mirror of
https://gitea.wildfiregames.com/0ad/0ad
synced 2026-06-16 05:13:58 -07:00
3d2561f096
Accepted By: @wraitii, @vladislavbelov Comments By: @Stan Differential Revision: https://code.wildfiregames.com/D4728 This was SVN commit r27821.
388 lines
15 KiB
C++
388 lines
15 KiB
C++
/* Copyright (C) 2023 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef INCLUDED_FUNCTIONWRAPPER
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#define INCLUDED_FUNCTIONWRAPPER
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#include "ScriptConversions.h"
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#include "ScriptExceptions.h"
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#include "ScriptRequest.h"
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#include <tuple>
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#include <type_traits>
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#include <utility>
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class ScriptInterface;
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/**
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* This class introduces templates to conveniently wrap C++ functions in JSNative functions.
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* This _is_ rather template heavy, so compilation times beware.
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* The C++ code can have arbitrary arguments and arbitrary return types, so long
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* as they can be converted to/from JS using Script::ToJSVal (FromJSVal respectively),
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* and they are default-constructible (TODO: that can probably changed).
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* (This could be a namespace, but I like being able to specify public/private).
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*/
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class ScriptFunction
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{
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private:
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ScriptFunction() = delete;
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ScriptFunction(const ScriptFunction&) = delete;
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ScriptFunction(ScriptFunction&&) = delete;
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/**
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* In JS->C++ calls, types are converted using FromJSVal,
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* and this requires them to be default-constructible (as that function takes an out parameter)
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* thus constref needs to be removed when defining the tuple.
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* Exceptions are:
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* - const ScriptRequest& (as the first argument only, for implementation simplicity).
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* - const ScriptInterface& (as the first argument only, for implementation simplicity).
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* - JS::HandleValue
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*/
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template<typename T>
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using type_transform = std::conditional_t<
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std::is_same_v<const ScriptRequest&, T> || std::is_same_v<const ScriptInterface&, T>,
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T,
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std::remove_const_t<typename std::remove_reference_t<T>>
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>;
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/**
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* Convenient struct to get info on a [class] [const] function pointer.
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* TODO VS19: I ran into a really weird bug with an auto specialisation on this taking function pointers.
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* It'd be good to add it back once we upgrade.
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*/
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template <class T> struct args_info;
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template<typename R, typename ...Types>
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struct args_info<R(*)(Types ...)>
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{
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static constexpr const size_t nb_args = sizeof...(Types);
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using return_type = R;
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using object_type = void;
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using arg_types = std::tuple<type_transform<Types>...>;
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};
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template<typename C, typename R, typename ...Types>
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struct args_info<R(C::*)(Types ...)> : public args_info<R(*)(Types ...)> { using object_type = C; };
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template<typename C, typename R, typename ...Types>
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struct args_info<R(C::*)(Types ...) const> : public args_info<R(C::*)(Types ...)> {};
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///////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////
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/**
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* DoConvertFromJS takes a type, a JS argument, and converts.
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* The type T must be default constructible (except for HandleValue, which is handled specially).
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* (possible) TODO: this could probably be changed if FromJSVal had a different signature.
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* @param wentOk - true if the conversion succeeded and wentOk was true before, false otherwise.
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*/
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template<size_t idx, typename T>
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static T DoConvertFromJS(const ScriptRequest& rq, JS::CallArgs& args, bool& wentOk)
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{
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// No need to convert JS values.
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if constexpr (std::is_same_v<T, JS::HandleValue>)
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{
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// Default-construct values that aren't passed by JS.
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// TODO: this should perhaps be removed, as it's distinct from C++ default values and kind of tricky.
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if (idx >= args.length())
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return JS::UndefinedHandleValue;
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else
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{
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// GCC (at least < 9) & VS17 prints warnings if arguments are not used in some constexpr branch.
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UNUSED2(rq); UNUSED2(args); UNUSED2(wentOk);
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return args[idx]; // This passes the null handle value if idx is beyond the length of args.
