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-rw-r--r--vendor/thread_local/src/lib.rs683
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diff --git a/vendor/thread_local/src/lib.rs b/vendor/thread_local/src/lib.rs
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-// Copyright 2017 Amanieu d'Antras
-//
-// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
-// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
-// http://opensource.org/licenses/MIT>, at your option. This file may not be
-// copied, modified, or distributed except according to those terms.
-
-//! Per-object thread-local storage
-//!
-//! This library provides the `ThreadLocal` type which allows a separate copy of
-//! an object to be used for each thread. This allows for per-object
-//! thread-local storage, unlike the standard library's `thread_local!` macro
-//! which only allows static thread-local storage.
-//!
-//! Per-thread objects are not destroyed when a thread exits. Instead, objects
-//! are only destroyed when the `ThreadLocal` containing them is destroyed.
-//!
-//! You can also iterate over the thread-local values of all thread in a
-//! `ThreadLocal` object using the `iter_mut` and `into_iter` methods. This can
-//! only be done if you have mutable access to the `ThreadLocal` object, which
-//! guarantees that you are the only thread currently accessing it.
-//!
-//! Note that since thread IDs are recycled when a thread exits, it is possible
-//! for one thread to retrieve the object of another thread. Since this can only
-//! occur after a thread has exited this does not lead to any race conditions.
-//!
-//! # Examples
-//!
-//! Basic usage of `ThreadLocal`:
-//!
-//! ```rust
-//! use thread_local::ThreadLocal;
-//! let tls: ThreadLocal<u32> = ThreadLocal::new();
-//! assert_eq!(tls.get(), None);
-//! assert_eq!(tls.get_or(|| 5), &5);
-//! assert_eq!(tls.get(), Some(&5));
-//! ```
-//!
-//! Combining thread-local values into a single result:
-//!
-//! ```rust
-//! use thread_local::ThreadLocal;
-//! use std::sync::Arc;
-//! use std::cell::Cell;
-//! use std::thread;
-//!
-//! let tls = Arc::new(ThreadLocal::new());
-//!
-//! // Create a bunch of threads to do stuff
-//! for _ in 0..5 {
-//! let tls2 = tls.clone();
-//! thread::spawn(move || {
-//! // Increment a counter to count some event...
-//! let cell = tls2.get_or(|| Cell::new(0));
-//! cell.set(cell.get() + 1);
-//! }).join().unwrap();
-//! }
-//!
-//! // Once all threads are done, collect the counter values and return the
-//! // sum of all thread-local counter values.
-//! let tls = Arc::try_unwrap(tls).unwrap();
-//! let total = tls.into_iter().fold(0, |x, y| x + y.get());
-//! assert_eq!(total, 5);
-//! ```
-
-#![warn(missing_docs)]
-#![allow(clippy::mutex_atomic)]
-#![cfg_attr(feature = "nightly", feature(thread_local))]
-
-mod cached;
-mod thread_id;
-mod unreachable;
-
-#[allow(deprecated)]
-pub use cached::{CachedIntoIter, CachedIterMut, CachedThreadLocal};
-
-use std::cell::UnsafeCell;
-use std::fmt;
-use std::iter::FusedIterator;
-use std::mem;
-use std::mem::MaybeUninit;
-use std::panic::UnwindSafe;
-use std::ptr;
-use std::sync::atomic::{AtomicBool, AtomicPtr, AtomicUsize, Ordering};
-use thread_id::Thread;
-use unreachable::UncheckedResultExt;
-
-// Use usize::BITS once it has stabilized and the MSRV has been bumped.
-#[cfg(target_pointer_width = "16")]
-const POINTER_WIDTH: u8 = 16;
-#[cfg(target_pointer_width = "32")]
-const POINTER_WIDTH: u8 = 32;
-#[cfg(target_pointer_width = "64")]
-const POINTER_WIDTH: u8 = 64;
-
-/// The total number of buckets stored in each thread local.
