Added support for caching in card ( variant and type sequence ) (Boos…

…tGSoC19#163)

include/boost/astronomy/io/card.hpp

@@ -1,5 +1,7 @@
 /*=============================================================================
 Copyright 2018 Pranam Lashkari <[email protected]>
+Copyright 2020 Gopi Krishna Menon <[email protected]>
+
 
 Distributed under the Boost Software License, Version 1.0. (See accompanying
 file License.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
@@ -14,29 +16,27 @@ file License.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 #include <boost/algorithm/string/trim.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/type.hpp>
+#include <boost/variant.hpp>
 
 #include <boost/astronomy/io/default_card_policy.hpp>
 #include <boost/astronomy/exception/fits_exception.hpp>
 
-/**
- * @file    card.hpp
- * @author  Pranam Lashkari
- * @details Contains the definition for <strong>card</strong> structure
- */
 
 
 namespace boost { namespace astronomy { namespace io {
 
 /**
  * @brief   Represents the concept of <strong>card</strong> associated with the FITS standard.
  * @details This structure provides functions for storage, manipulation and access of FITS cards.
- * @author  Pranam Lashkari
+ * @author  Pranam Lashkari, Gopi Krishna Menon
  */
 template<typename CardPolicy>
 struct card: CardPolicy
 {
 private:
     std::string card_;
+    typedef typename boost::make_variant_over< typename CardPolicy::supported_types>::type cache;
+    mutable cache card_cache;
 
 public:
 
@@ -146,15 +146,15 @@ struct card: CardPolicy
     /**
      * @brief   Returns the value associated with the card
      * @tparam  ReturnType  The type to which the value should be converted and returned
-     * @pre     The ReturnType can be int, long long( If more than 10 digits) ,double,long double,float ,bool,string
      * @return  The value associated with the card
-     * @throws  boost::bad_lexical_cast If the conversion could not succeed
-     * @todo    Support for complex numbers and date is required
     */
     template <typename ReturnType>
     ReturnType value() const
     {
-        return value_imp(boost::type<ReturnType>());
+        if (!value_cached()) {
+            card_cache =value_imp(boost::type<ReturnType>());
+        }
+        return boost::get<ReturnType>(card_cache); 
     }
 
     /**
@@ -173,14 +173,14 @@ struct card: CardPolicy
     template<typename DataType>
     void set_value(DataType value)
     {
-
         std::string serialized_value = this->serialize_to_fits_format(value);
 
         if (this->is_card_valid(this->keyword(), serialized_value, "")) { 
             std::string key = this->keyword(true);
             this->card_.clear();
             this->card_.append(key);
             this->card_.append(serialized_value);
+            card_cache = value;
         }
     }
 
@@ -190,6 +190,11 @@ struct card: CardPolicy
     const std::string& raw_card() { return card_; }
 
 private:
+    /**
+     * @brief Checks if the value is internally cached
+    */
+    bool value_cached() const { return card_cache.which() != 0; }
+
 
     /**
      * @brief Creates a card from key, value and comment supplied to the method

include/boost/astronomy/io/default_card_policy.hpp

@@ -17,6 +17,7 @@ file License.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 #include <boost/astronomy/exception/fits_exception.hpp>
 #include <boost/astronomy/io/string_conversion_utility.hpp>
 #include <boost/algorithm/string/trim.hpp>
+#include <boost/mpl/vector.hpp>
 
 namespace boost{namespace astronomy{namespace io{
 
@@ -25,6 +26,22 @@ class card_policy {
     std::vector<std::string> reserved_keywords;
 
 public:
+    typedef boost::mpl::vector<
+        boost::blank,
+        bool,
+        int,
+        float,
+        double,
+        unsigned int,
+        long long,
+        std::size_t,
+        std::string,
+        std::complex<int>,
+        std::complex<double>,
+        std::complex<float>,
+        std::complex<std::size_t>
+    >  supported_types;
+
 
     /**
      * @brief Constructs a default object of card and initializes the reserved keyword list