src/dawn/wire/InlineSharedMemoryManager_win.cpp

// Copyright 2026 The Dawn & Tint Authors
//
// 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.
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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.
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// 3. Neither the name of the copyright holder nor the names of its
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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#include "src/utils/windows_with_undefs.h"

#include <cstddef>
#include <cstdint>
#include <memory>
#include <span>
#include <utility>

#include "src/dawn/common/Constants.h"
#include "src/dawn/common/Math.h"
#include "src/dawn/common/Ref.h"
#include "src/dawn/common/SystemHandle.h"
#include "src/dawn/wire/InlineSharedMemoryManager.h"
#include "src/utils/span.h"

namespace dawn::wire {

namespace {

class SharedMemoryWin : public SharedMemory {
  public:
    SharedMemoryWin(SystemHandle handle, std::span<std::byte> data, uint64_t allocatedSize)
        : SharedMemory(std::move(handle), data, allocatedSize) {}

    ~SharedMemoryWin() override {
        std::span<std::byte> data = GetMappedSpan();
        if (data.data() != nullptr) {
            UnmapViewOfFile(data.data());
        }
    }
};

class InlineSharedMemoryManagerImpl_Win : public InlineSharedMemoryManager {
  public:
    Ref<SharedMemory> CreateSharedMemory(size_t size) override {
        const uint64_t alignedSize = Align(static_cast<uint64_t>(size),
                                           kD3D12SharedBufferMemoryFileMappingHandleSizeAlignment);
        HANDLE rawHandle = CreateFileMappingW(
            INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, static_cast<DWORD>(alignedSize >> 32),
            static_cast<DWORD>(alignedSize & 0xFFFFFFFF), nullptr);
        if (rawHandle == nullptr) {
            return nullptr;
        }
        SystemHandle handle = SystemHandle::Acquire(rawHandle);

        // Map the whole shared memory into the process's address space which is required by
        // `OpenExistingHeapFromAddress`.
        void* pointer =
            MapViewOfFile(rawHandle, FILE_MAP_ALL_ACCESS, 0, 0, checked_cast<size_t>(alignedSize));
        if (pointer == nullptr) {
            return nullptr;
        }

        // SAFETY: the pointer returned by MapViewOfFile points to at least `size` valid bytes.
        auto data = DAWN_UNSAFE_BUFFERS(Span<std::byte>{static_cast<std::byte*>(pointer), size});
        return AcquireRef(new SharedMemoryWin(std::move(handle), data, alignedSize));
    }
};

}  // namespace

std::shared_ptr<InlineSharedMemoryManager> CreateInlineSharedMemoryManager() {
    return std::make_shared<InlineSharedMemoryManagerImpl_Win>();
}

}  // namespace dawn::wire