lib/strutil/filevercmp.c

   1 /*
   2    Copyright (C) 1995 Ian Jackson <iwj10@cus.cam.ac.uk>
   3    Copyright (C) 2001 Anthony Towns <aj@azure.humbug.org.au>
   4    Copyright (C) 2008-2022 Free Software Foundation, Inc.
   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
  20 #include <config.h>
  21
  22 #include <stdlib.h>
  23 #include <limits.h>
  24
  25 #include "lib/strutil.h"
  26
  27 /*** global variables ****************************************************************************/
  28
  29 /*** file scope macro definitions ****************************************************************/
  30
  31 /*** file scope type declarations ****************************************************************/
  32
  33 /*** forward declarations (file scope functions) *************************************************/
  34
  35 /*** file scope variables ************************************************************************/
  36
  37 /* --------------------------------------------------------------------------------------------- */
  38 /*** file scope functions ************************************************************************/
  39 /* --------------------------------------------------------------------------------------------- */
  40
  41 /* Return the length of a prefix of @s that corresponds to the suffix defined by this extended
  42  * regular expression in the C locale: (\.[A-Za-z~][A-Za-z0-9~]*)*$
  43  *
  44  * Use the longest suffix matching this regular expression, except do not use all of s as a suffix
  45  * if s is nonempty.
  46  *
  47  * If *len is -1, s is a string; set *lem to s's length.
  48  * Otherwise, *len should be nonnegative, s is a char array, and *len does not change.
  49  */
  50 static ssize_t
  51 file_prefixlen (const char *s, ssize_t *len)
  52 {
  53     size_t n = (size_t) (*len); /* SIZE_MAX if N == -1 */
  54     size_t i = 0;
  55     size_t prefixlen = 0;
  56
  57     while (TRUE)
  58     {
  59         gboolean done;
  60
  61         if (*len < 0)
  62             done = s[i] == '\0';
  63         else
  64             done = i == n;
  65
  66         if (done)
  67         {
  68             *len = (ssize_t) i;
  69             return (ssize_t) prefixlen;
  70         }
  71
  72         i++;
  73         prefixlen = i;
  74
  75         while (i + 1 < n && s[i] == '.' && (g_ascii_isalpha (s[i + 1]) || s[i + 1] == '~'))
  76             for (i += 2; i < n && (g_ascii_isalnum (s[i]) || s[i] == '~'); i++)
  77                 ;
  78     }
  79 }
  80
  81 /* --------------------------------------------------------------------------------------------- */
  82
  83 /* Return a version sort comparison value for @s's byte at position @pos.
  84  *
  85  * @param s a string
  86  * @param pos a position in @s
  87  * @param len a length of @s. If @pos == @len, sort before all non-'~' bytes.
  88  */
  89
  90 static int
  91 order (const char *s, size_t pos, size_t len)
  92 {
  93     unsigned char c;
  94
  95     if (pos == len)
  96         return (-1);
  97
  98     c = s[pos];
  99
 100     if (g_ascii_isdigit (c))
 101         return 0;
 102     if (g_ascii_isalpha (c))
 103         return c;
 104     if (c == '~')
 105         return (-2);
 106
 107     g_assert (UCHAR_MAX <= (INT_MAX - 1 - 2) / 2);
 108
 109     return (int) c + UCHAR_MAX + 1;
 110 }
 111
 112 /* --------------------------------------------------------------------------------------------- */
 113
 114 /* Slightly modified verrevcmp function from dpkg
 115  *
 116  * This implements the algorithm for comparison of version strings
 117  * specified by Debian and now widely adopted.  The detailed
 118  * specification can be found in the Debian Policy Manual in the
 119  * section on the 'Version' control field.  This version of the code
 120  * implements that from s5.6.12 of Debian Policy v3.8.0.1
 121  * https://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version
 122  *
 123  * @param s1 first char array to compare
 124  * @param s1_len length of @s1
 125  * @param s2 second char array to compare
 126  * @param s2_len length of @s2
 127  *
 128  * @return an integer less than, equal to, or greater than zero, if @s1 is <, == or > than @s2.
