view src/fswatcher.h @ 571:012ba1b83328

Show cancel button with progress bar only when running an operation that it makes sense to cancel (we don't really want people cancelling e.g. initial folder scan because it would leave things in an inconsistent state)

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    EasyMercurial

    Based on HgExplorer by Jari Korhonen
    Copyright (c) 2010 Jari Korhonen
    Copyright (c) 2012 Chris Cannam
    Copyright (c) 2012 Queen Mary, University of London
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef FSWATCHER_H
#define FSWATCHER_H

#include <QObject>
#include <QMutex>
#include <QString>
#include <QSet>
#include <QHash>
#include <QMap>
#include <QStringList>
#include <QFileSystemWatcher>

class FsWatcher : public QObject
{
    Q_OBJECT

public:
    FsWatcher();
    virtual ~FsWatcher();

    /**
     * Set the root path of the work directory to be monitored. This
     * directory and all its subdirectories (recursively) will be
     * monitored for changes.
     *
     * If this path differs from the currently set work dir path, then
     * the tracked file paths will also be cleared. Call
     * setTrackedFilePaths afterwards to ensure non-directory files
     * are monitored.
     */
    void setWorkDirPath(QString path);

    /**
     * Provide a set of paths for files which should be tracked. These
     * will be the only non-directory files monitored for changes. The
     * paths should be relative to the work directory.
     */
    void setTrackedFilePaths(QStringList paths);
    
    /**
     * Provide a set of prefixes to ignore. Files whose names start
     * with a prefix in this set will be ignored when they change.
     */
    void setIgnoredFilePrefixes(QStringList prefixes);

    /**
     * Provide a set of suffixes to ignore. Files whose names end
     * with a suffix in this set will be ignored when they change.
     */
    void setIgnoredFileSuffixes(QStringList suffixes);

    /**
     * Return a token to identify the current caller in subsequent
     * calls to getChangedPaths().  Only changes that occur after this
     * has been called can be detected by the caller.
     */
    int getNewToken();
    
    /**
     * Return a list of all non-ignored file paths that have been
     * observed to have changed since the last call to getChangedPaths
     * with the same token.
     */
    QSet<QString> getChangedPaths(int token);
    
signals:
    /**
     * Emitted when something has changed. Use the asynchronous
     * interface to find out what.
     */
    void changed();

private slots:
    void fsDirectoryChanged(QString);
    void fsFileChanged(QString);

private:
    // call with lock already held
    void addWorkDirectory(QString path);

    // call with lock already held
    bool shouldIgnore(QString path);

    // call with lock already held. Returns set of non-ignored files in dir
    QSet<QString> scanDirectory(QString path);

    // call with lock already held
    void debugPrint();

private:
    /**
     * A change associates a filename with a counter (the
     * size_t). Each time a file is changed, its counter is assigned
     * from m_lastCounter and m_lastCounter is incremented.
     *
     * This is not especially efficient -- we often want to find "all
     * files whose counter is greater than X" which involves a
     * traversal. Maybe something better later.
     */
    QHash<QString, size_t> m_changes;

    /**
     * Associates a token (the client identifier) with a counter. The
     * counter represents the value of m_lastCounter at the moment
     * getChangedPaths last completed for that token. Any files in
     * m_changes whose counters are larger must have been modified.
     */
    QMap<int, size_t> m_tokenMap;

    /**
     * Associates a directory path with a list of all the files in it
     * that do not match our ignore patterns. When a directory is
     * signalled as having changed, then we need to rescan it and
     * compare against this list before we can determine whether to
     * notify about the change or not.
     */
    QHash<QString, QSet<QString> > m_dirContents;

    QStringList m_ignoredPrefixes;
    QStringList m_ignoredSuffixes;

    /// Everything in this class is synchronised.
    QMutex m_mutex;

    QString m_workDirPath;
    int m_lastToken;
    size_t m_lastCounter;
    QFileSystemWatcher m_watcher;
};

#endif