RE: [CODE] Requesting help with lua and C

["Leonardo Maciel" <leonardo@...>]

> however this is the place I would call "lua_to_user" with the
You mean "c_to_user", right?

If I understand your problem correctly, one of many ways to do it. Not the
most elegant, but the easiest to explain that I can think of is:

/* 
 * Redirect the output to a temporary file.
 * Run this (not tested) code snippet once during initialization.
 */
lua_getglobal(L, "io")         /* get the io table */
lua_getfield(L, -1, "output")  /* pushes the io.output function onto the
stack */
lua_getfield(L, -2, "tmpfile") /* pushes the io.tmpfile function onto the
stack */
lua_remove(L, -3)              /* remove the io table from the stack */
lua_call(L, 0, 1)              /* call io.tmpfile, returns a file descriptor
*/
lua_call(L, 1, 0)              /* call the io.output function with fd as
argument */

/* 
 * Now you may call luaL_dostring anywhere in your program.
 * The stdout is now written to a temporary file.
 */
luaL_dostring(L, txt);

/* 
 * Finally write the contents of the temporary file to your user_data
structure
 */
lua_getglobal(L, "io")         /* get the io table */
lua_getfield(L, -1, "read")    /* pushes the io.read function onto the stack
*/
lua_remove(L, -2)              /* remove the io table from the stack */
lua_pushstring("*a")           /* reads the whole file */
lua_call(L, 1, 1)              /* call io.tmpfile, leaves file contents on
stack */
txt = lua_tostring(L, -1);     /* get file contents from the top of the
stack */
c_to_user(usr, txt);
lua_remove(L, -1);             /* remove the string only when finished using
it */



Hope this helps. And don't forget to rewrite your c_to_user function to
check for the string length in order to avoid an overflow.

--
Leonardo Maciel 

-----Original Message-----
From: lua-bounces@bazar2.conectiva.com.br
[mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Shane Lee
Sent: domingo, 17 de junho de 2007 00:12
To: Lua
Subject: [CODE] Requesting help with lua and C

Generally, I would hesitate to unlurk on a mailing list with what seems to
be a newbie problem. However, I am relatively new to Lua and even even
though I have the manual and have read quite a bit of the "Programming in
Lua" online help I am still unable to find the aswer to my problem. Perhaps
there isn't a real answer. What I am hoping to avoid is a generic answer or
RTFM, which I was able to find all over the internet via google searches and
wiki studies.
Here is what I have thus far, and the comments should explain my problem:

-------------Begin Psuedo-Code--------------------
Lua:
--Simple string stored in a table
 t = { [[And this is from the Lua script!]] }
 print(t[1])
--End of script

C code:

struct user_data {
 int uuid;			/* User's unique ID num			*/
 char inbuf[8192];		/* Users's input buffer control		*/
 char outbuf[8192];		/* Socket's output buffer control	*/
};

/*
 * c_to_user:
 * Psuedo function that takes a variable (txt) and stores it in the
 * "user's" outbuf for later processing.
 */
void c_to_user(struct user_data *usr, char *txt) {

  /* Do some basic error checking... */
  if (!usr || !txt || txt[0] == '\0') { return; }

  /* Use 'sprintf' to store the input to the user's outbuf */
  sprintf(usr->outbuf, "%s", txt);

 return;
}

/*
 * lua_to_user:
 * Run a lua script and send the output to c_to_user.
 */
void lua_to_user(struct user_data *usr, char *txt, lua_State *L) {
  const char *s = NULL;
  char buf[8192];
  memset(buf, '\0', 8192);

  c_to_user(usr, "This is stored in C.");

  /* "txt" would be a !validated! path to the Lua script */
  luaL_dostring(L, txt);

  /* At this point my knowledge breaks down and I run out of ideas,
   * however this is the place I would call "lua_to_user" with the
   * script's output.
   */
 return;
}

-------------  End Psuedo-Code--------------------

If anyone out there is able to figure out my problem, I would greatly
appreciate their response.

Thanks in advance,
-Shane