finally methods that actually do something, some testing of them

src/cursor.h

@@ -53,23 +53,36 @@ public:
     std::pair<K, V> prev() const;
     std::pair<K, V> current() const;
 
-    void first(std::pair<K, V>& out) const;
-    void last(std::pair<K, V>& out) const;
-    void next(std::pair<K, V>& out) const;
-    void prev(std::pair<K, V>& out) const;
-    void current(std::pair<K, V>& out) const;
+    void first(K& key, V& value) const;
+    void last(K& key, V& value) const;
+    void next(K& key, V& value) const;
+    void prev(K& key, V& value) const;
+    void current(K& key, V& value) const;
 
 private:
     void terminated() const;
+    void operateCursorRead(K& key, V& value, MDB_cursor_op operation, const std::string& methodName, const std::string& operationName) const;
 
 private:
     Storage<K, V>* storage;
     mutable MDB_cursor* cursor;
     mutable State state;
 
-    inline static const std::string openRecordMethodName = "Cursor::open";   /**<\brief member function name, just for exceptions*/
-    inline static const std::string closeRecordMethodName = "Cursor::close"; /**<\brief member function name, just for exceptions*/
-    inline static const std::string renewRecordMethodName = "Cursor::renew"; /**<\brief member function name, just for exceptions*/
+    inline static const std::string openCursorMethodName = "Cursor::open";      /**<\brief member function name, just for exceptions*/
+    inline static const std::string closeCursorMethodName = "Cursor::close";    /**<\brief member function name, just for exceptions*/
+    inline static const std::string renewCursorMethodName = "Cursor::renew";    /**<\brief member function name, just for exceptions*/
+
+    inline static const std::string firstMethodName = "first";                  /**<\brief member function name, just for exceptions*/
+    inline static const std::string lastMethodName = "last";                    /**<\brief member function name, just for exceptions*/
+    inline static const std::string nextMethodName = "next";                    /**<\brief member function name, just for exceptions*/
+    inline static const std::string prevMethodName = "prev";                    /**<\brief member function name, just for exceptions*/
+    inline static const std::string currentMethodName = "current";              /**<\brief member function name, just for exceptions*/
+
+    inline static const std::string firstOperationName = "Cursor::first";       /**<\brief member function name, just for exceptions*/
+    inline static const std::string lastOperationName = "Cursor::last";         /**<\brief member function name, just for exceptions*/
+    inline static const std::string nextOperationName = "Cursor::next";         /**<\brief member function name, just for exceptions*/
+    inline static const std::string prevOperationName = "Cursor::prev";         /**<\brief member function name, just for exceptions*/
+    inline static const std::string currentOperationName = "Cursor::current";   /**<\brief member function name, just for exceptions*/
 };
 
 };

src/cursor.hpp

@@ -42,7 +42,7 @@ void LMDBAL::Cursor<K, V>::terminated () const {
 
 template<class K, class V>
 void LMDBAL::Cursor<K, V>::open () const {
-    storage->ensureOpened(openRecordMethodName);
+    storage->ensureOpened(openCursorMethodName);
     switch (state) {
         case closed: {
             TransactionID txn = storage->beginReadOnlyTransaction();
@@ -60,7 +60,7 @@ void LMDBAL::Cursor<K, V>::open () const {
 
 template<class K, class V>
 void LMDBAL::Cursor<K, V>::open (TransactionID txn) const {
-    storage->ensureOpened(openRecordMethodName);
+    storage->ensureOpened(openCursorMethodName);
     switch (state) {
         case closed: {
             int result = mdb_cursor_open(txn, storage->dbi, &cursor);
@@ -76,7 +76,7 @@ void LMDBAL::Cursor<K, V>::open (TransactionID txn) const {
 
 template<class K, class V>
 void LMDBAL::Cursor<K, V>::renew () const {
-    storage->ensureOpened(openRecordMethodName);
+    storage->ensureOpened(renewCursorMethodName);
     switch (state) {
         case openedPrivate: {
             TransactionID txn = mdb_cursor_txn(cursor);
@@ -100,7 +100,7 @@ void LMDBAL::Cursor<K, V>::renew () const {
 
