329 lines
12 KiB
Rust
329 lines
12 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use option::*;
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// use either::{Either, Left, Right};
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use rt::kill::BlockedTask;
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use rt::sched::Scheduler;
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use rt::local::Local;
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/// Trait for message-passing primitives that can be select()ed on.
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pub trait Select {
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// Returns true if data was available.
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fn optimistic_check(&mut self) -> bool;
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// Returns true if data was available. If so, shall also wake() the task.
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fn block_on(&mut self, &mut Scheduler, BlockedTask) -> bool;
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// Returns true if data was available.
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fn unblock_from(&mut self) -> bool;
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}
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/// Trait for message-passing primitives that can use the select2() convenience wrapper.
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// (This is separate from the above trait to enable heterogeneous lists of ports
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// that implement Select on different types to use select().)
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pub trait SelectPort<T> : Select {
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fn recv_ready(self) -> Option<T>;
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}
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/// Receive a message from any one of many ports at once.
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pub fn select<A: Select>(ports: &mut [A]) -> uint {
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if ports.is_empty() {
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fail!("can't select on an empty list");
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}
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for (index, port) in ports.mut_iter().enumerate() {
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if port.optimistic_check() {
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return index;
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}
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}
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// If one of the ports already contains data when we go to block on it, we
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// don't bother enqueueing on the rest of them, so we shouldn't bother
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// unblocking from it either. This is just for efficiency, not correctness.
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// (If not, we need to unblock from all of them. Length is a placeholder.)
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let mut ready_index = ports.len();
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let sched = Local::take::<Scheduler>();
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do sched.deschedule_running_task_and_then |sched, task| {
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let task_handles = task.make_selectable(ports.len());
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for (index, (port, task_handle)) in
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ports.mut_iter().zip(task_handles.consume_iter()).enumerate() {
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// If one of the ports has data by now, it will wake the handle.
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if port.block_on(sched, task_handle) {
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ready_index = index;
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break;
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}
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}
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}
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// Task resumes. Now unblock ourselves from all the ports we blocked on.
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// If the success index wasn't reset, 'take' will just take all of them.
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// Iterate in reverse so the 'earliest' index that's ready gets returned.
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for (index, port) in ports.mut_slice(0, ready_index).mut_rev_iter().enumerate() {
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if port.unblock_from() {
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ready_index = index;
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}
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}
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assert!(ready_index < ports.len());
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return ready_index;
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}
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/* FIXME(#5121, #7914) This all should be legal, but rust is not clever enough yet.
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impl <'self> Select for &'self mut Select {
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fn optimistic_check(&mut self) -> bool { self.optimistic_check() }
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fn block_on(&mut self, sched: &mut Scheduler, task: BlockedTask) -> bool {
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self.block_on(sched, task)
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}
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fn unblock_from(&mut self) -> bool { self.unblock_from() }
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}
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pub fn select2<TA, A: SelectPort<TA>, TB, B: SelectPort<TB>>(mut a: A, mut b: B)
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-> Either<(Option<TA>, B), (A, Option<TB>)> {
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let result = {
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let mut ports = [&mut a as &mut Select, &mut b as &mut Select];
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select(ports)
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};
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match result {
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0 => Left ((a.recv_ready(), b)),
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1 => Right((a, b.recv_ready())),
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x => fail!("impossible case in select2: %?", x)
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}
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}
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*/
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#[cfg(test)]
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mod test {
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use super::*;
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use option::*;
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use rt::comm::*;
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use rt::test::*;
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use vec::*;
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use comm::GenericChan;
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use task;
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use cell::Cell;
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use iterator::{Iterator, range};
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#[test] #[ignore(cfg(windows))] #[should_fail]
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fn select_doesnt_get_trolled() {
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select::<PortOne<()>>([]);
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}
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/* non-blocking select tests */
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#[cfg(test)]
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fn select_helper(num_ports: uint, send_on_chans: &[uint]) {
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// Unfortunately this does not actually test the block_on early-break
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// codepath in select -- racing between the sender and the receiver in
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// separate tasks is necessary to get around the optimistic check.
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let (ports, chans) = unzip(from_fn(num_ports, |_| oneshot::<()>()));
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let mut dead_chans = ~[];
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let mut ports = ports;
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for (i, chan) in chans.consume_iter().enumerate() {
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if send_on_chans.contains(&i) {
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chan.send(());
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} else {
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dead_chans.push(chan);
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}
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}
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let ready_index = select(ports);
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assert!(send_on_chans.contains(&ready_index));
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assert!(ports.swap_remove(ready_index).recv_ready().is_some());
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let _ = dead_chans;
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// Same thing with streams instead.
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// FIXME(#7971): This should be in a macro but borrowck isn't smart enough.
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let (ports, chans) = unzip(from_fn(num_ports, |_| stream::<()>()));
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let mut dead_chans = ~[];
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let mut ports = ports;
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for (i, chan) in chans.consume_iter().enumerate() {
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if send_on_chans.contains(&i) {
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chan.send(());
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} else {
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dead_chans.push(chan);
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}
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}
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let ready_index = select(ports);
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assert!(send_on_chans.contains(&ready_index));
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assert!(ports.swap_remove(ready_index).recv_ready().is_some());
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let _ = dead_chans;
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}
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#[test]
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fn select_one() {
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do run_in_newsched_task { select_helper(1, [0]) }
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}
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#[test]
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fn select_two() {
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// NB. I would like to have a test that tests the first one that is
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// ready is the one that's returned, but that can't be reliably tested
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// with the randomized behaviour of optimistic_check.
