From 69cd8b5fcb559ff3342258273f2cc81023f699ba Mon Sep 17 00:00:00 2001
From: Eric Holk <eric.holk@gmail.com>
Date: Mon, 9 Jul 2012 13:53:55 -0700
Subject: [PATCH] Added select2 for pipes.

---
 src/libcore/pipes.rs             | 27 ++++++++++++++++++++++++++-
 src/test/run-pass/pipe-select.rs | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/src/libcore/pipes.rs b/src/libcore/pipes.rs
index f1617c59ac7d..1d6d70defb95 100644
--- a/src/libcore/pipes.rs
+++ b/src/libcore/pipes.rs
@@ -1,6 +1,7 @@
 // Runtime support for pipes.
 
-import unsafe::{forget, reinterpret_cast};
+import unsafe::{forget, reinterpret_cast, transmute};
+import either::{either, left, right};
 
 enum state {
     empty,
@@ -243,6 +244,30 @@ fn wait_many(pkts: ~[&a.packet_header]) -> uint {
     ready_packet
 }
 
+fn select2<A: send, B: send>(
+    +a: recv_packet<A>,
+    +b: recv_packet<B>)
+    -> either<(option<A>, recv_packet<B>), (recv_packet<A>, option<B>)>
+{
+    let a = unsafe { uniquify(a.unwrap()) };
+    let b = unsafe { uniquify(b.unwrap()) };
+    let i = {
+        let headers = ~[&a.header,
+                        &b.header];
+        wait_many(headers)
+    };
+
+    unsafe {
+        alt i {
+          0 { left((recv(recv_packet(transmute(a))),
+                    recv_packet(transmute(b)))) }
+          1 { right((recv_packet(transmute(a)),
+                     recv(recv_packet(transmute(b))))) }
+          _ { fail "select2 return an invalid packet" }
+        }
+    }
+}
+
 #[doc = "Waits on a set of endpoints. Returns a message, its index,
  and a list of the remaining endpoints."]
 fn select<T: send>(+endpoints: ~[recv_packet<T>])
diff --git a/src/test/run-pass/pipe-select.rs b/src/test/run-pass/pipe-select.rs
index af01e568ffd4..09066eebd37e 100644
--- a/src/test/run-pass/pipe-select.rs
+++ b/src/test/run-pass/pipe-select.rs
@@ -72,4 +72,34 @@ fn main() {
     sleep(iotask, 1000);
 
     signal(c2);
-}
\ No newline at end of file
+
+    test_select2();
+}
+
+fn test_select2() {
+    let (ac, ap) = stream::init();
+    let (bc, bp) = stream::init();
+
+    stream::client::send(ac, 42);
+
+    alt pipes::select2(ap, bp) {
+      either::left(*) { }
+      either::right(*) { fail }
+    }
+
+    stream::client::send(bc, "abc");
+
+    #error("done with first select2");
+
+    let (ac, ap) = stream::init();
+    let (bc, bp) = stream::init();
+
+    stream::client::send(bc, "abc");
+
+    alt pipes::select2(ap, bp) {
+      either::left(*) { fail }
+      either::right(*) { }
+    }
+
+    stream::client::send(ac, 42);
+}