 template<class K, class V>
 void LMDBAL::Cursor<K, V>::renew (TransactionID txn) const {
-    storage->ensureOpened(openRecordMethodName);
+    storage->ensureOpened(renewCursorMethodName);
     switch (state) {
         case openedPrivate: {
             TransactionID txn = mdb_cursor_txn(cursor);
@@ -141,4 +141,90 @@ void LMDBAL::Cursor<K, V>::close () const {
     }
 }
 
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::first (K& key, V& value) const {
+    operateCursorRead(key, value, MDB_FIRST, firstMethodName, firstOperationName);
+}
+
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::last (K& key, V& value) const {
+    operateCursorRead(key, value, MDB_LAST, lastMethodName, lastOperationName);
+}
+
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::next (K& key, V& value) const {
+    operateCursorRead(key, value, MDB_NEXT, nextMethodName, nextOperationName);
+}
+
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::prev (K& key, V& value) const {
+    operateCursorRead(key, value, MDB_PREV, prevMethodName, prevOperationName);
+}
+
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::current (K& key, V& value) const {
+    operateCursorRead(key, value, MDB_GET_CURRENT, currentMethodName, currentOperationName);
+}
+
+template<class K, class V>
+std::pair<K, V> LMDBAL::Cursor<K, V>::first () const {
+    std::pair<K, V> result;
+    operateCursorRead(result.first, result.second, MDB_FIRST, firstMethodName, firstOperationName);
+    return result;
+}
+
+template<class K, class V>
+std::pair<K, V> LMDBAL::Cursor<K, V>::last () const {
+    std::pair<K, V> result;
+    operateCursorRead(result.first, result.second, MDB_LAST, lastMethodName, lastOperationName);
+    return result;
+}
+
+template<class K, class V>
+std::pair<K, V> LMDBAL::Cursor<K, V>::next () const {
+    std::pair<K, V> result;
+    operateCursorRead(result.first, result.second, MDB_NEXT, nextMethodName, nextOperationName);
+    return result;
+}
+
+template<class K, class V>
+std::pair<K, V> LMDBAL::Cursor<K, V>::prev () const {
+    std::pair<K, V> result;
+    operateCursorRead(result.first, result.second, MDB_PREV, prevMethodName, prevOperationName);
+    return result;
+}
+
+template<class K, class V>
+std::pair<K, V> LMDBAL::Cursor<K, V>::current () const {
+    std::pair<K, V> result;
+    operateCursorRead(result.first, result.second, MDB_GET_CURRENT, currentMethodName, currentOperationName);
+    return result;
+}
+
+
+template<class K, class V>
+void LMDBAL::Cursor<K, V>::operateCursorRead(
+    K& key,
+    V& value,
+    MDB_cursor_op operation,
+    const std::string& methodName,
+    const std::string& operationName
+) const {
+    if (state == closed)
+        storage->throwCursorNotReady(methodName);
+
+    MDB_val mdbKey, mdbValue;
+    int result = mdb_cursor_get(cursor, &mdbKey, &mdbValue, operation);
+    if (result != MDB_SUCCESS)
+        storage->throwNotFoundOrUnknown(result, operationName);
+
+    storage->keySerializer.deserialize(mdbKey, key);
+    storage->valueSerializer.deserialize(mdbValue, value);
+
+    if (state == openedPrivate)
+        storage->discoveredRecord(key, value);
+    else
+        storage->discoveredRecord(key, value, mdb_cursor_txn(cursor));
+}
+
 #endif //LMDBAL_CURSOR_HPP

src/exceptions.cpp

@@ -55,6 +55,23 @@ std::string LMDBAL::Closed::getMessage() const {
     return msg;
 }
 
