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

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. 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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 */

#ifndef FontCacheKey_h
#define FontCacheKey_h

#include "FontFaceCreationParams.h"
#include "platform/fonts/opentype/FontSettings.h"
#include "wtf/Allocator.h"
#include "wtf/HashMap.h"
#include "wtf/HashTableDeletedValueType.h"
#include "wtf/text/AtomicStringHash.h"
#include "wtf/text/StringHash.h"

namespace blink {

// Multiplying the floating point size by 100 gives two decimal point
// precision which should be sufficient.
static const unsigned s_fontSizePrecisionMultiplier = 100;

struct FontCacheKey {
  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();

 public:
  FontCacheKey() : m_creationParams(), m_fontSize(0), m_options(0) {}
  FontCacheKey(FontFaceCreationParams creationParams,
               float fontSize,
               unsigned options,
               PassRefPtr<FontVariationSettings> variationSettings)
      : m_creationParams(creationParams),
        m_fontSize(fontSize * s_fontSizePrecisionMultiplier),
        m_options(options),
        m_variationSettings(variationSettings) {}

  FontCacheKey(WTF::HashTableDeletedValueType)
      : m_fontSize(hashTableDeletedSize()) {}

  unsigned hash() const {
    unsigned hashCodes[4] = {
        m_creationParams.hash(), m_fontSize, m_options,
        m_variationSettings ? m_variationSettings->hash() : 0};
    return StringHasher::hashMemory<sizeof(hashCodes)>(hashCodes);
  }

  bool operator==(const FontCacheKey& other) const {
    return m_creationParams == other.m_creationParams &&
           m_fontSize == other.m_fontSize && m_options == other.m_options &&
           m_variationSettings == other.m_variationSettings;
  }

  bool isHashTableDeletedValue() const {
    return m_fontSize == hashTableDeletedSize();
  }

  static unsigned precisionMultiplier() {
    return s_fontSizePrecisionMultiplier;
  }

  void clearFontSize() { m_fontSize = 0; }

 private:
  static unsigned hashTableDeletedSize() { return 0xFFFFFFFFU; }

  FontFaceCreationParams m_creationParams;
  unsigned m_fontSize;
  unsigned m_options;
  RefPtr<FontVariationSettings> m_variationSettings;
};

struct FontCacheKeyHash {
  STATIC_ONLY(FontCacheKeyHash);
  static unsigned hash(const FontCacheKey& key) { return key.hash(); }

  static bool equal(const FontCacheKey& a, const FontCacheKey& b) {
    return a == b;
  }

  static const bool safeToCompareToEmptyOrDeleted = true;
};

struct FontCacheKeyTraits : WTF::SimpleClassHashTraits<FontCacheKey> {
  STATIC_ONLY(FontCacheKeyTraits);
};

}  // namespace blink

#endif  // FontCacheKey_h