michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0:  * vim: set ts=4 sw=4 et tw=79 ft=cpp:
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef gc_Nursery_inl_h
michael@0: #define gc_Nursery_inl_h
michael@0: 
michael@0: #ifdef JSGC_GENERATIONAL
michael@0: 
michael@0: #include "gc/Nursery.h"
michael@0: 
michael@0: #include "gc/Heap.h"
michael@0: 
michael@0: namespace js {
michael@0: namespace gc {
michael@0: 
michael@0: /*
michael@0:  * This structure overlays a Cell in the Nursery and re-purposes its memory
michael@0:  * for managing the Nursery collection process.
michael@0:  */
michael@0: class RelocationOverlay
michael@0: {
michael@0:     friend class MinorCollectionTracer;
michael@0: 
michael@0:     /* The low bit is set so this should never equal a normal pointer. */
michael@0:     static const uintptr_t Relocated = uintptr_t(0xbad0bad1);
michael@0: 
michael@0:     /* Set to Relocated when moved. */
michael@0:     uintptr_t magic_;
michael@0: 
michael@0:     /* The location |this| was moved to. */
michael@0:     Cell *newLocation_;
michael@0: 
michael@0:     /* A list entry to track all relocated things. */
michael@0:     RelocationOverlay *next_;
michael@0: 
michael@0:   public:
michael@0:     static RelocationOverlay *fromCell(Cell *cell) {
michael@0:         JS_ASSERT(!cell->isTenured());
michael@0:         return reinterpret_cast<RelocationOverlay *>(cell);
michael@0:     }
michael@0: 
michael@0:     bool isForwarded() const {
michael@0:         return magic_ == Relocated;
michael@0:     }
michael@0: 
michael@0:     Cell *forwardingAddress() const {
michael@0:         JS_ASSERT(isForwarded());
michael@0:         return newLocation_;
michael@0:     }
michael@0: 
michael@0:     void forwardTo(Cell *cell) {
michael@0:         JS_ASSERT(!isForwarded());
michael@0:         magic_ = Relocated;
michael@0:         newLocation_ = cell;
michael@0:         next_ = nullptr;
michael@0:     }
michael@0: 
michael@0:     RelocationOverlay *next() const {
michael@0:         return next_;
michael@0:     }
michael@0: };
michael@0: 
michael@0: } /* namespace gc */
michael@0: } /* namespace js */
michael@0: 
michael@0: template <typename T>
michael@0: MOZ_ALWAYS_INLINE bool
michael@0: js::Nursery::getForwardedPointer(T **ref)
michael@0: {
michael@0:     JS_ASSERT(ref);
michael@0:     JS_ASSERT(isInside(*ref));
michael@0:     const gc::RelocationOverlay *overlay = reinterpret_cast<const gc::RelocationOverlay *>(*ref);
michael@0:     if (!overlay->isForwarded())
michael@0:         return false;
michael@0:     /* This static cast from Cell* restricts T to valid (GC thing) types. */
michael@0:     *ref = static_cast<T *>(overlay->forwardingAddress());
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: #endif /* JSGC_GENERATIONAL */
michael@0: 
michael@0: #endif /* gc_Nursery_inl_h */