DaniWeb Forum Index > Software Development > C++

character hexadeximal

•

Join Date: Apr 2008

Posts: 29

Reputation: savinki is an unknown quantity at this point

Solved Threads: 0

savinki

Offline

Light Poster

character hexadeximal

Apr 21st, 2008

I want to convert a character to hexadecimal value.
and that value should be a unsigned char value.
e.g.
unsigned char a[16] = {0x00,0x44,...};

this is the code segment i wrote.
but its not working properly.
unsigned char a1= 'D';
unsigned char a[4] ;
unsigned char temp[16];
sprintf((char *)a,"0x%02X",a1);
cout<<a;
unsigned char *b=a;
cout<<b;
temp[0] = b;

can anyone help me to overcome from this issue

•

Join Date: Sep 2004

Posts: 8,313

Reputation: Narue has a reputation beyond repute

Solved Threads: 825

Narue

Offline

Code Goddess

Re: character hexadeximal

Apr 21st, 2008

'D' isn't likely to have the value 13. You need to convert the character to a hexadecimal digit value:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <cctype>
 
// Return [0,15] on success, -1 on failure
int hex_value ( unsigned char c )
{
  if ( std::isxdigit ( c ) ) {
    // Assume 'A' - 'F' have consecutive values
    return std::isdigit ( c ) ? c - '0' : toupper ( c ) - 'A' + 10;
  }
 
  return -1;
}
#include <cctype>

// Return [0,15] on success, -1 on failure
int hex_value ( unsigned char c )
{
  if ( std::isxdigit ( c ) ) {
    // Assume 'A' - 'F' have consecutive values
    return std::isdigit ( c ) ? c - '0' : toupper ( c ) - 'A' + 10;
  }

  return -1;
}

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
sprintf ( a, "0x%02X", hex_value ( a1 ) );
sprintf ( a, "0x%02X", hex_value ( a1 ) );

By the way, you store the hexadecimal values as unsigned char, but the string representation should be char. There's no type mismatch here as you're using sprintf to convert the values to a character representation.