Source/JavaScriptCore/heap/PreciseSubspace.h

/*
 * Copyright (C) 2025 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
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 * 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
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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#pragma once

#include "Subspace.h"
#include "SubspaceAccess.h"

namespace JSC {

// Unlike other Subspaces, PreciseSubspace doesn't support LocalAllocators as it's meant for large, rarely allocated objects
// that wouldn't be profitable to allocate directly in JIT code.
class PreciseSubspace : public Subspace {
    WTF_MAKE_TZONE_ALLOCATED_EXPORT(PreciseSubspace, JS_EXPORT_PRIVATE);
public:
    JS_EXPORT_PRIVATE PreciseSubspace(CString name, Heap&, const HeapCellType&, AlignedMemoryAllocator*);
    JS_EXPORT_PRIVATE ~PreciseSubspace() override;

    void* tryAllocate(size_t cellSize);
    void* allocate(VM&, size_t, GCDeferralContext*, AllocationFailureMode);

private:
    void didResizeBits(unsigned newSize) override;
    void didRemoveBlock(unsigned blockIndex) override;
    void didBeginSweepingToFreeList(MarkedBlock::Handle*) override;
};

namespace GCClient {
// This doesn't do anything interesting right now but we keep the GCClient namespace for consistency/templates.
using PreciseSubspace = JSC::PreciseSubspace;
}

} // namespace JSC