VMS/C_Libraries/Queue_impl: PrivateQueue.c comparison

added pushPrivQ -- treats Q as stack, pushed elem is first out

comparison

equal deleted inserted replaced

-:ae4ea439d8dd
+:9a6475f2cbc9
 }
 //Q is full
 return FALSE;
 }
+/*Treats queue as a stack -- no matter contents, if read done right after
+* a push, then the pushed item is what comes out.
+* Expands the queue size automatically when it's full.
+*/
+void
+pushPrivQ( void * in, PrivQueueStruc* Q )
+{
+void **startOfData = Q->startOfData;
+void **endOfData   = Q->endOfData;
+void **insertPos  = Q->insertPos;
+void **extractPos = Q->extractPos;
+tryAgain:
+//Full? (insert is just below extract when full)
+if( extractPos - insertPos != 1 &&
+!(insertPos == endOfData && extractPos == startOfData))
+{    //insert -- but go backwards, inserting at read position then
+// move read pos backwards
+*(Q->extractPos) = in;
+if( extractPos == startOfData ) //write new pos exactly once, correctly
+{ Q->extractPos = endOfData;   //can't overrun then fix it 'cause
+}                              // other thread might read bad pos
+else
+{ Q->extractPos--;
+}
+return;
+}
+//Q is full
+enlargePrivQ( Q );
+goto tryAgain;
+}
 void
 freePrivQ( PrivQueueStruc *Q )
 {
 VMS__free( Q->startOfData );
 VMS__free( Q );

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