Templatize parameter

wasm_func_template.cc

#include <functional>
#include <type_traits>

class Context;
class Word;

template <size_t N, class ReturnType, class ContextType, class ParamType,
          class FuncBase = ReturnType(ContextType)>
struct WasmFuncTypeHelper {};

template <size_t N, class ReturnType, class ContextType, class ParamType, class... Args>
struct WasmFuncTypeHelper<N, ReturnType, ContextType, ParamType, ReturnType(ContextType, Args...)> {
  using type = typename WasmFuncTypeHelper<N - 1, ReturnType, ContextType, ParamType,
                                           ReturnType(ContextType, Args..., ParamType)>::type;
};

template <class ReturnType, class ContextType, class ParamType, class... Args>
struct WasmFuncTypeHelper<0, ReturnType, ContextType, ParamType, ReturnType(ContextType, Args...)> {
  using type = ReturnType(ContextType, Args...);
};

template <size_t N, class ReturnType, class ContextType, class ParamType>
using WasmFuncType = typename WasmFuncTypeHelper<N, ReturnType, ContextType, ParamType>::type;

template <size_t N> using WasmCallVoid = std::function<WasmFuncType<N, void, Context*, Word>>;

template <size_t N> using WasmCallWord = std::function<WasmFuncType<N, Word, Context*, Word>>;

template <size_t N> using WasmCallbackVoid = WasmFuncType<N, void, void*, Word>*;

template <size_t N> using WasmCallbackWord = WasmFuncType<N, Word, void*, Word>*;

static_assert(std::is_same<WasmCallVoid<3>, std::function<void(Context*, Word, Word, Word)>>::value,
              "");
static_assert(std::is_same<WasmCallWord<3>, std::function<Word(Context*, Word, Word, Word)>>::value,
              "");
static_assert(std::is_same<WasmCallbackVoid<3>, void (*)(void*, Word, Word, Word)>::value, "");
static_assert(std::is_same<WasmCallbackWord<3>, Word (*)(void*, Word, Word, Word)>::value, "");