src/servers/registrar/PriorityMessageQueue.cpp

   1 //----------------------------------------------------------------------
   2 //  This software is part of the OpenBeOS distribution and is covered
   3 //  by the MIT License.
   4 //---------------------------------------------------------------------
   5
   6 #include <Message.h>
   7
   8 #include "PriorityMessageQueue.h"
   9
  10 // MessageInfo
  11 class PriorityMessageQueue::MessageInfo {
  12 public:
  13         MessageInfo(BMessage *message, int32 priority)
  14                 : fMessage(message),
  15                   fPriority(priority)
  16         {
  17         }
  18
  19         BMessage *Message() const       { return fMessage; }
  20         int32 Priority() const          { return fPriority; }
  21
  22 private:
  23         BMessage        *fMessage;
  24         int32           fPriority;
  25 };
  26
  27
  28 // constructor
  29 PriorityMessageQueue::PriorityMessageQueue()
  30         : fLock(),
  31           fMessages(20, true)
  32 {
  33 }
  34
  35 // destructor
  36 PriorityMessageQueue::~PriorityMessageQueue()
  37 {
  38         // delete the messages
  39         for (int32 i = 0; MessageInfo *info = fMessages.ItemAt(i); i++)
  40                 delete info->Message();
  41         // the infos are deleted automatically
  42 }
  43
  44 // Lock
  45 bool
  46 PriorityMessageQueue::Lock()
  47 {
  48         return fLock.Lock();
  49 }
  50
  51 // Unlock
  52 void
  53 PriorityMessageQueue::Unlock()
  54 {
  55         fLock.Unlock();
  56 }
  57
  58 // PushMessage
  59 bool
  60 PriorityMessageQueue::PushMessage(BMessage *message, int32 priority)
  61 {
  62         bool result = (message);
  63         if (result)
  64                 result = Lock();
  65         if (result) {
  66                 if (MessageInfo *info = new MessageInfo(message, priority)) {
  67                         // find the insertion index
  68                         int32 index = _FindInsertionIndex(priority);
  69                         if (!fMessages.AddItem(info, index)) {
  70                                 result = false;
  71                                 delete info;
  72                         }
  73                 } else  // no memory
  74                         result = false;
  75                 Unlock();
  76         }
  77         return result;
  78 }
  79
  80 // PopMessage
  81 BMessage *
  82 PriorityMessageQueue::PopMessage()
  83 {
  84         BMessage *result = NULL;
  85         if (Lock()) {
  86                 if (MessageInfo *info = fMessages.RemoveItemAt(0)) {
  87                         result = info->Message();
  88                         delete info;
  89                 }
  90                 Unlock();
  91         }
  92         return result;
  93 }
  94
  95 // CountMessages
  96 int32
  97 PriorityMessageQueue::CountMessages() const
  98 {
  99         int32 result = 0;
 100         if (fLock.Lock()) {
 101                 result = fMessages.CountItems();
 102                 fLock.Unlock();
 103         }
 104         return result;
 105 }
 106
 107 // IsEmpty
 108 bool
 109 PriorityMessageQueue::IsEmpty() const
 110 {
 111         return (CountMessages() == 0);
 112 }
 113
 114 // _FindInsertionIndex
 115 int32
 116 PriorityMessageQueue::_FindInsertionIndex(int32 priority)
 117 {
 118         int32 lower = 0;
 119         int32 upper = fMessages.CountItems();
 120         while (lower < upper) {
 121                 int32 mid = (lower + upper) / 2;
 122                 MessageInfo *info = fMessages.ItemAt(mid);
 123                 if (info->Priority() >= priority)
 124                         lower = mid + 1;
 125                 else
 126                         upper = mid;
 127         }
 128         return lower;
 129 }
 130