `Prc`.
///
/// [`upgrade`]: ./struct.Weak.html#upgrade
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
/// let _weak_five = Prc::downgrade(&five, j);
/// }).unwrap()
/// ```
pub fn downgrade(this: &Self, journal: &Journal<A>) -> Weak<T, A> {
this.inc_weak(journal);
debug_assert!(!this.ptr.is_dangling());
Weak { ptr: this.ptr }
}
/// Creates a new `Weak` volatile to this allocation.
///
/// The `Weak` pointer can later be [`promote`]d to a `Prc`.
///
/// [`promote`]: ./struct.VWeak.html#upgrade
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
/// let weak_five = Prc::demote(&five);
///
/// assert_eq!(Prc::strong_count(&five), 1);
///
/// if let Some(f) = weak_five.promote(j) {
/// assert_eq!(*f, 5);
/// assert_eq!(Prc::strong_count(&five), 2);
/// }
///
/// assert_eq!(Prc::strong_count(&five), 1);
/// }).unwrap()
/// ```
pub fn demote(this: &Self) -> VWeak<T, A> {
debug_assert!(!this.ptr.is_dangling());
VWeak::new(this)
}
/// Demote without dynamically checking transaction boundaries
pub unsafe fn unsafe_demote(&self) -> VWeak<T, A> {
debug_assert!(!self.ptr.is_dangling());
VWeak::new(self)
}
#[inline]
/// Gets the number of `Weak` pointers to this allocation.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
///
/// let _weak_five = Prc::downgrade(&five, j);
/// assert_eq!(1, Prc::weak_count(&five));
/// }).unwrap()
/// ```
pub fn weak_count(this: &Self) -> usize {
this.weak() - 1
}
#[inline]
/// Gets the number of `Weak` pointers to this allocation.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
/// use corundum::clone::PClone;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
/// let _also_five = Prc::pclone(&five, j);
/// assert_eq!(2, Prc::strong_count(&five));
/// }).unwrap();
/// ```
pub fn strong_count(this: &Self) -> usize {
this.strong()
}
#[inline]
fn is_unique(this: &Self) -> bool {
Prc::weak_count(this) == 0 && Prc::strong_count(this) == 1
}
#[inline]
/// Returns `true` if the two `Prc`s point to the same allocation
/// (in a vein similar to [`ptr::eq`]).
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
/// use corundum::clone::PClone;
///
/// P::transaction(|j| {
/// let five = Prc::new(5, j);
/// let same_five = Prc::pclone(&five, j);
/// let other_five = Prc::new(5, j);
///
/// assert!(Prc::ptr_eq(&five, &same_five));
/// assert!(!Prc::ptr_eq(&five, &other_five));
/// }).unwrap();
/// ```
///
/// [`ptr::eq`]: std::ptr::eq
pub fn ptr_eq(this: &Self, other: &Self) -> bool {
this.ptr.off() == other.ptr.off()
}
}
impl<T: PSafe, A: MemPool> PmemUsage for Prc<T, A> {
default fn size_of() -> usize {
Ptr::<PrcBox<T, A>, A>::size_of()
}
}
impl<T: PSafe + PmemUsage + ?Sized, A: MemPool> PmemUsage for Prc<T, A> {
fn size_of() -> usize {
Ptr::<PrcBox<T, A>, A>::size_of() + T::size_of()
}
}
impl<T: PSafe + ?Sized, A: MemPool> Deref for Prc<T, A> {
type Target = T;
#[inline(always)]
fn deref(&self) -> &T {
&self.inner().value
}
}
impl<T: PSafe, A: MemPool> Prc<T, A> {
/// Initializes boxed data with `value` in-place if it is `None`
///
/// This function should not be called from a transaction as it updates
/// data without taking high-level logs. If transaction is unsuccessful,
/// there is no way to recover data.
/// However, it is safe to use it outside a transaction because it uses
/// low-level logs to provide safety for a single update without drop.
/// A dynamic check at the beginning makes sure of that.
