1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
|
/*
* SPDX-FileCopyrightText: 2014 Frank Reininghaus <[email protected]>
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#ifndef MOUNTPOINTOBSERVER_H
#define MOUNTPOINTOBSERVER_H
#include <KIO/Job>
#include <QObject>
#include <QUrl>
/**
* A MountPointObserver can be used to determine the free space on a mount
* point. It will then check the free space periodically, and emit the signal
* spaceInfoChanged() if the return value of spaceInfo() has changed.
*
* Since multiple users which watch paths on the same mount point can share
* a MountPointObserver, it is not possible to create a MountPointObserver
* manually. Instead, the function observerForPath(QString&) should be called,
* which returns either an existing or a newly created MountPointObserver for
* the mount point where the path is mounted. observerForPath(QString&) looks
* for a suitable MountPointObserver in an internal cache and creates new
* MountPointObservers and adds them to the cache if necessary.
*
* Reference counting is used to keep track of the number of users, and to
* decide when the object can be deleted. A user of this class should call
* the method ref() when it starts using it, and deref() when it does not need
* the MountPointObserver any more.
*
* The object will not be deleted immediately if the reference count reaches
* zero. The object will only be destroyed when the next periodic update of
* the free space information happens, and the reference count is still zero.
* This approach makes it possible to re-use the object if a new user requests
* the free space for the same mount point before the next update.
*/
class MountPointObserver : public QObject
{
Q_OBJECT
explicit MountPointObserver(const QUrl& url, QObject* parent = nullptr);
~MountPointObserver() override {}
public:
/**
* Call this function to indicate that the caller intends to continue using this object. An
* internal reference count is increased then. When the observer is not needed any more,
* deref() should be called, which decreases the reference count again.
*/
void ref() { ++m_referenceCount; }
/**
* This function can be used to indicate that the caller does not need this MountPointObserver
* any more. Internally, a reference count is decreased. If the reference count is zero while
* update() is called, the object deletes itself.
*/
void deref()
{
--m_referenceCount;
Q_ASSERT(m_referenceCount >= 0);
}
/**
* Returns a MountPointObserver for the given \a url. If the caller intends to continue using
* the returned object, it must call its ref() method.
*/
static MountPointObserver* observerForUrl(const QUrl& url);
Q_SIGNALS:
/**
* This signal is emitted when the size has been retrieved.
*/
void spaceInfoChanged(quint64 size, quint64 available);
public Q_SLOTS:
/**
* If this slot is invoked, MountPointObserver starts a new driveSize job
* to get the drive's size.
*/
void update();
private Q_SLOTS:
void freeSpaceResult(KIO::Job* job, KIO::filesize_t size, KIO::filesize_t available);
private:
const QUrl m_url;
int m_referenceCount;
friend class MountPointObserverCache;
};
#endif
|
