test_wait_for_single_fd: ensure this works with kqueue

Regardless of future features, this needs to work with
kqueue descriptors across platforms.

Today this will be useful for 3rd-party libraries using
kqueue.  In the future, Ruby may use kqueue natively
and we shall ensure we can wait on it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63421 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/-test-/wait_for_single_fd/extconf.rb

@@ -1,2 +1,4 @@
 # frozen_string_literal: false
+headers = %w(sys/types.h sys/time.h sys/event.h).select { |h| have_header(h) }
+have_func('kqueue', headers)
 create_makefile("-test-/wait_for_single_fd")

ext/-test-/wait_for_single_fd/wait_for_single_fd.c

@@ -19,6 +19,67 @@ wait_for_single_fd(VALUE ign, VALUE fd, VALUE events, VALUE timeout)
     return INT2NUM(rc);
 }
 
+#ifdef HAVE_KQUEUE
+/* ensure rb_wait_for_single_fd works on kqueue descriptors */
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/event.h>
+static VALUE
+kqueue_test_wait(VALUE klass)
+{
+    int kqfd = -1;
+    int p[2] = { -1, -1 };
+    struct timeval tv = { 0, 0 };
+    const struct timespec ts = { 1, 0 };
+    struct kevent kev;
+    const char *msg;
+    VALUE ret = Qfalse;
+    int e = 0;
+    int n;
+
+    msg = "pipe";
+    if (rb_cloexec_pipe(p) < 0) goto err;
+
+    msg = "kqueue";
+    kqfd = kqueue();
+    if (kqfd < 0) goto err;
+
+    n = rb_wait_for_single_fd(kqfd, RB_WAITFD_IN, &tv);
+    if (n != 0) {
+        msg = "spurious wakeup";
+        errno = 0;
+        goto err;
+    }
+
+    msg = "write";
+    if (write(p[1], "", 1) < 0) goto err;
+
+    EV_SET(&kev, p[0], EVFILT_READ, EV_ADD, 0, 0, 0);
+
+    msg = "kevent";
+    n = kevent(kqfd, &kev, 1, &kev, 1, &ts);
+    if (n < 0) goto err;
+    msg = NULL;
+    if (n == 1) {
+        n = rb_wait_for_single_fd(kqfd, RB_WAITFD_IN, &tv);
+        ret = INT2NUM(n);
+    }
+    else {
+        rb_warn("kevent did not return readiness");
+    }
+err:
+    if (msg) e = errno;
+    if (p[0] >= 0) close(p[0]);
+    if (p[1] >= 0) close(p[1]);
+    if (kqfd >= 0) close(kqfd);
+    if (msg) {
+        if (e) rb_syserr_fail(e, msg);
+        rb_raise(rb_eRuntimeError, msg);
+    }
+    return ret;
+}
+#endif /* HAVE_KQUEUE */
+
 void
 Init_wait_for_single_fd(void)
 {
@@ -27,4 +88,7 @@ Init_wait_for_single_fd(void)
     rb_define_const(rb_cObject, "RB_WAITFD_PRI", INT2NUM(RB_WAITFD_PRI));
     rb_define_singleton_method(rb_cIO, "wait_for_single_fd",
                                wait_for_single_fd, 3);
+#ifdef HAVE_KQUEUE
+    rb_define_singleton_method(rb_cIO, "kqueue_test_wait", kqueue_test_wait, 0);
+#endif
 }

test/-ext-/wait_for_single_fd/test_wait_for_single_fd.rb

@@ -52,5 +52,8 @@ class TestWaitForSingleFD < Test::Unit::TestCase
     end
   end
 
-
+  def test_wait_for_kqueue
+    skip 'no kqueue' unless IO.respond_to?(:kqueue_test_wait)
+    assert_equal RB_WAITFD_IN, IO.kqueue_test_wait
+  end
 end