///
/// # Examples
///
/// ```
/// use corundum::default::*;
///
/// type P = Allocator;
///
/// let root = P::open::<Option<Prc<i32>>>("foo.pool", O_CF).unwrap();
///
/// Prc::initialize(&*root, 25);
///
/// let value = **root.as_ref().unwrap();
/// assert_eq!(value, 25);
/// ```
///
pub fn initialize(rc: &Option<Prc<T, A>>, value: T) -> crate::result::Result<()> {
assert!(
!Journal::<A>::is_running(),
"Prc::initialize() cannot be used inside a transaction"
);
match rc {
Some(_) => Err("already initialized".to_string()),
None => if A::valid(rc) {
unsafe {
let new = A::atomic_new(
PrcBox::<T, A> {
counter: Counter {
strong: 1,
weak: 1,
#[cfg(not(any(
feature = "no_log_rc",
feature = "use_pspd",
feature = "use_vspd"
)))]
has_log: 0,
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))]
temp: TCell::new_invalid(None),
phantom: PhantomData
},
#[cfg(not(feature = "no_volatile_pointers"))]
vlist: VCell::new(VWeakList::default()),
dummy: [],
value,
});
let pnew = Some(Prc::<T, A>::from_inner(Ptr::from_off_unchecked(new.1)));
let src = crate::utils::as_slice64(&pnew);
let mut base = A::off_unchecked(rc);
for i in src {
A::log64(base, *i, new.3);
base += 8;
}
A::perform(new.3);
}
Ok(())
} else {
Err("The object is not in the PM".to_string())
}
}
}
}
unsafe impl<#[may_dangle] T: PSafe + ?Sized, A: MemPool> Drop for Prc<T, A> {
/// Drops the `Prc` safely
///
/// This will decrement the strong reference count. If the strong reference
/// count reaches zero then the only other references (if any) are
/// `Weak`, so we `drop` the inner value on commit using a `DropOnCommit` log.
///
/// # Examples
///
/// ```
/// # use corundum::alloc::heap::*;
/// # type P = Heap;
/// use corundum::prc::Prc;
/// use corundum::clone::PClone;
///
/// struct Foo;
///
/// impl Drop for Foo {
/// fn drop(&mut self) {
/// println!("dropped!");
/// }
/// }
///
/// P::transaction(|j| {
/// let foo = Prc::new(Foo, j);
/// let foo2 = Prc::pclone(&foo, j);
///
/// drop(foo); // Doesn't print anything
/// drop(foo2); // Prints "dropped!"
/// }).unwrap();
/// ```
///
fn drop(&mut self) {
unsafe {
let journal = Journal::<A>::current(true).unwrap();
let j = &*journal.0;
self.dec_strong(j);
if self.strong() == 0 { // TODO: Add "or it is unreachable from the root"
// destroy the contained object
std::ptr::drop_in_place(&mut self.ptr.as_mut().value);
self.dec_weak(j);
if self.weak() == 0 {
A::free(self.ptr.as_mut());
#[cfg(not(feature = "no_volatile_pointers"))]
std::ptr::drop_in_place(&mut self.ptr.as_mut().vlist);
}
}
}
}
}
impl<T: PSafe + ?Sized, A: MemPool> PClone<A> for Prc<T, A> {
#[inline]
/// Creates a new strong reference to the object
///
/// It increments the strong reference counter in a failure-atomic manner.
/// When a transaction is aborted or power fails, every strong references
/// to the object should be gone, and the counters should rollback to the
/// consistent state before the transaction.
