1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/glue/nsJSThingHashtable.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,58 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef nsJSThingHashtable_h__
1.10 +#define nsJSThingHashtable_h__
1.11 +
1.12 +#include "nsHashKeys.h"
1.13 +#include "nsBaseHashtable.h"
1.14 +
1.15 +namespace JS {
1.16 +template <class T>
1.17 +class Heap;
1.18 +} /* namespace JS */
1.19 +
1.20 +/**
1.21 + * A wrapper for hash keys that sets ALLOW_MEMMOVE to false.
1.22 + *
1.23 + * This is used in the implementation of nsJSThingHashtable and is not intended
1.24 + * to be used directly.
1.25 + *
1.26 + * It is necessary for hash tables containing JS::Heap<T> values as these must
1.27 + * be copied rather than memmoved.
1.28 + */
1.29 +template<class T>
1.30 +class nsHashKeyDisallowMemmove : public T
1.31 +{
1.32 + public:
1.33 + nsHashKeyDisallowMemmove(const T& key) : T(key) {}
1.34 + enum { ALLOW_MEMMOVE = false };
1.35 +};
1.36 +
1.37 +
1.38 +/**
1.39 + * Templated hashtable class for use on the heap where the values are JS GC things.
1.40 + *
1.41 + * Storing JS GC thing pointers on the heap requires wrapping them in a
1.42 + * JS::Heap<T>, and this class takes care of that while presenting an interface
1.43 + * in terms of the wrapped type T.
1.44 + *
1.45 + * For example, to store a hashtable mapping strings to JSObject pointers, you
1.46 + * can declare a data member like this:
1.47 + *
1.48 + * nsJSThingHashtable<nsStringHashKey, JSObject*> mStringToObjectMap;
1.49 + *
1.50 + * See nsBaseHashtable for complete declaration
1.51 + * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
1.52 + * for a complete specification.
1.53 + * @param DataType the datatype being wrapped, must be a JS GC thing.
1.54 + * @see nsInterfaceHashtable, nsClassHashtable
1.55 + */
1.56 +template<class KeyClass,class DataType>
1.57 +class nsJSThingHashtable :
1.58 + public nsBaseHashtable<nsHashKeyDisallowMemmove<KeyClass>, JS::Heap<DataType>, DataType>
1.59 +{ };
1.60 +
1.61 +#endif // nsJSThingHashtable_h__
