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

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#ifndef FontDataCache_h
#define FontDataCache_h

#include "platform/fonts/FontCache.h"
#include "platform/fonts/FontPlatformData.h"
#include "wtf/HashMap.h"
#include "wtf/ListHashSet.h"

namespace blink {

class SimpleFontData;

struct FontDataCacheKeyHash {
  STATIC_ONLY(FontDataCacheKeyHash);
  static unsigned hash(const FontPlatformData* platformData) {
    return platformData->hash();
  }

  static bool equal(const FontPlatformData* a, const FontPlatformData* b) {
    const FontPlatformData* emptyValue =
        reinterpret_cast<FontPlatformData*>(-1);

    if (a == emptyValue)
      return b == emptyValue;
    if (b == emptyValue)
      return a == emptyValue;

    if (!a || !b)
      return a == b;

    CHECK(a && b);

    return *a == *b;
  }

  static const bool safeToCompareToEmptyOrDeleted = true;
};

class FontDataCache {
  USING_FAST_MALLOC(FontDataCache);
  WTF_MAKE_NONCOPYABLE(FontDataCache);

 public:
  FontDataCache() {}

  PassRefPtr<SimpleFontData> get(const FontPlatformData*,
                                 ShouldRetain = Retain);
  bool contains(const FontPlatformData*) const;
  void release(const SimpleFontData*);

  // This is used by FontVerticalDataCache to mark all items with vertical data
  // that are currently in cache as "in cache", which is later used to sweep the
  // FontVerticalDataCache.
  void markAllVerticalData();

  // Purges items in FontDataCache according to provided severity.
  // Returns true if any removal of cache items actually occurred.
  bool purge(PurgeSeverity);

 private:
  bool purgeLeastRecentlyUsed(int count);

  typedef HashMap<const FontPlatformData*,
                  std::pair<RefPtr<SimpleFontData>, unsigned>,
                  FontDataCacheKeyHash>
      Cache;
  Cache m_cache;
  ListHashSet<RefPtr<SimpleFontData>> m_inactiveFontData;
};

}  // namespace blink

#endif