Creating a hash-value of a directory in Qt - c++

Question

Is there any mean to determine if the directory content (including deep subdirectory structure) has changed since last access? I'm looking for a portable solution in C/C++, preferably in Qt.
P.S.:
If relevant, the background of the question.
In my application I have to scan recursively many directories and import some data in a database, when some conditions are true. Once the directory was imported, I mark it with a file ".imported" and ignore next times.
Now I want to mark also scanned but not imported directories. For this I'd store a file containing a directory hash. So, prior to scan I could compare the hash calculated with the last hash in file and skip scanning if they are equal.

Answer 1

There is a QFileSystemWatcher class that will notify you of changes.
If you want to create a Cryptographic Hash of a directory and its contents, this is how I do it: -
void AddToHash(const QFileInfo& fileInf, QCryptographicHash& cryptHash)
{
QDir directory(fileInf.absoluteFilePath());
directory.setFilter(QDir::NoDotAndDotDot | QDir::AllDirs | QDir::Files);
QFileInfoList fileInfoList = directory.entryInfoList();
foreach(QFileInfo info, fileInfoList)
{
if(info.isDir())
{
// recurse through all directories
AddToHash(info, cryptHash);
continue;
}
// add all file contents to the hash
if(info.isFile())
{
QFile file(info.absoluteFilePath());
if(!file.open(QIODevice::ReadOnly))
{
// failed to open file, so skip
continue;
}
cryptHash.addData(&file);
file.close();
}
}
}
// create a fileInfo from the top-level directory
QFileInfo fileInfo(filePath);
QString hash;
// Choose an arbitrary hash, say Sha1
QCryptographicHash cryptHash(QCryptographicHash::Sha1);
// add all files to the hash
AddToHash(fileInfo, cryptHash);
// get a printable version of the hash
hash = cryptHash.result().toHex();