llstr.c

/*
  avp 2011

  Convert long-long fixed integer (64-bit) to string in the specified radix
  (any 2..64 (bin, octal, decimal, hex ...) )
  Returns string length.
 */

#ifdef TEST
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#endif

int
my_llstr (long long v, // source for 'printing'
      int radix,
      int unsign,  // if 1 then unsigned source
      char *res)   // memory for result
{
  const char *dig = "0123456789abcdef";
  static const char cb64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  int          rem[65], sp = 0;   // stack for reminders
  char        *p = res;           // for return length
  unsigned long long   u = v;     // use if unsign == 1

  if (!res)
    return 0;
  if (radix < 2)
    radix = 2;
  if (radix > 64)
    radix = 64;
  if (radix > 16)
    dig = cb64;

  if (unsign) {
    while (u >= radix) {
      rem[sp++] = u%radix;
      u = u/radix;
    }
    //  *res++ = (radix > 16)? cb64[u]: dig[u];
    *res++ = dig[u];
  } else {
    if (v < 0) {
      *res++ = '-';
      if (v == (1LL << 63)) {
    rem[sp++] = (unsigned long long)(1LL << 63) % radix;
    v = -(v / radix);
      } else
    v = -v;
    }
    while (v >= radix) {
      rem[sp++] = v%radix;
      v = v/radix;
    }
    //    *res++ =  (radix > 16)? cb64[v]: dig[v];
    *res++ = dig[v];
  }

  while (sp)
    //    *res++ =  (radix > 16)? cb64[rem[--sp]]: dig[rem[--sp]];
    *res++ = dig[rem[--sp]];
  *res = 0;
  return res-p;
}

#ifdef TEST
main (int ac, char *av[])
{
  long long x;
  int  n;
  char buf[100];
  int r = av[1]? atoi(av[1]): 10;

  while (scanf("%lld",&x) == 1) {
    n = my_llstr(x, r, 0, buf);
    //    buf[n] = 0;
    printf ("%s\n",buf);
  }

  my_llstr((1LL <<63), r, 0, buf);
  printf ("LLONG_MIN: %s (%lld)\n", buf, (1LL <<63));
  my_llstr((1LL <<63), r, 1, buf);
  printf ("unsigned LLONG_MIN: %s (%llu)\n",buf, (1LL <<63));

}
#endif