Category: Multiple Programming Languages

Calling a C Function From Lua

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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

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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

Profile : Linux

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Example 1

Add -pg

  1. arm-linux-gnueabihf-g++ -Wall -g -pg hello.cpp -o hello -std=c++17

Test

  1. root@imx6ul7d:~# gprof -b hello 
  2. Flat profile:
  3.  
  4. Each sample counts as 0.01 seconds.
  5.   %   cumulative   self              self     total           
  6.  time   seconds   seconds    calls   s/call   s/call  name    
  7. 100.00      3.45     3.45        1     3.45     3.45  hehe()
  8.   0.00      3.45     0.00        4     0.00     0.00  std::_Optional_base<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::_M_is_engaged() const
  9. ......

Routes stream to specified buffer

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Developer Command Prompt for VS 2019

  1. cl basic_ios_rdbuf.cpp /EHsc

MSDN Source Code

  1. #include <ios>
  2. #include <iostream>
  3. #include <fstream>
  4.  
  5. int main( ) 
  6. {
  7.    using namespace std;
  8.    ofstream file( "rdbuf.txt" );
  9.    streambuf *x = cout.rdbuf( file.rdbuf( ) );
  10.    cout << "test" << endl; // Goes to file
  11.    cout.rdbuf(x);
  12.    cout << "test2" << endl; //normal
  13. }