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/*!
    \since 4.3
    \class QDirIterator
    \brief The QDirIterator class provides an iterator for directory entrylists.

    You can use QDirIterator to navigate entries of a directory one at a time.
    It is similar to QDir::entryList() and QDir::entryInfoList(), but because
    it lists entries one at a time instead of all at once, it scales better
    and is more suitable for large directories. It also supports listing
    directory contents recursively, and following symbolic links. Unlike
    QDir::entryList(), QDirIterator does not support sorting.

    The QDirIterator constructor takes a QDir or a directory as
    argument. After construction, the iterator is located before the first
    directory entry. Here's how to iterate over all the entries sequentially:

    \snippet doc/src/snippets/code/src_corelib_io_qdiriterator.cpp 0

    The next() function returns the path to the next directory entry and
    advances the iterator. You can also call filePath() to get the current
    file path without advancing the iterator.  The fileName() function returns
    only the name of the file, similar to how QDir::entryList() works. You can
    also call fileInfo() to get a QFileInfo for the current entry.

    Unlike Qt's container iterators, QDirIterator is uni-directional (i.e.,
    you cannot iterate directories in reverse order) and does not allow random
    access.

    QDirIterator works with all supported file engines, and is implemented
    using QAbstractFileEngineIterator.

    \sa QDir, QDir::entryList(), QAbstractFileEngineIterator
*/

/*! \enum QDirIterator::IteratorFlag

    This enum describes flags that you can combine to configure the behavior
    of QDirIterator.

    \value NoIteratorFlags The default value, representing no flags. The
    iterator will return entries for the assigned path.

    \value Subdirectories List entries inside all subdirectories as well.

    \value FollowSymlinks When combined with Subdirectories, this flag
    enables iterating through all subdirectories of the assigned path,
    following all symbolic links. Symbolic link loops (e.g., "link" => "." or
    "link" => "..") are automatically detected and ignored.
*/

#include "qdiriterator.h"

#include "qabstractfileengine.h"

#include <QtCore/qset.h>
#include <QtCore/qstack.h>
#include <QtCore/qvariant.h>

QT_BEGIN_NAMESPACE

class QDirIteratorPrivate
{
public:
    QDirIteratorPrivate(const QString &path, const QStringList &nameFilters,
                        QDir::Filters filters, QDirIterator::IteratorFlags flags);
    ~QDirIteratorPrivate();

    void pushSubDirectory(const QFileInfo &fileInfo, const QStringList &nameFilters,
                          QDir::Filters filters);
    void advance();
    bool shouldFollowDirectory(const QFileInfo &);
    bool matchesFilters(const QAbstractFileEngineIterator *it) const;

    QSet<QString> visitedLinks;
    QAbstractFileEngine *engine;
    QStack<QAbstractFileEngineIterator *> fileEngineIterators;
    QString path;
    QFileInfo nextFileInfo;
    //This fileinfo is the current that we will return from the public API
    QFileInfo currentFileInfo;
    QDirIterator::IteratorFlags iteratorFlags;
    QDir::Filters filters;
    QStringList nameFilters;
    bool followNextDir;
    bool first;
    bool done;

    QDirIterator *q;
};

/*!
    \internal
*/
QDirIteratorPrivate::QDirIteratorPrivate(const QString &path, const QStringList &nameFilters,
                                         QDir::Filters filters, QDirIterator::IteratorFlags flags)
    : engine(0), path(path), iteratorFlags(flags), followNextDir(false), first(true), done(false)
{
    if (filters == QDir::NoFilter)
        filters = QDir::AllEntries;
    this->filters = filters;
    this->nameFilters = nameFilters;

    nextFileInfo.setFile(path);
    pushSubDirectory(nextFileInfo, nameFilters, filters);
}

/*!
    \internal
*/
QDirIteratorPrivate::~QDirIteratorPrivate()
{
    delete engine;
}

/*!
    \internal
*/
void QDirIteratorPrivate::pushSubDirectory(const QFileInfo &fileInfo, const QStringList &nameFilters,
                                           QDir::Filters filters)
{
    QString path = fileInfo.filePath();

#ifdef Q_OS_WIN
    if (fileInfo.isSymLink())
        path = fileInfo.canonicalFilePath();
#endif

    if (iteratorFlags & QDirIterator::FollowSymlinks)
        visitedLinks << fileInfo.canonicalFilePath();

    if (engine || (engine = QAbstractFileEngine::create(this->path))) {
        engine->setFileName(path);
        QAbstractFileEngineIterator *it = engine->beginEntryList(filters, nameFilters);
        if (it) {
            it->setPath(path);
            fileEngineIterators << it;
        } else {
            // No iterator; no entry list.
        }
    }
}

/*!
    \internal
*/
void QDirIteratorPrivate::advance()
{
    // Advance to the next entry
    if (followNextDir) {
        // Start by navigating into the current directory.
        QAbstractFileEngineIterator *it = fileEngineIterators.top();
        pushSubDirectory(it->currentFileInfo(), it->nameFilters(), it->filters());
        followNextDir = false;
    }

    while (!fileEngineIterators.isEmpty()) {
        QAbstractFileEngineIterator *it = fileEngineIterators.top();

