strncasecmp.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.
//
//  strncasecmp.c
//

// This is the standard "strncasecmp" function, as found in standard C
// libraries

#include <string.h>


int strncasecmp(const char *s1, const char *s2, size_t length)
{
  int result = 0;

  // Go through the strings, counting as we go.  If we get to the end, or
  // "length" and everything matches, we return 0.  Otherwise, if the strings
  // match partially, we return the count at which they diverge.  If they
  // don't match at all, we return -1

  for (result = 0; ((result < MAXSTRINGLENGTH) &&
		    ((unsigned) result < length)); result ++)
    {
      if ((s1[result] == '\0') && (s2[result] == '\0'))
	return (result = 0);

      // Is the ascii code a lowercase alphabet character?
      else if ((s1[result] >= (char) 97) &&
	       (s1[result] <= (char) 122) &&
	       (s2[result] == (s1[result] - (char) 32)))
	// We call it a match
	continue;
      
      // Is the ascii code an uppercase alphabet character?
      else if ((s1[result] >= (char) 65) &&
	       (s1[result] <= (char) 90) &&
	       (s2[result] == (s1[result] + (char) 32)))
	// We call it a match
	continue;

      else if (s1[result] != s2[result])
	{
	  if (result == 0) 
	    return (result = -1);

	  else
	    return (result);
	}
    }

  // If we fall through to here, we matched as many as we could
  return (result = 0);
}