KexiBLOBBuffer Class Reference

#include <kexiblobbuffer.h>

Detailed Description

Application-wide buffer for local BLOB data like pixmaps.

For now only pixmaps are supported

Todo:: support any KPart-compatible objects and more...

Use this class by acessing to its singleton: KexiBLOBBuffer::self().

This class is used for buffering BLOB data, to avoid duplicating object's data in memory and a need for loding (decoding) the same object many times. The data is always local, what means database storage is not employed here.

Each BLOB instance is identified by an unsigned integer number (Id_t type), uniquely generated on BLOB loading. Each BLOB can have assigned source url it has been loaded from (the url can be empty though, e.g. for data coming from clipboard).

References to KexiBLOBBuffer are counted, so when last reference is lost, data is freed and the integer identifier is no longer pointing any valid data. KexiBLOBBuffer::Handle is value-based class that describes handle based in an identifier. Objects of this class are obtained e.g. from insertPixmap() method.

There are two kinds of identifiers:

integers assigned for BLOBs already saved to a db backend, when KexiBLOBBuffer::Handle::stored() is true
temporary integers assigned for new BLOBs not yet saved to a db backend, when KexiBLOBBuffer::Handle::stored() is false KexiBLOBBuffer::Handle::setStoredWidthID() can be used to switch from unstored to stored state. Among others, the state has effect on saving forms: only unstored BLOBs will be saved back to the database; when a BLOB need to be removed, only it will be physically removed only if it was stored.

KexiBLOBBuffer is also useful for two more reasons:

Property editor's item for "image" property displays a preview of pixmap contents. Without buffering, it would be needed to load pixmap data again: what if the file it is loaded from is located remote and connection is slow? Memory would be also unnecessary doubled.
Undo/Redo frameword requires to store previous property values. Having a reference defined by a single interger, memory can be handled more effectively.

Example use cases: A large pixmap file "abc.jpg" is loaded as QByteArray once and buffered: integer identifier is returned. Then, multiple image widgets are using "abc.jpg" for displaying. Duplicating an image widget means only duplicating it's properties like position and BLOB's id: BLOB itself (data of "abc.jpg")is not duplicated. Creating a new image widget and assiging the same "abc.jpg" pixmap, means only referencing KexiBLOBBuffer using the same identifier.

Definition at line 80 of file kexiblobbuffer.h.

Public Types

typedef long Id_t

Public Member Functions

KexiBLOBBuffer ()

~KexiBLOBBuffer ()

Handle insertPixmap (const KURL &url)

Handle insertObject (const QByteArray &data, const QString &name, const QString &caption, const QString &mimeType, Id_t identifier=0)

Handle insertPixmap (const QPixmap &pixmap)

Handle objectForId (Id_t id, bool stored)

Handle objectForId (Id_t id)

Static Public Member Functions

static KexiBLOBBuffer * self ()

Access to KexiBLOBBuffer singleton.

static void setConnection (KexiDB::Connection *conn)

Protected Member Functions

void removeItem (Id_t id, bool stored)

void takeItem (Item *item)

void insertItem (Item *item)

Friends

class Handle

Classes

class Handle

Object handle used by KexiBLOBBuffer. More...

class Item

Member Typedef Documentation

typedef long KexiBLOBBuffer::Id_t

Todo:
Qt4: will be changed

Definition at line 85 of file kexiblobbuffer.h.

Constructor & Destructor Documentation

KexiBLOBBuffer::KexiBLOBBuffer ( )

Definition at line 173 of file kexiblobbuffer.cpp.
Referenced by self().

KexiBLOBBuffer::~KexiBLOBBuffer ( )

Definition at line 182 of file kexiblobbuffer.cpp.

Member Function Documentation

void KexiBLOBBuffer::insertItem ( Item * item ) [protected]

Inserts an object for a given id into the buffer.
Definition at line 351 of file kexiblobbuffer.cpp.
Referenced by insertObject(), insertPixmap(), and objectForId().

KexiBLOBBuffer::Handle KexiBLOBBuffer::insertObject ( const QByteArray & data,

const QString & name,

const QString & caption,

const QString & mimeType,

Id_t identifier = 0

)

Inserts a new BLOB data.
Parameters:

data The data for BLOB object.

name The name for the object, usually a file name or empty

caption The more friendly than name, can be based on file name or empty or defined by a user (this case is not yet used)

mimeType The mimeType for the object for easier and mor accurate decoding.

identifier Object's identifier. If positive, the "stored" flag for the data will be set to true with identifer, otherwise (the default) the BLOB data will have "stored" flag set to false, and a new temporary identifier will be assigned.

