Function s2b

strings/dtoa.c:800–827

Converts a string to Bigint. Now we have nd0 digits, starting at s, followed by a decimal point, followed by nd-nd0 digits. Unless nd0 == nd, in which case we have a number of the form: ".xxxxxx" or "xxxxxx." @param s Input string, already partially parsed by my_strtod_int(). @param nd0 Number of digits before decimal point. @param nd Total number of digits.

  @param alloc Stack allocator for Bigints.
 */
static Bigint *s2b(const char *s, int nd0, int nd, ULong y9, Stack_alloc *alloc)
{
  Bigint *b;
  int i, k;
  Long x, y;

  x= (nd + 8) / 9;
  for (k= 0, y= 1; x > y; y <<= 1, k++) ;
  b= Balloc(k, alloc);
  b->p.x[0]= y9;
  b->wds= 1;
  
  i= 9;
  if (9 < nd0)
  {
    s+= 9;
    do
      b= multadd(b, 10, *s++ - '0', alloc);
    while (++i < nd0);
    s++;                                        /* skip '.' */
  }
  else
    s+= 10;
  /* now do the fractional part */
  for(; i < nd; i++)
    b= multadd(b, 10, *s++ - '0', alloc);
  return b;
}


static int hi0bits(register ULong x)