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//! Thread-safe appendable list that can create a lock-free iterator
use crate::{node::Node, prelude::*};
use parking_lot::RwLock;
use std::fmt::{self, Debug, Formatter};
use std::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
use std::{iter::Extend, iter::FromIterator, mem::swap, ptr::null_mut, ptr::NonNull, sync::Arc};
/// Holds actual [`VoluntaryServitude`]'s data, abstracts safety
///
/// [`VoluntaryServitude`]: ./struct.VoluntaryServitude.html
#[derive(Debug)]
pub struct Inner<T> {
/// Number of elements inside `Inner`
size: AtomicUsize,
/// First node in `Inner`
first_node: FillOnceAtomicOption<Node<T>>,
/// Last node in `Inner`
last_node: AtomicPtr<Node<T>>,
}
unsafe impl<T: Sync> Sync for Inner<T> {}
unsafe impl<T: Send> Send for Inner<T> {}
impl<T> Default for Inner<T> {
#[inline]
fn default() -> Self {
trace!("default()");
Self {
size: AtomicUsize::new(0),
first_node: FillOnceAtomicOption::default(),
last_node: AtomicPtr::new(null_mut()),
}
}
}
impl<T> Inner<T> {
/// Atomically extracts pointer to first node
#[inline]
pub fn first_node(&self) -> Option<NonNull<Node<T>>> {
let nn = NonNull::new(self.first_node.get_raw(Ordering::SeqCst));
trace!("first_node() = {:?}", nn);
nn
}
/// Atomically extracts pointer to last node
#[inline]
pub fn last_node(&self) -> Option<NonNull<Node<T>>> {
let nn = NonNull::new(self.last_node.load(Ordering::SeqCst));
trace!("last_node() = {:?}", nn);
nn
}
/// Atomically extracts `Inner`'s size
#[inline]
pub fn len(&self) -> usize {
let len = self.size.load(Ordering::SeqCst);
trace!("len() = {}", len);
len
}
/// Atomically checks if `Inner`'s size is `0`
#[inline]
pub fn is_empty(&self) -> bool {
trace!("is_empty()");
self.len() == 0
}
/// Set first node in chain
#[inline]
fn set_first(&self, node: Box<Node<T>>) -> Result<(), NotEmpty> {
trace!("set_first({:p})", node);
let ret = self.first_node.try_store(node, Ordering::SeqCst);
debug_assert!(ret.is_ok());
ret
}
/// Swaps last node, returning old one
#[inline]
fn swap_last(&self, ptr: *mut Node<T>) -> Option<NonNull<Node<T>>> {
trace!("swap_last({:p})", ptr);
NonNull::new(self.last_node.swap(ptr, Ordering::SeqCst))
}
/// Unsafelly append a `Node<T>` chain to `Inner<T>`
#[inline]
pub unsafe fn append_chain(&self, first: *mut Node<T>, last: *mut Node<T>, length: usize) {
debug!("append_chain({:p}, {:p}, {})", first, last, length);
if let Some(nn) = self.swap_last(last) {
#[allow(unused)]
let old = nn.as_ref().try_store_next(Box::from_raw(first));
debug_assert!(old.is_ok());
} else {
let _ = self.set_first(Box::from_raw(first));
}
info!("Increased size by {}", length);
let _ = self.size.fetch_add(length, Ordering::SeqCst);
}
/// Appends node to end of `Inner` (inserts first_node if it's the first)
#[inline]
pub fn append(&self, value: T) {
let ptr = Node::new(value).into_ptr();
unsafe { self.append_chain(ptr, ptr, 1) };
}
#[inline]
/// Extracts chain and drops itself without dropping it
pub fn into_inner(mut self) -> (usize, *mut Node<T>, *mut Node<T>) {
trace!("into_inner()");
let size = self.size.swap(0, Ordering::SeqCst);
let first = self.first_node.take(Ordering::SeqCst).into_ptr();
let last = self.last_node.swap(null_mut(), Ordering::SeqCst);
(size, first, last)
}
}
impl<T> FromIterator<T> for Inner<T> {
#[inline]
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
trace!("FromIterator<T>");
let inner = Self::default();
for element in iter {
inner.append(element);
}
inner
}
}
/// Appendable list with lock-free iterator (also called [`VS`])
///
///
/// # Examples
/// - [`Single-thread`]
/// - [`Multi-producer, multi-consumer`]
///
/// [`Single-thread`]: #single-thread
/// [`Multi-producer, multi-consumer`]: #multi-producer-multi-consumer
/// [`VS`]: ./type.VS.html
///
/// # Single thread
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let (a, b, c) = (0usize, 1usize, 2usize);
/// // VS alias to VoluntaryServitude
/// // vs! alias to voluntary_servitude! (and operates like vec!)
