String to Hexadecimal conversion (help!)

[cobra]

Hi guys. I need to convert a string to a hexadecimal char.

I am currently trying this:

Array of characters and hexadecimal units:

Code: Select all

string letters[95] = {" ","!","\"","#","$","%","&","'","(",")","*","+",",","-",
                     ".","/","0","1","2","3","4","5","6","7","8","9",":",";","<",
                     "=",">","?","@","A","B","C","D","E","F","G","H","I","J","K","L","M","N",
                     "O","P","Q","R","S","T","U","V","W","X","Y","Z","[","\\","]","^","_",
                     "'","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p",
                     "q","r","s","t","u","v","w","x","y","z","{","|","}","~"};

string hexadecimals[95] = {"20","21","22","23","24","25","26","27","28","29","2A","2B","2C","2D",
                     "2E","2F","30","31","32","33","34","35","36","37","38","39","3A","3B","3C",
                     "3D","3E","3F","40","41","42","43","44","45","46","47","48","49","4A","4B","4C","4D","4E",
                     "4F","50","51","52","53","54","55","56","57","58","59","5A","5B","5C","5D","5E","5F",
                     "60","61","62","63","64","65","66","67","68","69","6A","6B","6C","6D","6E","6F","70",
                     "71","72","73","74","75","76","77","78","79","7A","7B","7C","7E","7F"};

Then I try to convert them like this:

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char *charToHex(string st)
{
    char *hex = "";
    hex = new char[st.length()];


    for(unsigned int i=0; i<95; i++)
    {
        if(st.find(letters[i]) !=string::npos)
        {
            st = ReplaceAllG(st, letters[i], hexadecimals[i]);
        }
    }

    strcpy(hex, st.c_str());
    return hex;
    delete[] hex;
}

It all works fine unless there is an integer or other non-letter character such as $, %, #, and ;.

Any idea WHY it does this? It's driving me insane, I've looked over it several times and tried new solutions, to no avail.

Also, instead of using that way, I also tried this:

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for(unsigned int i=0; i<95; i++)
    {
        pos = st.find(letters[i]);
        if(pos != string::npos)
            st.replace(pos, 1, hexadecimals[i]);
            pos += 2;*/
    }

Which replaces them fine, except it only does it for one instance. I need to replace all occurences of the found character.

This should be simple, but for some reason the ways I'm doing it aren't working. Any ideas, or a better way to do it? thanks..[/code]

[Seven]

out of curiosity, why are you trying to do this?

[wITTus]

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#include <string>
#include <sstream>
#include <iostream>
 
int main() {
        std::string Test("Yo. Test! #§%\"%)(/");
        std::string Result;

        std::string::const_iterator it = Test.begin();

        for (; it != Test.end(); ++it) {
                std::stringstream ss;
                std::string Tmp;

                ss << std::hex << static_cast<unsigned int>(static_cast<unsigned char>((*it)));
                ss >> Tmp;
                Result += Tmp;
        }  
        std::cout << Test << std::endl;
        std::cout << Result << std::endl;
}

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wittus@hell ~ $ ./test 
Yo. Test! #§%"%)(/
596f2e2054657374212023c2a725222529282f

lol, maybe you should switch to C++. Just kidding

[vitek]

There are lots of problems with the original code. The code above is also terribly inefficient.

If you just want to convert a string to its hex representation, the following C++ code sould work...

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#include <sstream>
#include <string>

std::string to_hex(const std::string& s)
{
  std::ostringstream os;
  os.setf (std::ios::hex, std::ios::basefield);

  for (std::string::const_iterator it = s.begin(); it != s.end(); ++it)
  {
    os << int(*it);
  }

  return os.str();
}

If you don't want to use the C++ standard library, you could use the C standard library...

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#include <stdio.h>

const char* to_hex(const char* s, size_t n, char* ss, size_t nn)
{
  size_t j = 0;
  for (size_t i = 0; i < n; ++i)
  { 
    int c = snprintf (ss + j, nn - j, "%hhx", s [i]);
    if (c < 2)
      return 0;

    j += c;
    if ((nn - j) < 1)
      return 0;
  }

  ss [j] = 0;

  return ss;
}

Of course both of the above snippets will give different results on systems that use a non-ascii character set. You can avoid that by using a lookup table.

Travis

[cobra]

Thanks for your replies, and thanks to Vitek for the solution! I didn't think it was that easy.

@Seven: The reason I need to do this, is because I'm also programming a network extension program aside from my main project, that extends the online capabilities of a free flight simulator. The TCP packets are encoded in hexadecimal characters.

Also, Vitek, could you give me a snippet to convert hex to ascii please?

Sorry, my time is mainly at my FTW project but partly at the extension, so once I figure this out, there isn't much other hassle to it since I can read and write packets to send/receive. Thanks.

[wITTus]

Vitek, your function yields to "c2ffffff" for '#'. Mine is better.