The Tor Browser: js/src/gc/Nursery-inl.h@6474c204b198

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-

     2  * vim: set ts=4 sw=4 et tw=79 ft=cpp:

     3  *

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

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

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

     8 #ifndef gc_Nursery_inl_h

     9 #define gc_Nursery_inl_h

    11 #ifdef JSGC_GENERATIONAL

    13 #include "gc/Nursery.h"

    15 #include "gc/Heap.h"

    17 namespace js {

    18 namespace gc {

    20 /*

    21  * This structure overlays a Cell in the Nursery and re-purposes its memory

    22  * for managing the Nursery collection process.

    23  */

    24 class RelocationOverlay

    25 {

    26     friend class MinorCollectionTracer;

    28     /* The low bit is set so this should never equal a normal pointer. */

    29     static const uintptr_t Relocated = uintptr_t(0xbad0bad1);

    31     /* Set to Relocated when moved. */

    32     uintptr_t magic_;

    34     /* The location |this| was moved to. */

    35     Cell *newLocation_;

    37     /* A list entry to track all relocated things. */

    38     RelocationOverlay *next_;

    40   public:

    41     static RelocationOverlay *fromCell(Cell *cell) {

    42         JS_ASSERT(!cell->isTenured());

    43         return reinterpret_cast<RelocationOverlay *>(cell);

    44     }

    46     bool isForwarded() const {

    47         return magic_ == Relocated;

    48     }

    50     Cell *forwardingAddress() const {

    51         JS_ASSERT(isForwarded());

    52         return newLocation_;

    53     }

    55     void forwardTo(Cell *cell) {

    56         JS_ASSERT(!isForwarded());

    57         magic_ = Relocated;

    58         newLocation_ = cell;

    59         next_ = nullptr;

    60     }

    62     RelocationOverlay *next() const {

    63         return next_;

    64     }

    65 };

    67 } /* namespace gc */

    68 } /* namespace js */

    70 template <typename T>

    71 MOZ_ALWAYS_INLINE bool

    72 js::Nursery::getForwardedPointer(T **ref)

    73 {

    74     JS_ASSERT(ref);

    75     JS_ASSERT(isInside(*ref));

    76     const gc::RelocationOverlay *overlay = reinterpret_cast<const gc::RelocationOverlay *>(*ref);

    77     if (!overlay->isForwarded())

    78         return false;

    79     /* This static cast from Cell* restricts T to valid (GC thing) types. */

    80     *ref = static_cast<T *>(overlay->forwardingAddress());

    81     return true;

    82 }

    84 #endif /* JSGC_GENERATIONAL */

    86 #endif /* gc_Nursery_inl_h */

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