util: add a vercmp function to compare version numbers

It is simple, supports simple x.y.z type numeric versions,
and does not attempt any kind of validation

src/common/util.cpp

@@ -568,4 +568,21 @@ std::string get_nix_version_display_string()
     MDEBUG("Address '" << address << "' is not local");
     return false;
   }
+  int vercmp(const char *v0, const char *v1)
+  {
+    std::vector<std::string> f0, f1;
+    boost::split(f0, v0, boost::is_any_of("."));
+    boost::split(f1, v1, boost::is_any_of("."));
+    while (f0.size() < f1.size())
+      f0.push_back("0");
+    while (f1.size() < f0.size())
+      f1.push_back("0");
+    for (size_t i = 0; i < f0.size(); ++i) {
+      int f0i = atoi(f0[i].c_str()), f1i = atoi(f1[i].c_str());
+      int n = f0i - f1i;
+      if (n)
+        return n;
+    }
+    return 0;
+  }
 }

src/common/util.h

@@ -183,4 +183,5 @@ namespace tools
   unsigned get_max_concurrency();
 
   bool is_local_address(const std::string &address);
+  int vercmp(const char *v0, const char *v1); // returns < 0, 0, > 0, similar to strcmp, but more human friendly than lexical - does not attempt to validate
 }

tests/unit_tests/CMakeLists.txt

@@ -58,7 +58,8 @@ set(unit_tests_sources
   uri.cpp
   varint.cpp
   ringct.cpp
-  output_selection.cpp)
+  output_selection.cpp
+  vercmp.cpp)
 
 set(unit_tests_headers
   unit_tests_utils.h)

tests/unit_tests/vercmp.cpp

@@ -0,0 +1,43 @@
+// Copyright (c) 2017, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gtest/gtest.h"
+
+#include "common/util.h"
+
+TEST(vercmp, empty) { ASSERT_TRUE(tools::vercmp("", "") == 0); }
+TEST(vercmp, empty0) { ASSERT_TRUE(tools::vercmp("", "0") == 0); }
+TEST(vercmp, empty1) { ASSERT_TRUE(tools::vercmp("0", "") == 0); }
+TEST(vercmp, zero_zero) { ASSERT_TRUE(tools::vercmp("0", "0") == 0); }
+TEST(vercmp, one_one) { ASSERT_TRUE(tools::vercmp("1", "1") == 0); }
+TEST(vercmp, one_two) { ASSERT_TRUE(tools::vercmp("1", "2") < 0); }
+TEST(vercmp, two_one) { ASSERT_TRUE(tools::vercmp("2", "1") > 0); }
+TEST(vercmp, ten_nine) { ASSERT_TRUE(tools::vercmp("10", "9") > 0); }
+TEST(vercmp, one_dot_ten_one_dot_nine) { ASSERT_TRUE(tools::vercmp("1.10", "1.9") > 0); }
+TEST(vercmp, one_one_dot_nine) { ASSERT_TRUE(tools::vercmp("1", "1.9") < 0); }
+