-/// All buckets combined can hold up to `usize::MAX - 1` entries.
-const BUCKETS: usize = (POINTER_WIDTH - 1) as usize;
-
-/// Thread-local variable wrapper
-///
-/// See the [module-level documentation](index.html) for more.
-pub struct ThreadLocal<T: Send> {
- /// The buckets in the thread local. The nth bucket contains `2^n`
- /// elements. Each bucket is lazily allocated.
- buckets: [AtomicPtr<Entry<T>>; BUCKETS],
-
- /// The number of values in the thread local. This can be less than the real number of values,
- /// but is never more.
- values: AtomicUsize,
-}
-
-struct Entry<T> {
- present: AtomicBool,
- value: UnsafeCell<MaybeUninit<T>>,
-}
-
-impl<T> Drop for Entry<T> {
- fn drop(&mut self) {
- unsafe {
- if *self.present.get_mut() {
- ptr::drop_in_place((*self.value.get()).as_mut_ptr());
- }
- }
- }
-}
-
-// ThreadLocal is always Sync, even if T isn't
-unsafe impl<T: Send> Sync for ThreadLocal<T> {}
-
-impl<T: Send> Default for ThreadLocal<T> {
- fn default() -> ThreadLocal<T> {
- ThreadLocal::new()
- }
-}
-
-impl<T: Send> Drop for ThreadLocal<T> {
- fn drop(&mut self) {
- // Free each non-null bucket
- for (i, bucket) in self.buckets.iter_mut().enumerate() {
- let bucket_ptr = *bucket.get_mut();
-
- let this_bucket_size = 1 << i;
-
- if bucket_ptr.is_null() {
- continue;
- }
-
- unsafe { deallocate_bucket(bucket_ptr, this_bucket_size) };
- }
- }
-}
-
-impl<T: Send> ThreadLocal<T> {
- /// Creates a new empty `ThreadLocal`.
- pub const fn new() -> ThreadLocal<T> {
- let buckets = [ptr::null_mut::<Entry<T>>(); BUCKETS];
- Self {
- buckets: unsafe { mem::transmute(buckets) },
- values: AtomicUsize::new(0),
- }
- }
-
- /// Creates a new `ThreadLocal` with an initial capacity. If less than the capacity threads
- /// access the thread local it will never reallocate. The capacity may be rounded up to the
- /// nearest power of two.
- pub fn with_capacity(capacity: usize) -> ThreadLocal<T> {
- let allocated_buckets = usize::from(POINTER_WIDTH) - (capacity.leading_zeros() as usize);
-
- let mut buckets = [ptr::null_mut(); BUCKETS];
- for (i, bucket) in buckets[..allocated_buckets].iter_mut().enumerate() {
- *bucket = allocate_bucket::<T>(1 << i);
- }
-
- Self {
- // Safety: AtomicPtr has the same representation as a pointer and arrays have the same
- // representation as a sequence of their inner type.
- buckets: unsafe { mem::transmute(buckets) },
- values: AtomicUsize::new(0),
- }
- }
-
- /// Returns the element for the current thread, if it exists.
- pub fn get(&self) -> Option<&T> {
- self.get_inner(thread_id::get())
- }
-
- /// Returns the element for the current thread, or creates it if it doesn't
- /// exist.
- pub fn get_or<F>(&self, create: F) -> &T
- where
- F: FnOnce() -> T,
- {
- unsafe {
- self.get_or_try(|| Ok::<T, ()>(create()))
- .unchecked_unwrap_ok()
- }
- }
-
- /// Returns the element for the current thread, or creates it if it doesn't
- /// exist. If `create` fails, that error is returned and no element is
- /// added.
- pub fn get_or_try<F, E>(&self, create: F) -> Result<&T, E>
- where
- F: FnOnce() -> Result<T, E>,
- {
- let thread = thread_id::get();
- if let Some(val) = self.get_inner(thread) {
- return Ok(val);
- }
-
- Ok(self.insert(thread, create()?))