/// let list = vs![a, b, c];
/// assert_eq!(list.iter().collect::<Vec<_>>(), vec![&a, &b, &c]);
///
/// // Current VS's length
/// // Be careful with race conditions since the value, when used, may not be true anymore
/// assert_eq!(list.len(), 3);
///
/// // The 'iter' method makes a lock-free iterator (Iter)
/// for (index, element) in list.iter().enumerate() {
/// assert_eq!(index, *element);
/// }
///
/// // You can get the current iteration index
/// // iter.index() == iter.len() means iteration ended (iter.next() == None)
/// let mut iter = &mut list.iter();
/// assert_eq!(iter.index(), 0);
/// assert_eq!(iter.next(), Some(&0));
/// assert_eq!(iter.index(), 1);
///
/// // List can also be cleared (but current iterators are not affected)
/// list.clear();
///
/// assert_eq!(iter.len(), 3);
/// assert_eq!(list.len(), 0);
/// assert_eq!(list.iter().len(), 0);
/// assert_eq!((&mut list.iter()).next(), None);
///
/// println!("Single thread example ended without errors");
/// ```
///
/// # Multi-producer, multi-consumer
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// use std::{sync::Arc, thread::spawn};
///
/// const CONSUMERS: usize = 8;
/// const PRODUCERS: usize = 4;
/// const ELEMENTS: usize = 10_000_000;
///
/// fn main() {
/// let list = Arc::new(vs![]);
/// let mut handlers = vec![];
///
/// // Creates producer threads to insert 10k elements
/// for _ in 0..PRODUCERS {
/// let l = Arc::clone(&list);
/// handlers.push(spawn(move || {
/// let _ = (0..ELEMENTS).map(|i| l.append(i)).count();
/// }));
/// }
///
/// // Creates consumer threads to print number of elements
/// // Until all of them are inserted
/// for _ in 0..CONSUMERS {
/// const TOTAL: usize = PRODUCERS * ELEMENTS;
/// let consumer = Arc::clone(&list);
/// handlers.push(spawn(move || loop {
/// let count = consumer.iter().count();
/// println!("{} elements", count);
/// if count >= TOTAL { break };
/// }));
/// }
///
/// // Join threads
/// for handler in handlers.into_iter() {
/// handler.join().expect("Failed to join thread");
/// }
///
/// println!("Multi-thread example ended without errors");
/// }
/// ```
pub struct VoluntaryServitude<T>(RwLock<Arc<Inner<T>>>);
/// [`VoluntaryServitude`]'s alias
///
/// [`VoluntaryServitude`]: ./struct.VoluntaryServitude.html
pub type VS<T> = VoluntaryServitude<T>;
impl<T> VoluntaryServitude<T> {
/// Exposes internal `Inner` to simplify implementations of other types based on it (like for `diesel` support)
#[cfg(feature = "diesel-traits")]
#[inline]
pub(crate) fn inner(&self) -> Arc<Inner<T>> {
self.0.read().clone()
}
/// Creates new empty `VS` (like `Default` trait)
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # use voluntary_servitude::VS;
/// # env_logger::init();
/// let list: VS<()> = VS::new();
/// assert!(list.is_empty());
/// ```
#[inline]
pub fn new() -> Self {
trace!("new()");
Self::default()
}
/// Inserts element after last node
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![];
/// let mut iter = list.iter();
///
/// list.append(3);
/// // Iter doesn't grow if it's empty (originally empty or was consumed)
/// assert!(iter.is_empty());
///
/// iter = list.iter();
/// list.append(8);
/// // Iter grows if it has not been consumed
/// assert_eq!(iter.collect::<Vec<_>>(), vec![&3, &8]);
/// ```
#[inline]
pub fn append(&self, value: T) {
self.0.read().append(value);
}
/// Makes lock-free iterator based on `VS`
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![3, 2];
/// assert_eq!(list.iter().collect::<Vec<_>>(), vec![&3, &2]);
///
/// for (element, expected) in list.iter().zip(&[3, 2][..]) {
/// assert_eq!(element, expected);
/// }
/// ```
#[inline]
pub fn iter(&self) -> Iter<T> {
debug!("iter()");
Iter::from(self.0.read().clone())
}
/// Returns current size, be careful with race conditions when using it since other threads can change it right after the read
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![3, 2];
/// assert_eq!(list.len(), 2);
/// list.append(5);
/// assert_eq!(list.len(), 3);
/// list.clear();
/// assert_eq!(list.len(), 0);
/// ```
#[inline]
pub fn len(&self) -> usize {
self.0.read().len()
}
/// Checks if `VS` is currently empty, be careful with race conditions when using it since other threads can change it right after the read
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![];
/// assert!(list.is_empty());
/// list.append(());
/// assert!(!list.is_empty());
/// ```
#[inline]
pub fn is_empty(&self) -> bool {
self.0.read().is_empty()
}
