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<  Advanced Erlang/OTP  ~  Decoding number with ei
flodis
Posted: Tue May 05, 2009 9:42 pm Reply with quote
User Joined: 09 Jul 2008 Posts: 27
I have trouble decoding numbers send from erlang to my C++ port.
What exactly should I decode when sending the number from erlang, is it a long, unsigned long, double? I have tried all of them.


The code for decoding my message is:
Code:
void set_mesh(ebyte* buf, int* index, ei_x_buff* reply)
{
     char arg[MAXATOMLEN];
     int type, size, arity;
     unsigned long id;
     char mesh[255];
 
     /* The format should be {id, Id}, {mesh, Mesh} */
     ei_decode_atom(buf, index, arg);
     ei_decode_ulong(buf, index, &id);
 
     ei_decode_atom(buf, index, arg);
    //ei_get_type(buf, index, &type, &size);
    ei_decode_string(buf, index, mesh);
    fprintf(stderr, "set_mesh: id, %f\n", id);
    //View::getSingleton()->setMesh(*id, mesh);
 
    ei_x_encode_tuple_header(reply, 2);
    ei_x_encode_atom(reply, "ok");
    ei_x_encode_atom(reply, "set_mesh");
}   


The result I get to stderr is:
set_mesh: id, -0.059527
The number I send to the port is 32.

I am doing alot of communication to and from the port with strings and atoms, and that is working fine.
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flodis
Posted: Wed May 06, 2009 7:09 am Reply with quote
User Joined: 09 Jul 2008 Posts: 27
I figured out this one myself.
It seems like if I send 0 I get an ERL_SMALL_INTEGER_EXT while a 0.0 or similar will give me an ERL_FLOAT_EXT.

Now I only need to figure out what decode function I should use on them, the docs does not reveal so much. I guess I have to do trial and error.
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