std::string to char array and char array to string (c++) - c++

Question

Right now in my current project i have a string like this :
std::string ordre="0x010x030x000x320x000x01";
And i would like to create a char array looking like this with it (and if possible the reverse action too) :
unsigned char Com[]= {0x01, 0x03, 0x00, 0x32, 0x00, 0x01};
I have no problem working with the string, creating another std::string and getting the 0x01 part in the beginning using ordre.at() for the characters i want. But i can't find a way to put this new string 0x01 into Com[1].
Writing directly :
Com[1]=0x01;
It works but i would like to make something where Com[1] could change.

Answer 1

Right now in my current project i have a string like this :
std::string ordre="0x010x030x000x320x000x01";
And i would like to create a char array looking like this with it (and if possible the reverse action too) :
unsigned char Com[]= {0x01, 0x03, 0x00, 0x32, 0x00, 0x01};
First, "0x01" is different than 0x01. To extract values from the string, you will need to read it in a loop, four characters at a time:
if(ordre.size() % 4)
throw std::runtime_error{ "invalid string length; format is different" };
std::vector<int> values;
auto b = std::begin(ordre);
const auto e = std::end(ordre);
while(b != e)
{
std::string s{ b, b+4 };
values.push_back(std::stoi(s, 0, 16));
b += 4;
}

Answer 2

If you use C++ : use STL structures instead of (strugling with) arrays
If I where you i'll build a std::vector<unsigned char> and fill it dynamically by iterating over the x in the loop.
I would do the vector filling as such:
Note: This code work ith any size input and is not limited to 4 chars substrings. It is therefore more general but less efficient then the other answers code. Choose according to your needs
std::string order = "0x010x020x030x2360x10240x9001";
std::vector<int> coms;
size_t pos = 0, it;
while ((it = order.find("0x", pos + 1)) != std::string::npos)
{
coms.push_back(std::stoi(order.substr(pos, it-pos), 0, 16));
pos = it;
}
coms.push_back(std::stoi(order.substr(pos), 0, 16));
gives:
0x01 = 1
0x02 = 2
0x03 = 3
0x236 = 556
0x1024 = 4132
0x9001 = 36865