/// Clears list (iterators referencing the old chain will still work)
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![3, 2];
/// let iter = list.iter();
/// list.clear();
/// assert_eq!(iter.len(), 2);
/// assert_eq!(list.len(), 0);
/// assert_eq!(list.iter().len(), 0);
/// ```
#[inline]
pub fn clear(&self) {
debug!("clear()");
*self.0.write() = Arc::new(Inner::default());
}
/// Clears list returning iterator to it (other iterators referencing the old chain will still work)
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![3, 2];
/// let iter = list.empty();
/// assert_eq!(iter.len(), 2);
/// assert_eq!(list.len(), 0);
/// assert_eq!(list.iter().len(), 0);
/// ```
#[inline]
pub fn empty(&self) -> Iter<T> {
debug!("empty()");
let old = Self::default();
self.swap(&old);
old.iter()
}
/// Swaps two `VS`
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![3, 2];
/// let list2 = vs![5, 4];
/// list.swap(&list2);
/// assert_eq!(list.iter().collect::<Vec<_>>(), vec![&5, &4]);
/// assert_eq!(list2.iter().collect::<Vec<_>>(), vec![&3, &2]);
/// ```
#[inline]
pub fn swap(&self, other: &Self) {
debug!("swap({:p})", other);
swap(&mut *self.0.write(), &mut *other.0.write());
}
/// Extends `VS` like the `Extend` trait, but without a mutable reference
///
/// ```rust
/// # #[macro_use] extern crate voluntary_servitude;
/// # env_logger::init();
/// let list = vs![1, 2, 3];
/// list.extend(vec![4, 5, 6]);
/// assert_eq!(list.iter().collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5, &6]);
///
/// // You can extend from another `VS` if you clone (or copy) each element
/// let list = vs![1, 2, 3];
/// list.extend(vs![4, 5, 6].iter().cloned());
/// assert_eq!(list.iter().collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5, &6]);
/// # let list = vs![1, 2, 3];
/// # list.extend(vec![&4, &5, &6].into_iter().cloned());
/// # assert_eq!(list.iter().collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5, &6]);
/// ```
#[inline]
pub fn extend<I: IntoIterator<Item = T>>(&self, iter: I) {
trace!("extend()");
let (size, first, last) = Inner::from_iter(iter).into_inner();
unsafe { self.0.read().append_chain(first, last, size) };
}
}
impl<T> Default for VoluntaryServitude<T> {
#[inline]
fn default() -> Self {
trace!("default()");
Self::from(Inner::default())
}
}
impl<T: Debug> Debug for VoluntaryServitude<T> {
#[inline]
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.debug_tuple("VoluntaryServitude")
.field(&self.iter().collect::<Vec<_>>())
.finish()
}
}
impl<T> Extend<T> for VoluntaryServitude<T> {
#[inline]
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
Self::extend(self, iter)
}
}
impl<'a, T: 'a + Copy> Extend<&'a T> for VoluntaryServitude<T> {
#[inline]
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
Self::extend(self, iter.into_iter().cloned())
}
}
impl<T> FromIterator<T> for VoluntaryServitude<T> {
#[inline]
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
Self::from(Inner::from_iter(iter))
}
}
impl<'a, T: 'a + Copy> FromIterator<&'a T> for VoluntaryServitude<T> {
#[inline]
fn from_iter<I: IntoIterator<Item = &'a T>>(iter: I) -> Self {
Self::from_iter(iter.into_iter().cloned())
}
}
impl<T> From<Inner<T>> for VoluntaryServitude<T> {
#[inline]
fn from(inner: Inner<T>) -> Self {
trace!("From<Inner<T>>");
VoluntaryServitude(RwLock::new(Arc::new(inner)))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::setup_logger;
use std::mem::drop;
#[test]
fn iter_outlives() {
setup_logger();
let vs = vs![1, 2, 3, 4];
let iter = vs.iter();
drop(vs);
drop(iter);
}
#[test]
fn voluntary_servitude_len_append_clear() {
setup_logger();
let list = vs![1, 2, 3];
assert_eq!(list.len(), 3);
list.append(4);
assert_eq!(list.len(), 4);
list.clear();
assert!(list.is_empty());
list.append(4);
assert_eq!(list.len(), 1);
}
#[test]
fn extend_partial_eq() {
setup_logger();
let vs: VS<u8> = vs![1, 2, 3, 4, 5];
let iter = &mut vs.iter();
vs.extend(iter.cloned());
assert_eq!(
vs.iter().collect::<Vec<_>>(),
vec![&1u8, &2, &3, &4, &5, &1, &2, &3, &4, &5]
);
}
#[test]
fn swap_empty() {
let vs: VS<u8> = vs![1, 2, 3, 4, 5];
let mut old: VS<u8> = vs![5, 4, 3, 2, 1];
vs.swap(&mut old);
assert_eq!(vs.empty().collect::<Vec<_>>(), vec![&5, &4, &3, &2, &1]);
assert_eq!(old.empty().collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5]);
assert!(vs.is_empty());
}
#[test]
fn test_send() {
fn assert_send<T: Send>() {}
assert_send::<VoluntaryServitude<()>>();
}
#[test]
fn test_sync() {
fn assert_sync<T: Sync>() {}
assert_sync::<VoluntaryServitude<()>>();
}
}