write variable to string

This is my first program in C++. I have written this same program in vb already. This seems like it should be very simple. I have this bit of code.

unsigned char hdr[2];
//the hdr array gets filled from another array

int i
for(i=0 ; i<2 ; i++)
{
fprintf(logfile, " %02", (unsigned int)hdr[i]);
}

This code will write something like "55BB" to the log file. Which is great, I am looking for "55BB". But what I really need is "55BB" in a string variable and not written to the log file. Funny thing is that I know 2 people that are C++ "experts" and this seems like a very difficult question. They always come back with more questions and no answers. Hopefully someone here will be able to help.

Norm Gunderson (112)

Perhaps a stringstream & some io manipulation will do the job:

#include <iostream>
#include <string>
#include <iomanip>
#include <sstream>

int main()
{
   unsigned char hdr[2];
   //the hdr array gets filled from another array
   hdr[0]='5';
   hdr[1]='B';

   int i;
   //for(i=0 ; i<2 ; i++)
   //{
   //   printf(" %02d", (unsigned int)hdr[i]);
   //}

   std::stringstream ss;
   for(i=0 ; i<2 ; i++)
   {
      ss << " " << std::setw(2) << (unsigned int)hdr[i];
   }
   std::string s;
   getline(ss, s);
   std::cout << s << std::endl ;
}

rlwhiterose (5)

Thanks for the reply. I tried your code but i get the message that std::setw is not a member of 'std'.

Norm Gunderson (112)

Should work if you #include <iomanip>

rlwhiterose (5)

that did work. Thanks. But now I realize that my result needs to be in hex. I got a result of 85 187, when what I really need is 55 BB. I guess that would be another topic. I will google that and see if I can come up with an answer.

Thanks Norm.

MiiNiPaa (8886)

Do you want it in C++ string or in C-style character array?

In first case, use stringstreams, in second, snprintf.

Norm Gunderson (112)

Easy peasy:

   for(i=0 ; i<2 ; i++)
   {
      ss << std::hex << " " << std::setw(2) << (unsigned int)hdr[i];
   }

rlwhiterose (5)

I guess I don't know the difference. I want 85 187 to be 55 BB. But I just changed some of my code to look for 85187 instead of 55BB.

Thanks for the fast responses. I am sure I will be back again soon. But I think I have enough to actually start writing this program.

closed account (E0p9LyTq)

#include <iostream>
#include <string>
#include <iomanip>
#include <sstream>

int main()
{
   int i = 21947;

   std::stringstream ss;

   ss << std::hex << i;

   std::string s;
   getline(ss, s);
   std::cout << s << std::endl;
}

55bb

closed account (E0p9LyTq)

@flwhiterose,

85187 is hex 0x14cc3. 21947 is 0x55bb.

MiiNiPaa (8886)

He has a two variables: unsigned char hdr[2];. One holds value of 85 (0x55) and second holds 187 (0xBB). He vants those to be printed in hex without separating space. That is all.

rlwhiterose (5)

That is correct MiiNiPaa. But I just went ahead and compared to 85 and 187 instead of 55 and BB. I think it is really stupid and real C++ programers would probably laugh at my code, but it works.

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