src/dawn/native/SystemHandle.h

// Copyright 2023 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_SYSTEMHANDLE_H_
#define SRC_DAWN_NATIVE_SYSTEMHANDLE_H_

#include <utility>

#include "dawn/common/NonCopyable.h"
#include "dawn/common/Platform.h"
#include "dawn/native/Error.h"

namespace dawn::native {

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.
    template <typename Arg>
    static ResultOrError<SystemHandle> Duplicate(Arg handle) {
        SystemHandle tmpOwnedHandle = SystemHandle::Acquire(handle);
        SystemHandle dupHandle;
        DAWN_TRY_ASSIGN(dupHandle, tmpOwnedHandle.Duplicate());
        tmpOwnedHandle.Detach();
        return ResultOrError<SystemHandle>{std::move(dupHandle)};
    }

    bool IsValid() const;

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

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

    ~SystemHandle();

  private:
    struct ErrorTag {};

    explicit SystemHandle(Handle handle);
    explicit SystemHandle(ErrorTag tag);

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

    void LogIncorrectHandleType();

    Handle mHandle;
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_SYSTEMHANDLE_H_