refactoring of the QWSSharedMemory class

drop old/unused API and obsolete code;
improve attach() for comon case;
cache the shm size at the first call;
fix the includes;
better debug strings;
minor code clean-ups

Merge-request: 1247
Reviewed-by: Harald Fernengel <harald.fernengel@nokia.com>

2 files changed, 47 insertions, 107 deletions

diff --git a/src/gui/embedded/qwssharedmemory.cpp b/src/gui/embedded/qwssharedmemory.cpp
index 66bedee..a677626 100644
--- a/src/gui/embedded/qwssharedmemory.cpp
+++ b/src/gui/embedded/qwssharedmemory.cpp
@@ -43,51 +43,51 @@
 
 #if !defined(QT_NO_QWS_MULTIPROCESS)
 
+#include <sys/types.h>
+#include <sys/ipc.h>
 #include <sys/shm.h>
 
+//#define QT_SHM_DEBUG
+
 QT_BEGIN_NAMESPACE
 
 QWSSharedMemory::QWSSharedMemory()
-    : shmBase(0), shmSize(0), character(0),  shmId(-1), key(-1)
+    : shmId(-1), shmBase(0), shmSize(0)
 {
 }
 
-
 QWSSharedMemory::~QWSSharedMemory()
 {
     detach();
 }
 
-/*
-  man page says:
-    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  spec-
-    ify this behaviour and many other implementations do not support it.
-*/
-
 bool QWSSharedMemory::create(int size)
 {
     if (shmId != -1)
         detach();
-    shmId = shmget(IPC_PRIVATE, size, IPC_CREAT|0600);
 
+    shmId = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
     if (shmId == -1) {
 #ifdef QT_SHM_DEBUG
-        perror("QWSSharedMemory::create allocating shared memory");
+        perror("QWSSharedMemory::create():");
         qWarning("Error allocating shared memory of size %d", size);
 #endif
         return false;
     }
-    shmBase = shmat(shmId,0,0);
+    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);
-    if (shmBase == (void*)-1) {
+    if (shmBase == (void*)-1 || !shmBase) {
 #ifdef QT_SHM_DEBUG
-        perror("QWSSharedMemory::create attaching to shared memory");
+        perror("QWSSharedMemory::create():");
         qWarning("Error attaching to shared memory id %d", shmId);
 #endif
-        shmBase = 0;
+        detach();
         return false;
     }
+
     return true;
 }
 
@@ -95,91 +95,49 @@ bool QWSSharedMemory::attach(int id)
 {
     if (shmId == id)
         return id != -1;
-    if (shmId != -1)
-        detach();
 
-    shmBase = shmat(id,0,0);
-    if (shmBase == (void*)-1) {
+    detach();
+
+    if (id == -1)
+        return false;
+
+    shmId = id;
+    shmBase = shmat(shmId, 0, 0);
+    if (shmBase == (void*)-1 || !shmBase) {
 #ifdef QT_SHM_DEBUG
-        perror("QWSSharedMemory::attach attaching to shared memory");
-        qWarning("Error attaching to shared memory 0x%x of size %d",
-                 id, size());
+        perror("QWSSharedMemory::attach():");
+        qWarning("Error attaching to shared memory id %d", shmId);
 #endif
-        shmBase = 0;
+        detach();
         return false;
     }
-    shmId = id;
+
     return true;
 }
 
-
-void QWSSharedMemory::detach ()
+void QWSSharedMemory::detach()
 {
-    if (!shmBase)
-        return;
-    shmdt (shmBase);
+    if (shmBase && shmBase != (void*)-1)
+        shmdt(shmBase);
     shmBase = 0;
     shmSize = 0;
     shmId = -1;
 }
 
-void QWSSharedMemory::setPermissions (mode_t mode)
+int QWSSharedMemory::size() const
 {
-  struct shmid_ds shm;
-  shmctl (shmId, IPC_STAT, &shm);
-  shm.shm_perm.mode = mode;
-  shmctl (shmId, IPC_SET, &shm);
-}
-
-int QWSSharedMemory::size () const
-{
-    struct shmid_ds shm;
-    shmctl (shmId, IPC_STAT, &shm);
-    return shm.shm_segsz;
-}
+    if (shmId == -1)
+        return 0;
 
+    if (!shmSize) {
+        struct shmid_ds shm;
+        shmctl(shmId, IPC_STAT, &shm);
+        const_cast<QWSSharedMemory *>(this)->shmSize = shm.shm_segsz;
+    }
 
-// old API
-
-
-
-QWSSharedMemory::QWSSharedMemory (int size, const QString &filename, char c)
-{
-  shmSize = size;
-  shmFile = filename;
-  shmBase = 0;
-  shmId = -1;
-  character = c;
-  key = ftok (shmFile.toLatin1().constData(), c);
-}
-
-
-
-bool QWSSharedMemory::create ()
-{
-  shmId = shmget (key, shmSize, IPC_CREAT | 0666);
-  return (shmId != -1);
-}
-
-void QWSSharedMemory::destroy ()
-{
-    if (shmId != -1)
-        shmctl(shmId, IPC_RMID, 0);
-}
-
-bool QWSSharedMemory::attach ()
-{
-  if (shmId == -1)
-    shmId = shmget (key, shmSize, 0);
-
-  shmBase = shmat (shmId, 0, 0);
-  if ((long)shmBase == -1)
-      shmBase = 0;
-
-  return (long)shmBase != 0;
+    return shmSize;
 }
 
-
 QT_END_NAMESPACE
 
 #endif // QT_NO_QWS_MULTIPROCESS
diff --git a/src/gui/embedded/qwssharedmemory_p.h b/src/gui/embedded/qwssharedmemory_p.h
index 31e69c4..f3ce241 100644
--- a/src/gui/embedded/qwssharedmemory_p.h
+++ b/src/gui/embedded/qwssharedmemory_p.h
@@ -53,49 +53,31 @@
 // We mean it.
 //
 
-#include "qplatformdefs.h"
-#include "QtCore/qstring.h"
+#include <qplatformdefs.h>
 
 QT_BEGIN_NAMESPACE
 
 #if !defined(QT_NO_QWS_MULTIPROCESS)
 
-class QWSSharedMemory {
+class QWSSharedMemory
+{
 public:
-
     QWSSharedMemory();
     ~QWSSharedMemory();
 
-    void setPermissions(mode_t mode);
-    int size() const;
-    void *address() { return shmBase; }
-
-    int id() const { return shmId; }
-
-    void detach();
-
     bool create(int size);
     bool attach(int id);
+    void detach();
 
-    //bool create(int size, const QString &filename, char c = 'Q');
-    //bool attach(const QString &filename, char c = 'Q');
-// old API
-
-    QWSSharedMemory(int, const QString &, char c = 'Q');
-    void * base() { return address(); }
-
-    bool create();
-    void destroy();
+    int id() const { return shmId; }
 
-    bool attach();
+    void *address() const { return shmBase; }
+    int size() const;
 
 private:
+    int shmId;
     void *shmBase;
     int shmSize;
-    QString shmFile;
-    char character;
-    int shmId;
-    key_t key;
 };
 
 #endif // QT_NO_QWS_MULTIPROCESS