third_party/WebKit/Source/platform/fonts/FontDataCache.h

   1 /*
   2  * Copyright (C) 2013 Google 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 are
   6  * met:
   7  *
   8  *     * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *     * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  *     * Neither the name of Google Inc. nor the names of its
  15  * contributors may be used to endorse or promote products derived from
  16  * this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #ifndef FontDataCache_h
  32 #define FontDataCache_h
  33
  34 #include "platform/fonts/FontCache.h"
  35 #include "platform/fonts/FontPlatformData.h"
  36 #include "wtf/HashMap.h"
  37 #include "wtf/ListHashSet.h"
  38
  39 namespace blink {
  40
  41 class SimpleFontData;
  42
  43 struct FontDataCacheKeyHash {
  44     static unsigned hash(const FontPlatformData& platformData)
  45     {
  46         return platformData.hash();
  47     }
  48
  49     static bool equal(const FontPlatformData& a, const FontPlatformData& b)
  50     {
  51         return a == b;
  52     }
  53
  54     static const bool safeToCompareToEmptyOrDeleted = true;
  55 };
  56
  57 struct FontDataCacheKeyTraits : WTF::GenericHashTraits<FontPlatformData> {
  58     static const bool emptyValueIsZero = true;
  59     static const FontPlatformData& emptyValue()
  60     {
  61         DEFINE_STATIC_LOCAL(FontPlatformData, key, (0.f, false, false));
  62         return key;
  63     }
  64     static void constructDeletedValue(FontPlatformData& slot, bool)
  65     {
  66         new (NotNull, &slot) FontPlatformData(WTF::HashTableDeletedValue);
  67     }
  68     static bool isDeletedValue(const FontPlatformData& value)
  69     {
  70         return value.isHashTableDeletedValue();
  71     }
  72 };
  73
  74 class FontDataCache {
  75 public:
  76     PassRefPtr<SimpleFontData> get(const FontPlatformData*, ShouldRetain = Retain);
  77     bool contains(const FontPlatformData*) const;
  78     void release(const SimpleFontData*);
  79
  80     // This is used by FontVerticalDataCache to mark all items with vertical data
  81     // that are currently in cache as "in cache", which is later used to sweep the FontVerticalDataCache.
  82     void markAllVerticalData();
  83
  84     // Purges items in FontDataCache according to provided severity.
  85     // Returns true if any removal of cache items actually occurred.
  86     bool purge(PurgeSeverity);
  87
  88 private:
  89     bool purgeLeastRecentlyUsed(int count);
  90
  91     typedef HashMap<FontPlatformData, pair<RefPtr<SimpleFontData>, unsigned>, FontDataCacheKeyHash, FontDataCacheKeyTraits> Cache;
  92     Cache m_cache;
  93     ListHashSet<RefPtr<SimpleFontData>> m_inactiveFontData;
  94 };
  95
  96 } // namespace blink
  97
  98 #endif