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Diffstat (limited to 'vendor/parking_lot-0.11.2/src/remutex.rs')
-rw-r--r-- | vendor/parking_lot-0.11.2/src/remutex.rs | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/vendor/parking_lot-0.11.2/src/remutex.rs b/vendor/parking_lot-0.11.2/src/remutex.rs new file mode 100644 index 000000000..103792301 --- /dev/null +++ b/vendor/parking_lot-0.11.2/src/remutex.rs @@ -0,0 +1,149 @@ +// Copyright 2016 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. + +use crate::raw_mutex::RawMutex; +use core::num::NonZeroUsize; +use lock_api::{self, GetThreadId}; + +/// Implementation of the `GetThreadId` trait for `lock_api::ReentrantMutex`. +pub struct RawThreadId; + +unsafe impl GetThreadId for RawThreadId { + const INIT: RawThreadId = RawThreadId; + + fn nonzero_thread_id(&self) -> NonZeroUsize { + // The address of a thread-local variable is guaranteed to be unique to the + // current thread, and is also guaranteed to be non-zero. The variable has to have a + // non-zero size to guarantee it has a unique address for each thread. + thread_local!(static KEY: u8 = 0); + KEY.with(|x| { + NonZeroUsize::new(x as *const _ as usize) + .expect("thread-local variable address is null") + }) + } +} + +/// A mutex which can be recursively locked by a single thread. +/// +/// This type is identical to `Mutex` except for the following points: +/// +/// - Locking multiple times from the same thread will work correctly instead of +/// deadlocking. +/// - `ReentrantMutexGuard` does not give mutable references to the locked data. +/// Use a `RefCell` if you need this. +/// +/// See [`Mutex`](type.Mutex.html) for more details about the underlying mutex +/// primitive. +pub type ReentrantMutex<T> = lock_api::ReentrantMutex<RawMutex, RawThreadId, T>; + +/// Creates a new reentrant mutex in an unlocked state ready for use. +/// +/// This allows creating a reentrant mutex in a constant context on stable Rust. +pub const fn const_reentrant_mutex<T>(val: T) -> ReentrantMutex<T> { + ReentrantMutex::const_new( + <RawMutex as lock_api::RawMutex>::INIT, + <RawThreadId as lock_api::GetThreadId>::INIT, + val, + ) +} + +/// An RAII implementation of a "scoped lock" of a reentrant mutex. When this structure +/// is dropped (falls out of scope), the lock will be unlocked. +/// +/// The data protected by the mutex can be accessed through this guard via its +/// `Deref` implementation. +pub type ReentrantMutexGuard<'a, T> = lock_api::ReentrantMutexGuard<'a, RawMutex, RawThreadId, T>; + +/// An RAII mutex guard returned by `ReentrantMutexGuard::map`, which can point to a +/// subfield of the protected data. +/// +/// The main difference between `MappedReentrantMutexGuard` and `ReentrantMutexGuard` is that the +/// former doesn't support temporarily unlocking and re-locking, since that +/// could introduce soundness issues if the locked object is modified by another +/// thread. +pub type MappedReentrantMutexGuard<'a, T> = + lock_api::MappedReentrantMutexGuard<'a, RawMutex, RawThreadId, T>; + +#[cfg(test)] +mod tests { + use crate::ReentrantMutex; + use std::cell::RefCell; + use std::sync::Arc; + use std::thread; + + #[cfg(feature = "serde")] + use bincode::{deserialize, serialize}; + + #[test] + fn smoke() { + let m = ReentrantMutex::new(2); + { + let a = m.lock(); + { + let b = m.lock(); + { + let c = m.lock(); + assert_eq!(*c, 2); + } + assert_eq!(*b, 2); + } + assert_eq!(*a, 2); + } + } + + #[test] + fn is_mutex() { + let m = Arc::new(ReentrantMutex::new(RefCell::new(0))); + let m2 = m.clone(); + let lock = m.lock(); + let child = thread::spawn(move || { + let lock = m2.lock(); + assert_eq!(*lock.borrow(), 4950); + }); + for i in 0..100 { + let lock = m.lock(); + *lock.borrow_mut() += i; + } + drop(lock); + child.join().unwrap(); + } + + #[test] + fn trylock_works() { + let m = Arc::new(ReentrantMutex::new(())); + let m2 = m.clone(); + let _lock = m.try_lock(); + let _lock2 = m.try_lock(); + thread::spawn(move || { + let lock = m2.try_lock(); + assert!(lock.is_none()); + }) + .join() + .unwrap(); + let _lock3 = m.try_lock(); + } + + #[test] + fn test_reentrant_mutex_debug() { + let mutex = ReentrantMutex::new(vec![0u8, 10]); + + assert_eq!(format!("{:?}", mutex), "ReentrantMutex { data: [0, 10] }"); + } + + #[cfg(feature = "serde")] + #[test] + fn test_serde() { + let contents: Vec<u8> = vec![0, 1, 2]; + let mutex = ReentrantMutex::new(contents.clone()); + + let serialized = serialize(&mutex).unwrap(); + let deserialized: ReentrantMutex<Vec<u8>> = deserialize(&serialized).unwrap(); + + assert_eq!(*(mutex.lock()), *(deserialized.lock())); + assert_eq!(contents, *(deserialized.lock())); + } +} |