unix: add Ppoll on openbsd

Change-Id: I3a13730e219e6f6df28829cf0d1e193c62073ac8
Reviewed-on: https://go-review.googlesource.com/c/144057
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_openbsd_test.go

@@ -6,10 +6,40 @@ package unix_test
 
 import (
 	"testing"
+	"time"
 
 	"golang.org/x/sys/unix"
 )
 
+func TestPpoll(t *testing.T) {
+	f, cleanup := mktmpfifo(t)
+	defer cleanup()
+
+	const timeout = 100 * time.Millisecond
+
+	ok := make(chan bool, 1)
+	go func() {
+		select {
+		case <-time.After(10 * timeout):
+			t.Errorf("Ppoll: failed to timeout after %d", 10*timeout)
+		case <-ok:
+		}
+	}()
+
+	fds := []unix.PollFd{{Fd: int32(f.Fd()), Events: unix.POLLIN}}
+	timeoutTs := unix.NsecToTimespec(int64(timeout))
+	n, err := unix.Ppoll(fds, &timeoutTs, nil)
+	ok <- true
+	if err != nil {
+		t.Errorf("Ppoll: unexpected error: %v", err)
+		return
+	}
+	if n != 0 {
+		t.Errorf("Ppoll: wrong number of events: got %v, expected %v", n, 0)
+		return
+	}
+}
+
 func TestSysctlUvmexp(t *testing.T) {
 	uvm, err := unix.SysctlUvmexp("vm.uvmexp")
 	if err != nil {