- }
-
- fn get_inner(&self, thread: Thread) -> Option<&T> {
- let bucket_ptr =
- unsafe { self.buckets.get_unchecked(thread.bucket) }.load(Ordering::Acquire);
- if bucket_ptr.is_null() {
- return None;
- }
- unsafe {
- let entry = &*bucket_ptr.add(thread.index);
- if entry.present.load(Ordering::Relaxed) {
- Some(&*(&*entry.value.get()).as_ptr())
- } else {
- None
- }
- }
- }
-
- #[cold]
- fn insert(&self, thread: Thread, data: T) -> &T {
- let bucket_atomic_ptr = unsafe { self.buckets.get_unchecked(thread.bucket) };
- let bucket_ptr: *const _ = bucket_atomic_ptr.load(Ordering::Acquire);
-
- // If the bucket doesn't already exist, we need to allocate it
- let bucket_ptr = if bucket_ptr.is_null() {
- let new_bucket = allocate_bucket(thread.bucket_size);
-
- match bucket_atomic_ptr.compare_exchange(
- ptr::null_mut(),
- new_bucket,
- Ordering::AcqRel,
- Ordering::Acquire,
- ) {
- Ok(_) => new_bucket,
- // If the bucket value changed (from null), that means
- // another thread stored a new bucket before we could,
- // and we can free our bucket and use that one instead
- Err(bucket_ptr) => {
- unsafe { deallocate_bucket(new_bucket, thread.bucket_size) }
- bucket_ptr
- }
- }
- } else {
- bucket_ptr
- };
-
- // Insert the new element into the bucket
- let entry = unsafe { &*bucket_ptr.add(thread.index) };
- let value_ptr = entry.value.get();
- unsafe { value_ptr.write(MaybeUninit::new(data)) };
- entry.present.store(true, Ordering::Release);
-
- self.values.fetch_add(1, Ordering::Release);
-
- unsafe { &*(&*value_ptr).as_ptr() }
- }
-
- /// Returns an iterator over the local values of all threads in unspecified
- /// order.
- ///
- /// This call can be done safely, as `T` is required to implement [`Sync`].
- pub fn iter(&self) -> Iter<'_, T>
- where
- T: Sync,
- {
- Iter {
- thread_local: self,
- raw: RawIter::new(),
- }
- }
-
- /// Returns a mutable iterator over the local values of all threads in
- /// unspecified order.
- ///
- /// Since this call borrows the `ThreadLocal` mutably, this operation can
- /// be done safely---the mutable borrow statically guarantees no other
- /// threads are currently accessing their associated values.
- pub fn iter_mut(&mut self) -> IterMut<T> {
- IterMut {
- thread_local: self,
- raw: RawIter::new(),
- }
- }
-
- /// Removes all thread-specific values from the `ThreadLocal`, effectively
- /// reseting it to its original state.
- ///
- /// Since this call borrows the `ThreadLocal` mutably, this operation can
- /// be done safely---the mutable borrow statically guarantees no other
- /// threads are currently accessing their associated values.
- pub fn clear(&mut self) {
- *self = ThreadLocal::new();
- }
-}
-
-impl<T: Send> IntoIterator for ThreadLocal<T> {
- type Item = T;
- type IntoIter = IntoIter<T>;
-
- fn into_iter(self) -> IntoIter<T> {
- IntoIter {
- thread_local: self,
- raw: RawIter::new(),
- }
- }
-}
-
-impl<'a, T: Send + Sync> IntoIterator for &'a ThreadLocal<T> {
- type Item = &'a T;
- type IntoIter = Iter<'a, T>;
-
- fn into_iter(self) -> Self::IntoIter {
- self.iter()
- }
-}
-
-impl<'a, T: Send> IntoIterator for &'a mut ThreadLocal<T> {
- type Item = &'a mut T;
- type IntoIter = IterMut<'a, T>;
-
- fn into_iter(self) -> IterMut<'a, T> {
- self.iter_mut()
- }
-}
-
-impl<T: Send + Default> ThreadLocal<T> {
- /// Returns the element for the current thread, or creates a default one if
- /// it doesn't exist.
