Add basic RomFS support

Seems to crash the 3DS if there is no actual RomFS data in the 3dsx
file, so there's room for improvement.

ctru-rs/src/lib.rs

@@ -34,6 +34,7 @@ pub mod console;
 pub mod error;
 pub mod gfx;
 pub mod sdmc;
+pub mod romfs;
 pub mod services;
 pub mod srv;
 pub mod thread;

ctru-rs/src/romfs.rs

@@ -0,0 +1,24 @@
+use std::ffi::CStr;
+
+#[non_exhaustive]
+pub struct RomFS;
+
+impl RomFS {
+    pub fn new() -> crate::Result<Self> {
+        let mount_name = CStr::from_bytes_with_nul(b"romfs\0").unwrap();
+        let result = unsafe { ctru_sys::romfsMountSelf(mount_name.as_ptr()) };
+
+        if result < 0 {
+            Err(result.into())
+        } else {
+            Ok(Self)
+        }
+    }
+}
+
+impl Drop for RomFS {
+    fn drop(&mut self) {
+        let mount_name = CStr::from_bytes_with_nul(b"romfs\0").unwrap();
+        unsafe { ctru_sys::romfsUnmount(mount_name.as_ptr()) };
+    }
+}