+LMDBAL::CursorNotReady::CursorNotReady(
+    const std::string& p_operation,
+    const std::string& p_dbName,
+    const std::string& p_tableName
+):
+    Exception(),
+    operation(p_operation),
+    dbName(p_dbName),
+    tableName(p_tableName) {}
+
+std::string LMDBAL::CursorNotReady::getMessage() const {
+    std::string msg = "An attempt to perform operation " + operation
+                    + " on closed cursor that belongs to the table " + tableName
+                    + " within database " + dbName;
+    return msg;
+}
+
 LMDBAL::Opened::Opened(const std::string& p_dbName, const std::string& p_action):
     Exception(),
     dbName(p_dbName),

src/exceptions.h

@@ -76,6 +76,27 @@ private:
     std::optional<std::string> tableName;
 };
 
+/**
+ * \brief Thrown if the cursor was operated in closed state
+ */
+class CursorNotReady : public Exception {
+public:
+    /**
+     * \brief Creates exception
+     *
+     * \param operation - text name of the method that was called on closed cursor
+     * \param dbName    - name of the database
+     * \param tableName - name of the storage owning the cursor
+     */
+    CursorNotReady(const std::string& operation, const std::string& dbName, const std::string& tableName);
+
+    std::string getMessage() const;
+private:
+    std::string operation;
+    std::string dbName;
+    std::string tableName;
+};
+
 /**
  * \brief Thrown if something in the database was called on opened state and it is not supported
  */

src/storage.cpp

@@ -277,6 +277,18 @@ void LMDBAL::iStorage::throwDuplicate(const std::string& key) const {
 void LMDBAL::iStorage::throwNotFound(const std::string& key) const {
     throw NotFound(key, db->name, name);}
 
+/**
+ * \brief Throws LMDBAL::CursorNotReady
+ *
+ * Helper function ment to be used in heirs and reduce the code a bit
+ *
+ * \param[in] method   - called cursor method name, just to show in std::exception::what() message
+ *
+ * \exception LMDBAL::CursorNotReady   thrown everytime
+ */
+void LMDBAL::iStorage::throwCursorNotReady(const std::string& method) const {
+    throw CursorNotReady(method, db->name, name);}
+
 /**
  * \brief Begins read-only transaction
  *

src/storage.h

@@ -50,6 +50,7 @@ protected:
     void throwUnknown(int rc) const;
     void throwDuplicate(const std::string& key) const;
     void throwNotFound(const std::string& key) const;
+    void throwCursorNotReady(const std::string& method) const;
 
     TransactionID beginReadOnlyTransaction() const;
     TransactionID beginTransaction() const;
@@ -99,6 +100,9 @@ protected:
     Storage(const std::string& name, Base* parent);
     ~Storage() override;
 
+    virtual void discoveredRecord(const K& key, const V& value) const;
+    virtual void discoveredRecord(const K& key, const V& value, TransactionID txn) const;
+
 public:
     using iStorage::drop;
     virtual void addRecord(const K& key, const V& value);

src/storage.hpp

@@ -22,6 +22,8 @@
 #include "storage.h"
 #include "exceptions.h"
 
+#define UNUSED(x) (void)(x)
+
 /**
  * \class LMDBAL::Storage
  * \brief This is a basic key value storage.
@@ -718,6 +720,19 @@ void LMDBAL::Storage<K, V>::destroyCursor(Cursor<K, V>* cursor) {
     delete cursor;
 }
 
+template<class K, class V>
+void LMDBAL::Storage<K, V>::discoveredRecord(const K& key, const V& value) const {
+    UNUSED(key);
+    UNUSED(value);
+}
+
+template<class K, class V>
+void LMDBAL::Storage<K, V>::discoveredRecord(const K& key, const V& value, TransactionID txn) const {
+    UNUSED(key);
+    UNUSED(value);
+    UNUSED(txn);
+}
+
 /**
  * \brief A functiion to actually open <a class="el" href="http://www.lmdb.tech/doc/group__mdb.html#gadbe68a06c448dfb62da16443d251a78b">MDB_dbi</a> storage
  *