Source/platform/fonts/GlyphPage.h

/*
 * Copyright (C) 2006, 2007, 2008, 2013 Apple Inc. All rights reserved.
 * Copyright (C) Research In Motion Limited 2011. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *     notice, this list of conditions and the following disclaimer in the
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 *     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
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#ifndef GlyphPage_h
#define GlyphPage_h

#include "platform/fonts/Glyph.h"
#include <string.h>
#include "wtf/PassRefPtr.h"
#include "wtf/RefCounted.h"
#include "wtf/RefPtr.h"
#include "wtf/unicode/Unicode.h"

namespace WebCore {

class SimpleFontData;
class GlyphPageTreeNode;

// Holds the glyph index and the corresponding SimpleFontData information for a given
// character.
struct GlyphData {
    GlyphData(Glyph g = 0, const SimpleFontData* f = 0)
        : glyph(g)
        , fontData(f)
    {
    }
    Glyph glyph;
    const SimpleFontData* fontData;
};

#if COMPILER(MSVC)
#pragma warning(push)
#pragma warning(disable: 4200) // Disable "zero-sized array in struct/union" warning
#endif

// A GlyphPage contains a fixed-size set of GlyphData mappings for a contiguous
// range of characters in the Unicode code space. GlyphPages are indexed
// starting from 0 and incrementing for each 256 glyphs.
//
// One page may actually include glyphs from other fonts if the characters are
// missing in the primary font. It is owned by exactly one GlyphPageTreeNode,
// although multiple nodes may reference it as their "page" if they are supposed
// to be overriding the parent's node, but provide no additional information.
class GlyphPage : public RefCounted<GlyphPage> {
public:
    static PassRefPtr<GlyphPage> createForMixedFontData(GlyphPageTreeNode* owner)
    {
        void* slot = fastMalloc(sizeof(GlyphPage) + sizeof(SimpleFontData*) * GlyphPage::size);
        return adoptRef(new (slot) GlyphPage(owner));
    }

    static PassRefPtr<GlyphPage> createForSingleFontData(GlyphPageTreeNode* owner, const SimpleFontData* fontData)
    {
        ASSERT(fontData);
        return adoptRef(new GlyphPage(owner, fontData));
    }

    PassRefPtr<GlyphPage> createCopiedSystemFallbackPage(GlyphPageTreeNode* owner) const
    {
        RefPtr<GlyphPage> page = GlyphPage::createForMixedFontData(owner);
        memcpy(page->m_glyphs, m_glyphs, sizeof(m_glyphs));
        if (hasPerGlyphFontData())
            memcpy(page->m_perGlyphFontData, m_perGlyphFontData, sizeof(SimpleFontData*) * GlyphPage::size);
        else {
            for (size_t i = 0; i < GlyphPage::size; ++i) {
                page->m_perGlyphFontData[i] = m_glyphs[i] ? m_fontDataForAllGlyphs : 0;
            }
        }
        return page.release();
    }

    ~GlyphPage() { }

    static const size_t size = 256; // Covers Latin-1 in a single page.
    static unsigned indexForCharacter(UChar32 c) { return c % GlyphPage::size; }

    ALWAYS_INLINE GlyphData glyphDataForCharacter(UChar32 c) const
    {
        return glyphDataForIndex(indexForCharacter(c));
    }

    ALWAYS_INLINE GlyphData glyphDataForIndex(unsigned index) const
    {
        ASSERT_WITH_SECURITY_IMPLICATION(index < size);
        Glyph glyph = m_glyphs[index];
        if (hasPerGlyphFontData())
            return GlyphData(glyph, m_perGlyphFontData[index]);
        return GlyphData(glyph, glyph ? m_fontDataForAllGlyphs : 0);
    }

    ALWAYS_INLINE Glyph glyphForCharacter(UChar32 c) const
    {
        return glyphAt(indexForCharacter(c));
    }

    ALWAYS_INLINE Glyph glyphAt(unsigned index) const
    {
        ASSERT_WITH_SECURITY_IMPLICATION(index < size);
        return m_glyphs[index];
    }

    ALWAYS_INLINE const SimpleFontData* fontDataForCharacter(UChar32 c) const
    {
        unsigned index = indexForCharacter(c);
        if (hasPerGlyphFontData())
            return m_perGlyphFontData[index];
        return m_glyphs[index] ? m_fontDataForAllGlyphs : 0;
    }

    void setGlyphDataForCharacter(UChar32 c, Glyph g, const SimpleFontData* f)
    {
        setGlyphDataForIndex(indexForCharacter(c), g, f);
    }

    void setGlyphDataForIndex(unsigned index, Glyph glyph, const SimpleFontData* fontData)
    {
        ASSERT_WITH_SECURITY_IMPLICATION(index < size);
        m_glyphs[index] = glyph;

        // GlyphPage getters will always return a null SimpleFontData* for glyph #0 if there's no per-glyph font array.
        if (hasPerGlyphFontData()) {
            m_perGlyphFontData[index] = glyph ? fontData : 0;
            return;
        }

        // A single-font GlyphPage already assigned m_fontDataForAllGlyphs in the constructor.
        ASSERT(!glyph || fontData == m_fontDataForAllGlyphs);
    }

    void setGlyphDataForIndex(unsigned index, const GlyphData& glyphData)
    {
        setGlyphDataForIndex(index, glyphData.glyph, glyphData.fontData);
    }

    void removeFontDataFromSystemFallbackPage(const SimpleFontData* fontData)
    {
        // This method should only be called on the system fallback page, which is never single-font.
        ASSERT(hasPerGlyphFontData());
        for (size_t i = 0; i < size; ++i) {
            if (m_perGlyphFontData[i] == fontData) {
                m_glyphs[i] = 0;
                m_perGlyphFontData[i] = 0;
            }
        }
    }

    GlyphPageTreeNode* owner() const { return m_owner; }

    // Implemented by the platform.
    bool fill(unsigned offset, unsigned length, UChar* characterBuffer, unsigned bufferLength, const SimpleFontData*);

private:
    explicit GlyphPage(GlyphPageTreeNode* owner, const SimpleFontData* fontDataForAllGlyphs = 0)
        : m_fontDataForAllGlyphs(fontDataForAllGlyphs)
        , m_owner(owner)
    {
        memset(m_glyphs, 0, sizeof(m_glyphs));
        if (hasPerGlyphFontData())
            memset(m_perGlyphFontData, 0, sizeof(SimpleFontData*) * GlyphPage::size);
    }

    bool hasPerGlyphFontData() const { return !m_fontDataForAllGlyphs; }

    const SimpleFontData* m_fontDataForAllGlyphs;
    GlyphPageTreeNode* m_owner;
    Glyph m_glyphs[size];

    // NOTE: This array has (GlyphPage::size) elements if m_fontDataForAllGlyphs is null.
    const SimpleFontData* m_perGlyphFontData[0];
};

#if COMPILER(MSVC)
#pragma warning(pop)
#endif

} // namespace WebCore

#endif // GlyphPage_h