Lua: introduce LuaJIT/Lua 5.1 compatibility

Introduce LuaJIT/Lua 5.1 compatibility by integrating
backports of currently used 5.2+ functionality from
https://github.com/keplerproject/lua-compat-5.2

Future functionality backports should be implemented
in corelib/lua_compat.c as well, serving as a central
place for this purpose.

Signed-off-by: Christian Storm <christian.storm@siemens.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Tested-by: Jörg Krause <joerg.krause@embedded.rocks>

corelib/Makefile

@@ -7,7 +7,7 @@ lib-y				+= installer.o \
 				   swupdate_dict.o
 lib-$(CONFIG_DOWNLOAD)		+= downloader.o
 lib-$(CONFIG_MTD)		+= mtd-interface.o
-lib-$(CONFIG_LUA)		+= lua_interface.o
+lib-$(CONFIG_LUA)		+= lua_interface.o lua_compat.o
 lib-$(CONFIG_HASH_VERIFY)	+= verify_signature.o
 lib-$(CONFIG_ENCRYPTED_IMAGES)	+= swupdate_decrypt.o
 lib-$(CONFIG_LIBCONFIG)		+= swupdate_settings.o \

corelib/lua_compat.c

@@ -0,0 +1,59 @@
+/*
+ * Author: Christian Storm
+ * Copyright (C) 2017, Siemens AG
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc.
+ */
+
+#include <lua.h>
+#include <lua_util.h>
+
+/*
+ * These LuaJIT/Lua 5.1 compatibility functions are taken from
+ * https://github.com/keplerproject/lua-compat-5.2
+ */
+#if !defined(LUA_VERSION_NUM) || LUA_VERSION_NUM == 501
+void luaL_setfuncs(lua_State *L, const luaL_Reg *l, int nup)
+{
+	luaL_checkstack(L, nup+1, "too many upvalues");
+	for (; l->name != NULL; l++) {  /* fill the table with given functions */
+		int i;
+		lua_pushstring(L, l->name);
+		for (i = 0; i < nup; i++)  /* copy upvalues to the top */
+		lua_pushvalue(L, -(nup + 1));
+		lua_pushcclosure(L, l->func, nup);  /* closure with those upvalues */
+		lua_settable(L, -(nup + 3)); /* table must be below the upvalues, the name and the closure */
+	}
+	lua_pop(L, nup);  /* remove upvalues */
+}
+
+void luaL_requiref(lua_State *L, char const* modname, lua_CFunction openf, int glb)
+{
+	luaL_checkstack(L, 3, "not enough stack slots");
+	lua_pushcfunction(L, openf);
+	lua_pushstring(L, modname);
+	lua_call(L, 1, 1);
+	lua_getglobal(L, "package");
+	lua_getfield(L, -1, "loaded");
+	lua_replace(L, -2);
+	lua_pushvalue(L, -2);
+	lua_setfield(L, -2, modname);
+	lua_pop(L, 1);
+	if (glb) {
+		lua_pushvalue(L, -1);
+		lua_setglobal(L, modname);
+	}
+}
+#endif

include/lua_util.h

@@ -36,6 +36,13 @@ int lua_parser_fn(lua_State *L, const char *fcn, struct img_type *img);
 int lua_handlers_init(void);
 #define lua_parser_exit(L) lua_close((lua_State *)L)
 
+#if !defined(LUA_VERSION_NUM) || LUA_VERSION_NUM == 501
+#define LUA_OK 0
+#define luaL_newlib(L, l) (lua_newtable((L)),luaL_setfuncs((L), (l), 0))
+void luaL_setfuncs(lua_State *L, const luaL_Reg *l, int nup);
+void luaL_requiref(lua_State *L, char const* modname, lua_CFunction openf, int glb);
+#endif
+
 #else
 
 #define lua_State void