        // Find the next valid iterator that matches the filters.
        bool foundDirectory = false;
        while (it->hasNext()) {
            it->next();
            if (matchesFilters(it)) {
                currentFileInfo = nextFileInfo;
                nextFileInfo = it->currentFileInfo();
                // Signal that we want to follow this entry.
                followNextDir = shouldFollowDirectory(nextFileInfo);
                //We found a matching entry.
                return;

            } else if (shouldFollowDirectory(it->currentFileInfo())) {
                pushSubDirectory(it->currentFileInfo(), it->nameFilters(), it->filters());
                foundDirectory = true;
                break;
            }
        }
        if (!foundDirectory)
            delete fileEngineIterators.pop();
    }
    currentFileInfo = nextFileInfo;
    done = true;
}

/*!
    \internal
 */
bool QDirIteratorPrivate::shouldFollowDirectory(const QFileInfo &fileInfo)
{
    // If we're doing flat iteration, we're done.
    if (!(iteratorFlags & QDirIterator::Subdirectories))
        return false;

    // Never follow non-directory entries
    if (!fileInfo.isDir())
        return false;

    // Never follow . and ..
    if (fileInfo.fileName() == QLatin1String(".") || fileInfo.fileName() == QLatin1String(".."))
        return false;

    // Check symlinks
    if (fileInfo.isSymLink() && !(iteratorFlags & QDirIterator::FollowSymlinks)) {
        // Follow symlinks only if FollowSymlinks was passed
        return false;
    }

    // Stop link loops
    if (visitedLinks.contains(fileInfo.canonicalFilePath()))
        return false;

    return true;
}

/*!
    \internal

    This convenience function implements the iterator's filtering logics and
    applies then to the current directory entry.

    It returns true if the current entry matches the filters (i.e., the
    current entry will be returned as part of the directory iteration);
    otherwise, false is returned.
*/
bool QDirIteratorPrivate::matchesFilters(const QAbstractFileEngineIterator *it) const
{
    const bool filterPermissions = ((filters & QDir::PermissionMask)
                                    && (filters & QDir::PermissionMask) != QDir::PermissionMask);
    const bool skipDirs     = !(filters & (QDir::Dirs | QDir::AllDirs));
    const bool skipFiles    = !(filters & QDir::Files);
    const bool skipSymlinks = (filters & QDir::NoSymLinks);
    const bool doReadable   = !filterPermissions || (filters & QDir::Readable);
    const bool doWritable   = !filterPermissions || (filters & QDir::Writable);
    const bool doExecutable = !filterPermissions || (filters & QDir::Executable);
    const bool includeHidden = (filters & QDir::Hidden);
    const bool includeSystem = (filters & QDir::System);

#ifndef QT_NO_REGEXP
    // Prepare name filters
    QList<QRegExp> regexps;
    bool hasNameFilters = !nameFilters.isEmpty() && !(nameFilters.contains(QLatin1String("*")));
    if (hasNameFilters) {
        for (int i = 0; i < nameFilters.size(); ++i) {
            regexps << QRegExp(nameFilters.at(i),
                               (filters & QDir::CaseSensitive) ? Qt::CaseSensitive : Qt::CaseInsensitive,
                               QRegExp::Wildcard);
        }
    }
#endif

    QString fileName = it->currentFileName();
    if (fileName.isEmpty()) {
        // invalid entry
        return false;
    }

    QFileInfo fi = it->currentFileInfo();
    QString filePath = it->currentFilePath();

#ifndef QT_NO_REGEXP
    // Pass all entries through name filters, except dirs if the AllDirs
    // filter is passed.
    if (hasNameFilters && !((filters & QDir::AllDirs) && fi.isDir())) {
        bool matched = false;
        for (int i = 0; i < regexps.size(); ++i) {
            if (regexps.at(i).exactMatch(fileName)) {
                matched = true;
                break;
            }
        }
        if (!matched)
            return false;
    }
#endif

    bool dotOrDotDot = (fileName == QLatin1String(".") || fileName == QLatin1String(".."));
    if ((filters & QDir::NoDotAndDotDot) && dotOrDotDot)
        return false;

    bool isHidden = !dotOrDotDot && fi.isHidden();
    if (!includeHidden && isHidden)
        return false;

    bool isSystem = (!fi.isFile() && !fi.isDir() && !fi.isSymLink())
                    || (!fi.exists() && fi.isSymLink());
    if (!includeSystem && isSystem)
        return false;

    bool alwaysShow = (filters & QDir::TypeMask) == 0
        && ((isHidden && includeHidden)
            || (includeSystem && isSystem));

    // Skip files and directories
    if ((filters & QDir::AllDirs) == 0 && skipDirs && fi.isDir()) {
        if (!alwaysShow)
            return false;
    }

    if ((skipFiles && (fi.isFile() || !fi.exists()))
        || (skipSymlinks && fi.isSymLink())) {
        if (!alwaysShow)
            return false;
    }

    if (filterPermissions
        && ((doReadable && !fi.isReadable())
            || (doWritable && !fi.isWritable())
            || (doExecutable && !fi.isExecutable()))) {
        return false;
    }

    if (!includeSystem && !dotOrDotDot && ((fi.exists() && !fi.isFile() && !fi.isDir() && !fi.isSymLink())
                                           || (!fi.exists() && fi.isSymLink()))) {
        return false;
    }

    return true;
}

/*!
    Constructs a QDirIterator that can iterate over \a dir's entrylist, using
    \a dir's name filters and regular filters. You can pass options via \a
    flags to decide how the directory should be iterated.

