hex to ascii and ascii to hex

ilnli · 08-29-2007, 01:51 PM

Can anyone tell me how can I convert a string into ascii, and hex?

my plateform is linux gcc.

pixellany · 08-29-2007, 02:07 PM

hexdump and printf, for starters. Look at the man page for each for more detail.

ilnli · 08-29-2007, 08:02 PM

I don't need a software I'm need to do this in a C program. So need some library function.

thanks

jeff_g · 08-30-2007, 03:26 AM

Are you saying that you want to take a C datatype such as an "int" and format it as a (printable) ascii string?

Of course, you'll use the C library function sprintf(), for example:

Code:

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

int i;
char buffer[80]; /* A buffer to hold the ascii string */

i = 44;
sprintf(&buffer[0], "%d", i);
/* buffer[] now contains the string "44" */

sprintf() has quite a few options for formatting various C datatypes as ascii strings, so consult a manual on it.

For going the other way (ie, converting an ascii string back to a C datatype such as long or int), you'll want to look at atoi() atol(), atof(), etc.

henk1420 · 08-30-2007, 11:14 AM

Quote:

Originally Posted by ilnli

Can anyone tell me how can I convert a string into ascii, and hex?

my plateform is linux gcc.

Code:

// Note: for reasons of 'safety' decstring and hexstring
// are longer than string itself
// This code is not very efficient

char string[64], decstring[256], hexstring[256], dummy[16];
int i;

// Fill the string somehow. Up to you.

// intialise to empty
decstring[0] ='\0';
hexstring[0] = '\0';

for (i=0; i<strlen(string); i++)
{
   sprintf(dummy, "%02X ", string[i]);  // Convert to hexadecimal notation
   strcat(hexstring, dummy);

   sprintf(dummy, "%03d ", string[i]);  // Convert to decimal notation
   strcat(decstring, dummy);
}

Regards,
H

95se · 08-30-2007, 01:57 PM

Turning a string into hex. For instance, "Hello" becomes "48 65 6C 6C 6F".

Code:

inline void hexify_ascii(char c, char * buf)
{
	int high = c >> 4;
	int low = c & 0xF;
	*buf       = high + '0' + (7 * (high / 10));
	*(buf + 1) = low  + '0' + (7 * (low  / 10));
}

int str_to_hex_str(const char * str, char * hex, int hex_len)
{
	int i;
	char * ptr = hex;
	int str_len = strlen(str);

	if (str_len * 3 > hex_len - 1) {
		return -1;		/* str won't fit in hex */
	}

	for (i = 0; i < str_len; i++) {
		hexify_ascii(str[i], ptr);
		*(ptr + 2) = ' ';
		ptr += 3;
	}

	*ptr = '\0';

	return i;
}

Going the other way is similar.

Wim Sturkenboom · 08-31-2007, 09:29 AM

sprintf to convert a value (integer) to a hex string , strtol or strtoul to convert a hex string to a value (integer).

jiml8 · 08-31-2007, 11:55 AM

Look at strtol() and related for converting strings to any base you choose. If you are in kernel space and can't use any of the standard libraries then you'll have to roll your own.

This routine converts an ascii string of the form 0x123abc to an integer, and it tests to make sure the string starts with 0x or 0X. I use this function in kernel space when I need to do this:

Code:

static int str2hex(char *str) {
  int strlen,result,intermed,intermedtop;
  char *s;
  s=str;
  while(*s != 0x0) {s++;}
  strlen=(int)(s-str);
  s=str;
  if(*s != 0x30) {
	return -1;
  } else {
	s++;
	if(*s != 0x78 && *s != 0x58){
		return -1;
	}
	s++;
  }
  strlen = strlen-3;
  result = 0;
  while(*s != 0x0) {
	intermed = *s & 0x0f;
	intermedtop = *s & 0xf0;
	if(intermedtop == 0x60 || intermedtop == 0x40) {
		intermed += 0x09;
	}
	intermed = intermed << (strlen << 2);
	result = result | intermed;
	strlen -= 1;
	s++;
  }
  return result;
}