Struct sync_2::RwLock

pub struct RwLock<T> { /* fields omitted */ }

An allocation-free RwLock made in pure Rust.

Implementations

impl<T> RwLock<T>

pub fn new(x: T) -> Self

Creates a new RwLock locking the value x.

This function it's constant only without debug_assertions due to declare a thread local storage to avoid acquire the lock twice from the same thread.

pub fn read(&self) -> LockResult<SharedGuard<'_, T>>

Locks this rwlock with shared read access, blocking the current thread until it can be acquired.

The calling thread will be blocked until there are no more writers which hold the lock. There may be other readers currently inside the lock when this method returns. This method does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Returns an RAII guard which will release this thread's shared access once it is dropped.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. The failure will occur immediately after the lock has been acquired.

Panics

This function panic when called if the lock is already held by the current thread with debug_assertions on.

Examples

use std::sync::Arc;
use std::thread;
use sync_2::RwLock;

let lock = Arc::new(RwLock::new(1));
let c_lock = lock.clone();

let n = lock.read().unwrap();
assert_eq!(*n, 1);

thread::spawn(move || {
    let r = c_lock.read();
    assert!(r.is_ok());
}).join().unwrap();

pub fn write(&self) -> LockResult<UniqueGuard<'_, T>>

Locks this rwlock with exclusive write access, blocking the current thread until it can be acquired.

This function will not return while other writers or other readers currently have access to the lock.

Returns an RAII guard which will drop the write access of this rwlock when dropped.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will be returned when the lock is acquired.

Panics

This function panic when called if the lock is already held by the current thread with debug_assertions on.

Examples

use sync_2::RwLock;

let lock = RwLock::new(1);

let mut n = lock.write().unwrap();
*n = 2;

assert!(lock.try_read().is_err());

pub fn try_read(&self) -> TryLockResult<SharedGuard<'_, T>>

Attempts to acquire this rwlock with shared read access.

If the access could not be granted at this time, then Err is returned. Otherwise, an RAII guard is returned which will release the shared access when it is dropped.

This function does not block.

This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Examples

use sync_2::RwLock;

let lock = RwLock::new(1);

match lock.try_read() {
    Ok(n) => assert_eq!(*n, 1),
    Err(_) => unreachable!(),
};

pub fn try_write(&self) -> TryLockResult<UniqueGuard<'_, T>>

Attempts to lock this rwlock with exclusive write access.

If the lock could not be acquired at this time, then Err is returned. Otherwise, an RAII guard is returned which will release the lock when it is dropped.

This function does not block.

This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Examples

use sync_2::RwLock;

let lock = RwLock::new(1);

let n = lock.read().unwrap();
assert_eq!(*n, 1);

println!("{:?}", lock);
assert!(lock.try_write().is_err());

pub fn is_poisoned(&self) -> bool

Determines whether the lock is poisoned.

If another thread is active, the lock can still become poisoned at any time. You should not trust a false value for program correctness without additional synchronization.

Examples

use std::sync::Arc;
use std::thread;
use sync_2::RwLock;

let lock = Arc::new(RwLock::new(0));
let c_lock = lock.clone();

let _ = thread::spawn(move || {
    let _lock = c_lock.write().unwrap();
    panic!(); // the lock gets poisoned
}).join();
assert_eq!(lock.is_poisoned(), true);

pub fn get_mut(&mut self) -> LockResult<&mut T>

Returns a mutable reference to the underlying data.

Since this call borrows the RwLock mutably, no actual locking needs to take place -- the mutable borrow statically guarantees no locks exist.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Examples

use sync_2::RwLock;

let mut lock = RwLock::new(0);
*lock.get_mut().unwrap() = 10;
assert_eq!(*lock.read().unwrap(), 10);

pub fn into_inner(self) -> LockResult<T>

Consumes this RwLock, returning the underlying data.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Examples

use sync_2::RwLock;

let lock = RwLock::new(String::new());
{
    let mut s = lock.write().unwrap();
    *s = "modified".to_owned();
}
assert_eq!(lock.into_inner().unwrap(), "modified");

Trait Implementations

impl<T: Debug> Debug for RwLock<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for RwLock<T>

fn default() -> Self

Creates a new RwLock<T>, with the Default value for T.

impl<T> From<T> for RwLock<T>

fn from(t: T) -> Self

Creates a new instance of an RwLock<T> which is unlocked. This is equivalent to RwLock::new.

impl<T: Send> Send for RwLock<T>

impl<T: Send> Sync for RwLock<T>