    By default, \a flags is NoIteratorFlags, which provides the same behavior
    as in QDir::entryList().

    The sorting in \a dir is ignored.

    \note To list symlinks that point to non existing files, QDir::System must be
     passed to the flags.

    \sa hasNext(), next(), IteratorFlags
*/
QDirIterator::QDirIterator(const QDir &dir, IteratorFlags flags)
    : d(new QDirIteratorPrivate(dir.path(), dir.nameFilters(), dir.filter(), flags))
{
    d->q = this;
}

/*!
    Constructs a QDirIterator that can iterate over \a path, with no name
    filtering and \a filters for entry filtering. You can pass options via \a
    flags to decide how the directory should be iterated.

    By default, \a filters is QDir::NoFilter, and \a flags is NoIteratorFlags,
    which provides the same behavior as in QDir::entryList().

    \note To list symlinks that point to non existing files, QDir::System must be
     passed to the flags.

    \warning This constructor expects \a flags to be left at its default value. Use
             the constructors that do not take the \a filters argument instead.

    \sa hasNext(), next(), IteratorFlags
*/
QDirIterator::QDirIterator(const QString &path, QDir::Filters filters, IteratorFlags flags)
    : d(new QDirIteratorPrivate(path, QStringList(QLatin1String("*")), filters, flags))
{
    d->q = this;
}

/*!
    Constructs a QDirIterator that can iterate over \a path. You can pass
    options via \a flags to decide how the directory should be iterated.

    By default, \a flags is NoIteratorFlags, which provides the same behavior
    as in QDir::entryList().

    \note To list symlinks that point to non existing files, QDir::System must be
     passed to the flags.

    \sa hasNext(), next(), IteratorFlags
*/
QDirIterator::QDirIterator(const QString &path, IteratorFlags flags)
    : d(new QDirIteratorPrivate(path, QStringList(QLatin1String("*")), QDir::NoFilter, flags))
{
    d->q = this;
}

/*!
    Constructs a QDirIterator that can iterate over \a path, using \a
    nameFilters and \a filters. You can pass options via \a flags to decide
    how the directory should be iterated.

    By default, \a flags is NoIteratorFlags, which provides the same behavior
    as QDir::entryList().

    \note To list symlinks that point to non existing files, QDir::System must be
     passed to the flags.

    \warning This constructor expects \c flags to be left at its default value. Use the
             constructors that do not take the \a filters argument instead.

    \sa hasNext(), next(), IteratorFlags
*/
QDirIterator::QDirIterator(const QString &path, const QStringList &nameFilters,
                           QDir::Filters filters, IteratorFlags flags)
    : d(new QDirIteratorPrivate(path, nameFilters, filters, flags))
{
    d->q = this;
}

/*!
    Destroys the QDirIterator.
*/
QDirIterator::~QDirIterator()
{
    qDeleteAll(d->fileEngineIterators);
    delete d;
}

/*!
    Advances the iterator to the next entry, and returns the file path of this
    new entry. If hasNext() returns false, this function does nothing, and
    returns a null QString.

    You can call fileName() or filePath() to get the current entry file name
    or path, or fileInfo() to get a QFileInfo for the current entry.

    \sa hasNext(), fileName(), filePath(), fileInfo()
*/
QString QDirIterator::next()
{
    if (!hasNext())
        return QString();
    d->advance();
    return filePath();
}

/*!
    Returns true if there is at least one more entry in the directory;
    otherwise, false is returned.

    \sa next(), fileName(), filePath(), fileInfo()
*/
bool QDirIterator::hasNext() const
{
    if (d->first) {
        d->first = false;
        d->advance();
    }
    return !d->done;
}

/*!
    Returns the file name for the current directory entry, without the path
    prepended.

    This function is convenient when iterating a single directory. When using
    the QDirIterator::Subdirectories flag, you can use filePath() to get the
    full path.

    \sa filePath(), fileInfo()
*/
QString QDirIterator::fileName() const
{
    return d->currentFileInfo.fileName();
}

/*!
    Returns the full file path for the current directory entry.

    \sa fileInfo(), fileName()
*/
QString QDirIterator::filePath() const
{
    return d->currentFileInfo.filePath();
}

/*!
    Returns a QFileInfo for the current directory entry.

    \sa filePath(), fileName()
*/
QFileInfo QDirIterator::fileInfo() const
{
    return d->currentFileInfo;
}

/*!
    Returns the base directory of the iterator.
*/
QString QDirIterator::path() const
{
    return d->path;
}

QT_END_NAMESPACE