1 files changed, 283 insertions, 0 deletions
diff --git a/src/libcore/unstable/sync.rs b/src/libcore/unstable/sync.rs
new file mode 100644
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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 cast;
+use libc;
+use option::*;
+use task;
+use task::atomically;
+use unstable::finally::Finally;
+use unstable::intrinsics;
+use ops::Drop;
+use clone::Clone;
+use kinds::Owned;
+
+/****************************************************************************
+ * Shared state & exclusive ARC
+ ****************************************************************************/
+
+struct ArcData<T> {
+    count:     libc::intptr_t,
+    // FIXME(#3224) should be able to make this non-option to save memory
+    data:      Option<T>,
+}
+
+struct ArcDestruct<T> {
+    data: *libc::c_void,
+}
+
+#[unsafe_destructor]
+impl<T> Drop for ArcDestruct<T>{
+    fn finalize(&self) {
+        unsafe {
+            do task::unkillable {
+                let mut data: ~ArcData<T> = cast::transmute(self.data);
+                let new_count =
+                    intrinsics::atomic_xsub(&mut data.count, 1) - 1;
+                assert!(new_count >= 0);
+                if new_count == 0 {
+                    // drop glue takes over.
+                } else {
+                    cast::forget(data);
+                }
+            }
+        }
+    }
+}
+
+fn ArcDestruct<T>(data: *libc::c_void) -> ArcDestruct<T> {
+    ArcDestruct {
+        data: data
+    }
+}
+
+/**
+ * COMPLETELY UNSAFE. Used as a primitive for the safe versions in std::arc.
+ *
+ * Data races between tasks can result in crashes and, with sufficient
+ * cleverness, arbitrary type coercion.
+ */
+pub type SharedMutableState<T> = ArcDestruct<T>;
+
+pub unsafe fn shared_mutable_state<T:Owned>(data: T) ->
+        SharedMutableState<T> {
+    let data = ~ArcData { count: 1, data: Some(data) };
+    let ptr = cast::transmute(data);
+    ArcDestruct(ptr)
+}
+
+#[inline(always)]
+pub unsafe fn get_shared_mutable_state<T:Owned>(
+    rc: *SharedMutableState<T>) -> *mut T
+{
+    let ptr: ~ArcData<T> = cast::transmute((*rc).data);
+    assert!(ptr.count > 0);
+    let r = cast::transmute(ptr.data.get_ref());
+    cast::forget(ptr);
+    return r;
+}
+#[inline(always)]
+pub unsafe fn get_shared_immutable_state<'a,T:Owned>(
+        rc: &'a SharedMutableState<T>) -> &'a T {
+    let ptr: ~ArcData<T> = cast::transmute((*rc).data);
+    assert!(ptr.count > 0);
+    // Cast us back into the correct region
+    let r = cast::transmute_region(ptr.data.get_ref());
+    cast::forget(ptr);
+    return r;
+}
+
+pub unsafe fn clone_shared_mutable_state<T:Owned>(rc: &SharedMutableState<T>)
+        -> SharedMutableState<T> {
+    let mut ptr: ~ArcData<T> = cast::transmute((*rc).data);
+    let new_count = intrinsics::atomic_xadd(&mut ptr.count, 1) + 1;
+    assert!(new_count >= 2);
+    cast::forget(ptr);
+    ArcDestruct((*rc).data)
+}
+
+impl<T:Owned> Clone for SharedMutableState<T> {
+    fn clone(&self) -> SharedMutableState<T> {
+        unsafe {
+            clone_shared_mutable_state(self)
+        }
+    }
+}
+
+/****************************************************************************/
+
+#[allow(non_camel_case_types)] // runtime type
+pub type rust_little_lock = *libc::c_void;
+
+struct LittleLock {
+    l: rust_little_lock,
+}
+
+impl Drop for LittleLock {
+    fn finalize(&self) {
+        unsafe {
+            rust_destroy_little_lock(self.l);
+        }
+    }
+}
+
+fn LittleLock() -> LittleLock {
+    unsafe {
+        LittleLock {
+            l: rust_create_little_lock()
+        }
+    }
+}
+
+pub impl LittleLock {
+    #[inline(always)]
+    unsafe fn lock<T>(&self, f: &fn() -> T) -> T {
+        do atomically {
+            rust_lock_little_lock(self.l);
+            do (|| {
+                f()
+            }).finally {
+                rust_unlock_little_lock(self.l);
+            }
+        }
+    }
+}
+
+struct ExData<T> {
+    lock: LittleLock,
+    failed: bool,
+    data: T,
+}
+
+/**
+ * An arc over mutable data that is protected by a lock. For library use only.
