The Tor Browser: xpcom/glue/nsJSThingHashtable.h@97036ab72558

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

     2 /* This Source Code Form is subject to the terms of the Mozilla Public

     3  * License, v. 2.0. If a copy of the MPL was not distributed with this

     4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 #ifndef nsJSThingHashtable_h__

     7 #define nsJSThingHashtable_h__

     9 #include "nsHashKeys.h"

    10 #include "nsBaseHashtable.h"

    12 namespace JS {

    13 template <class T>

    14 class Heap;

    15 } /* namespace JS */

    17 /**

    18  * A wrapper for hash keys that sets ALLOW_MEMMOVE to false.

    19  *

    20  * This is used in the implementation of nsJSThingHashtable and is not intended

    21  * to be used directly.

    22  *

    23  * It is necessary for hash tables containing JS::Heap<T> values as these must

    24  * be copied rather than memmoved.

    25  */

    26 template<class T>

    27 class nsHashKeyDisallowMemmove : public T

    28 {

    29  public:

    30   nsHashKeyDisallowMemmove(const T& key) : T(key) {}

    31   enum { ALLOW_MEMMOVE = false };

    32 };

    35 /**

    36  * Templated hashtable class for use on the heap where the values are JS GC things.

    37  *

    38  * Storing JS GC thing pointers on the heap requires wrapping them in a

    39  * JS::Heap<T>, and this class takes care of that while presenting an interface

    40  * in terms of the wrapped type T.

    41  *

    42  * For example, to store a hashtable mapping strings to JSObject pointers, you

    43  * can declare a data member like this:

    44  *

    45  *   nsJSThingHashtable<nsStringHashKey, JSObject*> mStringToObjectMap;

    46  *

    47  * See nsBaseHashtable for complete declaration

    48  * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h

    49  *   for a complete specification.

    50  * @param DataType the datatype being wrapped, must be a JS GC thing.

    51  * @see nsInterfaceHashtable, nsClassHashtable

    52  */

    53 template<class KeyClass,class DataType>

    54 class nsJSThingHashtable :

    55   public nsBaseHashtable<nsHashKeyDisallowMemmove<KeyClass>, JS::Heap<DataType>, DataType>

    56 { };

    58 #endif // nsJSThingHashtable_h__

The Tor Browser / file revision

xpcom/glue/nsJSThingHashtable.h@97036ab72558

xpcom/glue/nsJSThingHashtable.h