LMDBAL::CursorCommon Class Reference

An object to manage cursor internals and state. More...

Inheritance diagram for LMDBAL::CursorCommon:

Public Member Functions
void	open ()
	Opens the cursor for operations.
void	open (const Transaction &transaction)
	Opens the cursor for operations.
void	renew ()
	Renews a cursor.
void	renew (const Transaction &transaction)
	Renews a cursor.
bool	opened () const
	Tells if the cursor is open.
bool	empty () const
	Returns true if the cursor is empty.
void	close ()
	Termiates a sequence of operations with the cursor.

Protected Types
enum	State { closed , openedPublic , openedPrivate }

Protected Member Functions
	CursorCommon ()
	Creates a empty class.
	CursorCommon (StorageCommon *storage)
	Creates a cursor.
	CursorCommon (const CursorCommon &other)=delete
	CursorCommon (CursorCommon &&other)
	Moves other cursor into this class.
virtual	~CursorCommon () noexcept
	Destroys this cursor.
CursorCommon &	operator= (const CursorCommon &other)=delete
CursorCommon &	operator= (CursorCommon &&other)
	Move assignment operator.
void	terminated ()
	A private function called to inform the cursor he has been terminated.
void	dropped ()
	A private method that turns cursor into an empty one.
void	reset ()
	A private method that turns cursor into an empty one.

Protected Attributes
uint32_t	id
State	state
MDB_cursor *	handle
StorageCommon *	storage

Static Protected Attributes
static const std::string	firstMethodName = "first"
	member function name, just for exceptions in heir
static const std::string	lastMethodName = "last"
	member function name, just for exceptions in heir
static const std::string	nextMethodName = "next"
	member function name, just for exceptions in heir
static const std::string	prevMethodName = "prev"
	member function name, just for exceptions in heir
static const std::string	currentMethodName = "current"
	member function name, just for exceptions in heir
static const std::string	setMethodName = "set"
	member function name, just for exceptions in heir
static const std::string	firstOperationName = "Cursor::first"
	member function name, just for exceptions in heir
static const std::string	lastOperationName = "Cursor::last"
	member function name, just for exceptions in heir
static const std::string	nextOperationName = "Cursor::next"
	member function name, just for exceptions in heir
static const std::string	prevOperationName = "Cursor::prev"
	member function name, just for exceptions in heir
static const std::string	currentOperationName = "Cursor::current"
	member function name, just for exceptions in heir

Friends
class	Transaction

Detailed Description

An object to manage cursor internals and state.

Cursors are owned by the storage, they die with the storage. They also get closed if the storage is closed (if you close by the database for example)

You can obtain an instance of this class calling LMDBAL::Storage::createCursor() and destory it calling LMDBAL::Storage::destoryCursor() at any time, LMDBAL::Base doesn't necessarily need to be opened.

You are not supposed to instantiate or destory instances of this class yourself!

Member Enumeration Documentation

State

enum LMDBAL::CursorCommon::State

protected

Enumerator
closed	Cursor state: closed
openedPublic	opened with public transaction, all storages will be notified about it after it's done
openedPrivate	opened with private transaction, only current storage will be notified when cursor is closed

Constructor & Destructor Documentation

CursorCommon() [1/2]

LMDBAL::CursorCommon::CursorCommon ( StorageCommon * _storage )

protected

Creates a cursor.

Parameters

[in]

_storage

a storage that created this cursor

CursorCommon() [2/2]

LMDBAL::CursorCommon::CursorCommon ( CursorCommon && other )

protected

Moves other cursor into this class.

Parameters

[in]

other

other instance that is being moved

~CursorCommon()

LMDBAL::CursorCommon::~CursorCommon ( )

protectedvirtualnoexcept

Destroys this cursor.

If the cursor wasn't properly closed - it's going to be upon destruction

Member Function Documentation

close()

void LMDBAL::CursorCommon::close

(

)

Termiates a sequence of operations with the cursor.

This is a normal way to tell that you're done with the cursor and don't want to continue the sequence of queries. The state of the cursor is lost after calling this method, some inner resorce is freed.

If the cursor was opened with the private transaction - the owner storage will be notified of the aborted transaction.

