csu_util/version_compare.cc

   1 /*
   2  * Copyright (c) 2004 Max Bowsher
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     A copy of the GNU General Public License can be found at
  10  *     http://www.gnu.org/
  11  *
  12  * Written by Max Bowsher
  13  */
  14
  15 #include "version_compare.h"
  16
  17 static inline bool isdigit(char c) { return (c >= '0' && c <= '9'); }
  18
  19 /* Sort two version numbers, comparing equivalently seperated strings of
  20  * digits numerically.
  21  *
  22  * Returns a positive number if (a > b)
  23  * Returns a negative number if (a < b)
  24  * Returns zero if (a == b)
  25  *
  26  * Inspired but not equivalent to rpmvercmp().
  27  */
  28 int version_compare (std::string a, std::string b)
  29 {
  30   if (a == b) return 0;
  31
  32   size_t apos1, apos2 = 0, bpos1, bpos2 = 0;
  33   size_t alen = a.length(), blen = b.length();
  34   bool isnum;
  35   int cval;
  36
  37   while (apos2 < alen && bpos2 < blen)
  38   {
  39     apos1 = apos2;
  40     bpos1 = bpos2;
  41
  42     if (isdigit(a[apos2]))
  43     {
  44       while (apos2 < alen && isdigit(a[apos2])) apos2++;
  45       while (bpos2 < blen && isdigit(b[bpos2])) bpos2++;
  46       isnum = true;
  47     }
  48     else
  49     {
  50       while (apos2 < alen && !isdigit(a[apos2])) apos2++;
  51       while (bpos2 < blen && !isdigit(b[bpos2])) bpos2++;
  52       isnum = false;
  53     }
  54
  55     /* if (apos1 == apos2) { a logical impossibility has happened; } */
  56
  57     /* isdigit(a[0]) != isdigit(b[0])
  58      * arbitrarily sort the non-digit first */
  59     if (bpos1 == bpos2) return (isnum ? 1 : -1);
  60
  61     if (isnum)
  62     {
  63       /* skip numeric leading zeros */
  64       while (apos1 < alen && a[apos1] == '0') apos1++;
  65       while (bpos1 < blen && b[bpos1] == '0') bpos1++;
  66
  67       /* if one number has more digits, it is greater */
  68       if (apos2-apos1 > bpos2-bpos1) return 1;
  69       if (apos2-apos1 < bpos2-bpos1) return -1;
  70     }
  71
  72     /* do an ordinary lexicographic string comparison */
  73     cval = a.compare(apos1, apos2-apos1, b, bpos1, bpos2-bpos1);
  74     if (cval) return (cval < 1 ? -1 : 1);
  75   }
  76
  77   /* ran out of characters in one string, without finding a difference */
  78
  79   /* maybe they were the same version, but with different leading zeros */
  80   if (apos2 == alen && bpos2 == blen) return 0;
  81
  82   /* the version with a suffix remaining is greater */
  83   return (apos2 < alen ? 1 : -1);
  84 }
  85
  86 #ifdef TESTING_VERSION_COMPARE
  87
  88 #include <iostream>
  89 #include <iomanip>
  90
  91 struct version_pair
  92 {
  93   const char *a;
  94   const char *b;
  95 };
  96
  97 static version_pair test_data[] =
  98 {
  99   { "1.0.0", "2.0.0" },
 100   { ".0.0", "2.0.0" },
 101   { "alpha", "beta" },
 102   { "1.0", "1.0.0" },
 103   { "2.456", "2.1000" },
 104   { "2.1000", "3.111" },
 105   { "2.001", "2.1" },
 106   { "2.34", "2.34" },
 107   { NULL, NULL }
 108 };
 109
 110 int main(int argc, char* argv[])
 111 {
 112   version_pair *i = test_data;
 113
 114   while (i->a)
 115   {
 116     cout << setw(10) << i->a << ", " << setw(10) << i->b << " : "
 117       << version_compare(i->a, i->b) << ", " << version_compare(i->b, i->a)
 118       << endl;
 119     i++;
 120   }
 121
 122   return 0;
 123 }
 124
 125 #endif