toys/dbcc/binding/lua/dbcc_lua_wrapper.cpp

#include "lua.hpp"

#include "dbcc/dbc_iterator.h"
#include "dbcc/message.h"
#include "dbcc/signal.h"
#include "dbcc/version.h"

#define LUA_MODULE_NAME "dbcc"
#define LUA_DBC_ITERATOR_CLASS_NAME "DbcIterator"

// These are the definitions for the C functions that Lua will use to call the member functions.
// Consructor of 'ad::dbcc::DbcIterator'
static int lua_DbcIterator_new(lua_State* L)
{
    if (lua_gettop(L) != 1)
    {
        luaL_pushfail(L);
        return 1;
    }

    std::strting filePath = luaL_checkstring(L, 1);
    ad::dbcc::DbcIterator** iter = reinterpret_cast<ad::dbcc::DbcIterator**>(lua_newuserdata(L, sizeof(ad::dbcc::DbcIterator**)));
    *iter = new ad::dbcc::DbcIterator(filePath);
    luaL_setmetatable(L, LUA_DBC_ITERATOR_CLASS_NAME);

    return 1;
}

// `ad::dbcc::DbcIterator` destructor, which corresponds to the `__gc` metamethod in Lua.
int lua_DbcIterator_delete(lua_State* L)
{
    ad::dbcc::DbcIterator* iter = *reinterpret_cast<ad::dbcc::DbcIterator**>(luaL_checkudata(L, 1, LUA_DBC_ITERATOR_CLASS_NAME));
    delete iter;

    return 0;
}

// C function corresponding to the `ad::dbcc::DbcIterator` iterator.
int lua_MyClass_index(lua_State* L)
{
    ad::dbcc::DbcIterator* iter = *reinterpret_cast<ad::dbcc::DbcIterator**>(luaL_checkudata(L, 1, LUA_DBC_ITERATOR_CLASS_NAME));
    int something_in = static_cast<int>(luaL_checkinteger(L, 2));
    (*iter)[]->set(something_in);
    return 0;
}

// C function corresponding to `MyClass::get`.
int lua_MyClass_get(lua_State* L)
{
    ad::dbcc::DbcIterator* iter = *reinterpret_cast<ad::dbcc::DbcIterator**>(luaL_checkudata(L, 1, LUA_DBC_ITERATOR_CLASS_NAME));
    // Push a lua object
    lua_pushinteger(L, (*iter)[]);
    return 1;
}

// `__newindex` metamethod for `MyClass` userdata that prevents any members from being added.
int lua_MyClass_newindex(lua_State* L)
{
    return luaL_error(L, "attempt to modify a read-only object");
}

// `__newindex` metamethod for the `MyClass` table that prevents any methods from being added--I will explain more below.
int lua_MyClass_table_newindex(lua_State* L)
{
    return luaL_error(L, "attempt to modify a read-only table");
}

// Function to register all the above functions for use in Lua; this gets called in `main.cpp`.
void lua_MyClass_register(lua_State* L)
{
    // Create a global table that will contain all the `MyClass` methods as functions.
    // Include `lua_MyClass_new` as a constructor in the form `MyClass.new`.
    lua_newtable(L);
    lua_pushcfunction(L, lua_MyClass_new);
    lua_setfield(L, -2, "new");
    // Include `MyClass::get` and `MyClass::set` in this table as well.
    luaL_setfuncs(L, MyClass_methods, 0);

    // Create a metatable for the global table `MyClass`--which was just created.
    lua_newtable(L);
    // Prevent access to the metatable.
    lua_pushliteral(L, "metatable");
    lua_setfield(L, -2, "__metatable");
    lua_pushcfunction(L, lua_MyClass_table_newindex);
    lua_setfield(L, -2, "__newindex");
    // Set this second table as the metatable for the one created above.
    lua_setmetatable(L, -2);
    // Call the first table "MyClass" and add it to the global environment table (_ENV).
    lua_setglobal(L, LUA_MYCLASS);

    // Create a metatable to be used by `MyClass` objects--this is different from the above tables because it will not contain the `new` method.
    luaL_newmetatable(L, LUA_MYCLASS);
    // Same as before, lock the metatable.
    lua_pushliteral(L, "metatable");
    lua_setfield(L, -2, "__metatable");
    // Add metamethods contained in the `luaL_Reg` struct `MyClass_metamethods`.
    luaL_setfuncs(L, MyClass_metamethods, 0);

    // Create an index--the `__index` metamethod--for the above table to use for `MyClass` objects.
    lua_newtable(L);
    // Add methods.
    luaL_setfuncs(L, MyClass_methods, 0);
    lua_setfield(L, -2, "__index");
    // This pop operation is probably unnecessary since the Lua stack should be cleaned up when this function returns.
    lua_pop(L, 1);

    return;
}

#if defined(OS_WINDOWS)
#define __EXPORT extern "C" __declspec(dllexport)
#else
#define __EXPORT extern "C"
#endif //

__EXPORT int luaopen_dbcc(lua_State *L)
{
    static const struct luaL_Reg methods[] = {
        {"new", },
        {NULL, NULL}
    };

    luaL_newlib(L, methods);

    return 1;
}