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}
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}
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else
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{
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// Default-construct values that aren't passed by JS.
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// TODO: this should perhaps be removed, as it's distinct from C++ default values and kind of tricky.
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if (idx >= args.length())
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return {};
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else
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{
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T ret;
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wentOk &= Script::FromJSVal<T>(rq, args[idx], ret);
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return ret;
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}
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}
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}
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/**
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* Wrapper: calls DoConvertFromJS for each element in T.
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*/
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template<typename... T, size_t... idx>
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static std::tuple<T...> DoConvertFromJS(std::index_sequence<idx...>, const ScriptRequest& rq,
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JS::CallArgs& args, bool& wentOk)
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{
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return {DoConvertFromJS<idx, T>(rq, args, wentOk)...};
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}
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/**
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* ConvertFromJS is a wrapper around DoConvertFromJS, and handles specific cases for the
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* first argument (ScriptRequest, ...).
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*
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* Trick: to unpack the types of the tuple as a parameter pack, we deduce them from the function signature.
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* To do that, we want the tuple in the arguments, but we don't want to actually have to default-instantiate,
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* so we'll pass a nullptr that's static_cast to what we want.
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*/
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template<typename ...Types>
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static std::tuple<Types...> ConvertFromJS(const ScriptRequest& rq, JS::CallArgs& args, bool& wentOk,
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std::tuple<Types...>*)
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{
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return DoConvertFromJS<Types...>(std::index_sequence_for<Types...>(), rq, args, wentOk);
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}
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// Overloads for ScriptRequest& first argument.
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template<typename ...Types>
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static std::tuple<const ScriptRequest&, Types...> ConvertFromJS(const ScriptRequest& rq,
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JS::CallArgs& args, bool& wentOk, std::tuple<const ScriptRequest&, Types...>*)
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{
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return std::tuple_cat(std::tie(rq), DoConvertFromJS<Types...>(
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std::index_sequence_for<Types...>(), rq, args, wentOk));
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}
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// Overloads for ScriptInterface& first argument.
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template<typename ...Types>
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static std::tuple<const ScriptInterface&, Types...> ConvertFromJS(const ScriptRequest& rq,
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JS::CallArgs& args, bool& wentOk, std::tuple<const ScriptInterface&, Types...>*)
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{
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return std::tuple_cat(std::tie(rq.GetScriptInterface()),
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DoConvertFromJS<Types...>(std::index_sequence_for<Types...>(), rq, args, wentOk));
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}
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///////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////
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/**
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* Wrap std::apply for the case where we have an object method or a regular function.
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*/
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template <auto callable, typename T, typename tuple>
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static typename args_info<decltype(callable)>::return_type call(T* object, tuple& args)
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{
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if constexpr(std::is_same_v<T, void>)
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{
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// GCC (at least < 9) & VS17 prints warnings if arguments are not used in some constexpr branch.
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UNUSED2(object);
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return std::apply(callable, args);
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}
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else
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return std::apply(callable, std::tuple_cat(std::forward_as_tuple(*object), args));
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}
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///////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////
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struct IgnoreResult_t {};
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static inline IgnoreResult_t IgnoreResult;
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/**
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* Converts any number of arguments to a `JS::MutableHandleValueVector`.
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* If `idx` is empty this function does nothing. For that case there is a
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* `[[maybe_unused]]` on `argv`. GCC would issue a
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* "-Wunused-but-set-parameter" warning.
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* For references like `rq` this warning isn't issued.
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*/
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template<typename... Types, size_t... idx>
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static void ToJSValVector(std::index_sequence<idx...>, const ScriptRequest& rq,
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[[maybe_unused]] JS::MutableHandleValueVector argv, const Types&... params)
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{
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(Script::ToJSVal(rq, argv[idx], params), ...);
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}
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/**
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* Wrapper around calling a JS function from C++.
