bitfield example and link in docs

docs/source/usertypes.rst

@@ -24,3 +24,6 @@ The examples folder also has a number of really great examples for you to see. T
 	- Work on a copy by taking or returning a copy by value.
 * The actual metatable associated with the usertype has a long name and is defined to be opaque by the Sol implementation.
 * Containers get pushed as special usertypes, but can be disabled if problems arising as detailed :doc:`here<api/containers>`.
+* You can use bitfields but it requires some finesse on your part. We have an example to help you get started `here that uses a few tricks`_.
+
+.. _here that uses a few tricks: https://github.com/ThePhD/sol2/blob/develop/examples/usertype_bitfields.cpp

examples/usertype_bitfields.cpp

@@ -0,0 +1,164 @@
+#define SOL_CHECK_ARGUMENTS
+#include <sol.hpp>
+
+#include <cstddef>
+#include <cstdint>
+#include <climits>
+#include <type_traits>
+
+namespace itsy_bitsy {
+
+	template <std::size_t sz, typename C = void>
+	struct bit_type {
+		typedef uint64_t type;
+	};
+
+	template <std::size_t sz>
+	struct bit_type<sz, std::enable_if_t<(sz <= 1)>> {
+		typedef bool type;
+	};
+
+	template <std::size_t sz>
+	struct bit_type<sz, std::enable_if_t<(sz > 2 && sz <= 16)>> {
+		typedef uint16_t type;
+	};
+
+	template <std::size_t sz>
+	struct bit_type<sz, std::enable_if_t<(sz > 16 && sz <= 32)>> {
+		typedef uint32_t type;
+	};
+
+	template <std::size_t sz>
+	struct bit_type<sz, std::enable_if_t<(sz > 32 && sz <= 64)>> {
+		typedef uint64_t type;
+	};
+
+	template <std::size_t sz>
+	using bit_type_t = typename bit_type<sz>::type;
+
+	template <typename T, typename V>
+	bool vcxx_warning_crap(std::true_type, V val) {
+		return val != 0;
+	}
+
+	template <typename T, typename V>
+	T vcxx_warning_crap(std::false_type, V val) {
+		return static_cast<T>(val);
+	}
+
+	template <typename T, typename V>
+	auto vcxx_warning_crap(V val) {
+		return vcxx_warning_crap<T>(std::is_same<bool, T>(), val);
+	}
+
+	template <typename Base, std::size_t bit_target = 0x0, std::size_t size = 0x1>
+	void write(Base& b, bit_type_t<size> bits) {
+		typedef bit_type_t<sizeof(Base) * CHAR_BIT> aligned_type;
+		static const std::size_t aligned_type_bit_size = sizeof(aligned_type) * CHAR_BIT;
+		static_assert(sizeof(Base) * CHAR_BIT >= (bit_target + size), "bit offset and size are too large for the desired structure.");
+		static_assert((bit_target % aligned_type_bit_size) <= ((bit_target + size) % aligned_type_bit_size), "bit offset and size cross beyond largest integral constant boundary.");
+
+		const std::size_t aligned_target = (bit_target + size) / aligned_type_bit_size;
+		const aligned_type bits_left = static_cast<aligned_type>(bit_target - aligned_target);
+		const aligned_type shifted_mask = ((static_cast<aligned_type>(1) << size) - 1) << bits_left;
+		const aligned_type compl_shifted_mask = ~shifted_mask;
+		// Jump by native size of a pointer to target
+		// then OR the bits
+		aligned_type* jumper = static_cast<aligned_type*>(static_cast<void*>(&b));
+		jumper += aligned_target;
+		aligned_type& aligned = *jumper;
+		aligned &= compl_shifted_mask;
+		aligned |= (static_cast<aligned_type>(bits) << bits_left);
+	}
+
