QWSSharedMemory Class Reference

#include <qwssharedmemory_p.h>

Public Functions
void *	address () const
bool	attach (int id)
bool	create (int size)
void	detach ()
int	id () const
	QWSSharedMemory ()
int	size () const
	~QWSSharedMemory ()

Properties
void *	shmBase
int	shmId
int	shmSize

Detailed Description

Definition at line 62 of file qwssharedmemory_p.h.

Constructors and Destructors

QWSSharedMemory()

QWSSharedMemory::QWSSharedMemory

(

)

Definition at line 75 of file qwssharedmemory.cpp.

    : shmId(-1), shmBase(0), shmSize(0)
#ifdef QT_POSIX_IPC
    , hand(-1)
#endif
{
}

~QWSSharedMemory()

QWSSharedMemory::~QWSSharedMemory

(

)

Definition at line 83 of file qwssharedmemory.cpp.

{
    detach();
}

Functions

address()

void* QWSSharedMemory::address ( ) const

inline

Definition at line 74 of file qwssharedmemory_p.h.

Referenced by QWSSharedMemSurface::setGeometry(), QWSSharedMemSurface::setMemory(), and QWSSharedMemSurface::setPermanentState().

{ return shmBase; }

attach()

bool QWSSharedMemory::attach

(

int

id

)

Definition at line 146 of file qwssharedmemory.cpp.

Referenced by QWSSharedMemSurface::setMemory().

{
    if (shmId == id)
        return id != -1;

    detach();

    if (id == -1)
        return false;

    shmId = id;
#ifndef QT_POSIX_IPC
    shmBase = shmat(shmId, 0, 0);
#else
    QByteArray shmName = makeKey(shmId);
    EINTR_LOOP(hand, shm_open(shmName.constData(), O_RDWR, 0660));
    if (hand != -1) {
        // grab the size
        QT_STATBUF st;
        if (QT_FSTAT(hand, &st) != -1) {
            shmSize = st.st_size;
            // grab the memory
            shmBase = mmap(0, shmSize, PROT_READ | PROT_WRITE, MAP_SHARED, hand, 0);
        }
    }
#endif
    if (shmBase == (void*)-1 || !shmBase) {
#ifdef QT_SHM_DEBUG
        perror("QWSSharedMemory::attach():");
        qWarning("Error attaching to shared memory id %d", shmId);
#endif
        detach();
        return false;
    }

    return true;
}

create()

bool QWSSharedMemory::create

(

int

size

)

Definition at line 88 of file qwssharedmemory.cpp.

Referenced by QWSSharedMemSurface::setGeometry().

{
    if (shmId != -1)
        detach();

#ifndef QT_POSIX_IPC
    shmId = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
#else
    // ### generate really unique IDs
    shmId = (getpid() << 16) + (localUniqueId.fetchAndAddRelaxed(1) % ushort(-1));
    QByteArray shmName = makeKey(shmId);
    EINTR_LOOP(hand, shm_open(shmName.constData(), O_RDWR | O_CREAT, 0660));
    if (hand != -1) {
        // the size may only be set once; ignore errors
        int ret;
        EINTR_LOOP(ret, ftruncate(hand, size));
        if (ret == -1)
            shmId = -1;
    } else {
        shmId = -1;
    }
#endif
    if (shmId == -1) {
#ifdef QT_SHM_DEBUG
        perror("QWSSharedMemory::create():");
        qWarning("Error allocating shared memory of size %d", size);
#endif
        detach();
        return false;
    }

#ifndef QT_POSIX_IPC
    shmBase = shmat(shmId, 0, 0);
    // On Linux, it is possible to attach a shared memory segment even if it
    // is already marked to be deleted. However, POSIX.1-2001 does not specify
    // this behaviour and many other implementations do not support it.
    shmctl(shmId, IPC_RMID, 0);
#else
    // grab the size
    QT_STATBUF st;
    if (QT_FSTAT(hand, &st) != -1) {
        shmSize = st.st_size;
        // grab the memory
        shmBase = mmap(0, shmSize, PROT_READ | PROT_WRITE, MAP_SHARED, hand, 0);
    }
#endif
    if (shmBase == (void*)-1 || !shmBase) {
#ifdef QT_SHM_DEBUG
        perror("QWSSharedMemory::create():");
        qWarning("Error attaching to shared memory id %d", shmId);
#endif
        detach();
        return false;
    }

    return true;
}

detach()

void QWSSharedMemory::detach

(

)

Definition at line 184 of file qwssharedmemory.cpp.

Referenced by attach(), create(), QWSSharedMemSurface::releaseSurface(), QWSSharedMemSurface::setGeometry(), QWSSharedMemSurface::setMemory(), and ~QWSSharedMemory().

{
#ifndef QT_POSIX_IPC
    if (shmBase && shmBase != (void*)-1)
        shmdt(shmBase);
#else
    if (shmBase && shmBase != (void*)-1)
        munmap(shmBase, shmSize);
    if (hand > 0) {
        // get the number of current attachments
        int shm_nattch = 0;
        QT_STATBUF st;
        if (QT_FSTAT(hand, &st) == 0) {
            // subtract 2 from linkcount: one for our own open and one for the dir entry
            shm_nattch = st.st_nlink - 2;
        }
        qt_safe_close(hand);
        // if there are no attachments then unlink the shared memory
        if (shm_nattch == 0) {
            QByteArray shmName = makeKey(shmId);
            shm_unlink(shmName.constData());
        }
    }
#endif
    shmBase = 0;
    shmSize = 0;
    shmId = -1;
}

id()

int QWSSharedMemory::id ( ) const

inline

Definition at line 72 of file qwssharedmemory_p.h.

Referenced by attach(), QWSSharedMemSurface::permanentState(), and QWSSharedMemSurface::setMemory().

{ return shmId; }

size()

int QWSSharedMemory::size

(

)

const

Definition at line 213 of file qwssharedmemory.cpp.

Referenced by address(), and QWSSharedMemSurface::setGeometry().

{
    if (shmId == -1)
        return 0;

#ifndef QT_POSIX_IPC
    if (!shmSize) {
        struct shmid_ds shm;
        shmctl(shmId, IPC_STAT, &shm);
        shmSize = shm.shm_segsz;
    }
#endif

    return shmSize;
}

Properties

shmBase

void* QWSSharedMemory::shmBase

private

Definition at line 79 of file qwssharedmemory_p.h.

Referenced by address(), attach(), create(), and detach().

shmId

int QWSSharedMemory::shmId

private

Definition at line 78 of file qwssharedmemory_p.h.

Referenced by attach(), create(), detach(), id(), and size().

shmSize

int QWSSharedMemory::shmSize

mutableprivate

Definition at line 80 of file qwssharedmemory_p.h.

Referenced by attach(), create(), detach(), and size().

---

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

• /src/gui/embedded/qwssharedmemory_p.h
• /src/gui/embedded/qwssharedmemory.cpp