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unsigned char data[] = {0x01, 0x10};
// method 1 - bitwise operations
unsigned short result1 = (data[0]<<8) + data[1];
cout << result1 << endl;
// method 2 - memcpy
unsigned short result2;
memcpy(&result2, &data[0],2);
cout << result2 << endl;
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Neither one of these solutions is very elegant though, especially if we start to deal with longer arrays or larger numbers. One solution is to use structs to send your data. A struct can be defined that holds all the data you want to send and then memcpy can copy the whole thing to or from an array in one go.
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#include <iostream>
#include <string.h>
#include <vector>
#include <math.h>
using namespace std;
// our structure for sending data
struct MY_DATA {
unsigned char packet_id;
int latitude;
int longitude;
unsigned short heading;
};
int main() {
// fill a struct with data
MY_DATA data_to_send;
data_to_send.packet_id = 0x01;
data_to_send.latitude = (int) (42.358456 * pow(10,7));
data_to_send.longitude = (int) (-71.087589 * pow(10,7));
data_to_send.heading = 185;
// construct our array/vector and fill it with data
vector<unsigned char> packet (sizeof(data_to_send), 0);
memcpy(&packet[0], &data_to_send.packet_id, sizeof(data_to_send));
// to get our data out, do the reverse
MY_DATA data_received;
memcpy(&data_received.packet_id, &packet[0], sizeof(data_to_send));
// print out the data
cout << "packet id: 0x" << hex << (int) data_received.packet_id << dec << endl;
cout << "lat: " << data_received.latitude / pow(10,7) << endl;
cout << "lon: " << data_received.longitude / pow(10,7) << endl;
cout << "heading: " << data_received.heading << endl;
return 0;
}
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