lua_filehelpers.cpp: Add lua script function 'readlink()'

- Set Lua api version to 1.53


Origin commit data
------------------
Commit: b50886faca
Author: Michael Liebmann <tuxcode.bbg@gmail.com>
Date: 2016-09-04 (Sun, 04 Sep 2016)

src/gui/lua/lua_api_version.h

@@ -4,4 +4,4 @@
  * to luainstance.h changes
  */
 #define LUA_API_VERSION_MAJOR 1
-#define LUA_API_VERSION_MINOR 52
+#define LUA_API_VERSION_MINOR 53

src/gui/lua/lua_filehelpers.cpp

@@ -57,6 +57,7 @@ void CLuaInstFileHelpers::LuaFileHelpersRegister(lua_State *L)
 		{ "touch",      CLuaInstFileHelpers::FileHelpersTouch    },
 		{ "rmdir",      CLuaInstFileHelpers::FileHelpersRmdir    },
 		{ "mkdir",      CLuaInstFileHelpers::FileHelpersMkdir    },
+		{ "readlink",   CLuaInstFileHelpers::FileHelpersReadlink },
 		{ "__gc",       CLuaInstFileHelpers::FileHelpersDelete   },
 		{ NULL, NULL }
 	};
@@ -304,6 +305,40 @@ int CLuaInstFileHelpers::FileHelpersMkdir(lua_State *L)
 	return 1;
 }
 
+int CLuaInstFileHelpers::FileHelpersReadlink(lua_State *L)
+{
+	CLuaFileHelpers *D = FileHelpersCheckData(L, 1);
+	if (!D) return 0;
+
+	int numargs = lua_gettop(L) - 1;
+	int min_numargs = 1;
+	if (numargs < min_numargs) {
+		printf("luascript readlink: not enough arguments (%d, expected %d)\n", numargs, min_numargs);
+		lua_pushnil(L);
+		return 1;
+	}
+
+	const char *link = "";
+	link = luaL_checkstring(L, 2);
+
+	char buf[PATH_MAX];
+	memset(buf, '\0', sizeof(buf));
+	if (readlink(link, buf, sizeof(buf)-1) == -1) {
+		lua_Debug ar;
+		lua_getstack(L, 1, &ar);
+		lua_getinfo(L, "Sl", &ar);
+		const char* s = strerror(errno);
+		printf(">>> Lua script error [%s:%d] %s\n    (error from neutrino: [%s:%d])\n",
+		       ar.short_src, ar.currentline, s, __path_file__, __LINE__);
+
+		lua_pushnil(L);
+		return 1;
+	}
+
+	lua_pushstring(L, buf);
+	return 1;
+}
+
 
 
 int CLuaInstFileHelpers::FileHelpersDelete(lua_State *L)

src/gui/lua/lua_filehelpers.h

@@ -44,6 +44,7 @@ class CLuaInstFileHelpers
 		static int FileHelpersTouch(lua_State *L);
 		static int FileHelpersRmdir(lua_State *L);
 		static int FileHelpersMkdir(lua_State *L);
+		static int FileHelpersReadlink(lua_State *L);
 		static int FileHelpersDelete(lua_State *L);
 };