Reorganise Select traits to not expose internal runtime types. Close #5160. Pending #8215.

1 files changed, 324 insertions, 0 deletions

diff --git a/src/libstd/select.rs b/src/libstd/select.rs
new file mode 100644
index 00000000000..2053c971bce
--- /dev/null
+++ b/src/libstd/select.rs
@@ -0,0 +1,324 @@
+// 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 container::Container;
+use iterator::Iterator;
+use option::*;
+// use either::{Either, Left, Right};
+// use rt::kill::BlockedTask;
+use rt::sched::Scheduler;
+use rt::select::{SelectInner, SelectPortInner};
+use rt::local::Local;
+use vec::{OwnedVector, MutableVector};
+
+/// Trait for message-passing primitives that can be select()ed on.
+pub trait Select : SelectInner { }
+
+/// Trait for message-passing primitives that can use the select2() convenience wrapper.
+// (This is separate from the above trait to enable heterogeneous lists of ports
+// that implement Select on different types to use select().)
+pub trait SelectPort<T> : SelectPortInner<T> { }
+
+/// Receive a message from any one of many ports at once. Returns the index of the
+/// port whose data is ready. (If multiple are ready, returns the lowest index.)
+pub fn select<A: Select>(ports: &mut [A]) -> uint {
+    if ports.is_empty() {
+        fail!("can't select on an empty list");
+    }
+
+    for (index, port) in ports.mut_iter().enumerate() {
+        if port.optimistic_check() {
+            return index;
+        }
+    }
+
+    // If one of the ports already contains data when we go to block on it, we
+    // don't bother enqueueing on the rest of them, so we shouldn't bother
+    // unblocking from it either. This is just for efficiency, not correctness.
+    // (If not, we need to unblock from all of them. Length is a placeholder.)
+    let mut ready_index = ports.len();
+
+    let sched = Local::take::<Scheduler>();
+    do sched.deschedule_running_task_and_then |sched, task| {
+        let task_handles = task.make_selectable(ports.len());
+
+        for (index, (port, task_handle)) in
+                ports.mut_iter().zip(task_handles.move_iter()).enumerate() {
+            // If one of the ports has data by now, it will wake the handle.
+            if port.block_on(sched, task_handle) {
+                ready_index = index;
+                break;
+            }
+        }
+    }
+
+    // Task resumes. Now unblock ourselves from all the ports we blocked on.
+    // If the success index wasn't reset, 'take' will just take all of them.
+    // Iterate in reverse so the 'earliest' index that's ready gets returned.
+    for (index, port) in ports.mut_slice(0, ready_index).mut_rev_iter().enumerate() {
+        if port.unblock_from() {
+            ready_index = index;
+        }
+    }
+
+    assert!(ready_index < ports.len());
+    return ready_index;
+}
+
+/* FIXME(#5121, #7914) This all should be legal, but rust is not clever enough yet.
+
+impl <'self> Select for &'self mut Select {
+    fn optimistic_check(&mut self) -> bool { self.optimistic_check() }
+    fn block_on(&mut self, sched: &mut Scheduler, task: BlockedTask) -> bool {
+        self.block_on(sched, task)
+    }
+    fn unblock_from(&mut self) -> bool { self.unblock_from() }
+}
+
+pub fn select2<TA, A: SelectPort<TA>, TB, B: SelectPort<TB>>(mut a: A, mut b: B)
+        -> Either<(Option<TA>, B), (A, Option<TB>)> {
+    let result = {
+        let mut ports = [&mut a as &mut Select, &mut b as &mut Select];
+        select(ports)
+    };
+    match result {
+        0 => Left ((a.recv_ready(), b)),
+        1 => Right((a, b.recv_ready())),
+        x => fail!("impossible case in select2: %?", x)
+    }
+}
+
+*/
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use clone::Clone;
+    use iter::Times;
+    use option::*;
+    use rt::comm::*;
+    use rt::test::*;
+    use vec::*;
+    use comm::GenericChan;
+    use task;
+    use cell::Cell;
+    use iterator::{Iterator, range};
+
+    #[test] #[ignore(cfg(windows))] #[should_fail]
+    fn select_doesnt_get_trolled() {
+        select::<PortOne<()>>([]);
+    }
+
+    /* non-blocking select tests */
+
+    #[cfg(test)]
+    fn select_helper(num_ports: uint, send_on_chans: &[uint]) {
+        // Unfortunately this does not actually test the block_on early-break
+        // codepath in select -- racing between the sender and the receiver in
+        // separate tasks is necessary to get around the optimistic check.
+        let (ports, chans) = unzip(from_fn(num_ports, |_| oneshot::<()>()));
+        let mut dead_chans = ~[];
+        let mut ports = ports;
+        for (i, chan) in chans.move_iter().enumerate() {
+            if send_on_chans.contains(&i) {
+                chan.send(());
+            } else {
+                dead_chans.push(chan);
+            }
+        }
+        let ready_index = select(ports);
+        assert!(send_on_chans.contains(&ready_index));
+        assert!(ports.swap_remove(ready_index).recv_ready().is_some());
+        let _ = dead_chans;
+
+        // Same thing with streams instead.
+        // FIXME(#7971): This should be in a macro but borrowck isn't smart enough.
