Added sharedPage::exists() call

lib/shared_memory.cpp

@@ -348,6 +348,18 @@ namespace IPC {
     close();
   }
 
+  /// Returns true if the open file still exists.
+  /// Not implemented under Windows.
+  bool sharedPage::exists(){
+#ifdef SHM_ENABLED
+    struct stat sb;
+    if (fstat(handle, &sb)){return false;}
+    return (sb.st_nlink > 0);
+#else
+    return true;
+#endif
+  }
+
 #ifdef SHM_ENABLED
   ///\brief Unmaps a shared page if allowed
   void sharedPage::unmap() {

lib/shared_memory.h

@@ -109,6 +109,7 @@ namespace IPC {
       bool operator < (const sharedFile & rhs) const {
         return name < rhs.name;
       }
+      bool exists(){return true;}
       void close();
       void unmap();
       ///\brief The fd handle of the opened shared file
@@ -143,6 +144,7 @@ namespace IPC {
     }
     void unmap();
     void close();
+    bool exists();
     #if defined(__CYGWIN__) || defined(_WIN32)
     ///\brief The handle of the opened shared memory page
     HANDLE handle;