61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsJSThingHashtable_h__
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#define nsJSThingHashtable_h__
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#include "nsHashKeys.h"
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#include "nsBaseHashtable.h"
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namespace JS {
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template<class T>
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class Heap;
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} /* namespace JS */
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/**
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* A wrapper for hash keys that sets ALLOW_MEMMOVE to false.
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*
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* This is used in the implementation of nsJSThingHashtable and is not intended
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* to be used directly.
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*
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* It is necessary for hash tables containing JS::Heap<T> values as these must
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* be copied rather than memmoved.
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*/
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template<class T>
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class nsHashKeyDisallowMemmove : public T
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{
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public:
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explicit nsHashKeyDisallowMemmove(const typename T::KeyTypePointer aKey) : T(aKey) {}
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enum { ALLOW_MEMMOVE = false };
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};
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/**
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* Templated hashtable class for use on the heap where the values are JS GC things.
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*
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* Storing JS GC thing pointers on the heap requires wrapping them in a
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* JS::Heap<T>, and this class takes care of that while presenting an interface
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* in terms of the wrapped type T.
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*
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* For example, to store a hashtable mapping strings to JSObject pointers, you
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* can declare a data member like this:
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*
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* nsJSThingHashtable<nsStringHashKey, JSObject*> mStringToObjectMap;
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*
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* See nsBaseHashtable for complete declaration
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* @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
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* for a complete specification.
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* @param DataType the datatype being wrapped, must be a JS GC thing.
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* @see nsInterfaceHashtable, nsClassHashtable
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*/
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template<class KeyClass, class DataType>
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class nsJSThingHashtable
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: public nsBaseHashtable<nsHashKeyDisallowMemmove<KeyClass>,
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JS::Heap<DataType>, DataType>
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{
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};
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#endif // nsJSThingHashtable_h__
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