I read much about QResource now. That isn't what I really want.
To subclass QAbstractFileEngine seems the best solution. But IHMO it's a lot of work and the documentation of it is not as good as of the other Qt classes.
I have a some code which not working well:
// sqlfileengine.h
#ifndef SQLFILEENGINE_H
#define SQLFILEENGINE_H
#include <QAbstractFileEngine>
#include <QAbstractFileEngineHandler>
class QByteArray;
class QString;
class SqlFileEngine;
class SqlFileEngineHandler : public QAbstractFileEngineHandler
{
public:
SqlFileEngineHandler();
virtual QAbstractFileEngine* create(const QString& filename) const;
};
class SqlFileEngine : public QAbstractFileEngine
{
public:
SqlFileEngine();
explicit SqlFileEngine(const QString& file);
virtual QString fileName(FileName file=DefaultName) const;
virtual void setFileName(const QString& file);
bool open(QIODevice::OpenMode openMode);
qint64 read(char* data, qint64 maxlen);
bool atEnd () const;
qint64 size() const;
qint64 pos() const;
private:
void init();
QString _filename;
QByteArray _data;
qint64 _pos;
};
#endif /* end of SQLFILEENGINE_H */
// sqlfileengine.cpp
#include "sqlfileengine.h"
#include <QByteArray>
#include <QDebug>
#include <QString>
#include <QStringList>
#include <QSqlQuery>
#include <QVariant>
// SqlFileEngineHandler
SqlFileEngineHandler::SqlFileEngineHandler()
: QAbstractFileEngineHandler()
{
}
QAbstractFileEngine* SqlFileEngineHandler::create(const QString& filename) const
{
return filename.toLower().startsWith("sql:") ? new SqlFileEngine(filename) : 0;
}
// SqlFileEngine
SqlFileEngine::SqlFileEngine()
{
}
SqlFileEngine::SqlFileEngine(const QString& file)
: _pos(0)
{
qDebug() << "SqlFileEngine ctor";
setFileName(file);
init();
}
QString SqlFileEngine::fileName(FileName file) const
{
Q_UNUSED(file);
return _filename;
}
void SqlFileEngine::setFileName(const QString& file)
{
_filename=file.section(':', 1);
qDebug() << "SqlFileEngine::setFileName() " << _filename;
}
bool SqlFileEngine::open(QIODevice::OpenMode openMode)
{
Q_UNUSED(openMode);
qDebug() << "SqlFileEngine::open() ";
return true;
}
qint64 SqlFileEngine::read(char* data, qint64 maxlen)
{
qDebug() << "SqlFileEngine::read(" << data << "," << maxlen << ")";
if(atEnd())
return 0;
if(!_data.isEmpty())
{
QByteArray curData=_data.mid(_pos, _pos+maxlen);
qstrcpy(data, curData.data());
qDebug() << data;
_pos+=curData.size();
qDebug() << _pos;
}
return 0;
}
bool SqlFileEngine::atEnd() const
{
return (_pos>=size());
}
qint64 SqlFileEngine::size() const
{
return _data.size();
}
qint64 SqlFileEngine::pos() const
{
return _pos;
}
void SqlFileEngine::init()
{
// filename == table/col/id
QStringList strl=_filename.split("/");
QSqlQuery query;
query.prepare("SELECT "+strl.at(1)+" FROM "+strl.at(0)+" WHERE id=:id");
query.bindValue(":table", strl.at(0));
query.bindValue(":col", strl.at(1));
query.bindValue(":id", strl.at(2));
qDebug() << "SELECT " << strl.at(1) << " FROM " << strl.at(0) << " WHERE id=" << strl.at(2);
if(query.exec())
{
while(query.next())
{
qDebug() << query.value(0).toByteArray();
_data=query.value(0).toByteArray();
}
}
}
// main.cpp
#include "sqlfileengine.h"
#include <QApplication>
#include <QLabel>
#include <QSqlDatabase>
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
QSqlDatabase db=QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("/home/segi/user.db");
if(!db.open())
{
qWarning("Couldn't open database.");
return -1;
}
SqlFileEngineHandler engine;
QLabel label;
label.setText("<img src=\"sql:images/image/1\" />");
label.show();
return app.exec();
}
I only get something like that:
SqlFileEngine::setFileName() images/image/1
SELECT "image" FROM "images" WHERE id="1"
SqlFileEngine::open()
SqlFileEngine::read( ¶ôß3·iø캿ñs·▒ , 1 )
SqlFileEngine::read( PNG
▒
, 16384 )
SqlFileEngine::read( ¶ôß3·iø캿ñs·▒ , 1 )
SqlFileEngine::read( PNG
▒
, 16384 )
SqlFileEngine::read( ¶ôß3·iø캿ñs·▒8 , 1 )
SqlFileEngine::read( PNG
▒
, 16384 )
SqlFileEngine::read( ¶ôß3·iø캿ñs·▒8 , 1 )
SqlFileEngine::read( PNG
▒
, 16384 )
...
Is there another method to tell that the end of file is reached than return 0 in SqlFileEngine::read?
What do I wrong?
Where can I find better/more information about subclassing QAbstractFileEngine? (What have i to reimplement and so on.)
Bye