/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_DATA_CACHE_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_DATA_CACHE_H_

#include "third_party/blink/renderer/platform/fonts/font_platform_data.h"
#include "third_party/blink/renderer/platform/fonts/simple_font_data.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_map.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_linked_hash_set.h"

namespace blink {

struct FontDataCacheKeyHashTraits : GenericHashTraits<const FontPlatformData*> {
  STATIC_ONLY(FontDataCacheKeyHashTraits);
  static unsigned GetHash(const FontPlatformData* platform_data) {
    return platform_data->GetHash();
  }

  static bool Equal(const FontPlatformData* a, const FontPlatformData* b) {
    return *a == *b;
  }

  static constexpr bool kSafeToCompareToEmptyOrDeleted = false;
};

class FontDataCache final {
  DISALLOW_NEW();

 public:
  FontDataCache() = default;
  FontDataCache(const FontDataCache&) = delete;
  FontDataCache& operator=(const FontDataCache&) = delete;

  void Trace(Visitor* visitor) const {
    visitor->Trace(cache_);
    visitor->Trace(strong_reference_lru_);
  }

  const SimpleFontData* Get(const FontPlatformData*,
                            bool subpixel_ascent_descent = false);
  void Clear() {
    cache_.clear();
    strong_reference_lru_.clear();
  }

 private:
  HeapHashMap<Member<const FontPlatformData>,
              WeakMember<const SimpleFontData>,
              FontDataCacheKeyHashTraits>
      cache_;

  // The above `cache_` is weak, meaning its entries will potentially be
  // cleared if no other references exist.
  // This LRU keeps a small (limited) number of strong references alive so they
  // won't be cleared in the above cache for performance reasons.
  HeapLinkedHashSet<Member<const SimpleFontData>> strong_reference_lru_;
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_DATA_CACHE_H_