util, transport: add configuration file support and make default unix socket configurable

add sample library configuration file

refs: #1364

Change-Id: I3cb36d078aa3f0b0a50d9a83a521e95448df0a93
diff --git a/src/util/config-file.cpp b/src/util/config-file.cpp
new file mode 100644
index 0000000..031df25
--- /dev/null
+++ b/src/util/config-file.cpp
@@ -0,0 +1,123 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (C) 2014 Named Data Networking Project
+ * See COPYING for copyright and distribution information.
+ */
+
+
+#include "config-file.hpp"
+
+#include <boost/property_tree/ini_parser.hpp>
+#include <boost/filesystem.hpp>
+
+namespace ndn {
+
+ConfigFile::ConfigFile()
+  : m_path(findConfigFile())
+{
+  if (open())
+    {
+      parse();
+      close();
+    }
+}
+
+ConfigFile::~ConfigFile()
+{
+  if (m_input.is_open())
+    {
+      m_input.close();
+    }
+}
+
+boost::filesystem::path
+ConfigFile::findConfigFile()
+{
+  using namespace boost::filesystem;
+
+  path home(std::getenv("HOME"));
+  if (!home.empty())
+    {
+      home /= ".ndn/client.conf";
+      if (exists(home))
+        {
+          return absolute(home);
+        }
+    }
+
+#ifdef NDN_CPP_SYSCONFDIR
+  path sysconfdir(NDN_CPP_SYSCONFDIR);
+  sysconfdir /= "ndn/client.conf";
+
+  if (exists(sysconfdir))
+    {
+      return absolute(sysconfdir);
+    }
+#endif // NDN_CPP_SYSCONFDIR
+
+  path etc("/etc/ndn/client.conf");
+  if (exists(etc))
+    {
+      return absolute(etc);
+    }
+
+  return path();
+}
+
+
+
+bool
+ConfigFile::open()
+{
+  if (m_path.empty())
+    {
+      return false;
+    }
+
+  m_input.open(m_path.c_str());
+  if (!m_input.good() || !m_input.is_open())
+    {
+      return false;
+    }
+  return true;
+}
+
+void
+ConfigFile::close()
+{
+  if (m_input.is_open())
+    {
+      m_input.close();
+    }
+}
+
+
+const ConfigFile::Parsed&
+ConfigFile::parse()
+{
+  if (m_path.empty())
+    {
+      throw Error("Failed to locate configuration file for parsing");
+    }
+  else if (!m_input.is_open() && !open())
+    {
+      throw Error("Failed to open configuration file for parsing");
+    }
+
+  try
+    {
+      boost::property_tree::read_ini(m_input, m_config);
+    }
+  catch (const boost::property_tree::ini_parser_error& error)
+    {
+      std::stringstream msg;
+      msg << "Failed to parse configuration file";
+      msg << " " << m_path;
+      msg << " " << error.message() << " line " << error.line();
+      throw Error(msg.str());
+    }
+  return m_config;
+}
+
+}
+