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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.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 clone::Clone;
use kinds::Send;
use ops::Drop;
use option::{Option,Some,None};
use sync::arc::UnsafeArc;
use unstable::mutex::Mutex;
pub struct LittleLock {
priv l: Mutex,
}
pub struct LittleGuard<'a> {
priv l: &'a mut Mutex,
}
impl Drop for LittleLock {
fn drop(&mut self) {
unsafe { self.l.destroy(); }
}
}
#[unsafe_destructor]
impl<'a> Drop for LittleGuard<'a> {
fn drop(&mut self) {
unsafe { self.l.unlock(); }
}
}
impl LittleLock {
pub fn new() -> LittleLock {
unsafe { LittleLock { l: Mutex::new() } }
}
pub unsafe fn lock<'a>(&'a mut self) -> LittleGuard<'a> {
self.l.lock();
LittleGuard { l: &mut self.l }
}
pub unsafe fn try_lock<'a>(&'a mut self) -> Option<LittleGuard<'a>> {
if self.l.trylock() {
Some(LittleGuard { l: &mut self.l })
} else {
None
}
}
pub unsafe fn signal(&mut self) {
self.l.signal();
}
}
impl<'a> LittleGuard<'a> {
pub unsafe fn wait(&mut self) {
self.l.wait();
}
}
struct ExData<T> {
lock: LittleLock,
failed: bool,
data: T,
}
/**
* An arc over mutable data that is protected by a lock. For library use only.
*
* # Safety note
*
* This uses a pthread mutex, not one that's aware of the userspace scheduler.
* The user of an Exclusive must be careful not to invoke any functions that may
* reschedule the task while holding the lock, or deadlock may result. If you
* need to block or deschedule while accessing shared state, use extra::sync::RWArc.
*/
pub struct Exclusive<T> {
priv x: UnsafeArc<ExData<T>>
}
impl<T:Send> Clone for Exclusive<T> {
// Duplicate an Exclusive Arc, as std::arc::clone.
fn clone(&self) -> Exclusive<T> {
Exclusive { x: self.x.clone() }
}
}
impl<T:Send> Exclusive<T> {
pub fn new(user_data: T) -> Exclusive<T> {
let data = ExData {
lock: LittleLock::new(),
failed: false,
data: user_data
};
Exclusive {
x: UnsafeArc::new(data)
}
}
// Exactly like std::arc::MutexArc,access(), but with the LittleLock
// instead of a proper mutex. Same reason for being unsafe.
//
// Currently, scheduling operations (i.e., descheduling, receiving on a pipe,
// accessing the provided condition variable) are prohibited while inside
// the Exclusive. Supporting that is a work in progress.
#[inline]
pub unsafe fn with<U>(&self, f: |x: &mut T| -> U) -> U {
let rec = self.x.get();
let _l = (*rec).lock.lock();
if (*rec).failed {
fail!("Poisoned Exclusive::new - another task failed inside!");
}
(*rec).failed = true;
let result = f(&mut (*rec).data);
(*rec).failed = false;
result
}
#[inline]
pub unsafe fn with_imm<U>(&self, f: |x: &T| -> U) -> U {
self.with(|x| f(x))
}
#[inline]
pub unsafe fn hold_and_signal(&self, f: |x: &mut T|) {
let rec = self.x.get();
let _l = (*rec).lock.lock();
if (*rec).failed {
fail!("Poisoned Exclusive::new - another task failed inside!");
}
(*rec).failed = true;
f(&mut (*rec).data);
(*rec).failed = false;
(*rec).lock.signal();
}
#[inline]
pub unsafe fn hold_and_wait(&self, f: |x: &T| -> bool) {
let rec = self.x.get();
let mut l = (*rec).lock.lock();
if (*rec).failed {
fail!("Poisoned Exclusive::new - another task failed inside!");
}
(*rec).failed = true;
let result = f(&(*rec).data);
(*rec).failed = false;
if result {
l.wait();
}
}
}
#[cfg(test)]
mod tests {
use option::*;
use prelude::*;
use super::Exclusive;
use task;
#[test]
fn exclusive_new_arc() {
unsafe {
let mut futures = ~[];
let num_tasks = 10;
let count = 10;
let total = Exclusive::new(~0);
for _ in range(0u, num_tasks) {
let total = total.clone();
let (port, chan) = Chan::new();
futures.push(port);
do task::spawn {
for _ in range(0u, count) {
total.with(|count| **count += 1);
}
chan.send(());
}
};
for f in futures.mut_iter() { f.recv() }
total.with(|total| assert!(**total == num_tasks * count));
}
}
#[test] #[should_fail]
fn exclusive_new_poison() {
unsafe {
// Tests that if one task fails inside of an Exclusive::new, subsequent
// accesses will also fail.
let x = Exclusive::new(1);
let x2 = x.clone();
do task::try || {
x2.with(|one| assert_eq!(*one, 2))
};
x.with(|one| assert_eq!(*one, 1));
}
}
}
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