std: Second pass stabilization for `comm`

This commit is a second pass stabilization for the `std::comm` module,
performing the following actions:

* The entire `std::comm` module was moved under `std::sync::mpsc`. This movement
  reflects that channels are just yet another synchronization primitive, and
  they don't necessarily deserve a special place outside of the other
  concurrency primitives that the standard library offers.
* The `send` and `recv` methods have all been removed.
* The `send_opt` and `recv_opt` methods have been renamed to `send` and `recv`.
  This means that all send/receive operations return a `Result` now indicating
  whether the operation was successful or not.
* The error type of `send` is now a `SendError` to implement a custom error
  message and allow for `unwrap()`. The error type contains an `into_inner`
  method to extract the value.
* The error type of `recv` is now `RecvError` for the same reasons as `send`.
* The `TryRecvError` and `TrySendError` types have had public reexports removed
  of their variants and the variant names have been tweaked with enum
  namespacing rules.
* The `Messages` iterator is renamed to `Iter`

This functionality is now all `#[stable]`:

* `Sender`
* `SyncSender`
* `Receiver`
* `std::sync::mpsc`
* `channel`
* `sync_channel`
* `Iter`
* `Sender::send`
* `Sender::clone`
* `SyncSender::send`
* `SyncSender::try_send`
* `SyncSender::clone`
* `Receiver::recv`
* `Receiver::try_recv`
* `Receiver::iter`
* `SendError`
* `RecvError`
* `TrySendError::{mod, Full, Disconnected}`
* `TryRecvError::{mod, Empty, Disconnected}`
* `SendError::into_inner`
* `TrySendError::into_inner`

This is a breaking change due to the modification of where this module is
located, as well as the changing of the semantics of `send` and `recv`. Most
programs just need to rename imports of `std::comm` to `std::sync::mpsc` and
add calls to `unwrap` after a send or a receive operation.

[breaking-change]

1 files changed, 87 insertions, 0 deletions

diff --git a/src/libstd/sync/mpsc/blocking.rs b/src/libstd/sync/mpsc/blocking.rs
new file mode 100644
index 00000000000..412b7161305
--- /dev/null
+++ b/src/libstd/sync/mpsc/blocking.rs
@@ -0,0 +1,87 @@
+// Copyright 2014 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.
+
+//! Generic support for building blocking abstractions.
+
+use thread::Thread;
+use sync::atomic::{AtomicBool, INIT_ATOMIC_BOOL, Ordering};
+use sync::Arc;
+use kinds::{Sync, Send};
+use kinds::marker::{NoSend, NoSync};
+use mem;
+use clone::Clone;
+
+struct Inner {
+    thread: Thread,
+    woken: AtomicBool,
+}
+
+unsafe impl Send for Inner {}
+unsafe impl Sync for Inner {}
+
+#[deriving(Clone)]
+pub struct SignalToken {
+    inner: Arc<Inner>,
+}
+
+pub struct WaitToken {
+    inner: Arc<Inner>,
+    no_send: NoSend,
+    no_sync: NoSync,
+}
+
+pub fn tokens() -> (WaitToken, SignalToken) {
+    let inner = Arc::new(Inner {
+        thread: Thread::current(),
+        woken: INIT_ATOMIC_BOOL,
+    });
+    let wait_token = WaitToken {
+        inner: inner.clone(),
+        no_send: NoSend,
+        no_sync: NoSync,
+    };
+    let signal_token = SignalToken {
+        inner: inner
+    };
+    (wait_token, signal_token)
+}
+
+impl SignalToken {
+    pub fn signal(&self) -> bool {
+        let wake = !self.inner.woken.compare_and_swap(false, true, Ordering::SeqCst);
+        if wake {
+            self.inner.thread.unpark();
+        }
+        wake
+    }
+
+    /// Convert to an unsafe uint value. Useful for storing in a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_to_uint(self) -> uint {
+        mem::transmute(self.inner)
+    }
+
+    /// Convert from an unsafe uint value. Useful for retrieving a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_from_uint(signal_ptr: uint) -> SignalToken {
+        SignalToken { inner: mem::transmute(signal_ptr) }
+    }
+
+}
+
+impl WaitToken {
+    pub fn wait(self) {
+        while !self.inner.woken.load(Ordering::SeqCst) {
+            Thread::park()
+        }
+    }
+}