Changeset 47780 in webkit for trunk/JavaScriptCore/runtime/JSString.cpp

Timestamp:

Aug 26, 2009, 9:52:15 AM (16 years ago)

Author:

[email protected]

Message:

[ES5] Implement getOwnPropertyDescriptor
​https://bugs.webkit.org/show_bug.cgi?id=28724

Reviewed by Gavin Barraclough.

JavaScriptCore:
Implement the core runtime support for getOwnPropertyDescriptor.
This adds a virtual getOwnPropertyDescriptor method to every class
that implements getOwnPropertySlot that shadows the behaviour of
getOwnPropertySlot. The alternative would be to make getOwnPropertySlot
(or PropertySlots in general) provide property attribute information,
but quick testing showed this to be a regression.

WebCore:
Implement the WebCore side of getOwnPropertyDescriptor. This
requires a custom implementation of getOwnPropertyDescriptor
for every class with a custom implementation of getOwnPropertySlot.

The bindings generator has been updated to generate appropriate
versions of getOwnPropertyDescriptor for the general case where
a custom getOwnPropertyDescriptor is not needed. ES5 is vague
about how getOwnPropertyDescriptor should work in the context of
"host" functions with polymorphic GetOwnProperty, so it seems
okay that occasionally we "guess" what attributes -- eg. determining
whether a property is writable.

Test: fast/js/getOwnPropertyDescriptor.html

File:

• trunk/JavaScriptCore/runtime/JSString.cpp (modified) (1 diff)

trunk/JavaScriptCore/runtime/JSString.cpp

@@ -104 +104 @@
 }
 
+bool JSString::getStringPropertyDescriptor(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
+{
+    if (propertyName == exec->propertyNames().length) {
+        descriptor.setDescriptor(jsNumber(exec, m_value.size()), DontEnum | DontDelete | ReadOnly);
+        return true;
+    }
+    
+    bool isStrictUInt32;
+    unsigned i = propertyName.toStrictUInt32(&isStrictUInt32);
+    if (isStrictUInt32 && i < static_cast<unsigned>(m_value.size())) {
+        descriptor.setDescriptor(jsSingleCharacterSubstring(exec, m_value, i), DontDelete | ReadOnly);
+        return true;
+    }
+    
+    return false;
+}
+
+bool JSString::getOwnPropertyDescriptor(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
+{
+    if (getStringPropertyDescriptor(exec, propertyName, descriptor))
+        return true;
+    if (propertyName != exec->propertyNames().underscoreProto)
+        return false;
+    descriptor.setDescriptor(exec->lexicalGlobalObject()->stringPrototype(), DontEnum);
+    return true;
+}
+
 bool JSString::getOwnPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
 {