[gjs/wip/ptomato/mozjs38: 8/24] boxed: Use JSNative property accessors

[Philip Chimento <pchimento src gnome org>]

commit d1723117da3d311ae3cea8849df867de9e749706
Author: Philip Chimento <philip endlessm com>
Date:   Fri Jan 20 16:33:21 2017 -0800

    boxed: Use JSNative property accessors
    
    Property accessors of JSPropertyOp and JSStrictPropertyOp are going away
    in future versions of SpiderMonkey, to be replaced by JSNative.
    
    Unfortunately the property name was passed to the PropertyOp callbacks as
    a jsid, and it is not available to JSNative callbacks. The property
    accessors in Boxed do require the property name, however, so they can
    look up the GIFieldInfo. In order to achieve this we follow a suggestion
    from a Mozilla mailing list [1]: wrap the JSNative accessors in
    JSFunction objects, which can have "reserved slots" in which to store
    information with which we can retrieve the field info.
    
    For this, we need to use the jsfriend API, but such use is isolated to
    two functions.
    
    [1] https://groups.google.com/forum/#!msg/mozilla.dev.tech.js-engine.internals/TZznbH80zJw/BmRrMsuuAwAJ
    
    https://bugzilla.gnome.org/show_bug.cgi?id=776966

 gi/boxed.cpp |  159 +++++++++++++++++++++++++++++++++-------------------------
 1 files changed, 91 insertions(+), 68 deletions(-)
---
diff --git a/gi/boxed.cpp b/gi/boxed.cpp
index 9a76d5e..9a47769 100644
--- a/gi/boxed.cpp
+++ b/gi/boxed.cpp
@@ -39,6 +39,11 @@
 
 #include <girepository.h>
 
+/* Reserved slots of JSNative accessor wrappers */
+enum {
+    SLOT_PROP_NAME,
+};
+
 struct Boxed {
     /* prototype info */
     GIBoxedInfo *info;
@@ -512,43 +517,28 @@ boxed_finalize(JSFreeOp *fop,
 }
 
 static GIFieldInfo *
-get_field_info (JSContext *context,
-                Boxed     *priv,
-                jsid       id)
+get_field_info(JSContext *cx,
+               Boxed     *priv,
+               uint32_t   id)
 {
-    GIFieldInfo *field_info;
-    char *name;
-
-    if (!priv->field_map)
-        priv->field_map = get_field_map(priv->info);
-
-    if (!gjs_get_string_id(context, id, &name))
-        goto out;
-
-    field_info = (GIFieldInfo *) g_hash_table_lookup(priv->field_map, name);
+    GIFieldInfo *field_info = g_struct_info_get_field(priv->info, id);
     if (field_info == NULL) {
-        gjs_throw(context, "No field %s on boxed type %s",
-                  name, g_base_info_get_name((GIBaseInfo *)priv->info));
-        g_free(name);
-        goto out;
+        gjs_throw(cx, "No field %d on boxed type %s",
+                  id, g_base_info_get_name((GIBaseInfo *)priv->info));
+        return NULL;
     }
 
-    g_free(name);
-
     return field_info;
-
- out:
-    return NULL;
 }
 
 static bool
-get_nested_interface_object (JSContext   *context,
-                             JSObject    *parent_obj,
-                             Boxed       *parent_priv,
-                             GIFieldInfo *field_info,
-                             GITypeInfo  *type_info,
-                             GIBaseInfo  *interface_info,
-                             JS::Value   *value)
+get_nested_interface_object(JSContext             *context,
+                            JSObject              *parent_obj,
+                            Boxed                 *parent_priv,
+                            GIFieldInfo           *field_info,
+                            GITypeInfo            *type_info,
+                            GIBaseInfo            *interface_info,
+                            JS::MutableHandleValue value)
 {
     JSObject *obj;
     int offset;
@@ -594,27 +584,48 @@ get_nested_interface_object (JSContext   *context,
      */
     JS_SetReservedSlot(obj, 0, JS::ObjectValue(*parent_obj));
 
-    *value = JS::ObjectValue(*obj);
+    value.setObject(*obj);
     return true;
 }
 
+static JSObject *
+define_native_accessor_wrapper(JSContext  *cx,
+                               JSNative    call,
+                               unsigned    nargs,
+                               const char *func_name,
+                               uint32_t    id)
+{
+    JSFunction *func = js::NewFunctionWithReserved(cx, call, nargs, 0,
+                                                   NULL, func_name);
+    if (!func)
+        return NULL;
+
+    JSObject *func_obj = JS_GetFunctionObject(func);
+    js::SetFunctionNativeReserved(func_obj, SLOT_PROP_NAME,
+                                  JS::PrivateUint32Value(id));
+    return func_obj;
+}
+
+static uint32_t
+native_accessor_slot(JSObject *func_obj)
+{
+    return js::GetFunctionNativeReserved(func_obj, SLOT_PROP_NAME)
+        .toPrivateUint32();
+}
+
 static bool
-boxed_field_getter (JSContext              *context,
-                    JS::HandleObject        obj,
-                    JS::HandleId            id,
-                    JS::MutableHandleValue  value)
+boxed_field_getter(JSContext *context,
+                   unsigned   argc,
+                   JS::Value *vp)
 {
-    Boxed *priv;
+    GJS_GET_PRIV(context, argc, vp, args, obj, Boxed, priv);
     GIFieldInfo *field_info;
     GITypeInfo *type_info;
     GArgument arg;
     bool success = false;
 
