Large File Processing

[sankar]

Hello,
I would like to know which is the optimized way to append large file content to a small file. I did the following, but it doesn't work for more than a 1 GB file, it throws error, while reading file content during "QByteArray myFileData = fileHandle2.readAll();"



QFile fileHandle, fileHandle2;
fileHandle.setFileName("SourceFile.txt");
fileHandle2.setFileName("VectorFile.txt");
if(fileHandle.open(QIODevice::Append|QIODevice::Te xt))
{
if(fileHandle2.open(QIODevice::ReadOnly|QIODevice: :Text))
{
QByteArray myFileData = fileHandle2.readAll();

if(myFileData.isEmpty())
QMessageBox::critical(this,"File Operations","File read error...");

if(fileHandle.write(myFileData) == -1)
QMessageBox::critical(this,"File Operations","File append error...");
}
}

fileHandle.close();
fileHandle2.close();


Regards,
Sankar.

[sonulohani]

QString QTextStream::readAll ()

Reads the entire content of the stream, and returns it as a QString. Avoid this function when working on large files, as it will consume a significant amount of memory.

Calling readLine() is better if you do not know how much data is available.

[ChrisW67]

Use the QIODevice::read() and QIODevice::write() functions with a buffer of known size in a while loop.