I have a problem which looks like a bug in QTextStream.
I need to compress some text file which has pairs of numbers except 3 top lines and write it to the file.
To do it I read data from the file into QByteArray using QTextStream, on the 14066 line value read is not equal to value written.
At this point when value is read an extra character which belongs to the next value is read as a part of current value.
// values written into QByteArray
// val = 0.275119
// val = 0.056078 ! this value is CORRECT
// val = 4.28628 ! this value is CORRECT
// values read from the QByteArray
// val = 0.275119
// val = 0.0560784 !!!!!!!!!!! expected 0.056078
// val = 0.28628 !!!!!!!!!!! expected 4.28628
Trying to localize problem allowed to come to conclusion that problem happens either:
- when value is written to QByteArray using QTextStream out ( &_array, QIODevice::WriteOnly );
- or when value is read from the same array using QTextStream in ( &_array, QIODevice::ReadOnly );
Any restriction on size of QByteArray I am missing?
QT 4.6.0 MSVC 2005, Windows XP 64 bit.
Regards,
Alex
///////////////////////////////////////////////////////
// reading data from file into
QTextStream in( &file );
// read number of fields
in >> numFields;
if( numFields <1 || numFields>MaxFields || in.status() != QTextStream::Ok )
{
label = UserNotifier::tr("Corrupted or unknown fornat file:' %1'").arg( fileTxt );
}
else
{
QByteArray _array;
_array.reserve( 1024*1024*24 );
QTextStream out ( &_array, QIODevice::WriteOnly );
ok = true;
// write number of fields
out << numFields;
QString name;
for( int i=0; i< numFields; i++ )
{
name.resize(0);
while( name.isEmpty() && in.status() == QTextStream::Ok )
{
name = in.readLine();
}
if( name.isEmpty() || in.status() != QTextStream::Ok )
{
ok=false;
break;
}
else
{
out << name <<"\n"; // write field name
}
}
label = UserNotifier::tr("reading field information from the file:'%1' to buffer").arg( fileTxt );
UserNotifier::glNotifyActionStarted( label );
int counter = 0;
double val;
while ( ok && !in.atEnd() )
{
in >> val;
int index = 14066-1;
if( counter >= ( index - 3)*2 && counter <= ( ( index - 3)*2 + 2) )
{
qDebug() << " counter =" << counter << " index = " << index << " val = " << val;
// counter = 28124 index = 14065 val = 0.275119
// counter = 28125 index = 14065 val = 0.056078 ! this value is CORRECT
// counter = 28126 index = 14065 val = 4.28628 ! this value is CORRECT
}
if( in.status() != QTextStream::Ok )
{
Q_ASSERT( in.status() != QTextStream::ReadCorruptData );
break;
}
else
{
out << val;
counter++;
}
}
// _array currently has a CORRECT data read from file
#ifdef DEBUG_CORRECT_ARRAY_WRITTEN
// Reading from the _array, checking that data is correct, right to another file
{
QString fileNameTmp = fileTxt+ ".createdArray2";
QFile fileTmp( fileNameTmp );
if ( fileTmp.open( QIODevice::WriteOnly | QIODevice::Text ) )
{
QTextStream tmpOut( &fileTmp );
QTextStream in ( &_array, QIODevice::ReadOnly );
in >> numFields;
tmpOut << numFields << "\n";;
QString name;
for( int i=0; i< numFields; i++ )
{
name.resize(0);
while( name.isEmpty() && in.status() == QTextStream::Ok )
{
in >> name;
tmpOut << name << "\n";;
}
}
for( int nline=0; nline< counter/2; ++nline )
{
for( int i=0; i< numFields; ++i )
{
in >> val; // any check before we assign the value?
int index = 14066-3-1;
if( nline >= index && nline <= index+6 )
{
qDebug() << " counter =" << counter << " index = " << nline << " val = " << val;
// Output
// counter = 1464832 index = 14062 val = 0.275119
// counter = 1464832 index = 14062 val = 0.0560784 !!!!!!!!!!! expected 0.056078
// counter = 1464832 index = 14063 val = 0.28628 !!!!!!!!!!! expected 4.28628
}
tmpOut << val;
tmpOut.flush();
if ( i == numFields-1 )
tmpOut << "\n";
else
tmpOut << " ";
}
}
}
}
#endif
counter = 28124 index = 14065 val = 0.275119
counter = 28125 index = 14065 val = 0.056078
counter = 28126 index = 14065 val = 4.28628
counter = 1464832 index = 14062 val = 0.275119
counter = 1464832 index = 14062 val = 0.0560784
counter = 1464832 index = 14063 val = 0.28628
Alex Malyushytsky
Research Engineer - Weidlinger Associates Inc.
office: 650 230 0210,
direct: 650 230 0349
web: http://www.wai.com
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