///
/// # Examples
///
/// ```
/// # use corundum::default::*;
/// # type P = Allocator;
/// let root = P::open::<Prc<i32>>("foo.pool", O_CF).unwrap();
///
/// let _ = P::transaction(|j| {
/// let _n1 = root.pclone(j);
/// let _n2 = root.pclone(j);
/// let _n3 = root.pclone(j);
/// assert_eq!(4, Prc::strong_count(&root));
/// panic!("abort")
/// });
///
/// assert_eq!(1, Prc::strong_count(&root));
/// ```
fn pclone(&self, journal: &Journal<A>) -> Prc<T, A> {
self.inc_strong(journal);
Self::from_inner(self.ptr)
}
}
impl<T: RootObj<A> + PSafe, A: MemPool> RootObj<A> for Prc<T, A> {
#[inline]
default fn init(journal: &Journal<A>) -> Prc<T, A> {
Prc::new(T::init(journal), journal)
}
}
// impl<T: Default + PSafe + ?Sized, A: MemPool> RootObj<A> for Prc<T, A> {
// #[inline]
// default fn init(journal: &Journal<A>) -> Prc<T, A> {
// Prc::new(T::default(), journal)
// }
// }
trait RcEqIdent<T: PartialEq + PSafe + ?Sized, A: MemPool> {
fn eq(&self, other: &Prc<T, A>) -> bool;
fn ne(&self, other: &Prc<T, A>) -> bool;
}
impl<T: PartialEq + PSafe + ?Sized, A: MemPool> RcEqIdent<T, A> for Prc<T, A> {
#[inline]
fn eq(&self, other: &Prc<T, A>) -> bool {
**self == **other
}
#[inline]
fn ne(&self, other: &Prc<T, A>) -> bool {
**self != **other
}
}
impl<T: PartialEq + PSafe + ?Sized, A: MemPool> PartialEq for Prc<T, A> {
#[inline]
fn eq(&self, other: &Prc<T, A>) -> bool {
RcEqIdent::eq(self, other)
}
}
impl<T: Eq + PSafe + ?Sized, A: MemPool> Eq for Prc<T, A> {}
impl<T: PartialOrd + PSafe + ?Sized, A: MemPool> PartialOrd for Prc<T, A> {
#[inline(always)]
fn partial_cmp(&self, other: &Prc<T, A>) -> Option<Ordering> {
(**self).partial_cmp(&**other)
}
#[inline(always)]
fn lt(&self, other: &Prc<T, A>) -> bool {
**self < **other
}
#[inline(always)]
fn le(&self, other: &Prc<T, A>) -> bool {
**self <= **other
}
#[inline(always)]
fn gt(&self, other: &Prc<T, A>) -> bool {
**self > **other
}
#[inline(always)]
fn ge(&self, other: &Prc<T, A>) -> bool {
**self >= **other
}
}
impl<T: Ord + PSafe + ?Sized, A: MemPool> Ord for Prc<T, A> {
#[inline]
fn cmp(&self, other: &Prc<T, A>) -> Ordering {
(**self).cmp(&**other)
}
}
impl<T: Hash + PSafe + ?Sized, A: MemPool> Hash for Prc<T, A> {
fn hash<H: Hasher>(&self, state: &mut H) {
(**self).hash(state);
}
}
impl<T: fmt::Display + PSafe + ?Sized, A: MemPool> fmt::Display for Prc<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&**self, f)
}
}
impl<T: fmt::Debug + PSafe + ?Sized, A: MemPool> fmt::Debug for Prc<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.deref().fmt(f)
}
}
impl<T: PSafe + ?Sized, A: MemPool> fmt::Pointer for Prc<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Pointer::fmt(&(&**self as *const T), f)
}
}
/// `Weak` is a version of [`Prc`] that holds a non-owning reference to the
/// managed allocation. The allocation is accessed by calling [`upgrade`] on the `Weak`
/// pointer, which returns an [`Option`]`<`[`Prc`]`<T>>`.
///
/// Since a `Weak` reference does not count towards ownership, it will not
/// prevent the value stored in the allocation from being dropped, and `Weak` itself makes no
/// guarantees about the value still being present. Thus it may return [`None`]
/// when [`upgrade`]d. Note however that a `Weak` reference *does* prevent the allocation
/// itself (the backing store) from being deallocated.
///
/// A `Weak` pointer is useful for keeping a temporary reference to the allocation
/// managed by [`Prc`] without preventing its inner value from being dropped. It is also used to
/// prevent circular references between [`Prc`] pointers, since mutual owning references
/// would never allow either [`Prc`] to be dropped. For example, a tree could
/// have strong [`Prc`] pointers from parent nodes to children, and `Weak`
/// pointers from children back to their parents.
///
/// The typical way to obtain a `Weak` pointer is to call [`Prc::downgrade`].
///
/// [`Prc`]: struct.Prc.html
/// [`Prc::downgrade`]: ./struct.Prc.html#method.downgrade
/// [`upgrade`]: #method.upgrade
/// [`Option`]: std::option::Option
/// [`None`]: std::option::Option::None
pub struct Weak<T: PSafe + ?Sized, A: MemPool> {
ptr: Ptr<PrcBox<T, A>, A>,
}
impl<T: ?Sized, A: MemPool> !TxOutSafe for Weak<T, A> {}
impl<T: ?Sized, A: MemPool> !Send for Weak<T, A> {}
impl<T: ?Sized, A: MemPool> !Sync for Weak<T, A> {}
impl<T: ?Sized, A: MemPool> !VSafe for Weak<T, A> {}
impl<T: ?Sized, A: MemPool> !PSend for Weak<T, A> {}
impl<T: PSafe, A: MemPool> Weak<T, A> {
pub fn as_raw(&self) -> *const T {
match self.inner() {
None => std::ptr::null(),
Some(inner) => {
let offset = data_offset_sized::<T, A>();
let ptr = inner as *const PrcBox<T, A>;
// Note: while the pointer we create may already point to dropped value, the
// allocation still lives (it must hold the weak point as long as we are alive).