This function does nothing on a closed cursor.

dropped()

void LMDBAL::CursorCommon::dropped ( )

protected

A private method that turns cursor into an empty one.

This function is called from LMDBAL::Storage, when it gets destroyed, but still has some valid cursors. Those cursors will become empty, and can't be used anymore

empty()

bool LMDBAL::CursorCommon::empty

(

)

const

Returns true if the cursor is empty.

Empty cursors can't be used, they can be only targets of move operations

open() [1/2]

void LMDBAL::CursorCommon::open

(

)

Opens the cursor for operations.

This is a normal way to start the sequence of operations with the cursor. This variant of the function creates a read only transaction just for this cursor

This function should be called when the LMDBAL::Storage is already opened and before any query with this cursor! It will do nothing to a cursor that was already opened (no matter what way).

Exceptions

LMDBAL::Closed	thrown if you try to open the cursor on a closed database
LMDBAL::Unknown	thrown if there was a problem opening the cursor by the lmdb, or to begin a transaction
LMDBAL::CursorEmpty	thrown if the cursor was empty

open() [2/2]

void LMDBAL::CursorCommon::open

(

const Transaction &

transaction

)

Opens the cursor for operations.

This is a normal way to start the sequence of operations with the cursor. This variant of the function uses for queries a transaction you have obtained somewhere else.

This function should be called when the LMDBAL::Storage is already opened and before any query with this cursor! It will do nothing to a cursor that was already opened (no matter what way).

Parameters

[in]

transaction

- a transaction, can be read only

Exceptions

LMDBAL::Closed	thrown if you try to open the cursor on a closed database
LMDBAL::Unknown	thrown if there was a problem opening the cursor by the lmdb
LMDBAL::TransactionTerminated	thrown if the passed transaction not active, any action with it's inner ID is an error
LMDBAL::CursorEmpty	thrown if the cursor was empty

operator=()

LMDBAL::CursorCommon & LMDBAL::CursorCommon::operator= ( CursorCommon && other )

protected

Move assignment operator.

Transfers other cursor into this one

renew() [1/2]

void LMDBAL::CursorCommon::renew

(

)

Renews a cursor.

This function aborts current transaction if the cursor was opened with it's own transaction (does not mess up if the transaction was public), creates new private transaction and rebinds this cursor to it.

Theoretically you could call this method if your public transaction was aborted (or commited) but you wish to continue to keep working with your cursor. Or if you just want to rebind your cursor to a new private transaction.

This function does nothing if the cursor is closed

Exceptions

LMDBAL::Closed	thrown if you try to renew the cursor on a closed database
LMDBAL::Unknown	thrown if there was a problem beginning new transaction or if there was a problem renewing the cursor by lmdb
LMDBAL::CursorEmpty	thrown if the cursor was empty

renew() [2/2]

void LMDBAL::CursorCommon::renew

(

const Transaction &

transaction

)

Renews a cursor.

This function aborts current transaction if the cursor was opened with it's own transaction (does not mess up if the transaction was public), and rebinds this cursor to a passed new transaction.

Theoretically you could call this method if your previous public transaction was aborted (or commited) but you wish to continue to keep working with your cursor. Or if you just want to rebind your cursor to another public transaction.

This function does nothing if the cursor is closed

Parameters

[in]

transaction

- a transaction you wish this cursor to be bound to

Exceptions

LMDBAL::Closed	thrown if you try to renew the cursor on a closed database
LMDBAL::Unknown	thrown if there was a problem renewing the cursor by lmdb
LMDBAL::TransactionTerminated	thrown if the passed transaction not active, any action with it's inner ID is an error
LMDBAL::CursorEmpty	thrown if the cursor was empty

reset()

void LMDBAL::CursorCommon::reset ( )

protected

A private method that turns cursor into an empty one.

This method is called from LMDBAL::Storage, when the cursor is getting destoryed. After this method cursors will become empty, and can't be used anymore

terminated()

void LMDBAL::CursorCommon::terminated ( )

protected

A private function called to inform the cursor he has been terminated.

Is expected to be called from transaction, database, storage or move constructor

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The documentation for this class was generated from the following files:

• /workspace/blue/lmdbal/src/cursorcommon.h
• /workspace/blue/lmdbal/src/cursorcommon.cpp