115 lines
3.3 KiB
Rust
115 lines
3.3 KiB
Rust
// Take a look at the license at the top of the repository in the LICENSE file.
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use std::{
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mem, ptr,
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sync::atomic::{AtomicUsize, Ordering},
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};
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fn next_thread_id() -> usize {
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static COUNTER: AtomicUsize = AtomicUsize::new(0);
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COUNTER.fetch_add(1, Ordering::SeqCst)
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}
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// rustdoc-stripper-ignore-next
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/// Returns a unique ID for the current thread.
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///
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/// Actual thread IDs can be reused by the OS once the old thread finished.
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/// This works around ambiguity created by ID reuse by using a separate TLS counter for threads.
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pub fn thread_id() -> usize {
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thread_local!(static THREAD_ID: usize = next_thread_id());
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THREAD_ID.with(|&x| x)
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}
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// rustdoc-stripper-ignore-next
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/// Thread guard that only gives access to the contained value on the thread it was created on.
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pub struct ThreadGuard<T> {
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thread_id: usize,
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value: T,
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}
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impl<T> ThreadGuard<T> {
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// rustdoc-stripper-ignore-next
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/// Create a new thread guard around `value`.
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///
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/// The thread guard ensures that access to the value is only allowed from the thread it was
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/// created on, and otherwise panics.
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///
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/// The thread guard implements the `Send` trait even if the contained value does not.
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#[inline]
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pub fn new(value: T) -> Self {
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Self {
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thread_id: thread_id(),
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value,
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}
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}
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// rustdoc-stripper-ignore-next
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/// Return a reference to the contained value from the thread guard.
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///
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/// # Panics
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///
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/// This function panics if called from a different thread than where the thread guard was
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/// created.
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#[inline]
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pub fn get_ref(&self) -> &T {
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assert!(
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self.thread_id == thread_id(),
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"Value accessed from different thread than where it was created"
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);
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&self.value
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}
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// rustdoc-stripper-ignore-next
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/// Return a mutable reference to the contained value from the thread guard.
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///
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/// # Panics
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///
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/// This function panics if called from a different thread than where the thread guard was
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/// created.
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#[inline]
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pub fn get_mut(&mut self) -> &mut T {
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assert!(
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self.thread_id == thread_id(),
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"Value accessed from different thread than where it was created"
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);
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&mut self.value
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}
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// rustdoc-stripper-ignore-next
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/// Return the contained value from the thread guard.
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///
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/// # Panics
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///
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/// This function panics if called from a different thread than where the thread guard was
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/// created.
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#[inline]
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pub fn into_inner(self) -> T {
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assert!(
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self.thread_id == thread_id(),
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"Value accessed from different thread than where it was created"
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);
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unsafe { ptr::read(&mem::ManuallyDrop::new(self).value) }
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}
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// rustdoc-stripper-ignore-next
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/// Returns `true` if the current thread owns the value, i.e. it can be accessed safely.
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#[inline]
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pub fn is_owner(&self) -> bool {
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self.thread_id == thread_id()
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}
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}
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impl<T> Drop for ThreadGuard<T> {
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#[inline]
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fn drop(&mut self) {
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assert!(
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self.thread_id == thread_id(),
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"Value dropped on a different thread than where it was created"
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);
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}
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}
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unsafe impl<T> Send for ThreadGuard<T> {}
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