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* Arguments are const& to avoid lvalue/rvalue issues, and so can't be used as out-parameters.
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* In particular, the problem is that Rooted are deduced as Rooted, not Handle, and so can't be copied.
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* This could be worked around with more templates, but it doesn't seem particularly worth doing.
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*/
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template<typename R, typename ...Args>
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static bool Call_(const ScriptRequest& rq, JS::HandleValue val, const char* name, R& ret, const Args&... args)
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{
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JS::RootedObject obj(rq.cx);
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if (!JS_ValueToObject(rq.cx, val, &obj) || !obj)
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return false;
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// Fetch the property explicitly - this avoids converting the arguments if it doesn't exist.
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JS::RootedValue func(rq.cx);
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if (!JS_GetProperty(rq.cx, obj, name, &func) || func.isUndefined())
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return false;
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JS::RootedValueVector argv(rq.cx);
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ignore_result(argv.resize(sizeof...(Args)));
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ToJSValVector(std::index_sequence_for<Args...>{}, rq, &argv, args...);
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bool success;
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if constexpr (std::is_same_v<R, JS::MutableHandleValue>)
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success = JS_CallFunctionValue(rq.cx, obj, func, argv, ret);
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else
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{
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JS::RootedValue jsRet(rq.cx);
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success = JS_CallFunctionValue(rq.cx, obj, func, argv, &jsRet);
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if constexpr (!std::is_same_v<R, IgnoreResult_t>)
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{
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if (success)
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Script::FromJSVal(rq, jsRet, ret);
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}
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else
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UNUSED2(ret); // VS2017 complains.
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}
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// Even if everything succeeded, there could be pending exceptions
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return !ScriptException::CatchPending(rq) && success;
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}
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///////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////
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public:
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template <typename T>
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using ObjectGetter = T*(*)(const ScriptRequest&, JS::CallArgs&);
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// TODO: the fact that this takes class and not auto is to work around an odd VS17 bug.
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// It can be removed with VS19.
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template <class callableType>
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using GetterFor = ObjectGetter<typename args_info<callableType>::object_type>;
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/**
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* The meat of this file. This wraps a C++ function into a JSNative,
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* so that it can be called from JS and manipulated in Spidermonkey.
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* Most C++ functions can be directly wrapped, so long as their arguments are
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* convertible from JS::Value and their return value is convertible to JS::Value (or void)
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* The C++ function may optionally take const ScriptRequest& or ScriptInterface& as its first argument.
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* The function may be an object method, in which case you need to pass an appropriate getter
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*
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* Optimisation note: the ScriptRequest object is created even without arguments,
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* as it's necessary for IsExceptionPending.
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*
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* @param thisGetter to get the object, if necessary.
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*/
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template <auto callable, GetterFor<decltype(callable)> thisGetter = nullptr>
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static bool ToJSNative(JSContext* cx, unsigned argc, JS::Value* vp)
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{
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using ObjType = typename args_info<decltype(callable)>::object_type;
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JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
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ScriptRequest rq(cx);
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// If the callable is an object method, we must specify how to fetch the object.
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static_assert(std::is_same_v<typename args_info<decltype(callable)>::object_type, void> || thisGetter != nullptr,
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"ScriptFunction::Register - No getter specified for object method");
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// GCC 7 triggers spurious warnings
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#ifdef __GNUC__
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Waddress"
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#endif
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ObjType* obj = nullptr;
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if constexpr (thisGetter != nullptr)
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{
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obj = thisGetter(rq, args);
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if (!obj)
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return false;
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}
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#ifdef __GNUC__
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#pragma GCC diagnostic pop
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#endif
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bool wentOk = true;
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typename args_info<decltype(callable)>::arg_types outs = ConvertFromJS(rq, args, wentOk,
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static_cast<typename args_info<decltype(callable)>::arg_types*>(nullptr));
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if (!wentOk)
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return false;
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/**
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* TODO: error handling isn't standard, and since this can call any C++ function,
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* there's no simple obvious way to deal with it.
