diff -r 000000000000 -r 6474c204b198 js/public/Id.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/public/Id.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,185 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef js_Id_h
+#define js_Id_h
+
+// A jsid is an identifier for a property or method of an object which is
+// either a 31-bit signed integer, interned string or object.
+//
+// Also, there is an additional jsid value, JSID_VOID, which does not occur in
+// JS scripts but may be used to indicate the absence of a valid jsid.  A void
+// jsid is not a valid id and only arises as an exceptional API return value,
+// such as in JS_NextProperty. Embeddings must not pass JSID_VOID into JSAPI
+// entry points expecting a jsid and do not need to handle JSID_VOID in hooks
+// receiving a jsid except when explicitly noted in the API contract.
+//
+// A jsid is not implicitly convertible to or from a jsval; JS_ValueToId or
+// JS_IdToValue must be used instead.
+
+#include "mozilla/NullPtr.h"
+
+#include "jstypes.h"
+
+#include "js/HeapAPI.h"
+#include "js/RootingAPI.h"
+#include "js/TypeDecls.h"
+#include "js/Utility.h"
+
+struct jsid
+{
+    size_t asBits;
+    bool operator==(jsid rhs) const { return asBits == rhs.asBits; }
+    bool operator!=(jsid rhs) const { return asBits != rhs.asBits; }
+};
+#define JSID_BITS(id) (id.asBits)
+
+#define JSID_TYPE_STRING                 0x0
+#define JSID_TYPE_INT                    0x1
+#define JSID_TYPE_VOID                   0x2
+#define JSID_TYPE_OBJECT                 0x4
+#define JSID_TYPE_MASK                   0x7
+
+// Avoid using canonical 'id' for jsid parameters since this is a magic word in
+// Objective-C++ which, apparently, wants to be able to #include jsapi.h.
+#define id iden
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_STRING(jsid id)
+{
+    return (JSID_BITS(id) & JSID_TYPE_MASK) == 0;
+}
+
+static MOZ_ALWAYS_INLINE JSString *
+JSID_TO_STRING(jsid id)
+{
+    MOZ_ASSERT(JSID_IS_STRING(id));
+    return (JSString *)JSID_BITS(id);
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_ZERO(jsid id)
+{
+    return JSID_BITS(id) == 0;
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_INT(jsid id)
+{
+    return !!(JSID_BITS(id) & JSID_TYPE_INT);
+}
+
+static MOZ_ALWAYS_INLINE int32_t
+JSID_TO_INT(jsid id)
+{
+    MOZ_ASSERT(JSID_IS_INT(id));
+    return ((uint32_t)JSID_BITS(id)) >> 1;
+}
+
+#define JSID_INT_MIN  0
+#define JSID_INT_MAX  INT32_MAX
+
+static MOZ_ALWAYS_INLINE bool
+INT_FITS_IN_JSID(int32_t i)
+{
+    return i >= 0;
+}
+
+static MOZ_ALWAYS_INLINE jsid
+INT_TO_JSID(int32_t i)
+{
+    jsid id;
+    MOZ_ASSERT(INT_FITS_IN_JSID(i));
+    JSID_BITS(id) = ((i << 1) | JSID_TYPE_INT);
+    return id;
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_OBJECT(jsid id)
+{
+    return (JSID_BITS(id) & JSID_TYPE_MASK) == JSID_TYPE_OBJECT &&
+           (size_t)JSID_BITS(id) != JSID_TYPE_OBJECT;
+}
+
+static MOZ_ALWAYS_INLINE JSObject *
+JSID_TO_OBJECT(jsid id)
+{
+    MOZ_ASSERT(JSID_IS_OBJECT(id));
+    return (JSObject *)(JSID_BITS(id) & ~(size_t)JSID_TYPE_MASK);
+}
+
+static MOZ_ALWAYS_INLINE jsid
+OBJECT_TO_JSID(JSObject *obj)
+{
+    jsid id;
+    MOZ_ASSERT(obj != nullptr);
+    MOZ_ASSERT(((size_t)obj & JSID_TYPE_MASK) == 0);
+    JS_ASSERT(!js::gc::IsInsideNursery(js::gc::GetGCThingRuntime(obj), obj));
+    JSID_BITS(id) = ((size_t)obj | JSID_TYPE_OBJECT);
+    return id;
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_GCTHING(jsid id)
+{
+    return JSID_IS_STRING(id) || JSID_IS_OBJECT(id);
+}
+
+static MOZ_ALWAYS_INLINE void *
+JSID_TO_GCTHING(jsid id)
+{
+    return (void *)(JSID_BITS(id) & ~(size_t)JSID_TYPE_MASK);
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_VOID(const jsid id)
+{
+    MOZ_ASSERT_IF(((size_t)JSID_BITS(id) & JSID_TYPE_MASK) == JSID_TYPE_VOID,
+                 JSID_BITS(id) == JSID_TYPE_VOID);
+    return ((size_t)JSID_BITS(id) == JSID_TYPE_VOID);
+}
+
+static MOZ_ALWAYS_INLINE bool
+JSID_IS_EMPTY(const jsid id)
+{
+    return ((size_t)JSID_BITS(id) == JSID_TYPE_OBJECT);
+}
+
+#undef id
+
+extern JS_PUBLIC_DATA(const jsid) JSID_VOID;
+extern JS_PUBLIC_DATA(const jsid) JSID_EMPTY;
+
+extern JS_PUBLIC_DATA(const JS::HandleId) JSID_VOIDHANDLE;
+extern JS_PUBLIC_DATA(const JS::HandleId) JSID_EMPTYHANDLE;
+
+namespace js {
+
+inline bool
+IsPoisonedId(jsid iden)
+{
+    if (JSID_IS_STRING(iden))
+        return JS::IsPoisonedPtr(JSID_TO_STRING(iden));
+    if (JSID_IS_OBJECT(iden))
+        return JS::IsPoisonedPtr(JSID_TO_OBJECT(iden));
+    return false;
+}
+
+template <> struct GCMethods<jsid>
+{
+    static jsid initial() { return JSID_VOID; }
+    static ThingRootKind kind() { return THING_ROOT_ID; }
+    static bool poisoned(jsid id) { return IsPoisonedId(id); }
+    static bool needsPostBarrier(jsid id) { return false; }
+#ifdef JSGC_GENERATIONAL
+    static void postBarrier(jsid *idp) {}
+    static void relocate(jsid *idp) {}
+#endif
+};
+
+}
+
+#endif /* js_Id_h */