- pub fn get_or_default(&self) -> &T {
- self.get_or(Default::default)
- }
-}
-
-impl<T: Send + fmt::Debug> fmt::Debug for ThreadLocal<T> {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "ThreadLocal {{ local_data: {:?} }}", self.get())
- }
-}
-
-impl<T: Send + UnwindSafe> UnwindSafe for ThreadLocal<T> {}
-
-#[derive(Debug)]
-struct RawIter {
- yielded: usize,
- bucket: usize,
- bucket_size: usize,
- index: usize,
-}
-impl RawIter {
- #[inline]
- fn new() -> Self {
- Self {
- yielded: 0,
- bucket: 0,
- bucket_size: 1,
- index: 0,
- }
- }
-
- fn next<'a, T: Send + Sync>(&mut self, thread_local: &'a ThreadLocal<T>) -> Option<&'a T> {
- while self.bucket < BUCKETS {
- let bucket = unsafe { thread_local.buckets.get_unchecked(self.bucket) };
- let bucket = bucket.load(Ordering::Acquire);
-
- if !bucket.is_null() {
- while self.index < self.bucket_size {
- let entry = unsafe { &*bucket.add(self.index) };
- self.index += 1;
- if entry.present.load(Ordering::Acquire) {
- self.yielded += 1;
- return Some(unsafe { &*(&*entry.value.get()).as_ptr() });
- }
- }
- }
-
- self.next_bucket();
- }
- None
- }
- fn next_mut<'a, T: Send>(
- &mut self,
- thread_local: &'a mut ThreadLocal<T>,
- ) -> Option<&'a mut Entry<T>> {
- if *thread_local.values.get_mut() == self.yielded {
- return None;
- }
-
- loop {
- let bucket = unsafe { thread_local.buckets.get_unchecked_mut(self.bucket) };
- let bucket = *bucket.get_mut();
-
- if !bucket.is_null() {
- while self.index < self.bucket_size {
- let entry = unsafe { &mut *bucket.add(self.index) };
- self.index += 1;
- if *entry.present.get_mut() {
- self.yielded += 1;
- return Some(entry);
- }
- }
- }
-
- self.next_bucket();
- }
- }
-
- #[inline]
- fn next_bucket(&mut self) {
- self.bucket_size <<= 1;
- self.bucket += 1;
- self.index = 0;
- }
-
- fn size_hint<T: Send>(&self, thread_local: &ThreadLocal<T>) -> (usize, Option<usize>) {
- let total = thread_local.values.load(Ordering::Acquire);
- (total - self.yielded, None)
- }
- fn size_hint_frozen<T: Send>(&self, thread_local: &ThreadLocal<T>) -> (usize, Option<usize>) {
- let total = unsafe { *(&thread_local.values as *const AtomicUsize as *const usize) };
- let remaining = total - self.yielded;
- (remaining, Some(remaining))
- }
-}
-
-/// Iterator over the contents of a `ThreadLocal`.
-#[derive(Debug)]
-pub struct Iter<'a, T: Send + Sync> {
- thread_local: &'a ThreadLocal<T>,
- raw: RawIter,
-}
-
-impl<'a, T: Send + Sync> Iterator for Iter<'a, T> {
- type Item = &'a T;
- fn next(&mut self) -> Option<Self::Item> {
- self.raw.next(self.thread_local)
- }
- fn size_hint(&self) -> (usize, Option<usize>) {
- self.raw.size_hint(self.thread_local)
- }
-}
-impl<T: Send + Sync> FusedIterator for Iter<'_, T> {}
-
-/// Mutable iterator over the contents of a `ThreadLocal`.
