I am implementing a way to transfer a set of data to a programmable dongle. The dongle is based on a smart card technology and can execute an arbitrary code inside. The input and output data is passed as a binary blocks that can be accessed via input and output pointers.
I would like to use an associative array to simplify the data processing code. Everything should work this way:
First the host application:
// Host application in C++
in_data["method"] = "calc_r";
in_data["id"] = 12;
in_data["loc_a"] = 56.19;
in_data["loc_l"] = 44.02;
processor->send(in_data);
Next the code inside the dongle:
// Some dongle function in C
char* method_name = assoc_get_string(in_data, "method");
int id = assoc_get_int(in_data, "id");
float loc_a = assoc_get_float(in_data, "loc_a");
float loc_l = assoc_get_float(in_data, "loc_l");
So my question is about the dongle part functionality. Is there C code or library to implement such an associative array behavior like the above?
My suspicion is that you would have to write your own. If I understand the architecture you are describing, then you will need to send the entire chunk of data in a single piece. If so, then most libraries will not work for that because they will most likely be allocating multiple pieces of memory, which would require multiple transfers (and an inside understanding of the structure). It would be similar to trying to use a library hash function and then sending its contents over the network on a socket just by passing the root pointer to the send function.
It would be possible to write some utilities of your own that manage a very simple associative array (or hash) in a single block of memory. If the amount of data is small, it could use a simple linear search for the entries and would be a fairly compact bit of code.