Extending C/C++ with Lua 5.1
Ong Hean KuanUnified CommunicationsEmail:
[email protected]
Who Am I ?
Software Engineer in Unified Communication
Telecommunication services solution provider
Linux c/c++
Open Source Advocate
Blogs:
Linux by Examples http://linux.byexamples.com
C/C++ by Examples http://cc.byexamples.com
What is Lua?
Programming language
Scripting language
Extensible embedded programming language.
Created by Roberto Ierusalimschy
(Assoc Prof PUC-Rio)
Open Source, Lua 5.0 onwards are under MIT license.
Fast, Lightweight and simple
Ivan's brain was written in Lua
Crazy Ivan was the robot that won the RoboCup 2000 in Denmark.
Crazy Ivan has a "brain" that uses Lua for scripting language. All
AI and logic is done in Lua. The brain is running on a Motorola
Coldfire 5206e processor, and Lua is modified to use only int's as
the Coldfire has no FPU.
Applications
Wireshark, Ettercap, Nmap, Snort
Used as in-game levels, AI, and as a Rules Engine for game
logic, game such as:
Homeworld 2, Ragnarok Online, SimCity 4, World of Warcraft.
Fusion Developer 2, Adobe Photoshop lightroom, lighttpd.
Cisco uses Lua to implement Dynamic Access Policies within the
Adaptive Security Appliance.
Etc, checkout wikipedia.org.
Fast and Lightweight?
Performance ~ Benchmarking
http://shootout.alioth.debian.org/gp4/benchmark.php
Performance ~ Benchmarking 2
The Language
Flexible data structure: Table
Table can be Array, Structure, Dictionary.
Object Oriented Programming
Global variables across the scripts
Standard lib such as io, math, file, string
Types and Values
Nil
Boolean
Numbers
String
Table
Functions
Userdata and Coroutines
Use type() to check:
print(type(a))
Table
Array or List
a = { 1,2,3,4,5,6}; print(a[1])
A = { [0]=1,2,3,4,5}; print(A[0])
Dictionary
d = {i=3,j=4,k=5}; print(d["i"])
d = {i=3,j=4,k=5}; print(d.i)
Elements in table can be anything, even a table or function, it
can be construct to as an object.
Me = { say=print }; Me.say(hi)
Statement
if then else
while
for ( Numeric, generic)
repeat
break
If then else
if type(a)== table then
io.write(a is table\n)
else if type(a)==number then
io.write(a is number\n)
end
while
a = { 1,2,3,4,5,6}
i = 1
while a[i] do
print(a[i])
i = i + 1
end
for
for a=1,10,2 do
print(a)
end
a = { 'a','b','c','d','e' }
for index,value in pairs(a) do
print(index.." = "..value)
end
C API
Lua Stack
Accessing Lua global variables
Calling C from Lua
Calling Lua from C
Lua Stack
All value passing through Lua Stack
Last IN First OUT
Push and Pop
-4 or 1-3 or 2-2 or 3-1 or 4
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("\nI am done with Lua in C++.\n");
lua_close(L);
return 0;}
-- foo.luaio.write(Happy Hacking with Lua\n)
g++ -o simple{,.cc} -llua -ldl
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\n");
return -1; } if (!lua_isnumber(L, -1)) { printf("`height' should be
a number\n"); return -1; } width = (int)lua_tonumber(L, -2); height
= (int)lua_tonumber(L, -1); printf("width: %d\nheight: %d\n",
width, height); lua_close(L);
return 0;
-- config.luawidth = 10height = 5
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.luafor i=1,9,1 do io.write(string.format("[%d]
Hello\n",i)) misc.msleep(1000) -- sleep 1 secend
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\n",lua_tostring(L, -1)); return -1; }
/* retrieve result */ if (!lua_isnumber(L, -1)) {
printf("function `f' must return a number\n"); return -1; } z =
lua_tonumber(L, -1); printf("Result: %f\n",z); lua_pop(L, 1);
lua_close(L);
return 0;}
-- last.luafunction f (x, y) return (x^2 * math.sin(y))/(1 -
x)end
References
Official Web
http://www.lua.org/
Lua 5.1 Online Reference
http://www.lua.org/manual/5.1/
Programming in Lua
http://www.lua.org/pil/
Lua Community
http://lua-users.org/
Thank you ;)
