On 7/7/06, Jay Taneja <[EMAIL PROTECTED]> wrote:
I have a program where some processing is performed in an included C
function. Ideally, I would like the C function to call and return the
result of a nesC command. The reason I am using C is because the
function takes a variable number of arguments, a feature not yet
supported in nesC. However, I am unsure if there is any way to call a
nesC command in my C function. I realize it is possible to have the C
function simply return the parameters to be passed to the nesC
command, but that involves two separate operations to be called in my
module. Any ideas how to get around this?
Here is some simple code:
# myfile.h
bool my_func(int number, ...);
# myfile.c
bool my_func(int number, ...) {
return call MyProg.my_cmd(number);
}
Hopefully I've described the issue enough. Thanks.
There's no direct way to do this. call refers to an interface, and
there's no interfaces in C code. But you can do this kind of thing
indirectly, by using the "C" attribute inside a module.
Here's how:
in your C function, call some function foo:
void foo(...); // declare foo's prototype
bool my_func(...) {
foo(...);
}
in your module which has access to the command you want to call
(either it defines it, or it uses an interface that contains it):
module MyModule {
...
}
implementation {
void foo(...) __attribute__((C)) {
call MyInterface.myCommand(...);
}
}
the __attribute__((C)) thing puts foo into the C name space, so that
you can call it from C code.
If you use nesC 1.2 or later, you can replace __attribute__((C)) my
@C() (identical but shorter). And, if using nesC 1.2 or later, don't
use @C() inside a generic component... (if you create several
instances, you'll end up with several C functions with the same name,
which won't work...).
David
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