Creates a new instance of an RwLock<T> which is unlocked.

Examples

use std::sync::RwLock;

let lock = RwLock::new(5);

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 might panic when called if the lock is already held by the current thread.

Examples

use std::sync::{Arc, RwLock};
use std::thread;

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();

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 std::sync::RwLock;

let lock = RwLock::new(1);

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

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 might panic when called if the lock is already held by the current thread.

Examples

use std::sync::RwLock;

let lock = RwLock::new(1);

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

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

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 std::sync::RwLock;

let lock = RwLock::new(1);

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

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

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, RwLock};
use std::thread;

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);

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 std::sync::RwLock;

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

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 std::sync::RwLock;

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