+	template <typename Base, std::size_t bit_target = 0x0, std::size_t size = 0x1>
+	bit_type_t<size> read(Base& b) {
+		typedef bit_type_t<sizeof(Base) * CHAR_BIT> aligned_type;
+		typedef bit_type_t<size> field_type;
+		static const std::size_t aligned_type_bit_size = sizeof(aligned_type) * CHAR_BIT;
+		static_assert(sizeof(Base) * CHAR_BIT >= (bit_target + size), "bit offset and size are too large for the desired structure.");
+		static_assert((bit_target % aligned_type_bit_size) <= ((bit_target + size) % aligned_type_bit_size), "bit offset and size cross beyond largest integral constant boundary.");
+
+		const std::size_t aligned_target = (bit_target + size) / aligned_type_bit_size;
+		const aligned_type bits_left = static_cast<aligned_type>(bit_target - aligned_target);
+		const aligned_type mask = (static_cast<aligned_type>(1) << size) - 1;
+		// Jump by native size of a pointer to target
+		// then OR the bits
+		aligned_type* jumper = static_cast<aligned_type*>(static_cast<void*>(&b));
+		jumper += aligned_target;
+		const aligned_type& aligned = *jumper;
+		aligned_type field_bits = (aligned >> bits_left) & mask;
+		field_type bits = vcxx_warning_crap<field_type>(field_bits);
+		return bits;
+	}
+
+}
+
+#include <iostream>
+#include <cassert>
+
+#if defined(_MSC_VER) || defined(__MINGW32__)
+#pragma pack(1)
+struct flags_t {
+#else
+struct __attribute__((packed, aligned(1))) flags_t {
+#endif
+	uint8_t C : 1;
+	uint8_t N : 1;
+	uint8_t PV : 1;
+	uint8_t _3 : 1;
+	uint8_t H : 1;
+	uint8_t _5 : 1;
+	uint8_t Z : 1;
+	uint8_t S : 1;
+	uint16_t D : 14;
+} flags{};
+
+int main() {
+	std::cout << "=== usertype_bitfields example ===" << std::endl;
+#ifdef __MINGW32__
+	std::cout << "MinGW Detected, packing structs is broken in MinGW and this test may fail" << std::endl;
+#endif
+	sol::state lua;
+	lua.open_libraries();
+
+	lua.new_usertype<flags_t>("flags_t",
+		"C", sol::property(itsy_bitsy::read<flags_t, 0>, itsy_bitsy::write<flags_t, 0>),
+		"N", sol::property(itsy_bitsy::read<flags_t, 1>, itsy_bitsy::write<flags_t, 1>),
+		"D", sol::property(itsy_bitsy::read<flags_t, 8, 14>, itsy_bitsy::write<flags_t, 8, 14>)
+	);
+
+	lua["f"] = std::ref(flags);
+
+	lua.script(R"(
+    print(f.C)
+    f.C = true;
+    print(f.C)
+
+    print(f.N)
+    f.N = true;
+    print(f.N)
+
+    print(f.D)
+    f.D = 0xDF;
+    print(f.D)
+)");
+
+	bool C = flags.C;
+	bool N = flags.N;
+	uint16_t D = flags.D;
+	
+	std::cout << std::hex;
+	std::cout << "sizeof(flags): " << sizeof(flags) << std::endl;
+	std::cout << "C: " << C << std::endl;
+	std::cout << "N: " << N << std::endl;
+	std::cout << "D: " << D << std::endl;
+
+	assert(C);
+	assert(N);
+	assert(D == 0xDF);
+
+	std::cout << std::endl;
+
+	return 0;
+}

single/sol/sol.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2016-11-15 09:39:55.397287 UTC
+// Generated 2016-11-16 03:43:41.504038 UTC
-// This header was generated with sol v2.15.1 (revision fe162b9)
+// This header was generated with sol v2.15.1 (revision 4aec055)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -6986,14 +6986,17 @@ namespace sol {
 			return call_into_lua(returns_list(), args_list(), L, start, std::forward<Fx>(fx), std::forward<FxArgs>(fxargs)...);
 		}
 