+ */
+pub struct Exclusive<T> {
+    x: SharedMutableState<ExData<T>>
+}
+
+pub fn exclusive<T:Owned>(user_data: T) -> Exclusive<T> {
+    let data = ExData {
+        lock: LittleLock(),
+        failed: false,
+        data: user_data
+    };
+    Exclusive {
+        x: unsafe {
+            shared_mutable_state(data)
+        }
+    }
+}
+
+impl<T:Owned> Clone for Exclusive<T> {
+    // Duplicate an exclusive ARC, as std::arc::clone.
+    fn clone(&self) -> Exclusive<T> {
+        Exclusive { x: unsafe { clone_shared_mutable_state(&self.x) } }
+    }
+}
+
+pub impl<T:Owned> Exclusive<T> {
+    // Exactly like std::arc::mutex_arc,access(), but with the little_lock
+    // instead of a proper mutex. Same reason for being unsafe.
+    //
+    // Currently, scheduling operations (i.e., yielding, receiving on a pipe,
+    // accessing the provided condition variable) are prohibited while inside
+    // the exclusive. Supporting that is a work in progress.
+    #[inline(always)]
+    unsafe fn with<U>(&self, f: &fn(x: &mut T) -> U) -> U {
+        let rec = get_shared_mutable_state(&self.x);
+        do (*rec).lock.lock {
+            if (*rec).failed {
+                fail!(
+                    ~"Poisoned exclusive - another task failed inside!");
+            }
+            (*rec).failed = true;
+            let result = f(&mut (*rec).data);
+            (*rec).failed = false;
+            result
+        }
+    }
+
+    #[inline(always)]
+    unsafe fn with_imm<U>(&self, f: &fn(x: &T) -> U) -> U {
+        do self.with |x| {
+            f(cast::transmute_immut(x))
+        }
+    }
+}
+
+fn compare_and_swap(address: &mut int, oldval: int, newval: int) -> bool {
+    unsafe {
+        let old = intrinsics::atomic_cxchg(address, oldval, newval);
+        old == oldval
+    }
+}
+
+extern {
+    fn rust_create_little_lock() -> rust_little_lock;
+    fn rust_destroy_little_lock(lock: rust_little_lock);
+    fn rust_lock_little_lock(lock: rust_little_lock);
+    fn rust_unlock_little_lock(lock: rust_little_lock);
+}
+
+#[cfg(test)]
+mod tests {
+    use comm;
+    use super::exclusive;
+    use task;
+    use uint;
+
+    #[test]
+    fn exclusive_arc() {
+        let mut futures = ~[];
+
+        let num_tasks = 10;
+        let count = 10;
+
+        let total = exclusive(~0);
+
+        for uint::range(0, num_tasks) |_i| {
+            let total = total.clone();
+            let (port, chan) = comm::stream();
+            futures.push(port);
+
+            do task::spawn || {
+                for uint::range(0, count) |_i| {
+                    do total.with |count| {
+                        **count += 1;
+                    }
+                }
+                chan.send(());
+            }
+        };
+
+        for futures.each |f| { f.recv() }
+
+        do total.with |total| {
+            assert!(**total == num_tasks * count)
+        };
+    }
+
+    #[test] #[should_fail] #[ignore(cfg(windows))]
+    fn exclusive_poison() {
+        // Tests that if one task fails inside of an exclusive, subsequent
+        // accesses will also fail.
+        let x = exclusive(1);
+        let x2 = x.clone();
+        do task::try || {
+            do x2.with |one| {
+                assert!(*one == 2);
+            }
+        };
+        do x.with |one| {
+            assert!(*one == 1);
+        }
+    }
+}