1  /* Case-insensitive string comparison function.
       2     Copyright (C) 1998-1999, 2005-2023 Free Software Foundation, Inc.
       3     Written by Bruno Haible <bruno@clisp.org>, 2005,
       4     based on earlier glibc code.
       5  
       6     This file is free software: you can redistribute it and/or modify
       7     it under the terms of the GNU Lesser General Public License as
       8     published by the Free Software Foundation, either version 3 of the
       9     License, or (at your option) any later version.
      10  
      11     This file is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14     GNU Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public License
      17     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <config.h>
      20  
      21  /* Specification.  */
      22  #include <string.h>
      23  
      24  #include <ctype.h>
      25  #include <limits.h>
      26  #include <stdlib.h>
      27  #include <uchar.h>
      28  
      29  #if GNULIB_MCEL_PREFER
      30  # include "mcel.h"
      31  #else
      32  # include "mbuiterf.h"
      33  #endif
      34  
      35  /* Compare the character strings S1 and S2, ignoring case, returning less than,
      36     equal to or greater than zero if S1 is lexicographically less than, equal to
      37     or greater than S2.
      38     Note: This function may, in multibyte locales, return 0 for strings of
      39     different lengths!  */
      40  int
      41  mbscasecmp (const char *s1, const char *s2)
      42  {
      43    if (s1 == s2)
      44      return 0;
      45  
      46    const char *iter1 = s1;
      47    const char *iter2 = s2;
      48  
      49    /* Be careful not to look at the entire extent of s1 or s2 until needed.
      50       This is useful because when two strings differ, the difference is
      51       most often already in the very few first characters.  */
      52    if (MB_CUR_MAX > 1)
      53      {
      54  #if GNULIB_MCEL_PREFER
      55        while (true)
      56          {
      57            mcel_t g1 = mcel_scanz (iter1); iter1 += g1.len;
      58            mcel_t g2 = mcel_scanz (iter2); iter2 += g2.len;
      59            int cmp = mcel_tocmp (c32tolower, g1, g2);
      60            if (cmp | !g1.ch)
      61              return cmp;
      62          }
      63  #else
      64        mbuif_state_t state1;
      65        mbuif_init (state1);
      66  
      67        mbuif_state_t state2;
      68        mbuif_init (state2);
      69  
      70        while (mbuif_avail (state1, iter1) && mbuif_avail (state2, iter2))
      71          {
      72            mbchar_t cur1 = mbuif_next (state1, iter1);
      73            mbchar_t cur2 = mbuif_next (state2, iter2);
      74            int cmp = mb_casecmp (cur1, cur2);
      75  
      76            if (cmp != 0)
      77              return cmp;
      78  
      79            iter1 += mb_len (cur1);
      80            iter2 += mb_len (cur2);
      81          }
      82        if (mbuif_avail (state1, iter1))
      83          /* s2 terminated before s1.  */
      84          return 1;
      85        if (mbuif_avail (state2, iter2))
      86          /* s1 terminated before s2.  */
      87          return -1;
      88        return 0;
      89  #endif
      90      }
      91    else
      92      for (;;)
      93        {
      94          unsigned char c1 = *iter1++;
      95          unsigned char c2 = *iter2++;
      96          /* On machines where 'char' and 'int' are types of the same size, the
      97             difference of two 'unsigned char' values - including the sign bit -
      98             doesn't fit in an 'int'.  */
      99          int cmp = UCHAR_MAX <= INT_MAX ? c1 - c2 : _GL_CMP (c1, c2);
     100          if (cmp != 0)
     101            {
     102              c1 = tolower (c1);
     103              if (c1 == c2)
     104                cmp = 0;
     105              else
     106                {
     107                  c2 = tolower (c2);
     108                  cmp = UCHAR_MAX <= INT_MAX ? c1 - c2 : _GL_CMP (c1, c2);
     109                }
     110            }
     111          if (cmp | !c1)
     112            return cmp;
     113        }
     114  }