[PATCH v2 07/16] rust/qobject: add from/to JSON bindings for QObject

These are used by tests.  However it could even be an idea to use
serde_json + transcoding and get rid of the C version...

Co-authored-by: Marc-André Lureau <[email protected]>
Signed-off-by: Marc-André Lureau <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
---
 rust/util/wrapper.h          |  1 +
 rust/util/src/qobject/mod.rs | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/rust/util/wrapper.h b/rust/util/wrapper.h
index 0907dd59142..c88820a5e5b 100644
--- a/rust/util/wrapper.h
+++ b/rust/util/wrapper.h
@@ -37,3 +37,4 @@ typedef enum memory_order {
 #include "qobject/qobject.h"
 #include "qobject/qlist.h"
 #include "qobject/qdict.h"
+#include "qobject/qjson.h"
diff --git a/rust/util/src/qobject/mod.rs b/rust/util/src/qobject/mod.rs
index b95dddddedc..95d41cec4f1 100644
--- a/rust/util/src/qobject/mod.rs
+++ b/rust/util/src/qobject/mod.rs
@@ -23,6 +23,7 @@
 use common::assert_field_type;
 pub use deserializer::from_qobject;
 pub use error::{Error, Result};
+use foreign::prelude::*;
 pub use serializer::to_qobject;
 
 use crate::bindings;
@@ -112,6 +113,22 @@ fn refcnt(&self) -> &AtomicUsize {
         let qobj = self.0.get();
         unsafe { AtomicUsize::from_ptr(addr_of_mut!((*qobj).base.refcnt)) }
     }
+
+    pub fn to_json(&self) -> String {
+        let qobj = self.0.get();
+        unsafe {
+            let json = bindings::qobject_to_json(qobj);
+            glib_sys::g_string_free(json, glib_sys::GFALSE).into_native()
+        }
+    }
+
+    pub fn from_json(json: &str) -> std::result::Result<Self, crate::Error> {
+        let c_json = std::ffi::CString::new(json)?;
+        unsafe {
+            crate::Error::with_errp(|errp| bindings::qobject_from_json(c_json.as_ptr(), errp))
+                .map(|qobj| QObject::from_raw(qobj))
+        }
+    }
 }
 
 /// Rust equivalent of the C `QOBJECT` macro; for internal use only, because
-- 
2.52.0