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do run_in_newsched_task { select_helper(2, [1]) }
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do run_in_newsched_task { select_helper(2, [0]) }
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do run_in_newsched_task { select_helper(2, [1,0]) }
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}
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#[test]
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fn select_a_lot() {
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do run_in_newsched_task { select_helper(12, [7,8,9]) }
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}
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#[test]
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fn select_stream() {
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use util;
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use comm::GenericChan;
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// Sends 10 buffered packets, and uses select to retrieve them all.
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// Puts the port in a different spot in the vector each time.
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do run_in_newsched_task {
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let (ports, _) = unzip(from_fn(10, |_| stream()));
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let (port, chan) = stream();
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do 10.times { chan.send(31337); }
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let mut ports = ports;
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let mut port = Some(port);
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let order = [5u,0,4,3,2,6,9,8,7,1];
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for &index in order.iter() {
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// put the port in the vector at any index
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util::swap(port.get_mut_ref(), &mut ports[index]);
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assert!(select(ports) == index);
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// get it back out
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util::swap(port.get_mut_ref(), &mut ports[index]);
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// NB. Not recv(), because optimistic_check randomly fails.
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let (data, new_port) = port.take_unwrap().recv_ready().unwrap();
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assert!(data == 31337);
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port = Some(new_port);
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}
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}
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}
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#[test]
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fn select_unkillable() {
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do run_in_newsched_task {
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do task::unkillable { select_helper(2, [1]) }
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}
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}
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/* blocking select tests */
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#[test]
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fn select_blocking() {
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select_blocking_helper(true);
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select_blocking_helper(false);
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fn select_blocking_helper(killable: bool) {
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do run_in_newsched_task {
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let (p1,_c) = oneshot();
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let (p2,c2) = oneshot();
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let mut ports = [p1,p2];
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let (p3,c3) = oneshot();
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let (p4,c4) = oneshot();
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let x = Cell::new((c2, p3, c4));
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do task::spawn {
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let (c2, p3, c4) = x.take();
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p3.recv(); // handshake parent
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c4.send(()); // normal receive
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task::yield();
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c2.send(()); // select receive
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}
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// Try to block before child sends on c2.
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c3.send(());
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p4.recv();
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if killable {
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assert!(select(ports) == 1);
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} else {
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do task::unkillable { assert!(select(ports) == 1); }
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}
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}
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}
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}
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#[test]
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fn select_racing_senders() {
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static NUM_CHANS: uint = 10;
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select_racing_senders_helper(true, ~[0,1,2,3,4,5,6,7,8,9]);
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select_racing_senders_helper(false, ~[0,1,2,3,4,5,6,7,8,9]);
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select_racing_senders_helper(true, ~[0,1,2]);
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select_racing_senders_helper(false, ~[0,1,2]);
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select_racing_senders_helper(true, ~[3,4,5,6]);
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select_racing_senders_helper(false, ~[3,4,5,6]);
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select_racing_senders_helper(true, ~[7,8,9]);
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select_racing_senders_helper(false, ~[7,8,9]);
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fn select_racing_senders_helper(killable: bool, send_on_chans: ~[uint]) {
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use rt::test::spawntask_random;
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do run_in_newsched_task {
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// A bit of stress, since ordinarily this is just smoke and mirrors.
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do 4.times {
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let send_on_chans = send_on_chans.clone();
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do task::spawn {
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let mut ports = ~[];
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for i in range(0u, NUM_CHANS) {
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let (p,c) = oneshot();
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ports.push(p);
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if send_on_chans.contains(&i) {
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let c = Cell::new(c);
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do spawntask_random {
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task::yield();
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c.take().send(());
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}
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}
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}
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// nondeterministic result, but should succeed
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if killable {
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select(ports);
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} else {
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do task::unkillable { select(ports); }
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}
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}
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}
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}
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}
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}
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#[test] #[ignore(cfg(windows))]
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fn select_killed() {
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do run_in_newsched_task {
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let (success_p, success_c) = oneshot::<bool>();
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let success_c = Cell::new(success_c);
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do task::try {
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let success_c = Cell::new(success_c.take());
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do task::unkillable {
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let (p,c) = oneshot();
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let c = Cell::new(c);
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do task::spawn {
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let (dead_ps, dead_cs) = unzip(from_fn(5, |_| oneshot::<()>()));
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let mut ports = dead_ps;
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select(ports); // should get killed; nothing should leak
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c.take().send(()); // must not happen
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// Make sure dead_cs doesn't get closed until after select.
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let _ = dead_cs;
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}
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do task::spawn {
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fail!(); // should kill sibling awake
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}
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// wait for killed selector to close (NOT send on) its c.
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// hope to send 'true'.
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success_c.take().send(p.try_recv().is_none());
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}
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};
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assert!(success_p.recv());
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}
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}
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}
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