+        let (ports, chans) = unzip(from_fn(num_ports, |_| stream::<()>()));
+        let mut dead_chans = ~[];
+        let mut ports = ports;
+        for (i, chan) in chans.move_iter().enumerate() {
+            if send_on_chans.contains(&i) {
+                chan.send(());
+            } else {
+                dead_chans.push(chan);
+            }
+        }
+        let ready_index = select(ports);
+        assert!(send_on_chans.contains(&ready_index));
+        assert!(ports.swap_remove(ready_index).recv_ready().is_some());
+        let _ = dead_chans;
+    }
+
+    #[test]
+    fn select_one() {
+        do run_in_newsched_task { select_helper(1, [0]) }
+    }
+
+    #[test]
+    fn select_two() {
+        // NB. I would like to have a test that tests the first one that is
+        // ready is the one that's returned, but that can't be reliably tested
+        // with the randomized behaviour of optimistic_check.
+        do run_in_newsched_task { select_helper(2, [1]) }
+        do run_in_newsched_task { select_helper(2, [0]) }
+        do run_in_newsched_task { select_helper(2, [1,0]) }
+    }
+
+    #[test]
+    fn select_a_lot() {
+        do run_in_newsched_task { select_helper(12, [7,8,9]) }
+    }
+
+    #[test]
+    fn select_stream() {
+        use util;
+        use comm::GenericChan;
+
+        // Sends 10 buffered packets, and uses select to retrieve them all.
+        // Puts the port in a different spot in the vector each time.
+        do run_in_newsched_task {
+            let (ports, _) = unzip(from_fn(10, |_| stream()));
+            let (port, chan) = stream();
+            do 10.times { chan.send(31337); }
+            let mut ports = ports;
+            let mut port = Some(port);
+            let order = [5u,0,4,3,2,6,9,8,7,1];
+            for &index in order.iter() {
+                // put the port in the vector at any index
+                util::swap(port.get_mut_ref(), &mut ports[index]);
+                assert!(select(ports) == index);
+                // get it back out
+                util::swap(port.get_mut_ref(), &mut ports[index]);
+                // NB. Not recv(), because optimistic_check randomly fails.
+                assert!(port.get_ref().recv_ready().unwrap() == 31337);
+            }
+        }
+    }
+
+    #[test]
+    fn select_unkillable() {
+        do run_in_newsched_task {
+            do task::unkillable { select_helper(2, [1]) }
+        }
+    }
+
+    /* blocking select tests */
+
+    #[test]
+    fn select_blocking() {
+        select_blocking_helper(true);
+        select_blocking_helper(false);
+
+        fn select_blocking_helper(killable: bool) {
+            do run_in_newsched_task {
+                let (p1,_c) = oneshot();
+                let (p2,c2) = oneshot();
+                let mut ports = [p1,p2];
+
+                let (p3,c3) = oneshot();
+                let (p4,c4) = oneshot();
+
+                let x = Cell::new((c2, p3, c4));
+                do task::spawn {
+                    let (c2, p3, c4) = x.take();
+                    p3.recv();   // handshake parent
+                    c4.send(()); // normal receive
+                    task::yield();
+                    c2.send(()); // select receive
+                }
+
+                // Try to block before child sends on c2.
+                c3.send(());
+                p4.recv();
+                if killable {
+                    assert!(select(ports) == 1);
+                } else {
+                    do task::unkillable { assert!(select(ports) == 1); }
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn select_racing_senders() {
+        static NUM_CHANS: uint = 10;
+
+        select_racing_senders_helper(true,  ~[0,1,2,3,4,5,6,7,8,9]);
+        select_racing_senders_helper(false, ~[0,1,2,3,4,5,6,7,8,9]);
+        select_racing_senders_helper(true,  ~[0,1,2]);
+        select_racing_senders_helper(false, ~[0,1,2]);
+        select_racing_senders_helper(true,  ~[3,4,5,6]);
+        select_racing_senders_helper(false, ~[3,4,5,6]);
+        select_racing_senders_helper(true,  ~[7,8,9]);
+        select_racing_senders_helper(false, ~[7,8,9]);
+
+        fn select_racing_senders_helper(killable: bool, send_on_chans: ~[uint]) {
+            use rt::test::spawntask_random;
+
+            do run_in_newsched_task {
+                // A bit of stress, since ordinarily this is just smoke and mirrors.
+                do 4.times {
+                    let send_on_chans = send_on_chans.clone();
+                    do task::spawn {
+                        let mut ports = ~[];
+                        for i in range(0u, NUM_CHANS) {
+                            let (p,c) = oneshot();
+                            ports.push(p);
+                            if send_on_chans.contains(&i) {
+                                let c = Cell::new(c);
+                                do spawntask_random {
+                                    task::yield();
+                                    c.take().send(());
+                                }
+                            }
+                        }
+                        // nondeterministic result, but should succeed
+                        if killable {
+                            select(ports);
+                        } else {
+                            do task::unkillable { select(ports); }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[test] #[ignore(cfg(windows))]
+    fn select_killed() {
+        do run_in_newsched_task {
+            let (success_p, success_c) = oneshot::<bool>();
+            let success_c = Cell::new(success_c);
+            do task::try {
+                let success_c = Cell::new(success_c.take());
+                do task::unkillable {
+                    let (p,c) = oneshot();
+                    let c = Cell::new(c);
+                    do task::spawn {
+                        let (dead_ps, dead_cs) = unzip(from_fn(5, |_| oneshot::<()>()));
+                        let mut ports = dead_ps;
+                        select(ports); // should get killed; nothing should leak
+                        c.take().send(()); // must not happen
+                        // Make sure dead_cs doesn't get closed until after select.
+                        let _ = dead_cs;
+                    }
+                    do task::spawn {
+                        fail!(); // should kill sibling awake
+                    }
+
+                    // wait for killed selector to close (NOT send on) its c.
+                    // hope to send 'true'.
+                    success_c.take().send(p.try_recv().is_none());
+                }
+            };
+            assert!(success_p.recv());
+        }
+    }
+}