Presented at the MyOSS March 2009 Meetup

1. Extending C/C++ with Lua 5.1 Ong Hean Kuan Unified Communications Email: mysurface@gmail.com

6. Fast and Lightweight?

8. Performance ~ Benchmarking 2

18. Simple c++ calling lua script extern "C" { #include "lua.h" #include "lualib.h" #include "lauxlib.h" } int main() { int s=0; lua_State *L = lua_open(); // load the libs luaL_openlibs(L); //run a Lua scrip here luaL_dofile(L,"foo.lua"); printf("I am done with Lua in C++."); lua_close(L); return 0; } -- foo.lua io.write(“Happy Hacking with Lua”) g++ -o simple{,.cc} -llua -ldl

19. Accessing Lua global variables int width=0,height=0; lua_State *L = lua_open(); luaL_openlibs(L); if (luaL_loadfile(L, "config.lua") || lua_pcall(L, 0, 0, 0)) printf("error: %s", lua_tostring(L, -1)); lua_getglobal(L, "width"); lua_getglobal(L, "height"); if (!lua_isnumber(L, -2)) { printf ("`width' should be a number"); return -1; } if (!lua_isnumber(L, -1)) { printf("`height' should be a number"); return -1; } width = (int)lua_tonumber(L, -2); height = (int)lua_tonumber(L, -1); printf("width: %dheight: %d", width, height); lua_close(L); return 0; -- config.lua width = 10 height = 5

20. Calling c from Lua int L_MSleep(lua_State* l) { int milisec=0; struct timespec req={0}; time_t sec; milisec=luaL_optint(l,1,0); if (milisec==0) return 0; sec=(int)(milisec/1000); milisec=milisec-(sec*1000); req.tv_sec=sec; req.tv_nsec=milisec*1000000L; while(nanosleep(&req,&req)==-1) continue; return 1; } int main() { const static struct luaL_reg misc [] = { {"msleep", &L_MSleep}, {NULL,NULL} //must! }; lua_State *L = lua_open(); luaL_openlibs(L); //open your lib luaL_openlib(L, "misc", misc, 0); if (luaL_loadfile(L, "callc.lua") || lua_pcall(L, 0, 0, 0)) printf("error: %s", lua_tostring(L, -1)); lua_close(L); return 0; } -- callc.lua for i=1,9,1 do io.write(string.format("[%d] Hello",i)) misc.msleep(1000) -- sleep 1 sec end

21. Calling Lua from c int main() { double z; lua_State *L = lua_open(); luaL_openlibs(L); if (luaL_loadfile(L, "last.lua") || lua_pcall(L, 0, 0, 0)) { printf("error: %s", lua_tostring(L, -1)); return -1; } lua_getglobal(L, "f"); lua_pushnumber(L, 2); /* push 1st argument */ lua_pushnumber(L, 3); /* push 2nd argument */ /* do the call (2 arguments, 1 result) */ if (lua_pcall(L, 2, 1, 0) != 0) { printf("error running function `f': %s",lua_tostring(L, -1)); return -1; } /* retrieve result */ if (!lua_isnumber(L, -1)) { printf("function `f' must return a number"); return -1; } z = lua_tonumber(L, -1); printf("Result: %f",z); lua_pop(L, 1); lua_close(L); return 0; } -- last.lua function f (x, y) return (x^2 * math.sin(y))/(1 - x) end

23. Thank you ;)