rust/src/libstd/unstable/atomics.rs

// Copyright 2012-2013 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.

/*!
 * Atomic types
 *
 * Basic atomic types supporting atomic operations. Each method takes an `Ordering` which
 * represents the strength of the memory barrier for that operation. These orderings are the same
 * as C++11 atomic orderings [http://gcc.gnu.org/wiki/Atomic/GCCMM/AtomicSync]
 *
 * All atomic types are a single word in size.
 */

use unstable::intrinsics;
use cast;
use option::{Option,Some,None};
use libc::c_void;
use ops::Drop;

/**
 * A simple atomic flag, that can be set and cleared. The most basic atomic type.
 */
pub struct AtomicFlag {
    priv v: int
}

/**
 * An atomic boolean type.
 */
pub struct AtomicBool {
    priv v: uint
}

/**
 * A signed atomic integer type, supporting basic atomic aritmetic operations
 */
pub struct AtomicInt {
    priv v: int
}

/**
 * An unsigned atomic integer type, supporting basic atomic aritmetic operations
 */
pub struct AtomicUint {
    priv v: uint
}

/**
 * An unsafe atomic pointer. Only supports basic atomic operations
 */
pub struct AtomicPtr<T> {
    priv p: *mut T
}

/**
 * An owned atomic pointer. Ensures that only a single reference to the data is held at any time.
 */
#[no_drop_flag]
pub struct AtomicOption<T> {
    priv p: *mut c_void
}

pub enum Ordering {
    Release,
    Acquire,
    SeqCst
}


impl AtomicFlag {

    pub fn new() -> AtomicFlag {
        AtomicFlag { v: 0 }
    }

    /**
     * Clears the atomic flag
     */
    #[inline]
    pub fn clear(&mut self, order: Ordering) {
        unsafe {atomic_store(&mut self.v, 0, order)}
    }

    /**
     * Sets the flag if it was previously unset, returns the previous value of the
     * flag.
     */
    #[inline]
    pub fn test_and_set(&mut self, order: Ordering) -> bool {
        unsafe {atomic_compare_and_swap(&mut self.v, 0, 1, order) > 0}
    }
}

impl AtomicBool {
    pub fn new(v: bool) -> AtomicBool {
        AtomicBool { v: if v { 1 } else { 0 } }
    }

    #[inline]
    pub fn load(&self, order: Ordering) -> bool {
        unsafe { atomic_load(&self.v, order) > 0 }
    }

    #[inline]
    pub fn store(&mut self, val: bool, order: Ordering) {
        let val = if val { 1 } else { 0 };

        unsafe { atomic_store(&mut self.v, val, order); }
    }

    #[inline]
    pub fn swap(&mut self, val: bool, order: Ordering) -> bool {
        let val = if val { 1 } else { 0 };

        unsafe { atomic_swap(&mut self.v, val, order) > 0}
    }

    #[inline]
    pub fn compare_and_swap(&mut self, old: bool, new: bool, order: Ordering) -> bool {
        let old = if old { 1 } else { 0 };
        let new = if new { 1 } else { 0 };

        unsafe { atomic_compare_and_swap(&mut self.v, old, new, order) > 0 }
    }
}

impl AtomicInt {
    pub fn new(v: int) -> AtomicInt {
        AtomicInt { v:v }
    }

    #[inline]
    pub fn load(&self, order: Ordering) -> int {
        unsafe { atomic_load(&self.v, order) }
    }

    #[inline]
    pub fn store(&mut self, val: int, order: Ordering) {
        unsafe { atomic_store(&mut self.v, val, order); }
    }

    #[inline]
    pub fn swap(&mut self, val: int, order: Ordering) -> int {
        unsafe { atomic_swap(&mut self.v, val, order) }
    }

    #[inline]
    pub fn compare_and_swap(&mut self, old: int, new: int, order: Ordering) -> int {
        unsafe { atomic_compare_and_swap(&mut self.v, old, new, order) }
    }

    /// Returns the old value (like __sync_fetch_and_add).
    #[inline]
    pub fn fetch_add(&mut self, val: int, order: Ordering) -> int {
        unsafe { atomic_add(&mut self.v, val, order) }
    }

    /// Returns the old value (like __sync_fetch_and_sub).
    #[inline]
    pub fn fetch_sub(&mut self, val: int, order: Ordering) -> int {
        unsafe { atomic_sub(&mut self.v, val, order) }
    }
}

impl AtomicUint {
    pub fn new(v: uint) -> AtomicUint {
        AtomicUint { v:v }
    }

    #[inline]
    pub fn load(&self, order: Ordering) -> uint {
        unsafe { atomic_load(&self.v, order) }
    }

    #[inline]
    pub fn store(&mut self, val: uint, order: Ordering) {
        unsafe { atomic_store(&mut self.v, val, order); }
    }

    #[inline]
    pub fn swap(&mut self, val: uint, order: Ordering) -> uint {
        unsafe { atomic_swap(&mut self.v, val, order) }
    }

    #[inline]
    pub fn compare_and_swap(&mut self, old: uint, new: uint, order: Ordering) -> uint {
        unsafe { atomic_compare_and_swap(&mut self.v, old, new, order) }
    }

    /// Returns the old value (like __sync_fetch_and_add).
    #[inline]
    pub fn fetch_add(&mut self, val: uint, order: Ordering) -> uint {
        unsafe { atomic_add(&mut self.v, val, order) }
    }

    /// Returns the old value (like __sync_fetch_and_sub)..
    #[inline]
    pub fn fetch_sub(&mut self, val: uint, order: Ordering) -> uint {
        unsafe { atomic_sub(&mut self.v, val, order) }
    }
}

impl<T> AtomicPtr<T> {
    pub fn new(p: *mut T) -> AtomicPtr<T> {
        AtomicPtr { p:p }
    }

