/* numscan
 * convert strings from bases 2, 8, 10 or 16 into integers
 * and integers into binary strings
 *
 * in numscan, base is indicated by the first digit(s) as follows:
 * b, 0b = binary
 * d, 0d, 1-9 = decimal
 * o, 0o, 0[0-7] = octal
 * x, 0x = hexadecimal
 * any of the prefix letters alone will return 0.
 */

#include <stdio.h>
#include "numscan.h"

unsigned long binscan(char *str)
{
  unsigned result = 0;  
  while ((*str-'0'|1)==1)
    result = (result<<1) + (*str++=='1');
  return result;
}

void printbin(unsigned long x, int n)
{
  if (--n) printbin(x>>1, n);
  putchar("01"[x&1]);
}

unsigned long numscan(char *str)
{
  unsigned long x = 0;
 rescan:
  switch(str[0]) {
  case 'd': sscanf(str+1,"%lu",&x); break;
  case 'o': sscanf(str+1,"%lo",&x); break;
  case 'x': sscanf(str+1,"%lx",&x); break;
  case 'b': x=binscan(str+1); break;
  case '0': if (str[1]<'0' || str[1]>'7') {
               str++; goto rescan;
            }
            sscanf(str,"%lo",&x); break;
  case '1': case '2': case '3': case '4': case '5': 
  case '6': case '7': case '8': case '9':
    sscanf(str,"%lu",&x); break;
  }
  return x;
}