C / C++ / MFC

typedef  unsigned char  byte;
 
cchar  *VkCharHexL = "0123456789abcdef";
 
//  convert 2 hex characters to their numeric equivalent
//  e.g.  "A3" -> 163 (or -93 signed)
//
byte  FkHex2ByteA( char C1, char C2 )
{
	C1 = tolower(C1);
	C2 = tolower(C2);
 
	cchar  *sp1 = strchr(VkCharHexL, C1),
	       *sp2 = strchr(VkCharHexL, C2);
 
	if( !sp1 || !sp2 )  return(0);
 
	return( ((sp1-VkCharHexL)<<4) + (sp2-VkCharHexL) );
}
 
//  convert byte to 2 hex characters
//  e.g.  163 (or -93 signed) -> "A3"
//
void  FkByte2HexA( byte B, char &C1, char &C2 )
{
	C1 = VkCharHexL[B >> 4];
	C2 = VkCharHexL[B & 0x0F];
}

borono wrote:

Why add 4 to it and then together

borono wrote:

I don't like that I have to split the value

void  HexToStr( cchar *HEX, char *STR )
{
    for( ulong i = 0, j = 0;  HEX[i] && HEX[i+1];  i+=2, j++ ) {
      STR[j] = (char)FkHex2ByteA(HEX[i], HEX[i+1]);
    }
}

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

int hexalpha_to_int(int c)
{
  char hexalpha[] = "aAbBcCdDeEfF";
  int i;
  int answer = 0;

  for(i = 0; answer == 0 && hexalpha[i] != '\0'; i++)
  {
    if(hexalpha[i] == c)
    {
      answer = 10 + (i / 2);
    }
  }

  return answer;
}

unsigned int htoi(const char s[])
{
  unsigned int answer = 0;
  int i = 0;
  int valid = 1;
  int hexit;

  if(s[i] == '0')
  {
    ++i;
    if(s[i] == 'x' || s[i] == 'X')
    {
      ++i;
    }
  }

  while(valid && s[i] != '\0')
  {
    answer = answer * 16;
    if(s[i] >= '0' && s[i] <= '9')
    {
      answer = answer + (s[i] - '0');
    }
    else
    {
      hexit = hexalpha_to_int(s[i]);
      if(hexit == 0)
      {
        valid = 0;
      }
      else
      {
        answer = answer + hexit;
      }
    }

    ++i;
  }

  if(!valid)
  {
    answer = 0;
  }

  return answer;
}

int conv(char *hex)
{
  char *endp = NULL;
  unsigned int result;
  unsigned int check;

    result = htoi(hex);
    check = (unsigned int)strtoul(hex, &endp, 16);

    if((*endp != '\0' && result == 0) || result == check)
    {
      printf("%u\n", result);
    }
    else
    {
     MessageBox(NULL,"Invalid hexadecimal value.",0,0);
    }
  
  return 0;
}

int main(void) 
{
	conv("4E");
	return 0;
}

char ch = 0x4e;

char ch = (char)strtol("4e", NULL, 16);