runtime/DateInstanceCache.h

   1 /*
   2  * Copyright (C) 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  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DateInstanceCache_h
  27 #define DateInstanceCache_h
  28
  29 #include <wtf/DateMath.h>
  30 #include <wtf/HashFunctions.h>
  31 #include <wtf/PassRefPtr.h>
  32 #include <wtf/RefCounted.h>
  33
  34 namespace JSC {
  35
  36     extern const double NaN;
  37
  38     class DateInstanceData : public RefCounted<DateInstanceData> {
  39     public:
  40         static PassRefPtr<DateInstanceData> create() { return adoptRef(new DateInstanceData); }
  41
  42         double m_gregorianDateTimeCachedForMS;
  43         GregorianDateTime m_cachedGregorianDateTime;
  44         double m_gregorianDateTimeUTCCachedForMS;
  45         GregorianDateTime m_cachedGregorianDateTimeUTC;
  46
  47     private:
  48         DateInstanceData()
  49             : m_gregorianDateTimeCachedForMS(NaN)
  50             , m_gregorianDateTimeUTCCachedForMS(NaN)
  51         {
  52         }
  53     };
  54
  55     class DateInstanceCache {
  56     public:
  57         DateInstanceCache()
  58         {
  59             reset();
  60         }
  61
  62         void reset()
  63         {
  64             for (size_t i = 0; i < cacheSize; ++i)
  65                 m_cache[i].key = NaN;
  66         }
  67
  68         DateInstanceData* add(double d)
  69         {
  70             CacheEntry& entry = lookup(d);
  71             if (d == entry.key)
  72                 return entry.value.get();
  73
  74             entry.key = d;
  75             entry.value = DateInstanceData::create();
  76             return entry.value.get();
  77         }
  78
  79     private:
  80         static const size_t cacheSize = 16;
  81
  82         struct CacheEntry {
  83             double key;
  84             RefPtr<DateInstanceData> value;
  85         };
  86
  87         CacheEntry& lookup(double d) { return m_cache[WTF::FloatHash<double>::hash(d) & (cacheSize - 1)]; }
  88
  89         CacheEntry m_cache[cacheSize];
  90     };
  91
  92 } // namespace JSC
  93
  94 #endif // DateInstanceCache_h