Hide most of the implementation of `struct rb_io`. (#6511)

* Add rb_io_path and rb_io_open_descriptor.

* Use rb_io_open_descriptor to create PTY objects

* Rename FMODE_PREP -> FMODE_EXTERNAL and expose it

FMODE_PREP I believe refers to the concept of a "pre-prepared" file, but
FMODE_EXTERNAL is clearer about what the file descriptor represents and
aligns with language in the IO::Buffer module.

* Ensure that rb_io_open_descriptor closes the FD if it fails

If FMODE_EXTERNAL is not set, then it's guaranteed that Ruby will be
responsible for closing your file, eventually, if you pass it to
rb_io_open_descriptor, even if it raises an exception.

* Rename IS_EXTERNAL_FD -> RUBY_IO_EXTERNAL_P

* Expose `rb_io_closed_p`.

* Add `rb_io_mode` to get IO mode.

---------

Co-authored-by: KJ Tsanaktsidis <ktsanaktsidis@zendesk.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/spec/ruby/optional/capi/ext/io_spec.c b/spec/ruby/optional/capi/ext/io_spec.c
index cd4bc80229..1c554a1a31 100644
--- a/spec/ruby/optional/capi/ext/io_spec.c
+++ b/spec/ruby/optional/capi/ext/io_spec.c
@@ -28,9 +28,13 @@ static int set_non_blocking(int fd) {
 }
 
 static int io_spec_get_fd(VALUE io) {
+#ifdef RUBY_VERSION_IS_3_1
+  return rb_io_descriptor(io);
+#else
   rb_io_t* fp;
   GetOpenFile(io, fp);
   return fp->fd;
+#endif
 }
 
 VALUE io_spec_GetOpenFile_fd(VALUE self, VALUE io) {
@@ -303,7 +307,7 @@ VALUE io_spec_rb_io_set_nonblock(VALUE self, VALUE io) {
   GetOpenFile(io, fp);
   rb_io_set_nonblock(fp);
 #ifdef F_GETFL
-  flags = fcntl(fp->fd, F_GETFL, 0);
+  flags = fcntl(io_spec_get_fd(io), F_GETFL, 0);
   return flags & O_NONBLOCK ? Qtrue : Qfalse;
 #else
   return Qfalse;
@@ -322,9 +326,13 @@ static VALUE io_spec_errno_set(VALUE self, VALUE val) {
 }
 
 VALUE io_spec_mode_sync_flag(VALUE self, VALUE io) {
+#ifdef RUBY_VERSION_IS_3_3
+  if (rb_io_mode(io) & FMODE_SYNC) {
+#else
   rb_io_t *fp;
   GetOpenFile(io, fp);
   if (fp->mode & FMODE_SYNC) {
+#endif
     return Qtrue;
   } else {
     return Qfalse;