Definition at line 226 of file kexiblobbuffer.cpp.
References Handle, and insertItem().

KexiBLOBBuffer::Handle KexiBLOBBuffer::insertPixmap ( const QPixmap & pixmap )

Inserts a new pixmap available in memory, e.g. coming from clipboard.
Definition at line 240 of file kexiblobbuffer.cpp.
References Handle, and insertItem().

KexiBLOBBuffer::Handle KexiBLOBBuffer::insertPixmap ( const KURL & url )

Inserts a new pixmap loaded from a file at url. If the same file has already been loaded before, it can be found in cache and returned instantly. It is assumed that the BLOB is unstored, because it is loaded from external source, so stored() will be equal to false for returned handle.
Returns:
handle to the pixmap data or a null handle if such pixmap could not be loaded.

Definition at line 187 of file kexiblobbuffer.cpp.
References Handle, insertItem(), and kexipluginswarn.

KexiBLOBBuffer::Handle KexiBLOBBuffer::objectForId ( Id_t id )

Returns:
an object for a given id. First, unstored object is checked, then unstored, if stored was not found.

Definition at line 320 of file kexiblobbuffer.cpp.
References objectForId().

KexiBLOBBuffer::Handle KexiBLOBBuffer::objectForId ( Id_t id,

bool stored

)

Returns:
an object for a given id. If stored is true, stored BLOBs buffer is browsed, otherwise unstored (in memory) BLOBs buffer is browsed. If no object is cached for this id, null handle is returned.

Definition at line 259 of file kexiblobbuffer.cpp.
References KexiDB::QuerySchema::addField(), KexiDB::QuerySchema::addToWhereExpression(), KexiDB::FieldList::field(), Handle, insertItem(), and tristate::toString().
Referenced by objectForId(), and KexiFormView::storeData().

void KexiBLOBBuffer::removeItem ( Id_t id,

bool stored

) [protected]

Removes an object for a given id. If stored is true, stored BLOB is removed, otherwise unstored (in memory) BLOB is removed.
Definition at line 328 of file kexiblobbuffer.cpp.

KexiBLOBBuffer * KexiBLOBBuffer::self ( ) [static]

Access to KexiBLOBBuffer singleton.

Definition at line 365 of file kexiblobbuffer.cpp.
References KexiBLOBBuffer(), and m_bufferDeleter.
Referenced by KexiImagePropertyEdit::drawViewer(), KexiDBImageBox::handleInsertFromFileAction(), KexiDBImageBox::handlePasteAction(), KexiImagePropertyEdit::selectPixmap(), setConnection(), KexiDBImageBox::setPixmapId(), KexiDBImageBox::setStoredPixmapId(), KexiBLOBBuffer::Handle::setStoredWidthID(), KexiImagePropertyEdit::setValue(), KexiFormView::storeData(), and KexiBLOBBuffer::Handle::~Handle().

void KexiBLOBBuffer::setConnection ( KexiDB::Connection * conn ) [static]

Definition at line 360 of file kexiblobbuffer.cpp.
References self().
Referenced by KexiProject::createConnection().

void KexiBLOBBuffer::takeItem ( Item * item ) [protected]

Takes an object for a item out of the buffer.
Definition at line 342 of file kexiblobbuffer.cpp.

Friends And Related Function Documentation

friend class Handle [friend]

Definition at line 220 of file kexiblobbuffer.h.
Referenced by insertObject(), insertPixmap(), and objectForId().

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


Public Types
typedef long	Id_t
Public Member Functions
	KexiBLOBBuffer ()
	~KexiBLOBBuffer ()
Handle	insertPixmap (const KURL &url)
Handle	insertObject (const QByteArray &data, const QString &name, const QString &caption, const QString &mimeType, Id_t identifier=0)
Handle	insertPixmap (const QPixmap &pixmap)
Handle	objectForId (Id_t id, bool stored)
Handle	objectForId (Id_t id)
Static Public Member Functions
static KexiBLOBBuffer *	self ()
	Access to KexiBLOBBuffer singleton.
static void	setConnection (KexiDB::Connection *conn)
Protected Member Functions
void	removeItem (Id_t id, bool stored)
void	takeItem (Item *item)
void	insertItem (Item *item)
Friends
class	Handle
Classes
class	Handle
	Object handle used by KexiBLOBBuffer. More...
class	Item

Kexi API Documentation (2.0 alpha)

KexiBLOBBuffer Class Reference

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Friends

Classes

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation