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Posted 11 Jan 2001

Convert a "Hex String" to an Integer

, 15 Jan 2001
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Convert a string containing a hex value to an integer
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    Convert a "Hex String" to an Integer

    Sometimes I have had a string containing a Hex Value like

    char s[10] = 
    that I would like to convert to an integer (in this case it would of course get the value 65000). I have not been able to find any standard C or C++ functions to do that, so I decided to write my own. It's declared as _httoi(const TCHAR *value) and is coded using TCHAR so it works both with and without UNICODE defined

    It's possible it could be done smarter and faster, but it works and if you like it it's yours to use for free.

    Here is the code to a small console application that uses the function, and demostrates its use.

    #include "stdafx.h"
    #include <tchar.h>
    #include <malloc.h>
    int _httoi(const TCHAR *value)
      struct CHexMap
        TCHAR chr;
        int value;
      const int HexMapL = 16;
      CHexMap HexMap[HexMapL] =
        {'0', 0}, {'1', 1},
        {'2', 2}, {'3', 3},
        {'4', 4}, {'5', 5},
        {'6', 6}, {'7', 7},
        {'8', 8}, {'9', 9},
        {'A', 10}, {'B', 11},
        {'C', 12}, {'D', 13},
        {'E', 14}, {'F', 15}
      TCHAR *mstr = _tcsupr(_tcsdup(value));
      TCHAR *s = mstr;
      int result = 0;
      if (*s == '0' && *(s + 1) == 'X') s += 2;
      bool firsttime = true;
      while (*s != '\0')
        bool found = false;
        for (int i = 0; i < HexMapL; i++)
          if (*s == HexMap[i].chr)
            if (!firsttime) result <<= 4;
            result |= HexMap[i].value;
            found = true;
        if (!found) break;
        firsttime = false;
      return result;
    int main(int argc, char* argv[])
      TCHAR *test[4] = {_T("0xFFFF"), _T("0xabcd"), _T("ffff"), _T("ABCD")};
      for (int i = 0; i < 4; i++)
        _tprintf(_T("Hex String: %s is int: %d\n\r"), test[i], _httoi(test[i]));
      return 0;

    Well, that's all there is to it. You can either copy the code from your browser, or download the project for Visual C++ 6.0.


    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

    A list of licenses authors might use can be found here


    About the Author

    Anders Molin
    Software Developer (Senior)
    Denmark Denmark
    Huh! Wink | ;-)

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    Comments and Discussions

    Generaldead horse Pin
    c. leamon11-Sep-07 4:08
    memberc. leamon11-Sep-07 4:08 

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