 129  */
 130 static int
 131 verrevcmp (const char *s1, ssize_t s1_len, const char *s2, ssize_t s2_len)
 132 {
 133     ssize_t s1_pos = 0;
 134     ssize_t s2_pos = 0;
 135
 136     while (s1_pos < s1_len || s2_pos < s2_len)
 137     {
 138         int first_diff = 0;
 139
 140         while ((s1_pos < s1_len && !g_ascii_isdigit (s1[s1_pos]))
 141                || (s2_pos < s2_len && !g_ascii_isdigit (s2[s2_pos])))
 142         {
 143             int s1_c, s2_c;
 144
 145             s1_c = order (s1, s1_pos, s1_len);
 146             s2_c = order (s2, s2_pos, s2_len);
 147
 148             if (s1_c != s2_c)
 149                 return (s1_c - s2_c);
 150
 151             s1_pos++;
 152             s2_pos++;
 153         }
 154
 155         while (s1_pos < s1_len && s1[s1_pos] == '0')
 156             s1_pos++;
 157         while (s2_pos < s2_len && s2[s2_pos] == '0')
 158             s2_pos++;
 159
 160         while (s1_pos < s1_len && s2_pos < s2_len
 161                && g_ascii_isdigit (s1[s1_pos]) && g_ascii_isdigit (s2[s2_pos]))
 162         {
 163             if (first_diff == 0)
 164                 first_diff = s1[s1_pos] - s2[s2_pos];
 165
 166             s1_pos++;
 167             s2_pos++;
 168         }
 169
 170         if (s1_pos < s1_len && g_ascii_isdigit (s1[s1_pos]))
 171             return 1;
 172         if (s2_pos < s2_len && g_ascii_isdigit (s2[s2_pos]))
 173             return (-1);
 174         if (first_diff != 0)
 175             return first_diff;
 176     }
 177
 178     return 0;
 179 }
 180
 181 /* --------------------------------------------------------------------------------------------- */
 182 /*** public functions ****************************************************************************/
 183 /* --------------------------------------------------------------------------------------------- */
 184
 185 /* Compare version strings.
 186  *
 187  * @param a first string to compare
 188  * @param alen length of @a or (-1)
 189  * @param b second string to compare
 190  * @param blen length of @b or (-1)
 191  *
 192  * @return an integer less than, equal to, or greater than zero, if @s1 is <, == or > than @s2.
 193  */
 194 int
 195 filenvercmp (const char *a, ssize_t alen, const char *b, ssize_t blen)
 196 {
 197     gboolean aempty, bempty;
 198     ssize_t aprefixlen, bprefixlen;
 199     gboolean one_pass_only;
 200     int result;
 201
 202     /* Special case for empty versions. */
 203     aempty = alen < 0 ? a[0] == '\0' : alen == 0;
 204     bempty = blen < 0 ? b[0] == '\0' : blen == 0;
 205
 206     if (aempty)
 207         return (bempty ? 0 : -1);
 208     if (bempty)
 209         return 1;
 210
 211     /* Special cases for leading ".": "." sorts first, then "..", then other names with leading ".",
 212        then other names. */
 213     if (a[0] == '.')
 214     {
 215         gboolean adot, bdot;
 216         gboolean adotdot, bdotdot;
 217
 218         if (b[0] != '.')
 219             return (-1);
 220
 221         adot = alen < 0 ? a[1] == '\0' : alen == 1;
 222         bdot = blen < 0 ? b[1] == '\0' : blen == 1;
 223
 224         if (adot)
 225             return (bdot ? 0 : -1);
 226         if (bdot)
 227             return 1;
 228
 229         adotdot = a[1] == '.' && (alen < 0 ? a[2] == '\0' : alen == 2);
 230         bdotdot = b[1] == '.' && (blen < 0 ? b[2] == '\0' : blen == 2);
 231         if (adotdot)
 232             return (bdotdot ? 0 : -1);
 233         if (bdotdot)
 234             return 1;
 235     }
 236     else if (b[0] == '.')
 237         return 1;
 238
 239     /* Cut file suffixes. */
 240     aprefixlen = file_prefixlen (a, &alen);
 241     bprefixlen = file_prefixlen (b, &blen);
 242
 243     /* If both suffixes are empty, a second pass would return the same thing. */
 244     one_pass_only = aprefixlen == alen && bprefixlen == blen;
 245
 246     result = verrevcmp (a, aprefixlen, b, bprefixlen);
 247
 248     /* Return the initial result if nonzero, or if no second pass is needed.
 249        Otherwise, restore the suffixes and try again. */
 250     return (result != 0 || one_pass_only ? result : verrevcmp (a, alen, b, blen));
 251 }
 252
 253 /* --------------------------------------------------------------------------------------------- */