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

/*
 * Copyright (C) 2006, 2009 Apple 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 Apple Computer, Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS 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, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef GlyphMetricsMap_h
#define GlyphMetricsMap_h

#include "platform/fonts/Glyph.h"
#include "platform/geometry/FloatRect.h"
#include "wtf/Allocator.h"
#include "wtf/Assertions.h"
#include "wtf/HashMap.h"
#include "wtf/PtrUtil.h"
#include "wtf/text/Unicode.h"
#include <memory>

namespace blink {

const float cGlyphSizeUnknown = -1;

template <class T>
class GlyphMetricsMap {
  USING_FAST_MALLOC(GlyphMetricsMap);
  WTF_MAKE_NONCOPYABLE(GlyphMetricsMap);

 public:
  GlyphMetricsMap() : m_filledPrimaryPage(false) {}
  T metricsForGlyph(Glyph glyph) {
    return locatePage(glyph / GlyphMetricsPage::size)->metricsForGlyph(glyph);
  }

  void setMetricsForGlyph(Glyph glyph, const T& metrics) {
    locatePage(glyph / GlyphMetricsPage::size)
        ->setMetricsForGlyph(glyph, metrics);
  }

 private:
  class GlyphMetricsPage {
    USING_FAST_MALLOC(GlyphMetricsPage);
    WTF_MAKE_NONCOPYABLE(GlyphMetricsPage);

   public:
    static const size_t size = 256;  // Usually covers Latin-1 in a single page.
    GlyphMetricsPage() {}

    T metricsForGlyph(Glyph glyph) const { return m_metrics[glyph % size]; }
    void setMetricsForGlyph(Glyph glyph, const T& metrics) {
      setMetricsForIndex(glyph % size, metrics);
    }
    void setMetricsForIndex(unsigned index, const T& metrics) {
      ASSERT_WITH_SECURITY_IMPLICATION(index < size);
      m_metrics[index] = metrics;
    }

   private:
    T m_metrics[size];
  };

  GlyphMetricsPage* locatePage(unsigned pageNumber) {
    if (!pageNumber && m_filledPrimaryPage)
      return &m_primaryPage;
    return locatePageSlowCase(pageNumber);
  }

  GlyphMetricsPage* locatePageSlowCase(unsigned pageNumber);

  static T unknownMetrics();

  bool m_filledPrimaryPage;
  // We optimize for the page that contains glyph indices 0-255.
  GlyphMetricsPage m_primaryPage;
  std::unique_ptr<HashMap<int, std::unique_ptr<GlyphMetricsPage>>> m_pages;
};

template <>
inline float GlyphMetricsMap<float>::unknownMetrics() {
  return cGlyphSizeUnknown;
}

template <>
inline FloatRect GlyphMetricsMap<FloatRect>::unknownMetrics() {
  return FloatRect(0, 0, cGlyphSizeUnknown, cGlyphSizeUnknown);
}

template <class T>
typename GlyphMetricsMap<T>::GlyphMetricsPage*
GlyphMetricsMap<T>::locatePageSlowCase(unsigned pageNumber) {
  GlyphMetricsPage* page;
  if (!pageNumber) {
    ASSERT(!m_filledPrimaryPage);
    page = &m_primaryPage;
    m_filledPrimaryPage = true;
  } else {
    if (m_pages) {
      page = m_pages->get(pageNumber);
      if (page)
        return page;
    } else {
      m_pages = wrapUnique(new HashMap<int, std::unique_ptr<GlyphMetricsPage>>);
    }
    page = new GlyphMetricsPage;
    m_pages->set(pageNumber, wrapUnique(page));
  }

  // Fill in the whole page with the unknown glyph information.
  for (unsigned i = 0; i < GlyphMetricsPage::size; i++)
    page->setMetricsForIndex(i, unknownMetrics());

  return page;
}

}  // namespace blink

#endif