Update readme.md

modules/readme.md

@@ -1,7 +1,75 @@
-This directory is used for custom C modules. Quick guide below:
+**This directory is used for custom C modules.**
 
+*Thanks to [@anzz1](https://github.com/anzz1) for the original work!*
+
+**Quick guide below:**
 - Create a subdirectory with your module name.
 - Add your module files (.c, .h etc).
 - Run cmake, this will automatically add a new project which compiles the appropriate .dll or .so file.
 - Place the .dll or .so file inside your lua_scripts directory.
-- Use "require modulename" in whichever script you use the module.
+- Use "require modulename" in whichever script you use the module.
+
+
+**Below is an example module:**
+
+example_module.c
+```C
+#include <lua.h>
+#include <lauxlib.h>
+
+#if defined(WIN32)
+#define MODULEAPI __declspec(dllexport) int
+#else
+#define MODULEAPI int
+#endif
+
+/*
+ * example_module.say_hello() will return the below defined message.
+ */
+const char MESSAGE[] = "hello world!";
+int say_hello(lua_State *L) {
+    lua_pushstring(L, MESSAGE);
+    return 1;
+}
+
+/*
+ * the unload function will run on the Lua state close.
+ * this can then be used to save, exit cleanly, etc.
+ */
+int Unload(lua_State* L) {
+    luaL_dostring(L, "print('goodbye world!');");
+    return 0;
+}
+
+/*
+ * functions is a list of C functions and their bound function name in the Lua namespace
+ */
+static const struct luaL_Reg functions [] = {
+    {"say_hello", say_hello},
+    {"unload", Unload},
+    {NULL, NULL}
+};
+
+/*
+ * all modules need a luaopen_xxxx function, where xxxx is the name of the module.
+ * this is automatically executed on require.
+ */
+MODULEAPI luaopen_example_module(lua_State* L) {
+    // register the example module and its function list in the global namespace
+    luaL_register(L, "example_module", functions);
+
+    // run the Unload function on ELUNA_EVENT_ON_LUA_STATE_CLOSE
+    if (luaL_loadstring(L, "RegisterServerEvent(16, example_module.unload)") != 0)
+        return lua_error(L);
+    lua_call(L, 0, 0);
+    return 1;
+}
+```
+This would generate into example_module.dll/.so, and you could call this as shown below:
+
+```Lua
+require "example_module"
+
+print("Testing say_hello()")
+print(example_module.say_hello())
+```