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//! Atomic `Option<Box<T>>` that can give references (but only be filled once) //! //! Since `FillOnceAtomicOption` can only be filled once it's safe to provide access to `Option<&T>` //! //! This is ideal for a iterator or some consumer that doesn't actually consume the data use crate::prelude::*; use std::fmt::{self, Debug, Formatter, Pointer}; use std::{ptr::NonNull, sync::atomic::Ordering}; /// Atomic abstraction of a `Option<Box<T>>` that can provide access to a `Option<&T>` /// /// This is ideal for a iterator or some consumer that doesn't actually consume the data /// /// To make that possible the API is heavily limited (can only write to it through `try_store`) pub struct FillOnceAtomicOption<T>(AtomicOption<T>); impl<T> FillOnceAtomicOption<T> { /// Creates new `FillOnceAtomicOption` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let empty: FillOnceAtomicOption<()> = FillOnceAtomicOption::new(None); /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicOption::new(Box::new(10)); /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub fn new<V>(data: V) -> Self where V: Into<Option<Box<T>>>, { Self::from(data.into()) } /// Stores new value if `FillOnceAtomicOption` was not initialized (contains a `None`) /// /// This operation is implemented as a single atomic `compare_and_swap`. /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let option = FillOnceAtomicOption::default(); /// let old = option.try_store(5, Ordering::Relaxed); /// assert!(old.is_ok()); /// assert_eq!(option.get_ref(Ordering::Relaxed), Some(&5)); /// /// let failed_to_store = option.try_store(10, Ordering::Relaxed); /// assert!(failed_to_store.is_err()); /// assert_eq!(option.get_ref(Ordering::Relaxed), Some(&5)); /// ``` #[inline] pub fn try_store<V>(&self, data: V, order: Ordering) -> Result<(), NotEmpty> where V: Into<Box<T>>, { self.0.try_store(data, order) } /// Replaces `FillOnceAtomicOption` value with `None` returning old value /// /// As opposed to `take` from [`AtomicOption`] /// /// [`AtomicOption`]: ./struct.AtomicOption.html#method.take /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let mut option = FillOnceAtomicOption::from(5); /// assert_eq!(option.take(Ordering::Relaxed), Some(Box::new(5))); /// assert_eq!(option.take(Ordering::Relaxed), None); /// # assert_eq!(option.take(Ordering::Relaxed), None); /// ``` #[inline] pub fn take(&mut self, order: Ordering) -> Option<Box<T>> { info!("empty()"); self.0.take(order) } } impl<T: Copy> FillOnceAtomicOption<T> { /// Returns a copy of the wrapped `T` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let empty: FillOnceAtomicOption<()> = FillOnceAtomicOption::new(None); /// assert_eq!(empty.load(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicOption::from(10); /// assert_eq!(filled.load(Ordering::Relaxed), Some(10)); /// ``` #[inline] pub fn load(&self, order: Ordering) -> Option<T> { self.get_ref(order).cloned() } } impl<T> FillOnceAtomicOption<T> { /// Atomically extracts a reference to the element stored /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let empty: FillOnceAtomicOption<()> = FillOnceAtomicOption::new(None); /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicOption::from(10); /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub fn get_ref<'a>(&'a self, order: Ordering) -> Option<&'a T> { let raw = self.0.get_raw(order); debug!("FillOnceAtomicOption get_ref: {:p}", raw); // This specific API ensures that the pointer is either `null`or won't ever change, so we can get a ref to it (with the same lifetime as `Self`) NonNull::new(raw).map(|nn| unsafe { &*nn.as_ptr() }) } /// Converts itself into a `Option<Box<T>>` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// let ten = FillOnceAtomicOption::from(10); /// assert_eq!