QtLP_Private::QtLockedFile Class Reference

#include <qtlockedfile.h>

Inheritance diagram for QtLP_Private::QtLockedFile:

Public Types
enum	LockMode { NoLock = 0 , ReadLock , WriteLock }

Public Member Functions
bool	isLocked () const
bool	lock (LockMode mode, bool block=true)
LockMode	lockMode () const
bool	open (OpenMode mode)
	QtLockedFile ()
	QtLockedFile (const QString &name)
bool	unlock ()
	~QtLockedFile ()

Private Attributes
LockMode	m_lock_mode

Detailed Description

Definition at line 14 of file qtlockedfile.h.

Member Enumeration Documentation

LockMode

enum QtLP_Private::QtLockedFile::LockMode

Enumerator
NoLock
ReadLock
WriteLock

Definition at line 17 of file qtlockedfile.h.

{ NoLock = 0, ReadLock, WriteLock };

Constructor & Destructor Documentation

QtLockedFile() [1/2]

QtLockedFile::QtLockedFile

(

)

Constructs an unlocked QtLockedFile object. This constructor behaves in the same way as QFile::QFile().

See also

QFile::QFile()

Definition at line 46 of file qtlockedfile.cpp.

    : QFile()
{
#ifdef Q_OS_WIN
    wmutex = 0;
    rmutex = 0;
#endif
    m_lock_mode = NoLock;
}

References m_lock_mode, and NoLock.

QtLockedFile() [2/2]

QtLockedFile::QtLockedFile

(

const QString &

name

)

Constructs an unlocked QtLockedFile object with file name. This constructor behaves in the same way as QFile::QFile(const QString&).

See also

QFile::QFile()

Definition at line 63 of file qtlockedfile.cpp.

    : QFile(name)
{
#ifdef Q_OS_WIN
    wmutex = 0;
    rmutex = 0;
#endif
    m_lock_mode = NoLock;
}

References m_lock_mode, and NoLock.

~QtLockedFile()

QtLockedFile::~QtLockedFile

(

)

Destroys the QtLockedFile object. If any locks were held, they are released.

Definition at line 73 of file qtlockedfile_unix.cpp.

{
    if (isOpen())
        unlock();
}

Member Function Documentation

isLocked()

bool QtLockedFile::isLocked

(

)

const

Returns true if this object has a in read or write lock; otherwise returns false.

See also

lockMode()

Definition at line 101 of file qtlockedfile.cpp.

{
    return m_lock_mode != NoLock;
}

References m_lock_mode, and NoLock.

lock()

bool QtLockedFile::lock	(	LockMode	mode,
		bool	block = true )

Obtains a lock of type mode. The file must be opened before it can be locked.

If block is true, this function will block until the lock is acquired. If block is false, this function returns false immediately if the lock cannot be acquired.

If this object already has a lock of type mode, this function returns true immediately. If this object has a lock of a different type than mode, the lock is first released and then a new lock is obtained.

This function returns true if, after it executes, the file is locked by this object, and false otherwise.

See also

unlock(), isLocked(), lockMode()

Definition at line 11 of file qtlockedfile_unix.cpp.

{
    if (!isOpen()) {
        qWarning("QtLockedFile::lock(): file is not opened");
        return false;
    }
 
    if (mode == NoLock)
        return unlock();
           
    if (mode == m_lock_mode)
        return true;
 
    if (m_lock_mode != NoLock)
        unlock();
 
    struct flock fl;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;
    int cmd = block ? F_SETLKW : F_SETLK;
    int ret = fcntl(handle(), cmd, &fl);
    
    if (ret == -1) {
        if (errno != EINTR && errno != EAGAIN)
            qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
        return false;
    }
 
    
    m_lock_mode = mode;
    return true;
}

lockMode()

QtLockedFile::LockMode QtLockedFile::lockMode

(

)

const

Returns the type of lock currently held by this object, or QtLockedFile::NoLock.

See also

isLocked()

Definition at line 112 of file qtlockedfile.cpp.

{
    return m_lock_mode;
}

References m_lock_mode.

open()

bool QtLockedFile::open

(

OpenMode

mode

)

Opens the file in OpenMode mode.

This is identical to QFile::open(), with the one exception that the Truncate mode flag is disallowed. Truncation would conflict with the advisory file locking, since the file would be modified before the write lock is obtained. If truncation is required, use resize(0) after obtaining the write lock.

Returns true if successful; otherwise false.

See also

QFile::open(), QFile::resize()

Definition at line 86 of file qtlockedfile.cpp.

{
    if (mode & QIODevice::Truncate) {
        qWarning("QtLockedFile::open(): Truncate mode not allowed.");
        return false;
    }
    return QFile::open(mode);
}

unlock()

bool QtLockedFile::unlock

(

)

Releases a lock.

If the object has no lock, this function returns immediately.

This function returns true if, after it executes, the file is not locked by this object, and false otherwise.

See also

lock(), isLocked(), lockMode()

Definition at line 47 of file qtlockedfile_unix.cpp.

{
    if (!isOpen()) {
        qWarning("QtLockedFile::unlock(): file is not opened");
        return false;
    }
 
    if (!isLocked())
        return true;
 
    struct flock fl;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_type = F_UNLCK;
    int ret = fcntl(handle(), F_SETLKW, &fl);
    
    if (ret == -1) {
        qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
        return false;
    }
    
    m_lock_mode = NoLock;
    return true;
}

Member Data Documentation

m_lock_mode

LockMode QtLP_Private::QtLockedFile::m_lock_mode

private

Definition at line 41 of file qtlockedfile.h.

---

The documentation for this class was generated from the following files:

• libs/ui/qtsingleapplication/qtlockedfile.h
• libs/ui/qtsingleapplication/qtlockedfile.cpp
• libs/ui/qtsingleapplication/qtlockedfile_unix.cpp
• libs/ui/qtsingleapplication/qtlockedfile_win.cpp