Fast solution to list directories recursively

[stereoMatching]

Do you know a faster solution to find all of the directories by Qt(QDirIterator is too slow)

QDirIterator directories(dir_, QDir::Dirs | QDir::NoSymLinks | QDir::NoDotAndDotDot, QDirIterator::Subdirectories);
    QStringList dirs;
    while(directories.hasNext()){                
           directories.next();
           dirs.push_back(directories.filePath());
    }

QDirIterator directories(dir_, QDir::Dirs | QDir::NoSymLinks | QDir::NoDotAndDotDot, QDirIterator::Subdirectories);
    QStringList dirs;
    while(directories.hasNext()){                
           directories.next();
           dirs.push_back(directories.filePath());
    }

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//codes base on BFS(breadth first search)
QStringList scan_dir_recursive(QDir const &dir)
{
    std::queue<QString> queue;
    queue.push(dir.absolutePath());
    QStringList results;
    while (!queue.empty()) {
        auto const subdir_name = queue.front();
        queue.pop();
        results.push_back(subdir_name);
        QDir subdir(subdir_name);
 
        auto const &directories = subdir.entryInfoList({},
                                                       QDir::AllDirs | QDir::NoSymLinks | QDir::NoDotAndDotDot);
        for (auto const &data : directories) {
            queue.push(data.absoluteFilePath());
        }
    }
 
    return results;
}

//codes base on BFS(breadth first search)
QStringList scan_dir_recursive(QDir const &dir)
{
    std::queue<QString> queue;
    queue.push(dir.absolutePath());
    QStringList results;
    while (!queue.empty()) {
        auto const subdir_name = queue.front();
        queue.pop();
        results.push_back(subdir_name);
        QDir subdir(subdir_name);

        auto const &directories = subdir.entryInfoList({},
                                                       QDir::AllDirs | QDir::NoSymLinks | QDir::NoDotAndDotDot);
        for (auto const &data : directories) {
            queue.push(data.absoluteFilePath());
        }
    }

    return results;
}

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[jho]

I dont know where to post, so I just use your post.

I found out that "QDir::NoSymLinks" is very slow. I compared it with the windows dir command. Now both methods runs in a similar speed. Both needed 3 seconds to run through the QT folder. 33000 files in 1100 folders.

With QDir::NoSymLinks on, it took 11 seconds.

I have to run my tool on a network and it is around 100 times slower than the dir command method.


my used code is quite simple:

StringList files; 
   QDirIterator it(source , QDir::Files , QDirIterator::Subdirectories); //QDir::Files | QDir::NoSymLinks | QDir::NoDotAndDotDot
 
    while (it.hasNext())
    {
 
        files.append(it.next());
    }

StringList files; 
   QDirIterator it(source , QDir::Files , QDirIterator::Subdirectories); //QDir::Files | QDir::NoSymLinks | QDir::NoDotAndDotDot

    while (it.hasNext())
    {

        files.append(it.next());
    }

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