auto merge of #6732 : Aatch/rust/atomic-types, r=brson

This pull request is more of an RFC than a finished implementation.

It adds some basic atomic types, with an interface modelled off of C++11's atomic types.

It also adds free functions that provide a slightly nicer interface for atomic operations, though they are unsafe because there isn't a way to be generic over "word-sized" types.

See also #5042

2 files changed, 344 insertions, 0 deletions

diff --git a/src/libstd/unstable/atomics.rs b/src/libstd/unstable/atomics.rs
new file mode 100644
index 00000000000..09febfebaac
--- /dev/null
+++ b/src/libstd/unstable/atomics.rs
@@ -0,0 +1,343 @@
+// 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
+ */
+
+use unstable::intrinsics;
+use cast;
+use option::{Option,Some,None};
+
+pub struct AtomicFlag {
+    priv v:int
+}
+
+pub struct AtomicBool {
+    priv v:uint
+}
+
+pub struct AtomicInt {
+    priv v:int
+}
+
+pub struct AtomicUint {
+    priv v:uint
+}
+
+pub struct AtomicPtr<T> {
+    priv p:~T
+}
+
+pub enum Ordering {
+    Release,
+    Acquire,
+    SeqCst
+}
+
+
+impl AtomicFlag {
+
+    fn new() -> AtomicFlag {
+        AtomicFlag { v: 0 }
+    }
+
+    /**
+     * Clears the atomic flag
+     */
+    #[inline(always)]
+    fn clear(&mut self, order:Ordering) {
+        unsafe {atomic_store(&mut self.v, 0, order)}
+    }
+
+    #[inline(always)]
+    /**
+     * Sets the flag if it was previously unset, returns the previous value of the
+     * flag.
+     */
+    fn test_and_set(&mut self, order:Ordering) -> bool {
+        unsafe {atomic_compare_and_swap(&mut self.v, 0, 1, order) > 0}
+    }
+}
+
+impl AtomicBool {
+    fn new(v:bool) -> AtomicBool {
+        AtomicBool { v: if v { 1 } else { 0 } }
+    }
+
+    #[inline(always)]
+    fn load(&self, order:Ordering) -> bool {
+        unsafe { atomic_load(&self.v, order) > 0 }
+    }
+
+    #[inline(always)]
+    fn store(&mut self, val:bool, order:Ordering) {
+        let val = if val { 1 } else { 0 };
+
+        unsafe { atomic_store(&mut self.v, val, order); }
+    }
+
+    #[inline(always)]
+    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(always)]
+    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 {
+    fn new(v:int) -> AtomicInt {
+        AtomicInt { v:v }
+    }
+
+    #[inline(always)]
+    fn load(&self, order:Ordering) -> int {
+        unsafe { atomic_load(&self.v, order) }
+    }
+
+    #[inline(always)]
+    fn store(&mut self, val:int, order:Ordering) {
+        unsafe { atomic_store(&mut self.v, val, order); }
+    }
+
+    #[inline(always)]
+    fn swap(&mut self, val:int, order:Ordering) -> int {
+        unsafe { atomic_swap(&mut self.v, val, order) }
+    }
+
+    #[inline(always)]
+    fn compare_and_swap(&mut self, old: int, new: int, order:Ordering) -> int {
+        unsafe { atomic_compare_and_swap(&mut self.v, old, new, order) }
+    }
+
+    #[inline(always)]
+    fn fetch_add(&mut self, val:int, order:Ordering) -> int {
+        unsafe { atomic_add(&mut self.v, val, order) }
+    }
+
+    #[inline(always)]
+    fn fetch_sub(&mut self, val:int, order:Ordering) -> int {
+        unsafe { atomic_sub(&mut self.v, val, order) }
+    }
+}
+
+impl AtomicUint {
+    fn new(v:uint) -> AtomicUint {
+        AtomicUint { v:v }
+    }
+
+    #[inline(always)]
+    fn load(&self, order:Ordering) -> uint {
+        unsafe { atomic_load(&self.v, order) }
+    }
+
+    #[inline(always)]
+    fn store(&mut self, val:uint, order:Ordering) {
+        unsafe { atomic_store(&mut self.v, val, order); }
+    }
+
+    #[inline(always)]
+    fn swap(&mut self, val:uint, order:Ordering) -> uint {
+        unsafe { atomic_swap(&mut self.v, val, order) }
+    }
+
+    #[inline(always)]
+    fn compare_and_swap(&mut self, old: uint, new: uint, order:Ordering) -> uint {
+        unsafe { atomic_compare_and_swap(&mut self.v, old, new, order) }
+    }
+
+    #[inline(always)]
+    fn fetch_add(&mut self, val:uint, order:Ordering) -> uint {
+        unsafe { atomic_add(&mut self.v, val, order) }
+    }
+
+    #[inline(always)]
+    fn fetch_sub(&mut self, val:uint, order:Ordering) -> uint {
+        unsafe { atomic_sub(&mut self.v, val, order) }
+    }
+}
+
+impl<T> AtomicPtr<T> {
+    fn new(p:~T) -> AtomicPtr<T> {
+        AtomicPtr { p:p }
+    }
+
+    /**
+     * Atomically swaps the stored pointer with the one given.
+     *
+     * Returns None if the pointer stored has been taken
+     */
+    #[inline(always)]
+    fn swap(&mut self, ptr:~T, order:Ordering) -> Option<~T> {
+        unsafe {
+            let p = atomic_swap(&mut self.p, ptr, order);
+            let pv : &uint = cast::transmute(&p);
+
+            if *pv == 0 {
+                None
+            } else {
+                Some(p)
+            }
+        }
+    }
+
+    /**
+     * Atomically takes the stored pointer out.
+     *
+     * Returns None if it was already taken.
+     */
+    #[inline(always)]
+    fn take(&mut self, order:Ordering) -> Option<~T> {
+        unsafe { self.swap(cast::transmute(0), order) }
+    }
+
+    /**
+     * Atomically stores the given pointer, this will overwrite
+     * and previous value stored.
+     */
+    #[inline(always)]
+    fn give(&mut self, ptr:~T, order:Ordering) {
+        let _ = self.swap(ptr, order);
+    }
+
+    /**
+     * Checks to see if the stored pointer has been taken.
+     */
+    fn taken(&self, order:Ordering) -> bool {
+        unsafe {
+            let p : ~T = atomic_load(&self.p, order);
+
+            let pv : &uint = cast::transmute(&p);
+
+            cast::forget(p);
+            *pv == 0
+        }
+    }
+}
+
+#[inline(always)]
+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(always)]
+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(always)]
+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)
+    })
+}
+
+#[inline(always)]
+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)
+    })
+}
+
+#[inline(always)]
+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(always)]
+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 pointer_swap() {
+        let mut p = AtomicPtr::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 pointer_take() {
+        let mut p = AtomicPtr::new(~1);
+
+        assert_eq!(p.take(SeqCst), Some(~1));
+        assert_eq!(p.take(SeqCst), None);
+        assert!(p.taken(SeqCst));
+
+        let p2 = ~2;
+        p.give(p2, SeqCst);
+
+        assert_eq!(p.take(SeqCst), Some(~2));
+    }
+
+}
diff --git a/src/libstd/unstable/mod.rs b/src/libstd/unstable/mod.rs
index 9681a3f36fc..afdc22a1c63 100644
--- a/src/libstd/unstable/mod.rs
+++ b/src/libstd/unstable/mod.rs
@@ -25,6 +25,7 @@ pub mod extfmt;
 #[cfg(not(test))]
 pub mod lang;
 pub mod sync;
+pub mod atomics;
 
 /**