wait.c: poll over nread

* ext/io/wait/wait.c (io_ready_p, io_wait_readable): try polling
  first and check FIONREAD optionally to see if EOF.
  [ruby-core:36805] [Feature #4849]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50262 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Sun Apr 12 15:08:13 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/io/wait/wait.c (io_ready_p, io_wait_readable): try polling
+	  first and check FIONREAD optionally to see if EOF.
+	  [ruby-core:36805] [Feature #4849]
+
 Sun Apr 12 14:53:23 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* lib/rubygems/test_case.rb: fixed json load error for rubygems tests.

ext/io/wait/wait.c

@@ -105,14 +105,13 @@ static VALUE
 io_ready_p(VALUE io)
 {
     rb_io_t *fptr;
-    ioctl_arg n;
+    struct timeval tv = {0, 0};
 
     GetOpenFile(io, fptr);
     rb_io_check_readable(fptr);
     if (rb_io_read_pending(fptr)) return Qtrue;
-    if (!FIONREAD_POSSIBLE_P(fptr->fd)) return Qnil;
-    if (ioctl(fptr->fd, FIONREAD, &n)) return Qnil;
-    if (n > 0) return Qtrue;
+    if (wait_for_single_fd(fptr, RB_WAITFD_IN, &tv))
+	return Qtrue;
     return Qfalse;
 }
 
@@ -131,7 +130,6 @@ static VALUE
 io_wait_readable(int argc, VALUE *argv, VALUE io)
 {
     rb_io_t *fptr;
-    ioctl_arg n;
     struct timeval timerec;
     struct timeval *tv;
 
@@ -139,10 +137,12 @@ io_wait_readable(int argc, VALUE *argv, VALUE io)
     rb_io_check_readable(fptr);
     tv = get_timeout(argc, argv, &timerec);
     if (rb_io_read_pending(fptr)) return Qtrue;
-    if (!FIONREAD_POSSIBLE_P(fptr->fd)) return Qfalse;
-    wait_for_single_fd(fptr, RB_WAITFD_IN, tv);
-    if (ioctl(fptr->fd, FIONREAD, &n)) rb_sys_fail(0);
-    if (n > 0) return io;
+    if (wait_for_single_fd(fptr, RB_WAITFD_IN, tv)) {
+	ioctl_arg n;
+	if (!FIONREAD_POSSIBLE_P(fptr->fd)) return io;
+	if (ioctl(fptr->fd, FIONREAD, &n)) rb_sys_fail(0);
+	if (n > 0) return io;
+    }
     return Qnil;
 }