bug 486106 - restoring JS*Lookup API compatibility with fast arrays. r=shaver

js/src/jsapi.cpp

@@ -3237,6 +3237,8 @@ LookupResult(JSContext *cx, JSObject *obj, JSObject *obj2, JSProperty *prop)
         rval = SPROP_HAS_VALID_SLOT(sprop, OBJ_SCOPE(obj2))
                ? LOCKED_OBJ_GET_SLOT(obj2, sprop->slot)
                : JSVAL_TRUE;
+    } else if (OBJ_IS_DENSE_ARRAY(cx, obj2)) {
+        rval = js_GetDenseArrayElementValue(obj2, prop);
     } else {
         /* XXX bad API: no way to return "defined but value unknown" */
         rval = JSVAL_TRUE;

js/src/jsarray.cpp

@@ -739,6 +739,23 @@ array_dropProperty(JSContext *cx, JSObject *obj, JSProperty *prop)
 #endif
 }
 
+jsval
+js_GetDenseArrayElementValue(JSObject *obj, JSProperty *prop)
+{
+    /* OBJ_IS_DENSE_ARRAY does not use the cx argument. */
+    JS_ASSERT(OBJ_IS_DENSE_ARRAY(cx, obj));
+    JS_ASSERT((void *) prop ==
+              (void *) &(obj->fslots[JSSLOT_ARRAY_LOOKUP_HOLDER]));
+    JS_ASSERT((jsval) prop->id == obj->fslots[JSSLOT_ARRAY_LOOKUP_HOLDER]);
+    JS_ASSERT(JSVAL_IS_INT(prop->id));
+
+    jsint i = JSID_TO_INT(prop->id);
+    JS_ASSERT(i >= 0);
+    jsval v = obj->dslots[i];
+    JS_ASSERT(v != JSVAL_HOLE);
+    return v;
+}
+
 static JSBool
 array_getProperty(JSContext *cx, JSObject *obj, jsid id, jsval *vp)
 {

js/src/jsarray.h

@@ -223,6 +223,12 @@ js_ArrayToJSDoubleBuffer(JSContext *cx, JSObject *obj, jsuint offset, jsuint cou
 JSBool
 js_PrototypeHasIndexedProperties(JSContext *cx, JSObject *obj);
 
+/*
+ * Utility to access the value from the id returned by array_lookupProperty.
+ */
+jsval
+js_GetDenseArrayElementValue(JSObject *obj, JSProperty *prop);
+
 JS_END_EXTERN_C
 
 #endif /* jsarray_h___ */