[Solved] stdin with QIODevice

t3chNo

Hi i have a class named StandardInputReader inherited QIODevice. It gets input from stdin. All iodevice functionality works except readAll function. When i call readAll, it waits forever. But if i call @device.read(device.bytesAvailable());@ all works fine. I redefined
@
bool isSequential() const;
qint64 bytesAvailable() const;
bool waitForReadyRead(int msecs);

protected:
qint64 readData(char *data, qint64 maxSize);
qint64 writeData(const char data, qint64 maxSize); / Does nothing */
@

these functions. I even looked at QIODevice source code and didn't figure out what causing this. Any suggestions?

giesbert

Hi,

if you look at the source of QIODevive::read all, you find:

@
QByteArray QIODevice::readAll()
{
....
do {
result.resize(result.size() + QIODEVICE_BUFFERSIZE);
readResult = read(result.data() + readBytes, result.size() - readBytes);
if (readResult > 0 || readBytes == 0)
readBytes += readResult;
} while (readResult > 0);
...
}
@

This means, unless StandardInputReader::read returns something bigger then 0 the while loop goes on iterating...

koahnig

[quote author="Gerolf" date="1318504064"]
This means, unless StandardInputReader::read returns something bigger then 0 the while loop goes on iterating...[/quote]
The other way around, or?

You mean, when StandardInputReader::read returns something bigger then 0 the while loop goes on iterating...

t3chNo

I think i figured it out. QIODevice::read function as Gerolf calls my readData function. i used standard c read function(man 2 read) to read from stdin. when readData calls read, process is blocked until new data available for reading. Because of this, QIODevice::read enters infinite loop and never returns. I just added @
if (bytesAvailable() == 0)
return 0;
@ before read and problem solved. Thanks for replies.

giesbert

[quote author="koahnig" date="1318507175"]
[quote author="Gerolf" date="1318504064"]
This means, unless StandardInputReader::read returns something bigger then 0 the while loop goes on iterating...[/quote]
The other way around, or?

You mean, when StandardInputReader::read returns something bigger then 0 the while loop goes on iterating...[/quote]

right,....