// Therefore, the offset is OK to do, it won't get out of the allocation.
let ptr = unsafe { (ptr as *const u8).offset(offset) };
ptr as *const T
}
}
}
pub fn into_raw(self) -> *const T {
let result = self.as_raw();
mem::forget(self);
result
}
#[allow(clippy::missing_safety_doc)]
pub unsafe fn from_raw(ptr: *const T) -> Self {
if ptr.is_null() {
Self::new()
} else {
// See Rc::from_raw for details
let offset = data_offset::<T, A>(ptr);
let fake_ptr = ptr as *mut PrcBox<T, A>;
let ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
Weak {
ptr: Ptr::from_raw(ptr),
}
}
}
}
impl<T: PSafe + ?Sized, A: MemPool> Weak<T, A> {
/// Creates a new dangling weak pointer
pub fn new() -> Weak<T, A> {
Weak {
ptr: Ptr::dangling(),
}
}
pub fn upgrade(&self, journal: &Journal<A>) -> Option<Prc<T, A>> {
let inner = self.inner()?;
if inner.strong() == 0 {
None
} else {
inner.inc_strong(journal);
Some(Prc::from_inner(self.ptr))
}
}
pub fn strong_count(&self) -> usize {
if let Some(inner) = self.inner() {
inner.strong()
} else {
0
}
}
pub fn weak_count(&self) -> Option<usize> {
self.inner().map(|inner| {
if inner.strong() > 0 {
inner.weak() - 1 // subtract the implicit weak ptr
} else {
inner.weak()
}
})
}
#[inline]
fn inner(&self) -> Option<&PrcBox<T, A>> {
if self.ptr.is_dangling() {
None
} else {
Some(self.ptr.get_mut())
}
}
#[inline]
pub fn ptr_eq(&self, other: &Self) -> bool {
self.ptr == other.ptr
}
}
impl<T: PSafe + ?Sized, A: MemPool> Drop for Weak<T, A> {
fn drop(&mut self) {
if let Some(inner) = self.inner() {
let journal = unsafe { &*Journal::<A>::current(true).unwrap().0 };
inner.dec_weak(journal);
if inner.weak() == 0 {
unsafe {
A::free(self.ptr.as_mut());
#[cfg(not(feature = "no_volatile_pointers"))]
std::ptr::drop_in_place(&mut self.ptr.as_mut().vlist);
}
}
}
}
}
impl<T: PSafe + ?Sized, A: MemPool> PClone<A> for Weak<T, A> {
#[inline]
fn pclone(&self, journal: &Journal<A>) -> Weak<T, A> {
if let Some(inner) = self.inner() {
inner.inc_weak(journal)
}
Weak { ptr: self.ptr }
}
}
impl<T: PSafe + fmt::Debug + ?Sized, A: MemPool> fmt::Debug for Weak<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "(Weak)")
}
}
impl<T: PSafe + ?Sized, A: MemPool> RootObj<A> for Weak<T, A> {
fn init(_: &Journal<A>) -> Weak<T, A> {
Weak::new()
}
}
trait PrcBoxPtr<T: PSafe + ?Sized, A: MemPool> {
#[allow(clippy::mut_from_ref)]
fn count(&self) -> &mut Counter<A>;
#[inline]
fn strong(&self) -> usize {
self.count().strong
}
#[inline]
#[cfg(not(feature = "no_log_rc"))]
fn log_count(&self, journal: &Journal<A>) {
let inner = self.count();
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] {
if inner.temp.is_none() {
if let Some(p) = journal.draft(inner) {
inner.temp.replace(p);
}
}
}
#[cfg(not(any(feature = "use_pspd", feature = "use_vspd")))] {
if inner.has_log == 0 {
unsafe {
inner.create_log(&*journal, Notifier::NonAtomic(Ptr::from_ref(&inner.has_log)));
}
}
}
}
#[inline]
fn inc_strong(&self, _journal: &Journal<A>) {
let inner = self.count();
let strong = inner.strong;
if strong == 0 || strong == usize::max_value() {
std::process::abort();
}
#[cfg(not(feature = "no_log_rc"))]
self.log_count(_journal);
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *inner.temp {
(*inner).strong += 1;
return;
}
}
inner.strong += 1;
}
#[inline]
fn dec_strong(&self, _journal: &Journal<A>) {
let inner = self.count();
#[cfg(not(feature = "no_log_rc"))]
