1  /* c-strncasecmp.c -- case insensitive string comparator in C locale
       2     Copyright (C) 1998-1999, 2005-2006, 2009-2023 Free Software Foundation, Inc.
       3  
       4     This file is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU Lesser General Public License as
       6     published by the Free Software Foundation; either version 2.1 of the
       7     License, or (at your option) any later version.
       8  
       9     This file is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12     GNU Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public License
      15     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      16  
      17  #include <config.h>
      18  
      19  /* Specification.  */
      20  #include "c-strcase.h"
      21  
      22  #include <limits.h>
      23  
      24  #include "c-ctype.h"
      25  
      26  int
      27  c_strncasecmp (const char *s1, const char *s2, size_t n)
      28  {
      29    register const unsigned char *p1 = (const unsigned char *) s1;
      30    register const unsigned char *p2 = (const unsigned char *) s2;
      31    unsigned char c1, c2;
      32  
      33    if (p1 == p2 || n == 0)
      34      return 0;
      35  
      36    do
      37      {
      38        c1 = c_tolower (*p1);
      39        c2 = c_tolower (*p2);
      40  
      41        if (--n == 0 || c1 == '\0')
      42          break;
      43  
      44        ++p1;
      45        ++p2;
      46      }
      47    while (c1 == c2);
      48  
      49    if (UCHAR_MAX <= INT_MAX)
      50      return c1 - c2;
      51    else
      52      /* On machines where 'char' and 'int' are types of the same size, the
      53         difference of two 'unsigned char' values - including the sign bit -
      54         doesn't fit in an 'int'.  */
      55      return _GL_CMP (c1, c2);
      56  }