1 /*

     2  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.

     3  *

     4  * Redistribution and use in source and binary forms, with or without

     5  * modification, are permitted provided that the following conditions

     6  * are met:

     7  *

     8  * 1.  Redistributions of source code must retain the above copyright

     9  *     notice, this list of conditions and the following disclaimer. 

    10  * 2.  Redistributions in binary form must reproduce the above copyright

    11  *     notice, this list of conditions and the following disclaimer in the

    12  *     documentation and/or other materials provided with the distribution. 

    13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

    14  *     its contributors may be used to endorse or promote products derived

    15  *     from this software without specific prior written permission. 

    16  *

    17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

    18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

    19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

    20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

    21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

    22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

    23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

    24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

    25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

    26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    27  */

    28 

    29 #include "config.h"

    30 #include "WorkQueue.h"

    31 

    32 #include "WorkQueueItem.h"

    33 #include <wtf/Assertions.h>

    34 

    35 static const unsigned queueLength = 1024;

    36 

    37 static WorkQueueItem* theQueue[queueLength];

    38 static unsigned startOfQueue;

    39 static unsigned endOfQueue;

    40 

    41 WorkQueue* WorkQueue::shared()

    42 {

    43     static WorkQueue* sharedInstance = new WorkQueue;

    44     return sharedInstance;

    45 }

    46 

    47 WorkQueue::WorkQueue()

    48     : m_frozen(false)

    49 {

    50 }

    51 

    52 void WorkQueue::queue(WorkQueueItem* item)

    53 {

    54     ASSERT(endOfQueue < queueLength);

    55     ASSERT(endOfQueue >= startOfQueue);

    56 

    57     if (m_frozen) {

    58         delete item;

    59         return;

    60     }

    61 

    62     theQueue[endOfQueue++] = item;

    63 }

    64 

    65 WorkQueueItem* WorkQueue::dequeue()

    66 {

    67     ASSERT(endOfQueue >= startOfQueue);

    68 

    69     if (startOfQueue == endOfQueue)

    70         return 0;

    71 

    72     return theQueue[startOfQueue++];

    73 }

    74 

    75 unsigned WorkQueue::count()

    76 {

    77     return endOfQueue - startOfQueue;

    78 }

    79 

    80 void WorkQueue::clear()

    81 {

    82     for (unsigned i = startOfQueue; i < endOfQueue; ++i) {

    83         delete theQueue[i];

    84         theQueue[i] = 0;

    85     }

    86 

    87     startOfQueue = 0;

    88     endOfQueue = 0;

    89 }

    90 

    91 bool WorkQueue::processWork()

    92 {

    93     bool startedLoad = false;

    94 

    95     while (!startedLoad && count()) {

    96         WorkQueueItem* item = dequeue();

    97         ASSERT(item);

    98         startedLoad = item->invoke();

    99         delete item;

   100     }

   101 

   102     // If we're done and we didn't start a load, then we're really done, so return true.

   103     return !startedLoad;

   104 }