_digits.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

// 
//  Visopsys
//  Copyright (C) 1998-2007 J. Andrew McLaughlin
//  
//  This library is free software; you can redistribute it and/or modify it
//  under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation; either version 2.1 of the License, or (at
//  your option) any later version.
//
//  This library is distributed in the hope that it will be useful, but
//  WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
//  General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public License
//  along with this library; if not, write to the Free Software Foundation,
//  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
//  _digits.c
//

// This function takes a numeric value and a base, and returns the number
// of digits required to represent it, including a sign character if
// applicable.

#include <errno.h>
#include <sys/cdefs.h>


int _digits(unsigned num, int base, int sign)
{
  int digits = 1;

  if (base < 2)
    {
      errno = ERR_INVALID;
      return (digits = -1);
    }

  if (sign && ((int) num < 0))
    {
      num = ((int) num * -1);
      digits += 1;
    }

  while (num >= (unsigned) base)
    {
      digits += 1;
      num /= (unsigned) base;
    }

  return (digits);
}