lib/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) 2008-2017 Free Software Foundation, 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 #include <config.h>
  20 #include "filevercmp.h"
  21
  22 #include <sys/types.h>
  23 #include <stdlib.h>
  24 #include <stdbool.h>
  25 #include <string.h>
  26 #include <c-ctype.h>
  27 #include <limits.h>
  28
  29 /* Match a file suffix defined by this regular expression:
  30    /(\.[A-Za-z~][A-Za-z0-9~]*)*$/
  31    Scan the string *STR and return a pointer to the matching suffix, or
  32    NULL if not found.  Upon return, *STR points to terminating NUL.  */
  33 static const char *
  34 match_suffix (const char **str)
  35 {
  36   const char *match = NULL;
  37   bool read_alpha = false;
  38   while (**str)
  39     {
  40       if (read_alpha)
  41         {
  42           read_alpha = false;
  43           if (!c_isalpha (**str) && '~' != **str)
  44             match = NULL;
  45         }
  46       else if ('.' == **str)
  47         {
  48           read_alpha = true;
  49           if (!match)
  50             match = *str;
  51         }
  52       else if (!c_isalnum (**str) && '~' != **str)
  53         match = NULL;
  54       (*str)++;
  55     }
  56   return match;
  57 }
  58
  59 /* verrevcmp helper function */
  60 static int
  61 order (unsigned char c)
  62 {
  63   if (c_isdigit (c))
  64     return 0;
  65   else if (c_isalpha (c))
  66     return c;
  67   else if (c == '~')
  68     return -1;
  69   else
  70     return (int) c + UCHAR_MAX + 1;
  71 }
  72
  73 /* slightly modified verrevcmp function from dpkg
  74    S1, S2 - compared string
  75    S1_LEN, S2_LEN - length of strings to be scanned
  76
  77    This implements the algorithm for comparison of version strings
  78    specified by Debian and now widely adopted.  The detailed
  79    specification can be found in the Debian Policy Manual in the
  80    section on the 'Version' control field.  This version of the code
  81    implements that from s5.6.12 of Debian Policy v3.8.0.1
  82    https://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version */
  83 static int _GL_ATTRIBUTE_PURE
  84 verrevcmp (const char *s1, size_t s1_len, const char *s2, size_t s2_len)
  85 {
  86   size_t s1_pos = 0;
  87   size_t s2_pos = 0;
  88   while (s1_pos < s1_len || s2_pos < s2_len)
  89     {
  90       int first_diff = 0;
  91       while ((s1_pos < s1_len && !c_isdigit (s1[s1_pos]))
  92              || (s2_pos < s2_len && !c_isdigit (s2[s2_pos])))
  93         {
  94           int s1_c = (s1_pos == s1_len) ? 0 : order (s1[s1_pos]);
  95           int s2_c = (s2_pos == s2_len) ? 0 : order (s2[s2_pos]);
  96           if (s1_c != s2_c)
  97             return s1_c - s2_c;
  98           s1_pos++;
  99           s2_pos++;
 100         }
 101       while (s1[s1_pos] == '0')
 102         s1_pos++;
 103       while (s2[s2_pos] == '0')
 104         s2_pos++;
 105       while (c_isdigit (s1[s1_pos]) && c_isdigit (s2[s2_pos]))
 106         {
 107           if (!first_diff)
 108             first_diff = s1[s1_pos] - s2[s2_pos];
 109           s1_pos++;
 110           s2_pos++;
 111         }
 112       if (c_isdigit (s1[s1_pos]))
 113         return 1;
 114       if (c_isdigit (s2[s2_pos]))
 115         return -1;
 116       if (first_diff)
 117         return first_diff;
 118     }
 119   return 0;
 120 }
 121
 122 /* Compare version strings S1 and S2.
 123    See filevercmp.h for function description.  */
 124 int
 125 filevercmp (const char *s1, const char *s2)
 126 {
 127   const char *s1_pos;
 128   const char *s2_pos;
 129   const char *s1_suffix, *s2_suffix;
 130   size_t s1_len, s2_len;
 131   int result;
 132
 133   /* easy comparison to see if strings are identical */
 134   int simple_cmp = strcmp (s1, s2);
 135   if (simple_cmp == 0)
 136     return 0;
 137
 138   /* special handle for "", "." and ".." */
 139   if (!*s1)
 140     return -1;
 141   if (!*s2)
 142     return 1;
 143   if (0 == strcmp (".", s1))
 144     return -1;
 145   if (0 == strcmp (".", s2))
 146     return 1;
 147   if (0 == strcmp ("..", s1))
 148     return -1;
 149   if (0 == strcmp ("..", s2))
 150     return 1;
 151
 152   /* special handle for other hidden files */
 153   if (*s1 == '.' && *s2 != '.')
 154     return -1;
 155   if (*s1 != '.' && *s2 == '.')
 156     return 1;
 157   if (*s1 == '.' && *s2 == '.')
 158     {
 159       s1++;
 160       s2++;
 161     }
 162
 163   /* "cut" file suffixes */
 164   s1_pos = s1;
 165   s2_pos = s2;
 166   s1_suffix = match_suffix (&s1_pos);
 167   s2_suffix = match_suffix (&s2_pos);
 168   s1_len = (s1_suffix ? s1_suffix : s1_pos) - s1;
 169   s2_len = (s2_suffix ? s2_suffix : s2_pos) - s2;
 170
 171   /* restore file suffixes if strings are identical after "cut" */
 172   if ((s1_suffix || s2_suffix) && (s1_len == s2_len)
 173       && 0 == strncmp (s1, s2, s1_len))
 174     {
 175       s1_len = s1_pos - s1;
 176       s2_len = s2_pos - s2;
 177     }
 178
 179   result = verrevcmp (s1, s1_len, s2, s2_len);
 180   return result == 0 ? simple_cmp : result;
 181 }