lib/memcoll.c

   1 /* Locale-specific memory comparison.
   2
   3    Copyright (C) 1999, 2002-2004, 2006, 2009-2020 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 }