Added FixedSizeString as one of the types that can be read/written fr…

…om/to files

docs/HTML/DateTime.html

@@ -91,6 +91,7 @@
   <H2 ID="0"><font color="blue">Summary <font size="+4">&#9730;</font></font></font></H2>
 <font size="+1">Since DataFrame is a statistical library, it often deals with time-series data. So, it needs to keep track of time.<BR>
 The most efficient way of indexing DataFrame by time is to use an index type of time_t for second precision or double or long long integer for more precision. DateTime class provides a more elaborate handling of time. Also, it is a general handy DateTime object. DateTime is a cool and handy object to manipulate date/time with nanosecond precision and multi timezone capability. It has a very simple and intuitive interface that allows you to break date/time to their components, reassemble date/time from their components, advance or pullback date/time with different granularities, and more.</font><BR>
+<I>DateTime</I> is one of the types that <I>DataFrame</I> library can read/write from/to files and serialization.<BR>
 
 <BR><HR COLOR="Gray" SIZE="5">
 

docs/HTML/VirtualString.html

@@ -61,8 +61,8 @@
       </td>
       <td>
         <I>FixedSizeString</I> is a fixed-size and null-terminated string. Since the size is a template parameter, each different size is a different object type. But since <I>FixedSizeString</I> is derived from <I>VirtualString</I> (which is not a templated object), different size instances can be interchanged through references to <I>VirtualString</I>. <I>VirtualString</I> implements almost all of std::string functionalities.<BR>
-There is no dynamic memory allocation and deallocation involved here.<BR>
-<I>FixedSizeString</I> is the type of column names in DataFrame and could be used by users for their other purposes.
+<I>FixedSizeString</I> does not do any dynamic memory allocation/deallocation.<BR>
+<I>FixedSizeString</I> "Convenient typedefs"  are among  the types that <I>DataFrame</I> library can read/write from/to files and serialization<BR>
 
       </td>
     </tr>

docs/HTML/read.html

@@ -120,10 +120,16 @@
 string     -- std::string
 string     -- const char *
 string     -- char *
+vstr32     -- Fixed-size string of 31 char length
+vstr64     -- Fixed-size string of 63 char length
+vstr128    -- Fixed-size string of 127 char length
+vstr512    -- Fixed-size string of 511 char length
+vstr1K     -- Fixed-size string of 1023 char length
+vstr2K     -- Fixed-size string of 2047 char length
 bool       -- bool
 DateTime   -- DateTime data in format of
-    <Epoch seconds>.<nanoseconds>
-    (1516179600.874123908)
+              <Epoch seconds>.<nanoseconds>
+              (1516179600.874123908)
         </PRE>
         In case of io_format::csv2, io_format::csv, and io_format::binary the following additional types are also supported:
         <PRE>

docs/HTML/write.html

@@ -118,10 +118,16 @@
 string     -- std::string
 string     -- const char *
 string     -- char *
+vstr32     -- Fixed-size string of 31 char length
+vstr64     -- Fixed-size string of 63 char length
+vstr128    -- Fixed-size string of 127 char length
+vstr512    -- Fixed-size string of 511 char length
+vstr1K     -- Fixed-size string of 1023 char length
+vstr2K     -- Fixed-size string of 2047 char length
 bool       -- bool
 DateTime   -- DateTime data in format of
-    <Epoch seconds>.<nanoseconds>
-    (1516179600.874123908)
+              <Epoch seconds>.<nanoseconds>
+              (1516179600.874123908)
         </PRE>
         In case of io_format::csv2, io_format::csv, and io_format::binary the following additional types are also supported:
         <PRE>

include/DataFrame/Internals/DataFrame_misc.tcc

@@ -244,7 +244,13 @@ DataFrame<I, H>::print_binary_functor_<Ts ...>::operator() (const T &vec)  {
     const long  local_start_row = std::min (long(vec.size()), start_row);
     const long  local_end_row = std::min (long(vec.size()), end_row);
 
-    if constexpr (std::is_same_v<ValueType, std::string>)
+    if constexpr (std::is_same_v<ValueType, std::string> ||
+                  std::is_same_v<ValueType, String32> ||
+                  std::is_same_v<ValueType, String64> ||
+                  std::is_same_v<ValueType, String128> ||
+                  std::is_same_v<ValueType, String512> ||
+                  std::is_same_v<ValueType, String1K> ||
+                  std::is_same_v<ValueType, String2K>)
         _write_binary_string_(os, vec, local_start_row, local_end_row);
     else if constexpr (std::is_same_v<ValueType, DateTime>)
         _write_binary_datetime_(os, vec, local_start_row, local_end_row);

include/DataFrame/Internals/DataFrame_private_decl.h

@@ -1373,8 +1373,9 @@ struct  ColVectorPushBack_<DateTime, StlVecType<DateTime>, Dummy>  {
 
 // ----------------------------------------------------------------------------
 
+template<typename STR>
 inline static void
-json_str_col_vector_push_back_(StlVecType<std::string> &vec,
+json_str_col_vector_push_back_(StlVecType<STR> &vec,
                                std::istream &file)  {
 
     char    value[2048];