A priority message queue. We will use it to handle system notifications faster than client requests.

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@2642 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/registrar/PriorityMessageQueue.cpp

@@ -0,0 +1,130 @@
+//----------------------------------------------------------------------
+//  This software is part of the OpenBeOS distribution and is covered 
+//  by the OpenBeOS license.
+//---------------------------------------------------------------------
+
+#include <Message.h>
+
+#include "PriorityMessageQueue.h"
+
+// MessageInfo
+class PriorityMessageQueue::MessageInfo {
+public:
+	MessageInfo(BMessage *message, int32 priority)
+		: fMessage(message),
+		  fPriority(priority)
+	{
+	}
+
+	BMessage *Message() const	{ return fMessage; }
+	int32 Priority() const		{ return fPriority; }
+
+private:
+	BMessage	*fMessage;
+	int32		fPriority;
+};
+
+
+// constructor
+PriorityMessageQueue::PriorityMessageQueue()
+	: fLock(),
+	  fMessages(20, true)
+{
+}
+
+// destructor
+PriorityMessageQueue::~PriorityMessageQueue()
+{
+	// delete the messages
+	for (int32 i = 0; MessageInfo *info = fMessages.ItemAt(i); i++)
+		delete info->Message();
+	// the infos are deleted automatically
+}
+
+// Lock
+bool
+PriorityMessageQueue::Lock()
+{
+	return fLock.Lock();
+}
+
+// Unlock
+void
+PriorityMessageQueue::Unlock()
+{
+	fLock.Unlock();
+}
+
+// PushMessage
+bool
+PriorityMessageQueue::PushMessage(BMessage *message, int32 priority)
+{
+	bool result = (message);
+	if (result)
+		result = Lock();
+	if (result) {
+		if (MessageInfo *info = new MessageInfo(message, priority)) {
+			// find the insertion index
+			int32 index = _FindInsertionIndex(priority);
+			if (!fMessages.AddItem(info, index)) {
+				result = false;
+				delete info;
+			}
+		} else	// no memory
+			result = false;
+		Unlock();
+	}
+	return result;
+}
+
+// PopMessage
+BMessage *
+PriorityMessageQueue::PopMessage()
+{
+	BMessage *result = NULL;
+	if (Lock()) {
+		if (MessageInfo *info = fMessages.RemoveItemAt(0)) {
+			result = info->Message();
+			delete info;
+		}
+		Unlock();
+	}
+	return result;
+}
+
+// CountMessages
+int32
+PriorityMessageQueue::CountMessages() const
+{
+	int32 result = 0;
+	if (fLock.Lock()) {
+		result = fMessages.CountItems();
+		fLock.Unlock();
+	}
+	return result;
+}
+
+// IsEmpty
+bool
+PriorityMessageQueue::IsEmpty() const
+{
+	return (CountMessages() == 0);
+}
+
+// _FindInsertionIndex
+int32
+PriorityMessageQueue::_FindInsertionIndex(int32 priority)
+{
+	int32 lower = 0;
+	int32 upper = fMessages.CountItems();
+	while (lower < upper) {
+		int32 mid = (lower + upper) / 2;
+		MessageInfo *info = fMessages.ItemAt(mid);
+		if (info->Priority() >= priority)
+			lower = mid + 1;
+		else
+			upper = mid;
+	}
+	return lower;
+}
+

src/servers/registrar/PriorityMessageQueue.h

@@ -0,0 +1,39 @@
+//----------------------------------------------------------------------
+//  This software is part of the OpenBeOS distribution and is covered 
+//  by the OpenBeOS license.
+//---------------------------------------------------------------------
+
+#ifndef PRIORITY_MESSAGE_QUEUE_H
+#define PRIORITY_MESSAGE_QUEUE_H
+
+#include <Locker.h>
+#include <ObjectList.h>
+
+class BMessage;
+
+class PriorityMessageQueue {
+public:
+	PriorityMessageQueue();
+	~PriorityMessageQueue();
+
+	bool Lock();
+	void Unlock();
+
+	bool PushMessage(BMessage *message, int32 priority = 0);
+	BMessage *PopMessage();
+
+	int32 CountMessages() const;
+	bool IsEmpty() const;
+
+private:
+	int32 _FindInsertionIndex(int32 priority);
+
+private:
+	class MessageInfo;
+
+private:
+	mutable BLocker				fLock;
+	BObjectList<MessageInfo>	fMessages;
+};
+
+#endif	// PRIORITY_MESSAGE_QUEUE_H