How to create lua coroutines using lua c api and expose it to lua?

I am writing a library in c for lua, And I was wondering how to implement lua coroutine using lua c api. I basically want to implement something like the following, where module is written in c programming language.

module = require("mymodule")

coroutine.resume(module.coroutine_function, ...)

CodePudding user response：

The following is C code yields the string "Wonderfull" 4 times. And returns the string "End" before terminating the coroutine.

static int kfunction(lua_State* L, int status, lua_KContext ctx)
{
    static int x = 0;
    
    if (x < 3)
    {
        x  ;
        lua_pushfstring(L, "Wonderfull");
        return lua_yieldk(L, 1, 0, kfunction);
    }
    lua_pushfstring(L, "End");
    return 1;
}

static int iter(lua_State* L)
{
    lua_pushfstring(L, "Wonderfull");
    return lua_yieldk(L, 1, 0, kfunction);
}


int luaopen_module(lua_State* L) {
    // initial function which is called when require("module") is run

    lua_State* n = lua_newthread(L);
    lua_setglobal(L, "coroutine_function");

    lua_pushcfunction(n, iter);

    return 0;
}

Using the C module in Lua:

require("module")

print(coroutine.resume(coroutine_function))  -- true  Wonderfull
print(coroutine.resume(coroutine_function))  -- true  Wonderfull
print(coroutine.resume(coroutine_function))  -- true  Wonderfull
print(coroutine.resume(coroutine_function))  -- true  Wonderfull
print(coroutine.resume(coroutine_function))  -- true  End
print(coroutine.resume(coroutine_function))  -- false cannot resume dead coroutine

int iter(lua_State* L) is called when coroutine.resume is called for the first time. The subsequent calls are to int kfunction(lua_State* L, int status, lua_KContext ctx).

4th argument to lua_yieldk can be thorugh as the next function Lua should call to get the next yield or return value.

Documentation: Handling Yields in C