Avoid direct access to IO internals. (#301)

Author: ioquatix

ext/nio4r/bytebuffer.c

@@ -36,6 +36,26 @@ static VALUE NIO_ByteBuffer_inspect(VALUE self);
 
 #define MARK_UNSET -1
 
+/* Compatibility for Ruby <= 3.1 */
+#ifndef HAVE_RB_IO_DESCRIPTOR
+static int
+io_descriptor_fallback(VALUE io)
+{
+    rb_io_t *fptr;
+    GetOpenFile(io, fptr);
+    return fptr->fd;
+}
+#define rb_io_descriptor io_descriptor_fallback
+#endif
+
+static void
+io_set_nonblock(VALUE io)
+{
+    rb_io_t *fptr;
+    GetOpenFile(io, fptr);
+    rb_io_set_nonblock(fptr);
+}
+
 void Init_NIO_ByteBuffer()
 {
     mNIO = rb_define_module("NIO");
@@ -281,19 +301,19 @@ static VALUE NIO_ByteBuffer_put(VALUE self, VALUE string)
 static VALUE NIO_ByteBuffer_read_from(VALUE self, VALUE io)
 {
     struct NIO_ByteBuffer *buffer;
-    rb_io_t *fptr;
     ssize_t nbytes, bytes_read;
 
     Data_Get_Struct(self, struct NIO_ByteBuffer, buffer);
-    GetOpenFile(rb_convert_type(io, T_FILE, "IO", "to_io"), fptr);
-    rb_io_set_nonblock(fptr);
+
+    io = rb_convert_type(io, T_FILE, "IO", "to_io");
+    io_set_nonblock(io);
 
     nbytes = buffer->limit - buffer->position;
     if (nbytes == 0) {
         rb_raise(cNIO_ByteBuffer_OverflowError, "buffer is full");
     }
 
-    bytes_read = read(FPTR_TO_FD(fptr), buffer->buffer + buffer->position, nbytes);
+    bytes_read = read(rb_io_descriptor(io), buffer->buffer + buffer->position, nbytes);
 
     if (bytes_read < 0) {
         if (errno == EAGAIN) {
@@ -311,19 +331,18 @@ static VALUE NIO_ByteBuffer_read_from(VALUE self, VALUE io)
 static VALUE NIO_ByteBuffer_write_to(VALUE self, VALUE io)
 {
     struct NIO_ByteBuffer *buffer;
-    rb_io_t *fptr;
     ssize_t nbytes, bytes_written;
 
     Data_Get_Struct(self, struct NIO_ByteBuffer, buffer);
-    GetOpenFile(rb_convert_type(io, T_FILE, "IO", "to_io"), fptr);
-    rb_io_set_nonblock(fptr);
+    io = rb_convert_type(io, T_FILE, "IO", "to_io");
+    io_set_nonblock(io);
 
     nbytes = buffer->limit - buffer->position;
     if (nbytes == 0) {
         rb_raise(cNIO_ByteBuffer_UnderflowError, "no data remaining in buffer");
     }
 
-    bytes_written = write(FPTR_TO_FD(fptr), buffer->buffer + buffer->position, nbytes);
+    bytes_written = write(rb_io_descriptor(io), buffer->buffer + buffer->position, nbytes);
 
     if (bytes_written < 0) {
         if (errno == EAGAIN) {

ext/nio4r/extconf.rb

@@ -16,6 +16,7 @@
 require "mkmf"
 
 have_header("unistd.h")
+have_func("rb_io_descriptor")
 
 $defs << "-DEV_USE_LINUXAIO"     if have_header("linux/aio_abi.h")
 $defs << "-DEV_USE_IOURING"      if have_header("linux/io_uring.h")

ext/nio4r/monitor.c

@@ -34,6 +34,18 @@ static VALUE NIO_Monitor_readiness(VALUE self);
 static int NIO_Monitor_symbol2interest(VALUE interests);
 static void NIO_Monitor_update_interests(VALUE self, int interests);
 
+/* Compatibility for Ruby <= 3.1 */
+#ifndef HAVE_RB_IO_DESCRIPTOR
+static int
+io_descriptor_fallback(VALUE io)
+{
+    rb_io_t *fptr;
+    GetOpenFile(io, fptr);
+    return fptr->fd;
+}
+#define rb_io_descriptor io_descriptor_fallback
+#endif
+
 /* Monitor control how a channel is being waited for by a monitor */
 void Init_NIO_Monitor()
 {
@@ -81,7 +93,6 @@ static VALUE NIO_Monitor_initialize(VALUE self, VALUE io, VALUE interests, VALUE
     struct NIO_Monitor *monitor;
     struct NIO_Selector *selector;
     ID interests_id;
-    rb_io_t *fptr;
 
     interests_id = SYM2ID(interests);
 
@@ -97,8 +108,8 @@ static VALUE NIO_Monitor_initialize(VALUE self, VALUE io, VALUE interests, VALUE
         rb_raise(rb_eArgError, "invalid event type %s (must be :r, :w, or :rw)", RSTRING_PTR(rb_funcall(interests, rb_intern("inspect"), 0)));
     }
 
-    GetOpenFile(rb_convert_type(io, T_FILE, "IO", "to_io"), fptr);
-    ev_io_init(&monitor->ev_io, NIO_Selector_monitor_callback, FPTR_TO_FD(fptr), monitor->interests);
+    io = rb_convert_type(io, T_FILE, "IO", "to_io");
+    ev_io_init(&monitor->ev_io, NIO_Selector_monitor_callback, rb_io_descriptor(io), monitor->interests);
 
     rb_ivar_set(self, rb_intern("io"), io);
     rb_ivar_set(self, rb_intern("interests"), interests);

ext/nio4r/nio4r.h

@@ -40,12 +40,6 @@ struct NIO_ByteBuffer {
     int position, limit, capacity, mark;
 };
 
-#ifdef GetReadFile
-#define FPTR_TO_FD(fptr) (fileno(GetReadFile(fptr)))
-#else
-#define FPTR_TO_FD(fptr) fptr->fd
-#endif /* GetReadFile */
-
 /* Thunk between libev callbacks in NIO::Monitors and NIO::Selectors */
 void NIO_Selector_monitor_callback(struct ev_loop *ev_loop, struct ev_io *io, int revents);