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 using namespace std;
  18
  19 static inline bool isdigit(char c) { return (c >= '0' && c <= '9'); }
  20
  21 /* Sort two version numbers, comparing equivalently seperated strings of
  22  * digits numerically.
  23  *
  24  * Returns a positive number if (a > b)
  25  * Returns a negative number if (a < b)
  26  * Returns zero if (a == b)
  27  *
  28  * Inspired but not equivalent to rpmvercmp().
  29  */
  30 int version_compare (string a, string b)
  31 {
  32   if (a == b) return 0;
  33
  34   size_t apos1, apos2 = 0, bpos1, bpos2 = 0;
  35   size_t alen = a.length(), blen = b.length();
  36   bool isnum;
  37   int cval;
  38
  39   while (apos2 < alen && bpos2 < blen)
  40   {
  41     apos1 = apos2;
  42     bpos1 = bpos2;
  43
  44     if (isdigit(a[apos2]))
  45     {
  46       while (apos2 < alen && isdigit(a[apos2])) apos2++;
  47       while (bpos2 < blen && isdigit(b[bpos2])) bpos2++;
  48       isnum = true;
  49     }
  50     else
  51     {
  52       while (apos2 < alen && !isdigit(a[apos2])) apos2++;
  53       while (bpos2 < blen && !isdigit(b[bpos2])) bpos2++;
  54       isnum = false;
  55     }
  56
  57     /* if (apos1 == apos2) { a logical impossibility has happened; } */
  58
  59     /* isdigit(a[0]) != isdigit(b[0])
  60      * arbitrarily sort the non-digit first */
  61     if (bpos1 == bpos2) return (isnum ? 1 : -1);
  62
  63     if (isnum)
  64     {
  65       /* skip numeric leading zeros */
  66       while (apos1 < alen && a[apos1] == '0') apos1++;
  67       while (bpos1 < blen && b[bpos1] == '0') bpos1++;
  68
  69       /* if one number has more digits, it is greater */
  70       if (apos2-apos1 > bpos2-bpos1) return 1;
  71       if (apos2-apos1 < bpos2-bpos1) return -1;
  72     }
  73
  74     /* do an ordinary lexicographic string comparison */
  75     cval = a.compare(apos1, apos2-apos1, b, bpos1, bpos2-bpos1);
  76     if (cval) return (cval < 1 ? -1 : 1);
  77   }
  78
  79   /* ran out of characters in one string, without finding a difference */
  80
  81   /* maybe they were the same version, but with different leading zeros */
  82   if (apos2 == alen && bpos2 == blen) return 0;
  83
  84   /* the version with a suffix remaining is greater */
  85   return (apos2 < alen ? 1 : -1);
  86 }
  87
  88 #ifdef TESTING_VERSION_COMPARE
  89
  90 #include <iostream>
  91 #include <iomanip>
  92 using namespace std;
  93
  94 struct version_pair
  95 {
  96   const char *a;
  97   const char *b;
  98 };
  99
 100 static version_pair test_data[] =
 101 {
 102   { "1.0.0", "2.0.0" },
 103   { ".0.0", "2.0.0" },
 104   { "alpha", "beta" },
 105   { "1.0", "1.0.0" },
 106   { "2.456", "2.1000" },
 107   { "2.1000", "3.111" },
 108   { "2.001", "2.1" },
 109   { "2.34", "2.34" },
 110   { NULL, NULL }
 111 };
 112
 113 int main(int argc, char* argv[])
 114 {
 115   version_pair *i = test_data;
 116
 117   while (i->a)
 118   {
 119     cout << setw(10) << i->a << ", " << setw(10) << i->b << " : "
 120       << version_compare(i->a, i->b) << ", " << version_compare(i->b, i->a)
 121       << endl;
 122     i++;
 123   }
 124
 125   return 0;
 126 }
 127
 128 #endif