[Solved] Duplicate finder

[alex.dadaev]

how can i make QString from QFileInfoList ?
is there any possibilities to do that?

[giesbert]

QFileInfo::path() ???

[goetz]

No.

QFileInfoList is a typedef for QList<QFileInfo>.

You know how many properties a QFileInfo object describing a single file has, don't you?

If you want a single string from these big bunch of information you will have to construct it yourself.

[giesbert]

Ok, forgpot to add the iteration by for(...)...

[alex.dadaev]

but how can i construct a path of a single file?

[goetz]

Read the docs on "QFileInfo":http://doc.qt.nokia.com/stable/qfileinfo.html - we did it too. Everything you need is documented there. Yes, it takes some 5 minutes to read it all through, but if you're too lazy we can't help you. If you have concrete questions or problems with any of the methods, ask them.

[giesbert]

If you read the documentation, you would find it ...

@
QFileInfoList list;
for(int i = 0; i < list.size(); ++i)
{
QString filePath = list[i].absoluteFilePath();
{
@

[alex.dadaev]

i've made it by myself already :) the reason why i ask so dumb questions is because i'm just starting using Qt and programming itself and i just want not to make stupid mistakes.
@QString path[list.size()];for (int i = 0; i < list.size(); ++i) {
QFileInfo fileInfo = list.at(i);
path[i] = fileInfo.path();}@

[giesbert]

I would suggest using a QStringList instead of QString path[xx];

[goetz]

First: Then show us your code and we comment on it; Don't ask dumb questions that are clearly answered in the very good API docs the Trolls have created for us. It is very likely that you will not get any answer (apart from "RTFM"). We all put some valuable amount of time into DevNet to answer questions - with that silly game you are stealing this time!

Second: Do not use C-Style arrays in C++ if you are not absolutely forced to. Use the fine "Container Classes":http://doc.qt.nokia.com/stable/containers.html of Qt (or the equivalents of C++ standard library or boost). In your case "QStringList":http://doc.qt.nokia.com/stable/qstringlist.html is what you want.

Third: C-Style arrays of unknown size at compile time are not supported by all compilers and therefore not portable. I leave you to google or bing to search for the details.

[ixSci]

Don't you think a hash computation is a little bit overkilling in the file duplicate determination?
Just read your files' contents into memory blocks and compare them with memcmp. If you may have big files it would be wiser to compare them block-by-block rather then the whole files at once.

Upd. function name

[giesbert]

memcpy copies in memory and does not compare them.

AFAIK, he wanted to search for duplicates, so hashes would be faster. YOu don't want to do a full compare for all files with all files....

[ixSci]

Gerolf, thank you for the function name correction.
And yes, you are right about the question. I've misinterpreted OP goal :)

[alex.dadaev]

How do you think, is it correct?
@
while(it.hasNext())
{
it.next();
if(it.peekPrevious().key()==it.peekNext().key())
std::cout<<it.peekPrevious().value()<<"="
<<it.peekNext().value()<<std::endl;
}
@

[goetz]

No it is not correct.

It compares only adjacent entries in your container.

If your container is a map (QMap or QHash) and you use insert() to populate it then you will get no duplicates at all, since every key occurs only once, hence the keys at different positions are all distinct.

You must use insertMulti() and values() to get a list of all entries with the same hash value. Or use QMultiMap/QMultiHash with the before mentioned methods.

[alex.dadaev]

Yes, you're right, thanks

[alex.dadaev]

i can't understand why it's not working :(
@
while(it.hasNext())
{
it.next();
if(it.key()==it.peekNext().key()) {
std::cout << "i've got you" << std::endl;
}
}
@

PS: i've used insertMulti() to add item to hash, as you said

[alex.dadaev]

maybe like this?
@int compare_flag;

while(it.hasNext())
{
    it.next();
    compare_flag = QString::compare(it.key(),it.peekNext().key(),Qt::CaseSensitive);
                   if(compare_flag==0) {
        std::cout << "i've got you" << std::endl;
    }
}@

[goetz]

The keys in a (hash) map are always distinct. You will never find two identical keys so your comparison will never be true.

And even if you had identical keys in your container you would only find them if they are adjacent in the list.

But I'm going to have a kind of déjà-vu...

To make things clearer for us to understand: You do have a multi hash/multi map. What do you put in there and what do you expect to come out?

[alex.dadaev]

@QHash<QString,int> FilesHash;@
QString key is MD5
int value - just a number of file

on output i want to see the names of similar files