(ten.into_inner().map(|a| *a), Some(10)); /// ``` #[inline] pub fn into_inner(self) -> Option<Box<T>> { self.0.into_inner() } /// Creates new `FillOnceAtomicOption` based on a raw pointer /// /// # Safety /// /// Unsafe because it uses a raw pointer, so it can't be sure of its origin (and ownership) /// /// You must own the pointer to call this /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::{sync::atomic::Ordering, ptr::null_mut}; /// let empty = unsafe { FillOnceAtomicOption::<()>::from_raw(null_mut()) }; /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let filled = unsafe { FillOnceAtomicOption::from_raw(Box::into_raw(10.into())) }; /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub unsafe fn from_raw(ptr: *mut T) -> Self { FillOnceAtomicOption(AtomicOption::from_raw(ptr)) } /// Atomically extracts the stored pointer /// /// If pointer returned is not null it's safe to deref as long as you don't drop the `FillOnceAtomicOption` /// /// # Safety /// /// To deref it you must ensure that it's not `null`, the `FillOnceAtomicOption` wasn't dropped /// /// Returns `null` if `FillOnceAtomicOption` is empty (was not initialized) /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicOption; /// # env_logger::init(); /// use std::{sync::atomic::Ordering, ptr::null_mut, ops::Deref}; /// let empty: FillOnceAtomicOption<()> = FillOnceAtomicOption::new(None); /// assert_eq!(empty.get_raw(Ordering::Relaxed), null_mut()); /// /// let filled = FillOnceAtomicOption::from(10); /// assert_eq!(unsafe { (&*filled.get_raw(Ordering::Relaxed)).deref() }, &10); /// ``` #[inline] pub fn get_raw(&self, order: Ordering) -> *mut T { self.0.get_raw(order) } } impl<T> Default for FillOnceAtomicOption<T> { #[inline] fn default() -> Self { Self::new(None) } } impl<T> From<T> for FillOnceAtomicOption<T> { #[inline] fn from(value: T) -> Self { Self::from(Box::new(value)) } } impl<T> From<Box<T>> for FillOnceAtomicOption<T> { #[inline] fn from(into_ptr: Box<T>) -> Self { Self::from(Some(into_ptr)) } } impl<T> From<Option<T>> for FillOnceAtomicOption<T> { #[inline] fn from(into_ptr: Option<T>) -> Self { Self::from(into_ptr.map(Box::new)) } } impl<T> From<Option<Box<T>>> for FillOnceAtomicOption<T> { #[inline] fn from(into_ptr: Option<Box<T>>) -> Self { trace!("From<Option<Box<T>>"); FillOnceAtomicOption(AtomicOption::from(into_ptr)) } } impl<T> From<AtomicOption<T>> for FillOnceAtomicOption<T> { #[inline] fn from(atomic: AtomicOption<T>) -> Self { trace!("From AtomicOption"); Self::from(atomic.into_inner()) } } impl<T> From<Atomic<T>> for FillOnceAtomicOption<T> { #[inline] fn from(atomic: Atomic<T>) -> Self { trace!("From Atomic"); Self::from(atomic.into_inner()) } } impl<T> Pointer for FillOnceAtomicOption<T> { #[inline] fn fmt(&self, f: &mut Formatter) -> fmt::Result { Debug::fmt(&self.get_raw(Ordering::Relaxed), f) } } impl<T: Debug> Debug for FillOnceAtomicOption<T> { #[inline] fn fmt(&self, f: &mut Formatter) -> fmt::Result { f.debug_tuple("FillOnceAtomicOption") .field(&self.get_ref(Ordering::Relaxed)) .finish() } } #[cfg(test)] mod tests { use super::*; #[test] fn fill_once_ref() { let atomic = FillOnceAtomicOption::from(Some(10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); assert_eq!(atomic.get_ref(Ordering::Relaxed), Some(&10)); } #[test] fn test_send() { fn assert_send<T: Send>() {} assert_send::<FillOnceAtomicOption<()>>(); } #[test] fn test_sync() { fn assert_sync<T: Sync>() {} assert_sync::<FillOnceAtomicOption<()>>(); } }