forked from blue/lmdbal
392 lines
16 KiB
C++
392 lines
16 KiB
C++
/*
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* LMDB Abstraction Layer.
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* Copyright (C) 2023 Yury Gubich <blue@macaw.me>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "cursor.h"
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#include <iostream>
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/**
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* \class LMDBAL::Cursor
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* \brief An object to iterate storages.
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*
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* \tparam K type of the keys in the storage that this cursor would iterate
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* \tparam V type of the values in the storage that this cursor would iterate
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*
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* Cursor allowes you to perform sequential querries, navigate from one element to another at reduced operation price.
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* For now Cursors are read only but in the future you might also be able to write to the storage with them.
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*
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* Cursors are owned by the storage, they die with the storage.
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* They also get closed if the storage is closed (if you close by the database for example)
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*
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* You can obtain an instance of this class calling LMDBAL::Storage::createCursor()
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* and destory it calling LMDBAL::Storage::destoryCursor() at any time, LMDBAL::Base doesn't necessarily need to be opened.
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*
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* You are not supposed to instantiate or destory instances of this class yourself!
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*/
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/**
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* \brief Creates a cursor
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*
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* \param[in] parent a storage that created this cursor
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*/
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template<class K, class V>
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LMDBAL::Cursor<K, V>::Cursor(Storage<K, V>* parent):
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CursorCommon(parent)
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{
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parent->cursors[id] = this;
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}
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/**
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* \brief Creates an empty cursor.
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*
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* It's not usable, but can exist just to be a target of moves
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*/
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template<class K, class V>
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LMDBAL::Cursor<K, V>::Cursor():
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CursorCommon()
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{}
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/**
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* \brief Moves from another cursor
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*/
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template<class K, class V>
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LMDBAL::Cursor<K, V>::Cursor(Cursor&& other):
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CursorCommon(std::move(other))
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{
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if (!empty())
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static_cast<Storage<K, V>*>(storage)->cursors[id] = this;
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}
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/**
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* \brief Move assignment operator
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*
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* Transfers other cursor into this one
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*/
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template<class K, class V>
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LMDBAL::Cursor<K, V>& LMDBAL::Cursor<K, V>::operator = (Cursor&& other) {
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if (!empty() && other.empty())
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static_cast<Storage<K, V>*>(storage)->cursors.erase(id);
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CursorCommon::operator=(std::move(other));
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if (!empty())
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static_cast<Storage<K, V>*>(storage)->cursors[id] = this;
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return *this;
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}
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/**
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* \brief Destroys this cursor
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*
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* If the cursor wasn't properly closed - it's going to be upon destruction
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*/
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template<class K, class V>
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LMDBAL::Cursor<K, V>::~Cursor () {
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if (id != 0)
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static_cast<Storage<K, V>*>(storage)->cursors.erase(id);
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}
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/**
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* \brief Turns cursor into an empty one, releasing resources
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*
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* This function is called from LMDBAL::Storage, when it gets destroyed, but still has some valid.
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* Those cursors will become empty, and can't be used anymore
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::drop () {
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close();
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if (id != 0)
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static_cast<Storage<K, V>*>(storage)->cursors.erase(id);
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reset();
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}
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/**
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* \brief Queries the first element in the storage
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::first (K& key, V& value) {
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operateCursorRead(key, value, MDB_FIRST, firstMethodName, firstOperationName);
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}
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/**
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* \brief Queries the last element in the storage
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::last (K& key, V& value) {
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operateCursorRead(key, value, MDB_LAST, lastMethodName, lastOperationName);
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}
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/**
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* \brief Queries the next element from the storage
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*
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* If there was no operation before this method positions the cursor on the first element and returns it
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* so, it's basically doing the same as LMDBAL::Cursor::first(K key, V value).
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*
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* It will also throw LMDBAL::NotFound if you call this method being on the last element
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* or if there are no elements in the database.
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if the cursor already was on the last element or if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::next (K& key, V& value) {
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operateCursorRead(key, value, MDB_NEXT, nextMethodName, nextOperationName);
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}
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/**
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* \brief Queries the previous element from the storage
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*
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* If there was no operation before this method positions the cursor on the last element and returns it
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* so, it's basically doing the same as LMDBAL::Cursor::last(K key, V value).
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*
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* It will also throw LMDBAL::NotFound if you call this method being on the first element
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* or if there are no elements in the database.
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if the cursor already was on the first element or if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::prev (K& key, V& value) {
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operateCursorRead(key, value, MDB_PREV, prevMethodName, prevOperationName);
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}
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/**
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* \brief Returns current cursor element from the storage
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*
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* If there was no operation before this method throws LMDBAL::Unknown for some reason
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound probably never thrown but there might be still some corner case I don't know about
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::current (K& key, V& value) const {
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operateCursorRead(key, value, MDB_GET_CURRENT, currentMethodName, currentOperationName);
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}
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/**
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* \brief Queries the first element in the storage
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \returns std::pair where first is element key and second is element value
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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std::pair<K, V> LMDBAL::Cursor<K, V>::first () {
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std::pair<K, V> result;
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operateCursorRead(result.first, result.second, MDB_FIRST, firstMethodName, firstOperationName);
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return result;
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}
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/**
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* \brief Queries the last element in the storage
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \returns std::pair where first is element key and second is element value
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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std::pair<K, V> LMDBAL::Cursor<K, V>::last () {
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std::pair<K, V> result;
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operateCursorRead(result.first, result.second, MDB_LAST, lastMethodName, lastOperationName);
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return result;
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}
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/**
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* \brief Queries the next element from the storage
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*
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* If there was no operation before this method positions the cursor on the first element and returns it
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* so, it's basically doing the same as LMDBAL::Cursor::first().
