chromium/src/third_party/blink/renderer/platform/fonts/fallback_list_composite_key.h

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FALLBACK_LIST_COMPOSITE_KEY_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FALLBACK_LIST_COMPOSITE_KEY_H_

#include "third_party/blink/renderer/platform/fonts/font_cache_key.h"
#include "third_party/blink/renderer/platform/fonts/font_description.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/hash_map.h"
#include "third_party/blink/renderer/platform/wtf/hash_table_deleted_value_type.h"

namespace blink {

class FontDescription;

// Cache key representing a font description and font fallback list combination
// as passed into shaping. Used to look up an applicable ShapeCache instance
// from the global FontCache.
// TODO(eae,drott): Ideally this should be replaced by a combination of
// FontDescription and CSSFontSelector.
struct FallbackListCompositeKey {
  DISALLOW_NEW();

 public:
  FallbackListCompositeKey(const FontDescription& font_description)
      : hash_(font_description.StyleHashWithoutFamilyList() << 1),
        computed_size_(font_description.ComputedSize()),
        letter_spacing_(font_description.LetterSpacing()),
        word_spacing_(font_description.WordSpacing()),
        bitmap_fields_(font_description.BitmapFields()),
        auxiliary_bitmap_fields_(font_description.AuxiliaryBitmapFields()) {}
  FallbackListCompositeKey()
      : hash_(0),
        computed_size_(0),
        letter_spacing_(0),
        word_spacing_(0),
        bitmap_fields_(0),
        auxiliary_bitmap_fields_(0) {}
  FallbackListCompositeKey(WTF::HashTableDeletedValueType)
      : hash_(kDeletedValueHash),
        computed_size_(0),
        letter_spacing_(0),
        word_spacing_(0),
        bitmap_fields_(0),
        auxiliary_bitmap_fields_(0) {}

  void Add(FontCacheKey key) {
    font_cache_keys_.push_back(key);
    // Djb2 with the first bit reserved for deleted.
    hash_ = (((hash_ << 5) + hash_) + key.GetHash()) << 1;
  }

  unsigned GetHash() const { return hash_; }

  bool operator==(const FallbackListCompositeKey& other) const {
    return hash_ == other.hash_ && computed_size_ == other.computed_size_ &&
           letter_spacing_ == other.letter_spacing_ &&
           word_spacing_ == other.word_spacing_ &&
           bitmap_fields_ == other.bitmap_fields_ &&
           auxiliary_bitmap_fields_ == other.auxiliary_bitmap_fields_ &&
           font_cache_keys_ == other.font_cache_keys_;
  }

  bool IsHashTableDeletedValue() const { return hash_ == kDeletedValueHash; }

 private:
  static const unsigned kDeletedValueHash = 1;
  Vector<FontCacheKey> font_cache_keys_;
  unsigned hash_;

  float computed_size_;
  float letter_spacing_;
  float word_spacing_;
  unsigned bitmap_fields_;
  unsigned auxiliary_bitmap_fields_;
};

struct FallbackListCompositeKeyHash {
  STATIC_ONLY(FallbackListCompositeKeyHash);
  static unsigned GetHash(const FallbackListCompositeKey& key) {
    return key.GetHash();
  }

  static bool Equal(const FallbackListCompositeKey& a,
                    const FallbackListCompositeKey& b) {
    return a == b;
  }

  static const bool safe_to_compare_to_empty_or_deleted = false;
};

struct FallbackListCompositeKeyTraits
    : WTF::SimpleClassHashTraits<FallbackListCompositeKey> {
  STATIC_ONLY(FallbackListCompositeKeyTraits);
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FALLBACK_LIST_COMPOSITE_KEY_H_