Category: Multiple Programming Languages

Calling a C Function From Lua

Posted on by admin

Prepare So

  1. #include <math.h>
  2. #include <lua.h>
  3. #include <lauxlib.h>
  4. #include <lualib.h>
  5.  
  6. static int my_sum(lua_State *L){
  7.     int d1 = luaL_checknumber(L, 1);
  8.     int d2 = luaL_checknumber(L, 2);
  9.     lua_pushnumber(L, d1+d2);
  10.     return 1;
  11. }
  12.  
  13. static int my_info(lua_State *L){
  14.     lua_pushstring(L, "qinuu");
  15.     return 1;
  16. }
  17.  
  18. static const struct luaL_Reg test_lib[] = {
  19.     {"my_sum" , my_sum},
  20.     {"my_info" , my_info},
  21.     {NULL, NULL}
  22. };
  23.  
  24. int luaopen_test_lib(lua_State *L){
  25.     //luaL_newlib(L, test_lib); // 5.2
  26.     luaL_register(L, "test_lib",test_lib); // lua 5.1
  27.     return 1;
  28. }

Test

  1. local my_lib = require "test_lib"
  2.  
  3. print(type(test_lib))
  4.  
  5. print(test_lib.my_sum(23,17))
  6.  
  7. print(test_lib.my_info())

Speed up by ignoring std::cout

Posted on by admin

Test Code

  1. #include <iostream>
  2.  
  3. int main(int argc, char *argv[])
  4. {
  5. 	//std::cout.setstate(std::ios_base::badbit);
  6. 	for(int i = 0; i < 100; i ++) {
  7. 		for(int i = 0; i < 100; i ++) {
  8. 			;//std::cout << "" << std::endl;
  9. 		}
  10. 	}
  11. 	return 0;
  12. }

Test it without std::cout

  1. root@imx6ul7d:~/tmp# time ./t1_1 
  2.  
  3. real    0m0.041s
  4. user    0m0.020s
  5. sys     0m0.000s

Test it with std::cout, but redirect to /dev/null

  1. root@imx6ul7d:~/tmp# time ./t1_0 > /dev/null
  2.  
  3. real    0m0.096s
  4. user    0m0.030s
  5. sys     0m0.030s

Test it with std::cout, but set io state

  1. root@imx6ul7d:~/tmp# time ./t1_2
  2.  
  3. real    0m0.061s
  4. user    0m0.040s
  5. sys     0m0.000s