1  /* Locale-specific memory comparison.
       2  
       3     Copyright (C) 1999, 2002-2004, 2006, 2009-2023 Free Software Foundation,
       4     Inc.
       5  
       6     This program is free software: you can redistribute it and/or modify
       7     it under the terms of the GNU General Public License as published by
       8     the Free Software Foundation, either version 3 of the License, or
       9     (at your option) any later version.
      10  
      11     This program 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 General Public License for more details.
      15  
      16     You should have received a copy of the GNU General Public License
      17     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      18  
      19  /* Contributed by Paul Eggert <eggert@twinsun.com>.  */
      20  
      21  #include <config.h>
      22  
      23  #include "memcoll.h"
      24  
      25  #include <errno.h>
      26  #include <stdlib.h>
      27  #include <string.h>
      28  
      29  /* Compare S1 (with size S1SIZE) and S2 (with length S2SIZE) according
      30     to the LC_COLLATE locale.  S1 and S2 are both blocks of memory with
      31     nonzero sizes, and the last byte in each block must be a null byte.
      32     Set errno to an error number if there is an error, and to zero
      33     otherwise.  */
      34  static int
      35  strcoll_loop (char const *s1, size_t s1size, char const *s2, size_t s2size)
      36  {
      37    int diff;
      38  
      39    while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
      40      {
      41        /* strcoll found no difference, but perhaps it was fooled by NUL
      42           characters in the data.  Work around this problem by advancing
      43           past the NUL chars.  */
      44        size_t size1 = strlen (s1) + 1;
      45        size_t size2 = strlen (s2) + 1;
      46        s1 += size1;
      47        s2 += size2;
      48        s1size -= size1;
      49        s2size -= size2;
      50  
      51        if (s1size == 0)
      52          return - (s2size != 0);
      53        if (s2size == 0)
      54          return 1;
      55      }
      56  
      57    return diff;
      58  }
      59  
      60  /* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
      61     to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
      62     adjacent.  Perhaps temporarily modify the bytes after S1 and S2,
      63     but restore their original contents before returning.  Set errno to an
      64     error number if there is an error, and to zero otherwise.  */
      65  int
      66  memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
      67  {
      68    int diff;
      69  
      70    /* strcoll is slow on many platforms, so check for the common case
      71       where the arguments are bytewise equal.  Otherwise, walk through
      72       the buffers using strcoll on each substring.  */
      73  
      74    if (s1len == s2len && memcmp (s1, s2, s1len) == 0)
      75      {
      76        errno = 0;
      77        diff = 0;
      78      }
      79    else
      80      {
      81        char n1 = s1[s1len];
      82        char n2 = s2[s2len];
      83  
      84        s1[s1len] = '\0';
      85        s2[s2len] = '\0';
      86  
      87        diff = strcoll_loop (s1, s1len + 1, s2, s2len + 1);
      88  
      89        s1[s1len] = n1;
      90        s2[s2len] = n2;
      91      }
      92  
      93    return diff;
      94  }
      95  
      96  /* Compare S1 (a memory block of size S1SIZE, with a NUL as last byte)
      97     and S2 (a memory block of size S2SIZE, with a NUL as last byte)
      98     according to the LC_COLLATE locale.  S1SIZE and S2SIZE must be > 0.
      99     Set errno to an error number if there is an error, and to zero
     100     otherwise.  */
     101  int
     102  memcoll0 (char const *s1, size_t s1size, char const *s2, size_t s2size)
     103  {
     104    if (s1size == s2size && memcmp (s1, s2, s1size) == 0)
     105      {
     106        errno = 0;
     107        return 0;
     108      }
     109    else
     110      return strcoll_loop (s1, s1size, s2, s2size);
     111  }