self.log_count(_journal);
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *inner.temp {
(*inner).strong -= 1;
return;
}
}
inner.strong -= 1;
}
#[inline]
fn weak(&self) -> usize {
self.count().weak
}
#[inline]
fn inc_weak(&self, _journal: &Journal<A>) {
let inner = self.count();
let weak = self.weak();
if weak == 0 || weak == usize::max_value() {
std::process::abort();
}
#[cfg(not(feature = "no_log_rc"))]
self.log_count(_journal);
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *inner.temp {
(*inner).weak += 1;
return;
}
}
inner.weak += 1;
}
#[inline]
fn dec_weak(&self, _journal: &Journal<A>) {
let inner = self.count();
#[cfg(not(feature = "no_log_rc"))]
self.log_count(_journal);
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *inner.temp {
(*inner).strong -= 1;
return;
}
}
inner.weak -= 1;
}
}
impl<T: PSafe + ?Sized, A: MemPool> PrcBoxPtr<T, A> for Prc<T, A> {
#[inline(always)]
fn count(&self) -> &mut Counter<A> {
let ret = &mut self.ptr.get_mut().counter;
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *ret.temp {
return &mut *inner;
}
}
ret
}
}
impl<T: PSafe + ?Sized, A: MemPool> PrcBoxPtr<T, A> for PrcBox<T, A> {
#[inline(always)]
fn count(&self) -> &mut Counter<A> {
let ret = unsafe {
let ptr: *const Self = self;
let ptr: *mut Self = ptr as *mut Self;
let rcbox: &mut Self = &mut *ptr;
&mut rcbox.counter
};
#[cfg(any(feature = "use_pspd", feature = "use_vspd"))] unsafe {
if let Some(inner) = *ret.temp {
return &mut *inner;
}
}
ret
}
}
impl<T: PSafe + ?Sized, A: MemPool> borrow::Borrow<T> for Prc<T, A> {
fn borrow(&self) -> &T {
&self.inner().value
}
}
impl<T: PSafe + ?Sized, A: MemPool> AsRef<T> for Prc<T, A> {
fn as_ref(&self) -> &T {
&self.inner().value
}
}
impl<T: PSafe + ?Sized, A: MemPool> Unpin for Prc<T, A> {}
unsafe fn data_offset<T: ?Sized, A: MemPool>(ptr: *const T) -> isize {
data_offset_align::<A>(mem::align_of_val(&*ptr))
}
fn data_offset_sized<T, A: MemPool>() -> isize {
data_offset_align::<A>(mem::align_of::<T>())
}
#[inline]
fn data_offset_align<A: MemPool>(align: usize) -> isize {
let layout = std::alloc::Layout::new::<PrcBox<(), A>>();
(layout.size() + layout.padding_needed_for(align)) as isize
}
/// `VWeak` is a version of [`Prc`] that holds a non-owning reference to the
/// managed allocation in the volatile heap. The allocation is accessed by
/// calling [`promote`] on the `VWeak` pointer, which returns an
/// [`Option`]`<`[`Prc`]`<T>>`.
///
/// Since a `VWeak` reference does not count towards ownership, it will not
/// prevent the value stored in the allocation from being dropped, and `VWeak`
/// itself makes no guarantees about the value still being present. Thus it may
/// return [`None`] when [`promote`]d. Note however that a `VWeak` reference,
/// unlike [`Weak`], *does NOT* prevent the allocation itself (the backing
/// store) from being deallocated.
///
/// A `VWeak` pointer is useful for keeping a temporary reference to the
/// persistent allocation managed by [`Prc`] without preventing its inner value
/// from being dropped from ... It is also used to
/// prevent circular references between [`Prc`] pointers, since mutual owning references
/// would never allow either [`Prc`] to be dropped. For example, a tree could
/// have strong [`Prc`] pointers from parent nodes to children, and `Weak`
/// pointers from children back to their parents.