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*
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* It will also throw LMDBAL::NotFound if you call this method being on the last element
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* or if there are no elements in the database.
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \returns std::pair where first is element key and second is element value
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if the cursor already was on the last element or if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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std::pair<K, V> LMDBAL::Cursor<K, V>::next () {
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std::pair<K, V> result;
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operateCursorRead(result.first, result.second, MDB_NEXT, nextMethodName, nextOperationName);
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return result;
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}
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/**
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* \brief Queries the previous element from the storage
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*
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* If there was no operation before this method positions the cursor on the last element and returns it
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* so, it's basically doing the same as LMDBAL::Cursor::last().
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*
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* It will also throw LMDBAL::NotFound if you call this method being on the first element
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* or if there are no elements in the database.
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \returns std::pair where first is element key and second is element value
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound thrown if the cursor already was on the first element or if there are no elements in the storage
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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std::pair<K, V> LMDBAL::Cursor<K, V>::prev () {
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std::pair<K, V> result;
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operateCursorRead(result.first, result.second, MDB_PREV, prevMethodName, prevOperationName);
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return result;
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}
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/**
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* \brief Returns current cursor element from the storage
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*
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* If there was no operation before this method throws LMDBAL::Unknown for some reason
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*
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* Notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \returns std::pair where first is element key and second is element value
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound probably never thrown but there might be still some corner case I don't know about
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* \exception LMDBAL::Unknown thrown if there was no positioning operation before of if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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std::pair<K, V> LMDBAL::Cursor<K, V>::current () const {
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std::pair<K, V> result;
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operateCursorRead(result.first, result.second, MDB_GET_CURRENT, currentMethodName, currentOperationName);
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return result;
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}
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/**
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* \brief Sets cursors to the defined position
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*
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* If exactly the same element wasn't found it sets the cursor to the first
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* element greater then the key and returns false
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*
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* \param[in] key a key of the element you would like the cursor to be
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* \returns true if the exact value was found, false otherwise
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::Unknown thrown if there was some unexpected problem
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*/
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template<class K, class V>
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bool LMDBAL::Cursor<K, V>::set (const K& key) {
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if (state == closed)
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static_cast<Storage<K, V>*>(storage)->throwCursorNotReady(setMethodName);
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MDB_val mdbKey = static_cast<Storage<K, V>*>(storage)->keySerializer.setData(key);
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int result = static_cast<Storage<K, V>*>(storage)->_mdbCursorSet(handle, mdbKey);
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if (result == MDB_SUCCESS)
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return true;
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else if (result == MDB_NOTFOUND)
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return false;
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static_cast<Storage<K, V>*>(storage)->throwUnknown(result);
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return false; //unreachable, just to suppress the warning
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}
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/**
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* \brief a private mothod that actually doing all the reading
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*
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* Queries the storage, deserializes the output, notifies the storage of the queried element calling LMDBAL::Storage::discoveredRecord()
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*
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* \param[out] key a reference to an object the key of queried element is going to be assigned
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* \param[out] value a reference to an object the value of queried element is going to be assigned
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* \param[in] operation LMDB cursor <a class="el" href="http://www.lmdb.tech/doc/group__mdb.html#ga1206b2af8b95e7f6b0ef6b28708c9127">operation code</a>
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* \param[in] methodName a name of the method you called it from, just for the exception message if something goes not as expected
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* \param[in] operationName a name of the opeartion, just for the exception message if something goes not as expected
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*
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* \exception LMDBAL::CursorNotReady thrown if you try to call this method on a closed cursor
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* \exception LMDBAL::NotFound mostly thrown if the query wasn't found
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* \exception LMDBAL::Unknown mostly thrown if there was some unexpected problem with lmdb
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*/
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template<class K, class V>
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void LMDBAL::Cursor<K, V>::operateCursorRead(
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K& key,
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V& value,
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MDB_cursor_op operation,
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const std::string& methodName,
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const std::string& operationName
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) const {
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if (state == closed)
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static_cast<Storage<K, V>*>(storage)->throwCursorNotReady(methodName);
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MDB_val mdbKey, mdbValue;
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int result = static_cast<Storage<K, V>*>(storage)->_mdbCursorGet(handle, mdbKey, mdbValue, operation);
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if (result != MDB_SUCCESS)
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static_cast<Storage<K, V>*>(storage)->throwNotFoundOrUnknown(result, operationName);
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static_cast<Storage<K, V>*>(storage)->keySerializer.deserialize(mdbKey, key);
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static_cast<Storage<K, V>*>(storage)->valueSerializer.deserialize(mdbValue, value);
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if (state == openedPrivate)
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static_cast<Storage<K, V>*>(storage)->discoveredRecord(key, value);
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else
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static_cast<Storage<K, V>*>(storage)->discoveredRecord(key, value, static_cast<Storage<K, V>*>(storage)->_mdbCursorTxn(handle));
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}
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