calling lua functions from C which use libraries
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- Subject: calling lua functions from C which use libraries
- From: Tassilo von Parseval <tassilo.von.parseval@...>
- Date: 2004年6月14日 10:38:03 +0200
Hi everyone,
I am currently working on an Inline::Lua module for Perl and I need some
help on triggering lua functions from C when those functions make use of
lua's shipped library. I did a rather thorough scan through the mailing
list archive, but apparently this issue hasn't yet been brought up.
Anyway, this is how the Perl/Lua code looks like:
use Inline 'Lua';
print bla(1);
__END__
__Lua__
function bla(a)
io.write(a)
return a*2
end
Running the above yields:
error: [string "_INLINED_LUA"]:2: attempt to index global `io' (a nil value)
Now for the C-code backing this up: There are essentially two parts
involved. One that is compiling the Lua code:
void
compile (lua, code)
lua_State *lua;
SV *code;
CODE:
{
STRLEN len;
char *codestr = SvPV(code, len);
int status;
status = lua_dobuffer(lua, codestr, len, "_INLINED_LUA");
switch(status) {
case 0:
XSRETURN_YES;
case LUA_ERRSYNTAX:
croak("Syntax error in function '%s'", name);
}
}
and then the function that eventually calls the Lua function:
void
call (lua, name, nargs, ...)
lua_State *lua;
char *name;
int nargs; /* number of arguments the function expects at least */
CODE:
{
int i, status;
int actual_args = 0;
items -= 3; /* special var being the number of items on
* the Perl stack */
lua_getglobal(lua, name);
/* push arguments (also does the necessary conversion
* from Perl to Lua types */
for (i = 0; i < items; i++, nargs--, actual_args++) {
push_val(lua, ST(i+3));
}
/* if less arguments were passed than mentioned in the
* lua function prototype, pad with 'nil' */
for (i = nargs; i > 0; nargs--, actual_args++)
push_val(lua, &PL_sv_undef);
status = lua_pcall(lua, actual_args, LUA_MULTRET, 0);
if (status != 0)
croak("error: %s\n", lua_tostring(lua, -1));
/* test a single return value */
fprintf(stderr, "result: %s\n", lua_tostring(lua, -1));
}
The above works as long as I use none of the functions/methods provided
in the lua library so this:
function bla(a)
return a*2
end
works.
Now, how do I go about this? I read in lua-5.0.2's manual (under
"Changes in the Libraries") that library functions are apparently no
longer global. I don't yet understand enough of Lua to know whether this
is what's biting me.
In short: how can my Lua functions use the Lua library when those are
called from C? Quite obviously, there's something rotten in my C code
which I don't yet see.
TIA,
Tassilo
--
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