pm_rlua

pm_rlua

This library is a high-level binding for Lua 5.3. You don't have access to the Lua stack, all you can do is read/write variables (including callbacks) and execute Lua code.

How to install it?

Add this to the Cargo.toml file of your project

[dependencies]
pm_rlua = "0.1.0"

How to use it?

use pm_rlua::Lua;

The Lua struct is the main element of this library. It represents a context in which you can execute Lua code.

let mut lua = Lua::new();     // mutable is mandatory

Reading and writing variables

lua.set("x", 2);
let _: () = lua.exec_string("x = x + 1").unwrap();
let x: i32 = lua.query("x").unwrap();
assert_eq!(x, 3);

Reading and writing global variables of the Lua context can be done with set and query. The query function returns an Option<T> and does a copy of the value.

The base types that can be read and written are: i8, i16, i32, u8, u16, u32, f32, f64, bool, String. &str can be written but not read.

If you wish so, you can also add other types by implementing the LuaPush and LuaRead traits.

Executing Lua

let x: u32 = lua.exec_string("return 6 * 2;").unwrap();    // equals 12

The exec_string function takes a &str and returns a Option<T> where T: LuaRead.

Writing functions

In order to write a function, you must wrap it around pm_rlua::functionX where X is the number of parameters. This is for the moment a limitation of Rust's inferrence system.

fn add(a: i32, b: i32) -> i32 {
    a + b
}

lua.set("add", pm_rlua::function2(add));
let _: () = lua.exec_string("c = add(2, 4)").unwrap();   // calls the `add` function above
let c: i32 = lua.query("c").unwrap();
assert_eq!(c, 6);

In Lua, functions are exactly like regular variables.

You can write regular functions as well as closures:

lua.set("mul", pm_rlua::function2(|a: i32, b: i32| a * b));

Note that the lifetime of the Lua context must be equal to or shorter than the lifetime of closures. This is enforced at compile-time.

let mut a = 5i;

{
    let mut lua = Lua::new();

    lua.set("inc", || a += 1);    // borrows 'a'
    for i in (0 .. 15) {
        let _: () = lua.exec_string("inc()").unwrap();
    }
} // unborrows `a`

assert_eq!(a, 20)

Error handling

extern "C" fn error_handle(lua: *mut c_lua::lua_State) -> libc::c_int {
    let err = unsafe { c_lua::lua_tostring(lua, -1) };
    let err = unsafe { CStr::from_ptr(err) };
    let err = String::from_utf8(err.to_bytes().to_vec()).unwrap();
    println!("error:{}", err);
    0
}
lua.register("error_handle", error_handle);

Default in exec_string will call pcall, and set the error_function _G["error_handle"] so you can reset 'error_handle' function to you custom.

Manipulating Lua tables

Manipulating a Lua table can be done by reading a LuaTable object. This can be achieved easily by reading a LuaTable object.

let _:() = lua.exec_string("a = { 9, 8, 7 }").unwrap();
let mut table : LuaTable = lua.query("a").unwrap();

let x: i32 = table.query(2).unwrap();
assert_eq!(x, 8);

table.set(3, "hello");
let y: String = table.query(3).unwrap();
assert_eq!(y, "hello");

let z: i32 = table.query(1).unwrap();
assert_eq!(z, 9);

You can then iterate through the table with the .iter() function. Note that the value returned by the iterator is an Option<(Key, Value)>, the Option being empty when either the key or the value is not convertible to the requested type. The filter_map function (provided by the standard Iterator trait) is very useful when dealing with this.

let _:() = lua.exec_string("a = { 9, 8, 7 }").unwrap();
let mut table : LuaTable = lua.query("a").unwrap();
for _ in 0 .. 10 {
    let table_content: Vec<Option<(u32, u32)>> = table.iter().collect();
    assert_eq!(table_content, vec![ Some((1,9)), Some((2,8)), Some((3,7)) ]);
}

User data

When you expose functions to Lua, you may wish to read or write more elaborate objects. This is called a user data.

