[PATCH] Use rb_io_descriptor if available for Ruby 3.3 compatibility

[Samuel Williams <samuel.williams@oriontransfer.co.nz>]

From: Jean Boussier <jean.boussier@gmail.com>

Ref: https://bugs.ruby-lang.org/issues/19057#note-17

Ruby 3.3 no longer fully expose rb_io_t which cause
kgio to think it's being compiled on an older Ruby.

The prefered API to use from Ruby 3.1 onwards is rb_io_descriptor.
---
 ext/kgio/extconf.rb  | 1 +
 ext/kgio/my_fileno.h | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/ext/kgio/extconf.rb b/ext/kgio/extconf.rb
index 5b0b74a..54063f5 100644
--- a/ext/kgio/extconf.rb
+++ b/ext/kgio/extconf.rb
@@ -7,6 +7,7 @@ unless have_macro('CLOCK_MONOTONIC', 'time.h')
 end
 have_type('clockid_t', 'time.h')
 have_library('rt', 'clock_gettime', 'time.h')
+have_func('rb_io_descriptor')
 
 # taken from ext/socket/extconf.rb in ruby/trunk:
 # OpenSolaris:
diff --git a/ext/kgio/my_fileno.h b/ext/kgio/my_fileno.h
index bdf1a5f..d9bda3c 100644
--- a/ext/kgio/my_fileno.h
+++ b/ext/kgio/my_fileno.h
@@ -22,6 +22,12 @@
 
 static int my_fileno(VALUE io)
 {
+#ifdef HAVE_RB_IO_DESCRIPTOR
+	if (TYPE(io) != T_FILE)
+		io = rb_convert_type(io, T_FILE, "IO", "to_io");
+
+	return rb_io_descriptor(io);
+#else
 	rb_io_t *fptr;
 	int fd;
 
@@ -33,4 +39,5 @@ static int my_fileno(VALUE io)
 	if (fd < 0)
 		rb_raise(rb_eIOError, "closed stream");
 	return fd;
+#endif
 }
-- 
2.39.2 (Apple Git-143)