Recursive directory scan with abort function in a non blocking manner

[MTK358]

Not sure if this is relavent, but the file extension is NOT a certain way to tell the type of a file. For example i use Linux, and file extensions have no meaning to it. The only real reason for them is for the user to tell the file type easily, and because *some* programs pay attention to them.

Unlike in Windows, in Linux I can call a PNG file "image.jpg" and it will work just fine, because *nix and most *nix programs look at the contents of the file, not the extension.

michael@michael-desktop ~ $ file image.jpg
image.jpg: JPEG image data, JFIF standard 1.01                              
michael@michael-desktop ~ $ mv image.jpg image.png            
michael@michael-desktop ~ $ file image.png
image.png: JPEG image data, JFIF standard 1.01

michael@michael-desktop ~ $ file image.jpg
image.jpg: JPEG image data, JFIF standard 1.01                              
michael@michael-desktop ~ $ mv image.jpg image.png            
michael@michael-desktop ~ $ file image.png
image.png: JPEG image data, JFIF standard 1.01

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[hobbyist]

I'd probably go with QThread as well. Something like

class Scanner : public QThread
{
  Q_OBJECT
 
public:
  explicit Scanner(const QDir &dir, QObject *parent = 0)
    : iterator(dir, QDirIterator::Subdirectories), QThread(parent), stopped(false)
  {
  }
 
  void run()
  {
    while(!stopped && iterator.hasNext()) {
      QString entry(iterator.next());
      if(QFileInfo(entry).suffix().toLower() == "png") {
	fileList << entry;
	emit fileCountChanged(fileList.count());
      }
    }
  }
 
  QStringList files() const
  {
    return fileList;
  }
 
public slots:
  void stop()
  {
    stopped = true;
  }
 
signals:
  void fileCountChanged(int);
 
private:
  QDirIterator iterator;
  QStringList fileList;
  bool stopped;
};

class Scanner : public QThread
{
  Q_OBJECT
  
public:
  explicit Scanner(const QDir &dir, QObject *parent = 0)
    : iterator(dir, QDirIterator::Subdirectories), QThread(parent), stopped(false)
  {
  }

  void run()
  {
    while(!stopped && iterator.hasNext()) {
      QString entry(iterator.next());
      if(QFileInfo(entry).suffix().toLower() == "png") {
	fileList << entry;
	emit fileCountChanged(fileList.count());
      }
    }
  }

  QStringList files() const
  {
    return fileList;
  }

public slots:
  void stop()
  {
    stopped = true;
  }

signals:
  void fileCountChanged(int);

private:
  QDirIterator iterator;
  QStringList fileList;
  bool stopped;
};

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Then simply start(), stop() and wait(), as in the original code snippet above.

[Lykurg]

Oh, I love Qt! And I should probably look more often in the docs, also for working solutions since I wasn't aware of QDirIterator. This will save me doing the recursive function. Nice! Thanks for pointing that out. (One small improvement if somebody want use it later: since the iterator uses a QFileInfo internal better use that (QDirIterator::fileInfo) instead of creating a second one.)

@franz: the map* functions are nice but personal I find them hard to maintain (especial in that case). A capsuled Thread is also easier to reuse.
@MTK358: The suffixes are of course meaningless. If you want be sure that it is really a png or any other file you have to do "deeper" tests.


And one follow up: Did you normally subclass QThread or use QObject::moveToThread()? (I am just curious how others did it.)

[MTK358]

The suffixes are of course meaningless. If you want be sure that it is really a png or any other file you have to do "deeper" tests.

Yes, sure. If I would make a simple example I would just have it search for *.png, too. Anyway, if it matters, in Wikipedia it says that a PNG file should always begin with:

89 50 4E 47 0D 0A 1A 0A

89 50 4E 47 0D 0A 1A 0A

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