-pub struct IterMut<'a, T: Send> {
- thread_local: &'a mut ThreadLocal<T>,
- raw: RawIter,
-}
-
-impl<'a, T: Send> Iterator for IterMut<'a, T> {
- type Item = &'a mut T;
- fn next(&mut self) -> Option<&'a mut T> {
- self.raw
- .next_mut(self.thread_local)
- .map(|entry| unsafe { &mut *(&mut *entry.value.get()).as_mut_ptr() })
- }
- fn size_hint(&self) -> (usize, Option<usize>) {
- self.raw.size_hint_frozen(self.thread_local)
- }
-}
-
-impl<T: Send> ExactSizeIterator for IterMut<'_, T> {}
-impl<T: Send> FusedIterator for IterMut<'_, T> {}
-
-// Manual impl so we don't call Debug on the ThreadLocal, as doing so would create a reference to
-// this thread's value that potentially aliases with a mutable reference we have given out.
-impl<'a, T: Send + fmt::Debug> fmt::Debug for IterMut<'a, T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- f.debug_struct("IterMut").field("raw", &self.raw).finish()
- }
-}
-
-/// An iterator that moves out of a `ThreadLocal`.
-#[derive(Debug)]
-pub struct IntoIter<T: Send> {
- thread_local: ThreadLocal<T>,
- raw: RawIter,
-}
-
-impl<T: Send> Iterator for IntoIter<T> {
- type Item = T;
- fn next(&mut self) -> Option<T> {
- self.raw.next_mut(&mut self.thread_local).map(|entry| {
- *entry.present.get_mut() = false;
- unsafe {
- std::mem::replace(&mut *entry.value.get(), MaybeUninit::uninit()).assume_init()
- }
- })
- }
- fn size_hint(&self) -> (usize, Option<usize>) {
- self.raw.size_hint_frozen(&self.thread_local)
- }
-}
-
-impl<T: Send> ExactSizeIterator for IntoIter<T> {}
-impl<T: Send> FusedIterator for IntoIter<T> {}
-
-fn allocate_bucket<T>(size: usize) -> *mut Entry<T> {
- Box::into_raw(
- (0..size)
- .map(|_| Entry::<T> {
- present: AtomicBool::new(false),
- value: UnsafeCell::new(MaybeUninit::uninit()),
- })
- .collect(),
- ) as *mut _
-}
-
-unsafe fn deallocate_bucket<T>(bucket: *mut Entry<T>, size: usize) {
- let _ = Box::from_raw(std::slice::from_raw_parts_mut(bucket, size));
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
-
- use std::cell::RefCell;
- use std::sync::atomic::AtomicUsize;
- use std::sync::atomic::Ordering::Relaxed;
- use std::sync::Arc;
- use std::thread;
-
- fn make_create() -> Arc<dyn Fn() -> usize + Send + Sync> {
- let count = AtomicUsize::new(0);
- Arc::new(move || count.fetch_add(1, Relaxed))
- }
-
- #[test]
- fn same_thread() {
- let create = make_create();
- let mut tls = ThreadLocal::new();
- assert_eq!(None, tls.get());
- assert_eq!("ThreadLocal { local_data: None }", format!("{:?}", &tls));
- assert_eq!(0, *tls.get_or(|| create()));
- assert_eq!(Some(&0), tls.get());
- assert_eq!(0, *tls.get_or(|| create()));
- assert_eq!(Some(&0), tls.get());
- assert_eq!(0, *tls.get_or(|| create()));
- assert_eq!(Some(&0), tls.get());
- assert_eq!("ThreadLocal { local_data: Some(0) }", format!("{:?}", &tls));
- tls.clear();
- assert_eq!(None, tls.get());
- }
-
- #[test]
- fn different_thread() {
- let create = make_create();
- let tls = Arc::new(ThreadLocal::new());
