michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef nsJSThingHashtable_h__
michael@0: #define nsJSThingHashtable_h__
michael@0: 
michael@0: #include "nsHashKeys.h"
michael@0: #include "nsBaseHashtable.h"
michael@0: 
michael@0: namespace JS {
michael@0: template <class T>
michael@0: class Heap;
michael@0: } /* namespace JS */
michael@0: 
michael@0: /**
michael@0:  * A wrapper for hash keys that sets ALLOW_MEMMOVE to false.
michael@0:  *
michael@0:  * This is used in the implementation of nsJSThingHashtable and is not intended
michael@0:  * to be used directly.
michael@0:  *
michael@0:  * It is necessary for hash tables containing JS::Heap<T> values as these must
michael@0:  * be copied rather than memmoved.
michael@0:  */
michael@0: template<class T>
michael@0: class nsHashKeyDisallowMemmove : public T
michael@0: {
michael@0:  public:
michael@0:   nsHashKeyDisallowMemmove(const T& key) : T(key) {}
michael@0:   enum { ALLOW_MEMMOVE = false };
michael@0: };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Templated hashtable class for use on the heap where the values are JS GC things.
michael@0:  *
michael@0:  * Storing JS GC thing pointers on the heap requires wrapping them in a
michael@0:  * JS::Heap<T>, and this class takes care of that while presenting an interface
michael@0:  * in terms of the wrapped type T.
michael@0:  *
michael@0:  * For example, to store a hashtable mapping strings to JSObject pointers, you
michael@0:  * can declare a data member like this:
michael@0:  *
michael@0:  *   nsJSThingHashtable<nsStringHashKey, JSObject*> mStringToObjectMap;
michael@0:  *
michael@0:  * See nsBaseHashtable for complete declaration
michael@0:  * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
michael@0:  *   for a complete specification.
michael@0:  * @param DataType the datatype being wrapped, must be a JS GC thing.
michael@0:  * @see nsInterfaceHashtable, nsClassHashtable
michael@0:  */
michael@0: template<class KeyClass,class DataType>
michael@0: class nsJSThingHashtable :
michael@0:   public nsBaseHashtable<nsHashKeyDisallowMemmove<KeyClass>, JS::Heap<DataType>, DataType>
michael@0: { };
michael@0: 
michael@0: #endif // nsJSThingHashtable_h__