Cursors refactoring part one

src/storagecommon.hpp

@@ -0,0 +1,99 @@
+/*
+ * LMDB Abstraction Layer.
+ * Copyright (C) 2023  Yury Gubich <blue@macaw.me>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "storagecommon.h"
+
+/**
+ * \brief A functiion to actually open <a class="el" href="http://www.lmdb.tech/doc/group__mdb.html#gadbe68a06c448dfb62da16443d251a78b">MDB_dbi</a> storage
+ *
+ * \tparam K type of keys in opening storage
+ *
+ * \param[in] transaction   - lmdb transaction to call <a class="el" href="http://www.lmdb.tech/doc/group__mdb.html#gac08cad5b096925642ca359a6d6f0562a">mdb_dbi_open</a>, must be a writable transaction!
+ * \param[in] duplicates    - true if key duplicates are allowed (false by default)
+ *
+ * \returns MDB_SUCCESS if everything went smooth or MDB_<error> -like error code
+ *
+ * This is a way to optimise database using MDB_INTEGERKEY flag,
+ * when the key is actually kind of an integer
+ * This infrastructure also allowes us to customize mdb_dbi_open call in the future
+ */
+template<class K, class V>
+inline int LMDBAL::StorageCommon::makeStorage(MDB_txn* transaction, bool duplicates) {
+    unsigned int flags = MDB_CREATE;
+    if constexpr (std::is_integral<K>::value)
+        flags |= MDB_INTEGERKEY;
+
+    if (duplicates) {
+        flags |= MDB_DUPSORT;
+
+        if constexpr (std::is_scalar<V>::value)
+            flags |= MDB_DUPFIXED;
+
+        if constexpr (
+            std::is_same<V, uint32_t>::value ||
+            std::is_same<V, int32_t>::value ||
+            std::is_same<V, uint64_t>::value ||
+            std::is_same<V, int64_t>::value
+        )                                   //for some reason lmdb breaks if it's not one of these types in MDB_DUPFIXED mode
+            flags |= MDB_INTEGERDUP;
+    }
+
+    return _mdbOpen(transaction, flags);
+}
+
+/**
+ * \brief A method to cast a value (which can be a value or a key) to string.
+ *
+ * This function is mainly used in exceptions, to report which key was duplicated or not found.
+ * You can define your own specializations to this function in case std::to_string doesn't cover your case
+ *
+ * \param[in]   value   a value that should be converted to string
+ * \returns     a string presentation of value
+ */
+template<class T>
+inline std::string LMDBAL::StorageCommon::toString(const T& value) {
+    return std::to_string(value);
+}
+
+/**
+ * \brief A method to cast a value (which can be a value or a key) to string.
+ *
+ * QString spectialization
+ *
+ * \param[in]   value   a value that should be converted to string
+ * \returns     a string presentation of value
+ */
+template<>
+inline std::string LMDBAL::StorageCommon::toString(const QString& value) {
+    return value.toStdString();
+}
+
+/**
+ * \brief A method to cast a value (which can be a value or a key) to string.
+ *
+ * std::string spectialization
+ *
+ * \param[in]   value   a value that should be converted to string
+ * \returns     a string presentation of value
+ */
+template<>
+inline std::string LMDBAL::StorageCommon::toString(const std::string& value) {
+    return value;
+}