To do so, you should implement the LuaPush for your types. This is usually done by redirecting the call to userdata::push_userdata. it will operate the ref of object if you use userdata::push_userdata the userdata will copy one time, for lua gc manager if you use userdata::push_lightuserdata the userdata life manager by rust, so none copy will occup

#[derive(Clone, Debug)]
struct Foo {
    a : i32,
};

impl<'a> pm_rlua::LuaPush for &'a mut  Foo {
    fn push_to_lua(self, lua: *mut c_lua::lua_State) -> i32 {
        pm_rlua::userdata::push_userdata(self, lua, |_|{})
    }
}
impl<'a> pm_rlua::LuaRead for &'a mut  Foo {
    fn lua_read_at_position(lua: *mut c_lua::lua_State, index: i32) -> Option<&'a mut Foo> {
        pm_rlua::userdata::read_userdata(lua, index)
    }
}

let xx  = &mut Foo {
    a : 10,
};
lua.set("a", xx);
let get: &mut Foo = lua.query("a").unwrap();
assert!(get.a == 10);
get.a = 100;

let get: &mut Foo = lua.query("a").unwrap();
assert!(get.a == 100);

use lightuserdata you can change

impl<'a> pm_rlua::LuaPush for &'a mut  Foo {
    fn push_to_lua(self, lua: *mut c_lua::lua_State) -> i32 {
        pm_rlua::userdata::push_lightuserdata(self, lua, |_|{})
    }
}

custom lua call userdata need impl NewStruct

#[derive(Clone, Debug)]
struct TestLuaSturct {
    index : i32,
}

impl NewStruct for TestLuaSturct {
    fn new() -> TestLuaSturct {
        println!("new !!!!!!!!!!!!!!");
        TestLuaSturct {
            index : 19,
        }
    }

    fn name() -> &'static str {
        "TestLuaSturct"
    }
}

impl<'a> LuaRead for &'a mut TestLuaSturct {
    fn lua_read_at_position(lua: *mut c_lua::lua_State, index: i32) -> Option<&'a mut TestLuaSturct> {
        pm_rlua::userdata::read_userdata(lua, index)
    }
}

now we can custom function

let mut lua = Lua::new();
lua.openlibs();
fn one_arg(obj : &mut TestLuaSturct) -> i32 { obj.index = 10; 5 };
fn two_arg(obj : &mut TestLuaSturct, index : i32) { obj.index = index;};

let mut value = pm_rlua::LuaStruct::<TestLuaSturct>::new(lua.state());
value.create().def("one_arg", pm_rlua::function1(one_arg)).def("two_arg", pm_rlua::function2(two_arg));

let _ : Option<()> = lua.exec_string("x = TestLuaSturct()");
let val : Option<i32> = lua.exec_string("return x:one_arg()");
assert_eq!(val, Some(5));
let obj : Option<&mut TestLuaSturct> = lua.query("x");
assert_eq!(obj.unwrap().index, 10);
let val : Option<i32> = lua.exec_string("x:two_arg(121)");
assert_eq!(val, None);
let obj : Option<&mut TestLuaSturct> = lua.query("x");
assert_eq!(obj.unwrap().index, 121);

let obj : Option<&mut TestLuaSturct> = lua.exec_string("return TestLuaSturct()");
assert_eq!(obj.unwrap().index, 19);

HotFix

in runtime, if we need change some logic, we need restart the process, it may lose some memory data so sometimes we need update the logic, add keep the memory data, so we need hotfix

let mut lua = Lua::new();
lua.openlibs();
lua.enable_hotfix();
let _ = lua.exec_func2("hotfix", r"
    local value = {3, 4}
    function get_a()
        value[2] = 3
        return value[1]
    end

    function get_b()
        return value[2]
    end
    ", "hotfix");