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* For now we check for pending JS exceptions, but it would probably be nicer
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* to standardise on something, or perhaps provide an "errorHandler" here.
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*/
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if constexpr (std::is_same_v<void, typename args_info<decltype(callable)>::return_type>)
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call<callable>(obj, outs);
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else if constexpr (std::is_same_v<JS::Value, typename args_info<decltype(callable)>::return_type>)
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args.rval().set(call<callable>(obj, outs));
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else
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Script::ToJSVal(rq, args.rval(), call<callable>(obj, outs));
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return !ScriptException::IsPending(rq);
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}
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/**
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* Call a JS function @a name, property of object @a val, with the arguments @a args.
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* @a ret will be updated with the return value, if any.
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* @return the success (or failure) thereof.
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*/
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template<typename R, typename ...Args>
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static bool Call(const ScriptRequest& rq, JS::HandleValue val, const char* name, R& ret, const Args&... args)
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{
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return Call_(rq, val, name, ret, std::forward<const Args>(args)...);
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}
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// Specialisation for MutableHandleValue return.
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template<typename ...Args>
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static bool Call(const ScriptRequest& rq, JS::HandleValue val, const char* name, JS::MutableHandleValue ret, const Args&... args)
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{
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return Call_(rq, val, name, ret, std::forward<const Args>(args)...);
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}
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/**
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* Call a JS function @a name, property of object @a val, with the arguments @a args.
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* @return the success (or failure) thereof.
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*/
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template<typename ...Args>
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static bool CallVoid(const ScriptRequest& rq, JS::HandleValue val, const char* name, const Args&... args)
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{
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return Call(rq, val, name, IgnoreResult, std::forward<const Args>(args)...);
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}
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/**
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* Return a function spec from a C++ function.
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*/
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template <auto callable, GetterFor<decltype(callable)> thisGetter = nullptr, u16 flags = JSPROP_ENUMERATE|JSPROP_READONLY|JSPROP_PERMANENT>
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static JSFunctionSpec Wrap(const char* name)
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{
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return JS_FN(name, (&ToJSNative<callable, thisGetter>), args_info<decltype(callable)>::nb_args, flags);
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}
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/**
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* Return a JSFunction from a C++ function.
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*/
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template <auto callable, GetterFor<decltype(callable)> thisGetter = nullptr, u16 flags = JSPROP_ENUMERATE|JSPROP_READONLY|JSPROP_PERMANENT>
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static JSFunction* Create(const ScriptRequest& rq, const char* name)
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{
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return JS_NewFunction(rq.cx, &ToJSNative<callable, thisGetter>, args_info<decltype(callable)>::nb_args, flags, name);
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}
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/**
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* Register a function on the native scope (usually 'Engine').
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*/
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template <auto callable, GetterFor<decltype(callable)> thisGetter = nullptr, u16 flags = JSPROP_ENUMERATE|JSPROP_READONLY|JSPROP_PERMANENT>
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static void Register(const ScriptRequest& rq, const char* name)
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{
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JS_DefineFunction(rq.cx, rq.nativeScope, name, &ToJSNative<callable, thisGetter>, args_info<decltype(callable)>::nb_args, flags);
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}
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/**
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* Register a function on @param scope.
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* Prefer the version taking ScriptRequest unless you have a good reason not to.
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* @see Register
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*/
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template <auto callable, GetterFor<decltype(callable)> thisGetter = nullptr, u16 flags = JSPROP_ENUMERATE|JSPROP_READONLY|JSPROP_PERMANENT>
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static void Register(JSContext* cx, JS::HandleObject scope, const char* name)
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{
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JS_DefineFunction(cx, scope, name, &ToJSNative<callable, thisGetter>, args_info<decltype(callable)>::nb_args, flags);
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}
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};
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#endif // INCLUDED_FUNCTIONWRAPPER
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