Replace code_elements in epsg with statically sized type for faster compile times and replace binary search with perfect hashing.

Author: tinko92

include/boost/geometry/srs/projections/code.hpp

@@ -10,42 +10,154 @@
 #ifndef BOOST_GEOMETRY_PROJECTIONS_CODE_HPP
 #define BOOST_GEOMETRY_PROJECTIONS_CODE_HPP
 
-
-#include <algorithm>
+#include <cstdint>
 
 #include <boost/geometry/srs/projections/dpar.hpp>
 
-
 namespace boost { namespace geometry { namespace projections
 {
 
-
 #ifndef DOXYGEN_NO_DETAIL
 namespace detail
 {
 
+    template <std::size_t MaxParams, bool HasTowgs84 = true>
     struct code_element
     {
+        union parameter_variant
+        {
+            bool b;
+            int i;
+            double v;
+            //spheroid
+            //nadgrids,
+            //towgs84
+        };
+
         int code;
-        srs::dpar::parameters<> parameters;
+        std::int8_t parameter_count;
+        std::int8_t towgs84_size {0};
+        // Not bundling the following together into a struct to avoid 8-byte-alignment.
+        std::int8_t parameter_variant_tags[MaxParams];
+        std::int16_t parameter_ids[MaxParams];
+        parameter_variant parameters[MaxParams];
+        double towgs84_data[7];
     };
 
-    struct code_element_less
+    template <std::size_t MaxParams>
+    struct code_element<MaxParams, false>
     {
-        inline bool operator()(code_element const& l, code_element const& r) const
+        union parameter_variant
         {
-            return l.code < r.code;
+            bool b;
+            int i;
+            double v;
+        };
+
+        int code;
+        std::int8_t parameter_count;
+        std::int8_t parameter_variant_tags[MaxParams];
+        std::int16_t parameter_ids[MaxParams];
+        parameter_variant parameters[MaxParams];
+    };
+
+    template <bool HasTowgs84 = true>
+    struct code_element_to_towgs84
+    {
+        template <std::size_t MaxParams>
+        static void apply(code_element<MaxParams, true> const& e,
+                          srs::dpar::parameters<double>& out)
+        {
+            using p = srs::dpar::parameter<double>;
+            out(p(srs::dpar::name_towgs84::towgs84,
+                  srs::detail::towgs84<double>(e.towgs84_data, e.towgs84_data + e.towgs84_size)));
         }
     };
 
-    template<typename RandIt>
-    inline RandIt binary_find_code_element(RandIt first, RandIt last, int code)
+    template <>
+    struct code_element_to_towgs84<false>
+    {
+        template <std::size_t MaxParams>
+        static void apply(code_element<MaxParams, false> const&, srs::dpar::parameters<double>&) {}
+    };
+
+
+    template <std::size_t MaxParams, bool HasTowgs84>
+    inline srs::dpar::parameters<>
+    code_element_to_dpar_parameters(code_element<MaxParams, HasTowgs84> const& e)
     {
-        code_element_less comp;
-        code_element value;
-        value.code = code;
-        first = std::lower_bound(first, last, value, comp);
-        return first != last && !comp(value, *first) ? first : last;
+        using namespace srs::dpar;
+        using p = srs::dpar::parameter<double>;
+        srs::dpar::parameters<> out;
+        out.reserve(e.parameter_count);
+        for (int i = 0; i < e.parameter_count; ++i)
+        {
+            auto const& id = e.parameter_ids[i];
+            auto const& pv = e.parameters[i];
+            auto const& tag = e.parameter_variant_tags[i];
+            if (id == -1)
+            {
+                out(p());
+            }
+            else if (id < static_cast<int>(name_r::alpha)) // f
+            {
+                out(p(static_cast<name_f>(id), pv.v));
+            }
+            else if (id < static_cast<int>(name_i::aperture)) // r
+            {
+                out(p(static_cast<name_r>(id), pv.v));
+            }
+            else if (id < static_cast<int>(name_be::czech)) // i
+            {
+                out(p(static_cast<name_i>(id), pv.i));
+            }
+            else if (id < static_cast<int>(name_datum::datum)) // be
+            {
+                out(p(static_cast<name_be>(id), pv.b));
+            }
+            else if (id == static_cast<int>(name_datum::datum)) //datum
+            {
+                out(p(name_datum::datum, static_cast<value_datum>(pv.i)));
+            }
+            else if ( id == static_cast<int>(name_ellps::ellps)) //ellps
+            {
+                out(p(name_ellps::ellps, static_cast<value_ellps>(pv.i)));
+            }
+            // no occurence of ellps with spheroid in arr
+            // no occurence of mode in arr
+            // no occurence of nadgrids in arr
+            // no occurence of orient in arr
+            else if (id == static_cast<name_pm>(name_pm::pm)) //pm
+            {
+                if (tag == 1)
+                {
+                    out(p(name_pm::pm, static_cast<value_pm>(pv.i)));
+                }
+                else //if tag == 2
+                {
+                    out(p(name_pm::pm, pv.v));
+                }
+            }
+            else if (id < static_cast<int>(name_sweep::sweep)) // proj
+            {
+                out(p(static_cast<name_proj>(id), static_cast<value_proj>(pv.i)));
+            }
+            else if (id == static_cast<int>(name_sweep::sweep)) // sweep
+            {
+                out(p(name_sweep::sweep, static_cast<value_sweep>(pv.i)));
+            }
+            else if (id == static_cast<int>(name_towgs84::towgs84)) //towgs84
+            {
+                code_element_to_towgs84<HasTowgs84>::apply(e, out);
+            }
+            // no occurence of axis in arr
+            else if (id == static_cast<int>(name_units::units)) //units
+            {
+                out(p(name_units::units, static_cast<value_units>(pv.i)));
+            }
+            // no occurence of vunits in arr
+        }
+        return out;
     }
 
 }

include/boost/geometry/srs/projections/dpar.hpp

@@ -722,8 +722,11 @@ struct parameter
     {
         return m_value.which() == srs::detail::find_type_index<variant_type, V>::value;
     }
-
+#if defined(BOOST_GEOMETRY_ENABLE_SRS_PARAMETER_DEBUGGING)
+public:
+#else
 private:
+#endif
     int m_id;
     variant_type m_value;
 };
@@ -801,8 +804,9 @@ class parameters
     const_iterator begin() const { return m_params.begin(); }
     const_iterator end() const { return m_params.end(); }
     const_reference operator[](size_type i) const { return m_params[i]; }
-    size_type size() { return m_params.size(); }
-    bool empty() { return m_params.empty(); }
+    size_type size() const { return m_params.size(); }
+    bool empty() const { return m_params.empty(); }
+    void reserve(std::size_t s) { m_params.reserve(s); }
 
 private:
     container_type m_params;