RE: C++ questions

[Emmanuel Stapf [ES]]

I'm not a C++ expert but looks like the tStatus C++ class needs its own wrapper in
Eiffel and when the signature of a C++ expects the tStatus & it means passing the
pointer to the memory area allocated for an instance of the tStatus class.

So in Eiffel, you will need to have a class which has `item: POINTER' available.
This is `item' that you will pass to your C++ code `cpp_create' or `c_get_nxt'.
For `cpp_create', I believe you could simplify it to be just:

cpp_create (bt: BOOLEAN; a_timeout: INTEGER; a_status: POINTER): POINTER
-- Call the C external to create an iNXTIterator
-- "The NXT iterator can be used to find all NXTs that are
connected (USB)
-- or in range (Bluetooth). The NXT iterator is not created if the
specified
-- status is fatal. The returned NXT iterator object should be
destroyed using
-- the iNXT::destroyNXTIterator method."
external
"C++ inline use %"iNXT.h%""
alias
"[
nFANTOM100::iNXTIterator* it;
it = nFANTOM100::iNXT::createNXTIterator (
(ViBoolean) $bt,
(ViUInt32) $a_timeout,
(nFANTOM100::tStatus &) $a_status);
if (((nFANTOM100::tStatus &) $a_status).isNotFatal()) {
return (EIF_POINTER) it;
} else {
return (EIF_POINTER) 0;
}
]"
end

The code you had for `c_get_nxt' seem just fine.

Regards,
Manu



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[Jimmy Johnson]

I am trying to wrap c++ function (LEGO Mindstorms fantom) calls but they all return a value in a "status" object which is then checked to see if the call succeeded. I'm not sure how to approach this, so I include two of my features for illustration.

The C++ calls use a parameter "a_status". I don't know if the call creates the object or if the object passed in is changed. My question is: how do I get this object out? Isn't "a_status" not writable? Can I even do an assignment in the c code to an Eiffel parameter? It compiles and runs, but I really don't know if the result I am getting is correct.

Second question: Is this the correct way to do these c++ calls? Which one is better?

thanks.

cpp_create (bt: BOOLEAN; a_timeout: INTEGER; a_status: POINTER): POINTER
-- Call the C external to create an iNXTIterator
-- "The NXT iterator can be used to find all NXTs that are connected (USB)
-- or in range (Bluetooth). The NXT iterator is not created if the specified
-- status is fatal. The returned NXT iterator object should be destroyed using
-- the iNXT::destroyNXTIterator method."
external
"C++ inline use %"iNXT.h%""
alias
"[
nFANTOM100::iNXTIterator* it;

nFANTOM100::tStatus & s = (nFANTOM100::tStatus &) $a_status;

it = nFANTOM100::iNXT::createNXTIterator (
(ViBoolean) $bt,
(ViUInt32) $a_timeout,

s);
$a_status = (EIF_POINTER) &s;
if (s.isNotFatal()) {

return (EIF_POINTER) it;
} else {
return (EIF_POINTER) 0;
}
]"
end

c_get_nxt (obj: POINTER; a_status: POINTER): POINTER
-- Call the cpp method to "create an NXT object for
-- the NXT referenced by this iterator."
-- virtual iNXT * getNXT (tStatus &status)=0
external
"C++ inline use %"iNXTIterator.h%""
alias
"[
return (EIF_POINTER) ((nFANTOM100::iNXTIterator *) ($obj))->getNXT (
(nFANTOM100::tStatus &) $a_status);
]"
end

[Liberty Lover]

Everyone,

See the following:

https://github.com/simple-eiffel/simple_bluetooth

https://github.com/simple-eiffel/simple_serial

You're welcome!

Best,

Larry

[Liberty Lover]

  see also:  claude_eiffel_op_docs/designs/simple_bluetooth_design.md at main · simple-eiffel/claude_eiffel_op_docs

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