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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 nsJSThingHashtable_h__
#define nsJSThingHashtable_h__
#include "js/RootingAPI.h"
#include "nsHashKeys.h"
#include "nsBaseHashtable.h"
namespace JS {
template <class T>
class Heap;
} /* namespace JS */
/**
* A wrapper for hash keys that sets ALLOW_MEMMOVE to false.
*
* This is used in the implementation of nsJSThingHashtable and is not intended
* to be used directly.
*
* It is necessary for hash tables containing JS::Heap<T> values as these must
* be copied rather than memmoved.
*/
template <class T>
class nsHashKeyDisallowMemmove : public T {
public:
explicit nsHashKeyDisallowMemmove(const typename T::KeyTypePointer aKey)
: T(aKey) {}
enum { ALLOW_MEMMOVE = false };
};
/**
* Templated hashtable class for use on the heap where the values are JS GC
* things.
*
* Storing JS GC thing pointers on the heap requires wrapping them in a
* JS::Heap<T>, and this class takes care of that while presenting an interface
* in terms of the wrapped type T.
*
* For example, to store a hashtable mapping strings to JSObject pointers, you
* can declare a data member like this:
*
* nsJSThingHashtable<nsStringHashKey, JSObject*> mStringToObjectMap;
*
* See nsBaseHashtable for complete declaration
* @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
* for a complete specification.
* @param DataType the datatype being wrapped, must be a JS GC thing.
* @see nsInterfaceHashtable, nsClassHashtable
*/
template <class KeyClass, class DataType>
class nsJSThingHashtable
: public nsBaseHashtable<nsHashKeyDisallowMemmove<KeyClass>,
JS::Heap<DataType>, DataType> {};
#endif // nsJSThingHashtable_h__
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