    #[inline]
    pub fn load(&self, order: Ordering) -> *mut T {
        unsafe { atomic_load(&self.p, order) }
    }

    #[inline]
    pub fn store(&mut self, ptr: *mut T, order: Ordering) {
        unsafe { atomic_store(&mut self.p, ptr, order); }
    }

    #[inline]
    pub fn swap(&mut self, ptr: *mut T, order: Ordering) -> *mut T {
        unsafe { atomic_swap(&mut self.p, ptr, order) }
    }

    #[inline]
    pub fn compare_and_swap(&mut self, old: *mut T, new: *mut T, order: Ordering) -> *mut T {
        unsafe { atomic_compare_and_swap(&mut self.p, old, new, order) }
    }
}

impl<T> AtomicOption<T> {
    pub fn new(p: ~T) -> AtomicOption<T> {
        unsafe {
            AtomicOption {
                p: cast::transmute(p)
            }
        }
    }

    pub fn empty() -> AtomicOption<T> {
        unsafe {
            AtomicOption {
                p: cast::transmute(0)
            }
        }
    }

    #[inline]
    pub fn swap(&mut self, val: ~T, order: Ordering) -> Option<~T> {
        unsafe {
            let val = cast::transmute(val);

            let p = atomic_swap(&mut self.p, val, order);
            let pv : &uint = cast::transmute(&p);

            if *pv == 0 {
                None
            } else {
                Some(cast::transmute(p))
            }
        }
    }

    #[inline]
    pub fn take(&mut self, order: Ordering) -> Option<~T> {
        unsafe {
            self.swap(cast::transmute(0), order)
        }
    }
}

#[unsafe_destructor]
impl<T> Drop for AtomicOption<T> {
    fn drop(&self) {
        // This will ensure that the contained data is
        // destroyed, unless it's null.
        unsafe {
            // FIXME(#4330) Need self by value to get mutability.
            let this : &mut AtomicOption<T> = cast::transmute(self);
            let _ = this.take(SeqCst);
        }
    }
}

#[inline]
pub unsafe fn atomic_store<T>(dst: &mut T, val: T, order:Ordering) {
    let dst = cast::transmute(dst);
    let val = cast::transmute(val);

    match order {
        Release => intrinsics::atomic_store_rel(dst, val),
        _       => intrinsics::atomic_store(dst, val)
    }
}

#[inline]
pub unsafe fn atomic_load<T>(dst: &T, order:Ordering) -> T {
    let dst = cast::transmute(dst);

    cast::transmute(match order {
        Acquire => intrinsics::atomic_load_acq(dst),
        _       => intrinsics::atomic_load(dst)
    })
}

#[inline]
pub unsafe fn atomic_swap<T>(dst: &mut T, val: T, order: Ordering) -> T {
    let dst = cast::transmute(dst);
    let val = cast::transmute(val);

    cast::transmute(match order {
        Acquire => intrinsics::atomic_xchg_acq(dst, val),
        Release => intrinsics::atomic_xchg_rel(dst, val),
        _       => intrinsics::atomic_xchg(dst, val)
    })
}

/// Returns the old value (like __sync_fetch_and_add).
#[inline]
pub unsafe fn atomic_add<T>(dst: &mut T, val: T, order: Ordering) -> T {
    let dst = cast::transmute(dst);
    let val = cast::transmute(val);

    cast::transmute(match order {
        Acquire => intrinsics::atomic_xadd_acq(dst, val),
        Release => intrinsics::atomic_xadd_rel(dst, val),
        _       => intrinsics::atomic_xadd(dst, val)
    })
}

/// Returns the old value (like __sync_fetch_and_sub).
#[inline]
pub unsafe fn atomic_sub<T>(dst: &mut T, val: T, order: Ordering) -> T {
    let dst = cast::transmute(dst);
    let val = cast::transmute(val);

    cast::transmute(match order {
        Acquire => intrinsics::atomic_xsub_acq(dst, val),
        Release => intrinsics::atomic_xsub_rel(dst, val),
        _       => intrinsics::atomic_xsub(dst, val)
    })
}

#[inline]
pub unsafe fn atomic_compare_and_swap<T>(dst:&mut T, old:T, new:T, order: Ordering) -> T {
    let dst = cast::transmute(dst);
    let old = cast::transmute(old);
    let new = cast::transmute(new);

    cast::transmute(match order {
        Acquire => intrinsics::atomic_cxchg_acq(dst, old, new),
        Release => intrinsics::atomic_cxchg_rel(dst, old, new),
        _       => intrinsics::atomic_cxchg(dst, old, new),
    })
}

#[cfg(test)]
mod test {
    use option::*;
    use super::*;

    #[test]
    fn flag() {
        let mut flg = AtomicFlag::new();
        assert!(!flg.test_and_set(SeqCst));
        assert!(flg.test_and_set(SeqCst));

        flg.clear(SeqCst);
        assert!(!flg.test_and_set(SeqCst));
    }

    #[test]
    fn option_swap() {
        let mut p = AtomicOption::new(~1);
        let a = ~2;

        let b = p.swap(a, SeqCst);

        assert_eq!(b, Some(~1));
        assert_eq!(p.take(SeqCst), Some(~2));
    }

    #[test]
    fn option_take() {
        let mut p = AtomicOption::new(~1);

        assert_eq!(p.take(SeqCst), Some(~1));
        assert_eq!(p.take(SeqCst), None);

        let p2 = ~2;
        p.swap(p2, SeqCst);

        assert_eq!(p.take(SeqCst), Some(~2));
    }

}