-		inline call_syntax get_call_syntax(lua_State* L, const std::string& key, int index = -2) {
+		inline call_syntax get_call_syntax(lua_State* L, const std::string& key, int index) {
+			if (lua_gettop(L) == 0) {
+				return call_syntax::dot;
+			}
 			luaL_getmetatable(L, key.c_str());
 			auto pn = pop_n(L, 1);
-			if (lua_compare(L, -1, index, LUA_OPEQ) == 1) {
+			if (lua_compare(L, -1, index, LUA_OPEQ) != 1) {
-				return call_syntax::colon;
-			}
 				return call_syntax::dot;
 			}
+			return call_syntax::colon;
+		}
 
 		inline void script(lua_State* L, const std::string& code) {
 			if (luaL_dostring(L, code.c_str())) {
@@ -7882,7 +7885,7 @@ namespace sol {
 			};
 
 			static int call(lua_State* L, F& f) {
-				call_syntax syntax = stack::get_call_syntax(L, &usertype_traits<T>::user_metatable()[0]);
+				call_syntax syntax = stack::get_call_syntax(L, &usertype_traits<T>::user_metatable()[0], 1);
 				int syntaxval = static_cast<int>(syntax);
 				int argcount = lua_gettop(L) - syntaxval;
 				return construct_match<T, meta::pop_front_type_t<meta::function_args_t<Cxs>>...>(onmatch(), L, argcount, 1 + syntaxval, f);

sol/call.hpp

@@ -443,7 +443,7 @@ namespace sol {
 			};
 
 			static int call(lua_State* L, F& f) {
-				call_syntax syntax = stack::get_call_syntax(L, &usertype_traits<T>::user_metatable()[0]);
+				call_syntax syntax = stack::get_call_syntax(L, &usertype_traits<T>::user_metatable()[0], 1);
 				int syntaxval = static_cast<int>(syntax);
 				int argcount = lua_gettop(L) - syntaxval;
 				return construct_match<T, meta::pop_front_type_t<meta::function_args_t<Cxs>>...>(onmatch(), L, argcount, 1 + syntaxval, f);

sol/stack.hpp

@@ -181,14 +181,17 @@ namespace sol {
 			return call_into_lua(returns_list(), args_list(), L, start, std::forward<Fx>(fx), std::forward<FxArgs>(fxargs)...);
 		}
 
-		inline call_syntax get_call_syntax(lua_State* L, const std::string& key, int index = -2) {
+		inline call_syntax get_call_syntax(lua_State* L, const std::string& key, int index) {
+			if (lua_gettop(L) == 0) {
+				return call_syntax::dot;
+			}
 			luaL_getmetatable(L, key.c_str());
 			auto pn = pop_n(L, 1);
-			if (lua_compare(L, -1, index, LUA_OPEQ) == 1) {
+			if (lua_compare(L, -1, index, LUA_OPEQ) != 1) {
-				return call_syntax::colon;
-			}
 				return call_syntax::dot;
 			}
+			return call_syntax::colon;
+		}
 
 		inline void script(lua_State* L, const std::string& code) {
 			if (luaL_dostring(L, code.c_str())) {

test_usertypes.cpp

@@ -1423,3 +1423,26 @@ TEST_CASE("usertype/destruction-test", "make sure usertypes are properly destruc
 		lua["testCrash"]();
 	}
 }
+
+TEST_CASE("usertype/call-initializers", "Ensure call constructors with initializers work well") {
+	struct A {
+		double f = 25.5;
+
+		static void init(A& x, double f) {
+			x.f = f;
+		}
+	};
+
+	sol::state lua;
+	lua.open_libraries();
+
+	lua.new_usertype<A>("A",
+		sol::call_constructor, sol::initializers(&A::init)
+		);
+
+	lua.script(R"(
+a = A(24.3)
+)");
+	A& a = lua["a"];
+	REQUIRE(a.f == 24.3);
+}