- assert_eq!(None, tls.get());
- assert_eq!(0, *tls.get_or(|| create()));
- assert_eq!(Some(&0), tls.get());
-
- let tls2 = tls.clone();
- let create2 = create.clone();
- thread::spawn(move || {
- assert_eq!(None, tls2.get());
- assert_eq!(1, *tls2.get_or(|| create2()));
- assert_eq!(Some(&1), tls2.get());
- })
- .join()
- .unwrap();
-
- assert_eq!(Some(&0), tls.get());
- assert_eq!(0, *tls.get_or(|| create()));
- }
-
- #[test]
- fn iter() {
- let tls = Arc::new(ThreadLocal::new());
- tls.get_or(|| Box::new(1));
-
- let tls2 = tls.clone();
- thread::spawn(move || {
- tls2.get_or(|| Box::new(2));
- let tls3 = tls2.clone();
- thread::spawn(move || {
- tls3.get_or(|| Box::new(3));
- })
- .join()
- .unwrap();
- drop(tls2);
- })
- .join()
- .unwrap();
-
- let mut tls = Arc::try_unwrap(tls).unwrap();
-
- let mut v = tls.iter().map(|x| **x).collect::<Vec<i32>>();
- v.sort_unstable();
- assert_eq!(vec![1, 2, 3], v);
-
- let mut v = tls.iter_mut().map(|x| **x).collect::<Vec<i32>>();
- v.sort_unstable();
- assert_eq!(vec![1, 2, 3], v);
-
- let mut v = tls.into_iter().map(|x| *x).collect::<Vec<i32>>();
- v.sort_unstable();
- assert_eq!(vec![1, 2, 3], v);
- }
-
- #[test]
- fn miri_iter_soundness_check() {
- let tls = Arc::new(ThreadLocal::new());
- let _local = tls.get_or(|| Box::new(1));
-
- let tls2 = tls.clone();
- let join_1 = thread::spawn(move || {
- let _tls = tls2.get_or(|| Box::new(2));
- let iter = tls2.iter();
- for item in iter {
- println!("{:?}", item);
- }
- });
-
- let iter = tls.iter();
- for item in iter {
- println!("{:?}", item);
- }
-
- join_1.join().ok();
- }
-
- #[test]
- fn test_drop() {
- let local = ThreadLocal::new();
- struct Dropped(Arc<AtomicUsize>);
- impl Drop for Dropped {
- fn drop(&mut self) {
- self.0.fetch_add(1, Relaxed);
- }
- }
-
- let dropped = Arc::new(AtomicUsize::new(0));
- local.get_or(|| Dropped(dropped.clone()));
- assert_eq!(dropped.load(Relaxed), 0);
- drop(local);
- assert_eq!(dropped.load(Relaxed), 1);
- }
-
- #[test]
- fn test_earlyreturn_buckets() {
- struct Dropped(Arc<AtomicUsize>);
- impl Drop for Dropped {
- fn drop(&mut self) {
- self.0.fetch_add(1, Relaxed);
- }
- }
- let dropped = Arc::new(AtomicUsize::new(0));
-
- // We use a high `id` here to guarantee that a lazily allocated bucket somewhere in the middle is used.
- // Neither iteration nor `Drop` must early-return on `null` buckets that are used for lower `buckets`.
- let thread = Thread::new(1234);
- assert!(thread.bucket > 1);
-
- let mut local = ThreadLocal::new();
- local.insert(thread, Dropped(dropped.clone()));
-
- let item = local.iter().next().unwrap();
- assert_eq!(item.0.load(Relaxed), 0);
- let item = local.iter_mut().next().unwrap();
- assert_eq!(item.0.load(Relaxed), 0);
- drop(local);
- assert_eq!(dropped.load(Relaxed), 1);
- }
-
- #[test]
- fn is_sync() {
- fn foo<T: Sync>() {}
- foo::<ThreadLocal<String>>();
- foo::<ThreadLocal<RefCell<String>>>();
- }
-}
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