From a7bba1bf486b812270a4ea8c45d79ff1984bb52d Mon Sep 17 00:00:00 2001
From: Lu Wang <coolwanglu@gmail.com>
Date: Wed, 30 Jan 2013 03:22:11 +0800
Subject: [PATCH] clean ArgParser

---
 src/util/ArgParser.cc |  2 +-
 src/util/ArgParser.h  | 25 +++++++++++++++----------
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/util/ArgParser.cc b/src/util/ArgParser.cc
index 433b579..9b66a20 100644
--- a/src/util/ArgParser.cc
+++ b/src/util/ArgParser.cc
@@ -163,7 +163,7 @@ ArgParser::ArgEntryBase::ArgEntryBase(const char * name, const char * descriptio
         }
         else
         {
-            cerr << "Warning: argument '" << this->name << "' may not be parsed correctly" << endl;
+            cerr << "Warning: argument '" << this->name << "' cannnot be parsed as a short option" << endl;
         }
     }
 }
diff --git a/src/util/ArgParser.h b/src/util/ArgParser.h
index d5aafde..a6c58c4 100644
--- a/src/util/ArgParser.h
+++ b/src/util/ArgParser.h
@@ -47,15 +47,14 @@ class ArgParser
         typedef void (*ArgParserCallBack) (const char * arg);
 
         /*
-         * optname: name of the argment, should be provided as --optname
-         * description: if description is "", the argument won't be shown in show_usage()
+         * The 1st is for arg without arguments (i.e. flags), and the 2nd is for general args.
+         * optname:
+         *  - if not nullptr, it should be the name of the arg, should be in the format of "<long name>[,<short char>]", e.g. "help,h"
+         *  - if nullptr, it denotes an optional arg, and description will be ignored
+         * description:
+         *  - if description is nullptr or "", the argument won't be shown in show_usage()
          */
-
         ArgParser & add(const char * optname, const char * description, ArgParserCallBack callback = nullptr);
-
-        /*
-         * location == nullptr means no argument is needed
-         */
         template <class T, class Tv>
         ArgParser & add(const char * optname, T * location, const Tv & default_value, const char * description, ArgParserCallBack callback = nullptr, bool dont_show_default = false);
 
@@ -70,6 +69,7 @@ class ArgParser
         class ArgEntryBase
         {
             public:
+                /* name or description cannot be nullptr */
                 ArgEntryBase(const char * name, const char * description, bool need_arg);
                 virtual ~ArgEntryBase() { }
                 char shortname;
@@ -107,11 +107,16 @@ class ArgParser
 template<class T, class Tv>
 ArgParser & ArgParser::add(const char * optname, T * location, const Tv & default_value, const char * description, ArgParserCallBack callback, bool dont_show_default)
 {
-    // use "" in case nullptr is provided
+    // ArgEntry does not accept nullptr as optname nor description
     if((!optname) || (!optname[0]))
+    {
+        // when optname is nullptr or "", it's optional, and description is dropped
         optional_arg_entries.push_back(new ArgEntry<T, Tv>("", location, default_value, callback, "", dont_show_default));
+    }
     else
-        arg_entries.push_back(new ArgEntry<T, Tv>(optname, location, default_value, callback, description, dont_show_default));
+    {
+        arg_entries.push_back(new ArgEntry<T, Tv>(optname, location, default_value, callback, (description ? description : ""), dont_show_default));
+    }
 
     return *this;
 }
@@ -152,7 +157,7 @@ void ArgParser::ArgEntry<T, Tv>::parse(const char * arg) const
 template<class T, class Tv>
 void ArgParser::ArgEntry<T, Tv>::show_usage(std::ostream & out) const
 { 
-    if(description == "")
+    if(description.empty())
         return;
 
     std::ostringstream sout;