///
/// The typical way to obtain a `VWeak` pointer is to call [`Prc::demote`].
///
/// [`Prc`]: struct.Prc.html
/// [`Weak`]: struct.Weak.html
/// [`Prc::downgrade`]: ./struct.Prc.html#method.downgrade
/// [`promote`]: #method.promote
/// [`Option`]: std::option::Option
/// [`None`]: std::option::Option::None
pub struct VWeak<T: ?Sized, A: MemPool> {
ptr: *const PrcBox<T, A>,
valid: *mut VWeakValid,
gen: u32,
}
impl<T: ?Sized, A: MemPool> !Send for VWeak<T, A> {}
impl<T: ?Sized, A: MemPool> !Sync for VWeak<T, A> {}
impl<T: ?Sized, A: MemPool> !PSend for VWeak<T, A> {}
impl<T: ?Sized, A: MemPool> UnwindSafe for VWeak<T, A> {}
impl<T: ?Sized, A: MemPool> RefUnwindSafe for VWeak<T, A> {}
unsafe impl<T: ?Sized, A: MemPool> TxInSafe for VWeak<T, A> {}
unsafe impl<T: ?Sized, A: MemPool> TxOutSafe for VWeak<T, A> {}
unsafe impl<T: ?Sized, A: MemPool> PSafe for VWeak<T, A> {}
impl<T: PSafe + ?Sized, A: MemPool> VWeak<T, A> {
fn new(prc: &Prc<T, A>) -> VWeak<T, A> {
let list = prc.ptr.vlist.as_mut();
VWeak {
ptr: prc.ptr.as_ref(),
valid: list.append(),
gen: A::gen(),
}
}
pub fn null() -> VWeak<T, A> where T: Sized {
VWeak {
ptr: std::ptr::null(),
valid: std::ptr::null_mut(),
gen: u32::MAX,
}
}
pub fn promote(&self, journal: &Journal<A>) -> Option<Prc<T, A>> {
let inner = self.inner()?;
let strong = inner.counter.strong;
if strong == 0 {
None
} else {
unsafe { Some(Prc::from_ptr(self.ptr as *const _ as *mut _, journal)) }
}
}
#[inline]
fn inner(&self) -> Option<&PrcBox<T, A>> {
unsafe {
if self.gen != A::gen() {
None
} else if !(*self.valid).valid {
None
} else {
Some(&*self.ptr)
}
}
}
}
impl<T: PSafe + ?Sized, A: MemPool> Clone for VWeak<T, A> {
fn clone(&self) -> Self {
if self.gen == A::gen() {
unsafe {
if (*self.valid).valid {
let list = (*self.ptr).vlist.as_mut();
return VWeak {
ptr: self.ptr,
valid: list.append(),
gen: self.gen,
};
}
}
}
VWeak {
ptr: self.ptr,
valid: self.valid,
gen: self.gen,
}
}
}
impl<T: ?Sized, A: MemPool> Drop for VWeak<T, A> {
fn drop(&mut self) {
unsafe {
let this = &mut *self.valid;
if A::is_open() {
if self.gen == A::gen() {
if !this.list.is_null() {
let head = &mut (*this.list).head;
if this.prev.is_null() {
*head = this.next;
} else {
(*this.prev).next = this.next;
}
if !this.next.is_null() {
(*this.next).prev = this.prev;
}
}
}
}
}
}
}
struct VWeakValid {
valid: bool,
next: *mut VWeakValid,
prev: *mut VWeakValid,
list: *mut VWeakList,
}
struct VWeakList {
head: *mut VWeakValid,
}
impl VWeakList {
fn append(&mut self) -> *mut VWeakValid {
let new = Box::into_raw(Box::new(VWeakValid {
valid: true,
next: self.head,
prev: std::ptr::null_mut(),
list: self as *mut Self,
}));
if !self.head.is_null() {
unsafe {
(*self.head).prev = new;
}
}
self.head = new;
new
}
}
impl Default for VWeakList {
fn default() -> Self {
VWeakList {
head: std::ptr::null_mut(),
}
}
}
impl Drop for VWeakList {
fn drop(&mut self) {
unsafe {
let mut curr = self.head;
while !curr.is_null() {
(*curr).valid = false;
(*curr).list = std::ptr::null_mut();
curr = (*curr).next;
}
}
}
}