added sqlite connection class (progress)

include/matador/sql/backend_provider.hpp

@@ -0,0 +1,43 @@
+#ifndef QUERY_BACKEND_PROVIDER_HPP
+#define QUERY_BACKEND_PROVIDER_HPP
+
+#include "matador/utils/library.hpp"
+
+#include <string>
+#include <unordered_map>
+
+namespace matador::sql {
+
+class connection_impl;
+class dialect;
+
+class backend_provider
+{
+public:
+  explicit backend_provider(std::string backends_path);
+
+  connection_impl* create_connection(const std::string &connection_type);
+  const dialect& connection_dialect(const std::string &connection_type);
+
+private:
+  struct backend_context {
+    backend_context(const std::string &connection_type,
+                    const std::string &backends_path);
+    ~backend_context();
+
+    typedef connection_impl*(*create_func)();
+    typedef void (*destroy_func)(connection_impl*);
+    typedef const dialect*(*dialect_func)();
+
+    create_func create_connection{};
+    destroy_func destroy_connection{};
+    dialect_func get_dialect{};
+    utils::library lib;
+  };
+private:
+  using backends_t = std::unordered_map<std::string, backend_context>;
+  backends_t backends_;
+  std::string backends_path_;
+};
+}
+#endif //QUERY_BACKEND_PROVIDER_HPP

include/matador/sql/dialect.hpp

@@ -10,7 +10,7 @@
 
 namespace matador::sql {
 
-class [[nodiscard]] dialect
+class dialect
 {
 public:
   enum class token_t : uint8_t
@@ -59,7 +59,15 @@ public:
     ESCAPE_CLOSING_BRACKET  /**< The escape quotes differ; escape the closing one */
   };
 
+  using token_to_string_map = std::unordered_map<token_t, std::string>;
+  using data_type_to_string_map = std::unordered_map<data_type_t, std::string>;
+
 public:
+  dialect() = default;
+  dialect(const token_to_string_map &token_replace_map, const data_type_to_string_map &data_type_replace_map);
+  explicit dialect(const data_type_to_string_map &data_type_replace_map);
+  explicit dialect(const token_to_string_map &token_replace_map);
+
   const std::string& token_at(token_t token) const;
   const std::string& data_type_at(data_type_t type) const;
 
@@ -124,8 +132,6 @@ public:
   const std::vector<std::string>& columns() const;
 
 private:
-  using token_to_string_map = std::unordered_map<token_t, std::string>;
-
   std::vector<std::string> host_vars_;
   std::vector<std::string> columns_;
 
@@ -167,7 +173,6 @@ private:
     {token_t::NONE, ""}
   };
 
-  using data_type_to_string_map = std::unordered_map<data_type_t, std::string>;
   data_type_to_string_map data_types_ {
     {data_type_t::type_char, "TINYINT"},
     {data_type_t::type_short, "SMALLINT"},

include/matador/utils/os.hpp

@@ -0,0 +1,14 @@
+#ifndef QUERY_OS_HPP
+#define QUERY_OS_HPP
+
+#include <string>
+
+namespace matador::utils::os {
+
+std::string getenv(const char* name);
+
+[[maybe_unused]] std::string getenv(const std::string &name);
+
+}
+
+#endif //QUERY_OS_HPP