-    priv = priv_from_js(context, obj);
-    if (!priv)
-        return false;
-
-    field_info = get_field_info(context, priv, id);
+    field_info = get_field_info(context, priv,
+                                native_accessor_slot(&args.callee()));
     if (!field_info)
         return false;
 
@@ -637,7 +648,7 @@ boxed_field_getter (JSContext              *context,
 
             success = get_nested_interface_object (context, obj, priv,
                                                    field_info, type_info, interface_info,
-                                                   value.address());
+                                                   args.rval());
 
             g_base_info_unref ((GIBaseInfo *)interface_info);
 
@@ -654,7 +665,8 @@ boxed_field_getter (JSContext              *context,
         goto out;
     }
 
-    if (!gjs_value_from_g_argument(context, value, type_info, &arg, true))
+    if (!gjs_value_from_g_argument(context, args.rval(), type_info,
+                                   &arg, true))
         goto out;
 
     success = true;
@@ -779,41 +791,36 @@ out:
 }
 
 static bool
-boxed_field_setter (JSContext              *context,
-                    JS::HandleObject        obj,
-                    JS::HandleId            id,
-                    bool                    strict,
-                    JS::MutableHandleValue  value)
+boxed_field_setter(JSContext *cx,
+                   unsigned   argc,
+                   JS::Value *vp)
 {
-    Boxed *priv;
+    GJS_GET_PRIV(cx, argc, vp, args, obj, Boxed, priv);
     GIFieldInfo *field_info;
-    bool success = false;
 
-    priv = priv_from_js(context, obj);
-    if (!priv)
-        return false;
-    field_info = get_field_info(context, priv, id);
+    field_info = get_field_info(cx, priv,
+                                native_accessor_slot(&args.callee()));
     if (!field_info)
         return false;
 
     if (priv->gboxed == NULL) { /* direct access to proto field */
-        gjs_throw(context, "Can't set field %s.%s on prototype",
+        gjs_throw(cx, "Can't set field %s.%s on prototype",
                   g_base_info_get_name ((GIBaseInfo *)priv->info),
                   g_base_info_get_name ((GIBaseInfo *)field_info));
-        goto out;
+        return false;
     }
 
-    success = boxed_set_field_from_value (context, priv, field_info, value);
-
-out:
+    if (!boxed_set_field_from_value(cx, priv, field_info, args[0]))
+        return false;
 
-    return success;
+    args.rval().setUndefined();  /* No stored value */
+    return true;
 }
 
 static bool
-define_boxed_class_fields (JSContext       *context,
-                           Boxed           *priv,
-                           JS::HandleObject proto)
+define_boxed_class_fields(JSContext       *cx,
+                          Boxed           *priv,
+                          JS::HandleObject proto)
 {
     int n_fields = g_struct_info_get_n_fields (priv->info);
     int i;
@@ -842,15 +849,31 @@ define_boxed_class_fields (JSContext       *context,
     for (i = 0; i < n_fields; i++) {
         GIFieldInfo *field = g_struct_info_get_field (priv->info, i);
         const char *field_name = g_base_info_get_name ((GIBaseInfo *)field);
-        bool result;
+        g_autofree char *getter_name = g_strconcat("boxed_field_get::",
+                                                   field_name, NULL);
+        g_autofree char *setter_name = g_strconcat("boxed_field_set::",
+                                                   field_name, NULL);
+        g_base_info_unref ((GIBaseInfo *)field);
 
-        result = JS_DefineProperty(context, proto, field_name, JS::NullHandleValue,
-                                   JSPROP_PERMANENT | JSPROP_SHARED,
-                                   boxed_field_getter, boxed_field_setter);
+        /* In order to have one getter and setter for all the properties
+         * we define, we must provide the property index in a "reserved
+         * slot" for which we must unfortunately use the jsfriendapi. */
+        JS::RootedObject getter(cx,
+            define_native_accessor_wrapper(cx, boxed_field_getter, 0,
+                                           getter_name, i));
+        if (!getter)
+            return false;
 
-        g_base_info_unref ((GIBaseInfo *)field);
+        JS::RootedObject setter(cx,
+            define_native_accessor_wrapper(cx, boxed_field_setter, 1,
+                                           setter_name, i));
+        if (!setter)
+            return false;
 
-        if (!result)
+        if (!JS_DefineProperty(cx, proto, field_name, JS::NullHandleValue,
+                               JSPROP_PERMANENT | JSPROP_SHARED | JSPROP_GETTER | JSPROP_SETTER,
+                               JS_DATA_TO_FUNC_PTR(JSPropertyOp, getter.get()),
+                               JS_DATA_TO_FUNC_PTR(JSStrictPropertyOp, setter.get())))
             return false;
     }