Placeholders.h

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//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//============================================================================
#ifndef vtk_m_worklet_internal_Placeholders_h
#define vtk_m_worklet_internal_Placeholders_h
 
#include <vtkmstd/integer_sequence.h>
 
#include <type_traits>
 
#include <vtkm/exec/arg/BasicArg.h>
 
namespace vtkm
{
namespace placeholders
{
 
//============================================================================
template <int ControlSignatureIndex>
struct Arg : vtkm::exec::arg::BasicArg<ControlSignatureIndex>
{
};
 
//============================================================================
template <typename>
struct FunctionSigArity;
template <typename R, typename... ArgTypes>
struct FunctionSigArity<R(ArgTypes...)>
{
  static constexpr std::size_t value = sizeof...(ArgTypes);
};
 
//============================================================================
template <int... Args>
auto DefaultSigGenerator(vtkmstd::integer_sequence<int, 0, Args...>) -> void (*)(Arg<Args>...);
 
template <int Length>
struct DefaultExecSig
{
  using seq = vtkmstd::make_integer_sequence<int, Length + 1>;
  using type = typename std::remove_pointer<decltype(DefaultSigGenerator(seq{}))>::type;
};
template <>
struct DefaultExecSig<1>
{
  using type = void(Arg<1>);
};
template <>
struct DefaultExecSig<2>
{
  using type = void(Arg<1>, Arg<2>);
};
template <>
struct DefaultExecSig<3>
{
  using type = void(Arg<1>, Arg<2>, Arg<3>);
};
template <>
struct DefaultExecSig<4>
{
  using type = void(Arg<1>, Arg<2>, Arg<3>, Arg<4>);
};
 
template <bool HasExecSig_, typename Sig_>
struct ExecSigQuery
{
  static constexpr bool HasExecSig = HasExecSig_;
  using Sig = Sig_;
};
 
template <typename U, typename S = decltype(std::declval<typename U::ExecutionSignature>())>
static ExecSigQuery<true, typename U::ExecutionSignature> get_exec_sig(int);
 
template <typename U>
static ExecSigQuery<false, void> get_exec_sig(...);
 
//============================================================================
template <typename WorkletType>
struct GetExecSig
{
  using cont_sig = typename WorkletType::ControlSignature;
  using cont_sig_info = vtkm::placeholders::FunctionSigArity<cont_sig>;
 
  using result = decltype(get_exec_sig<WorkletType>(0));
  static constexpr bool has_explicit_exec_sig = result::HasExecSig;
 
  using ExecutionSignature = typename std::conditional<
    has_explicit_exec_sig,
    typename result::Sig,
    typename vtkm::placeholders::DefaultExecSig<cont_sig_info::value>::type>::type;
};
}
}
 
#endif