/*
 * Copyright (C) 2017-2023 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#pragma once

#include <JavaScriptCore/AllocationFailureMode.h>
#include <JavaScriptCore/Allocator.h>
#include <JavaScriptCore/AllocatorForMode.h>
#include <JavaScriptCore/MarkedBlock.h>
#include <JavaScriptCore/MarkedSpace.h>
#include <wtf/TZoneMalloc.h>
#include <wtf/text/CString.h>

namespace JSC {

class AlignedMemoryAllocator;
class HeapCellType;

enum class SubspaceKind {
    CompleteSubspace,
    IsoSubspace,
    PreciseSubspace,
};

// The idea of subspaces is that you can provide some custom behavior for your objects if you
// allocate them from a custom Subspace in which you override some of the virtual methods. This
// class is the baseclass of all subspaces e.g. CompleteSubspace, IsoSubspace.
class Subspace {
    WTF_MAKE_NONCOPYABLE(Subspace);
    WTF_MAKE_TZONE_ALLOCATED(Subspace);
public:
    JS_EXPORT_PRIVATE virtual ~Subspace();

    const char* name() const LIFETIME_BOUND { return m_name.data(); }
    unsigned nameHash() const { return m_name.hash(); } // FIXME: rdar://139998916
    MarkedSpace& space() const { return m_space; }

    CellAttributes attributes() const;
    const HeapCellType* heapCellType() const { return m_heapCellType; }
    AlignedMemoryAllocator* alignedMemoryAllocator() const { return m_alignedMemoryAllocator; }
    
    void finishSweep(MarkedBlock::Handle&, FreeList*);
    void destroy(VM&, JSCell*);

    void prepareForAllocation();
    
    void didCreateFirstDirectory(BlockDirectory* directory) { m_directoryForEmptyAllocation = directory; }
    
    // Finds an empty block from any Subspace that agrees to trade blocks with us.
    MarkedBlock::Handle* findEmptyBlockToSteal();
    
    template<typename Func>
    void forEachDirectory(const Func&);
    
    Ref<SharedTask<BlockDirectory*()>> parallelDirectorySource();
    
    template<typename Func>
    void forEachMarkedBlock(const Func&);
    
    template<typename Func>
    void forEachNotEmptyMarkedBlock(const Func&);
    
    JS_EXPORT_PRIVATE Ref<SharedTask<MarkedBlock::Handle*()>> parallelNotEmptyMarkedBlockSource();
    
    template<typename Func>
    void forEachPreciseAllocation(const Func&);
    
    template<typename Func>
    void forEachMarkedCell(const Func&);
    
    template<typename Visitor, typename Func>
    Ref<SharedTask<void(Visitor&)>> forEachMarkedCellInParallel(const Func&);

    template<typename Func>
    void forEachLiveCell(const Func&);
    
    void sweepBlocks();
    
    Subspace* nextSubspaceInAlignedMemoryAllocator() const { return m_nextSubspaceInAlignedMemoryAllocator; }
    void setNextSubspaceInAlignedMemoryAllocator(Subspace* subspace) { m_nextSubspaceInAlignedMemoryAllocator = subspace; }
    
    virtual void didResizeBits(unsigned newSize);
    virtual void didRemoveBlock(unsigned blockIndex);
    virtual void didBeginSweepingToFreeList(MarkedBlock::Handle*);

    SubspaceKind kind() const { return m_kind; }
    bool isIsoSubspace() const { return kind() == SubspaceKind::IsoSubspace; }
    bool isPreciseOnly() const { return kind() == SubspaceKind::PreciseSubspace; }

protected:
    Subspace(SubspaceKind, CString name, Heap&);

    void initialize(const HeapCellType&, AlignedMemoryAllocator*);
    
    MarkedSpace& m_space;
    
    const HeapCellType* m_heapCellType { nullptr };
    AlignedMemoryAllocator* m_alignedMemoryAllocator { nullptr };
    
    BlockDirectory* m_firstDirectory { nullptr };
    BlockDirectory* m_directoryForEmptyAllocation { nullptr }; // Uses the MarkedSpace linked list of blocks.
    SentinelLinkedList<PreciseAllocation, BasicRawSentinelNode<PreciseAllocation>> m_preciseAllocations;

    SubspaceKind m_kind;
    uint8_t m_remainingLowerTierPreciseCount { 0 }; // Lower tier is a precise allocation but we use the term lower to avoid confusion with precise-only.

    Subspace* m_nextSubspaceInAlignedMemoryAllocator { nullptr };

    CString m_name;
};

} // namespace JSC

