src/dawn/utils/SystemHandle.h

// Copyright 2025 The Dawn & Tint Authors
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#ifndef SRC_DAWN_UTILS_SYSTEMHANDLE_H_
#define SRC_DAWN_UTILS_SYSTEMHANDLE_H_

#include <cstdint>
#include <type_traits>
#include <utility>

#include "src/utils/non_copyable.h"
#include "src/utils/platform.h"

namespace dawn::utils {

class SystemHandle : public NonCopyable {
  public:
    // Create an alias for the actual primitive handle type on a platform.
#if DAWN_PLATFORM_IS(WINDOWS)
    using Handle = void*;
#elif DAWN_PLATFORM_IS(FUCHSIA)
    using Handle = uint32_t;
#elif DAWN_PLATFORM_IS(POSIX)
    using Handle = int;
#else
#error "Platform not supported."
#endif

    SystemHandle();

    // Create a SystemHandle by taking ownership of `handle`.
    // Declaration is a template so that there is never implicit
    // conversion of the handle arg.
    template <typename Arg>
    static SystemHandle Acquire(Arg handle) {
        return SystemHandle(handle);
    }

    // Create a SystemHandle by duplicating `handle`.
    // Declaration is a template so that there is never implicit
    // conversion of the handle arg.
    // Fails fast with DAWN_CHECK on failure.
    template <typename Arg>
    static SystemHandle Duplicate(Arg handle) {
        SystemHandle tmpOwnedHandle = SystemHandle::Acquire(handle);
        SystemHandle dupHandle = tmpOwnedHandle.Duplicate();
        tmpOwnedHandle.Detach();
        return dupHandle;
    }

    bool IsValid() const;

    SystemHandle(SystemHandle&& rhs);
    SystemHandle& operator=(SystemHandle&& rhs);

    Handle Get() const;
    Handle* GetMut();
    Handle Detach();
    SystemHandle Duplicate() const;
    void Close();

    ~SystemHandle();

  private:
    struct ErrorTag {};

    explicit SystemHandle(Handle handle);
    [[noreturn]] explicit SystemHandle(ErrorTag tag);

    // Constructor when the type does not match the Handle type on this platform.
    template <typename Arg>
    explicit SystemHandle(Arg)
        requires(!std::is_same_v<Arg, Handle>)
        : SystemHandle(ErrorTag{}) {}

    void LogIncorrectHandleType();

    Handle mHandle;
};

}  // namespace dawn::utils

#endif  // SRC_DAWN_UTILS_SYSTEMHANDLE_H_