#include <string.h>
#include <ctype.h>
#include "hexbinpr.h"

/*--- function HexToBin ---------------------------------------------------
 *
 *  Converts a string of (an even number of) hex digits to binary.
 *
 *  Entry    hex      is a string of hex characters, upper or lower case.
 *                    Spaces are to be ignored.
 *                    Conversion stops at the first non-space that
 *                    is a non-hex digit.
 *           maxbytes is the amount of space set aside in "bin".
 *
 *  Exit     bin    is an array of binary bytes.
 *           Returns the number of bytes converted if successful, else 0
 *              (if the number of hex digits is odd).
 */
int
HexToBin(hex,maxbytes,bin)
char *hex;
int maxbytes;
unsigned char *bin;
{
   char ch, upper=1;
   unsigned char val;
   int nbytes = 0;


   for(; nbytes<maxbytes; hex++) {
      ch = *hex;
      if(ch == ' ') continue;
      if(islower(ch)) ch = (char)toupper(ch);
      if(isdigit(ch)) {
         val = (unsigned char) (ch - '0');
      } else if(ch>='A' && ch<='F') {
         val = (unsigned char)(ch - 'A' + 10);

      /* End of hex digits--time to bail out.
       */
      } else {
         return (upper ? nbytes : 0);
      }

      /* If this is an upper digit, set the top 4 bits of the destination
       * byte with this value, else -OR- in the value.
       */
      if(upper) {
         *bin = (unsigned char) (val << 4);
         upper = 0;
      } else {
         *(bin++) |= val;
         upper = 1;
         nbytes++;  /* Increment only after byte has been filled. */
      }
   }
   return (nbytes);
}


/*--- function BinToHex --------------------------------------------------
 *
 *  Convert an array of bytes to hexadecimal.
 *
 *  Entry   bin      is an array of bytes.
 *          nbytes   is the number of bytes in the array.
 *
 *  Exit    hex      is a string of hexadecimal digits, zero-terminated.
 */
void
BinToHex(bin,nbytes,hex)
unsigned char *bin;
int nbytes;
char *hex;
{
#define btoh(byte) (byte<10 ? byte+'0' : byte-10+'A')

   unsigned char byte;

   while(nbytes--) {
      byte = (unsigned char)((*(bin)>>4) & 0xf);
      *(hex++) = (char) btoh(byte);
      byte = (unsigned char) (*(bin++) & 0xf);
      *(hex++) = (char) btoh(byte);
   }
   *hex = '\0';
}