void TextIterator::handleTextBox()
{    
    RenderText* renderer = m_firstLetterText ? m_firstLetterText : toRenderText(m_node->renderer());
    if (renderer->style()->visibility() != VISIBLE && !m_ignoresStyleVisibility) {
        m_textBox = 0;
        return;
    }
    String str = renderer->text();
    unsigned start = m_offset;
    unsigned end = (m_node == m_endContainer) ? static_cast<unsigned>(m_endOffset) : UINT_MAX;
    while (m_textBox) {
        unsigned textBoxStart = m_textBox->start();
        unsigned runStart = max(textBoxStart, start);

        InlineTextBox* firstTextBox = renderer->containsReversedText() ? (m_sortedTextBoxes.isEmpty() ? 0 : m_sortedTextBoxes[0]) : renderer->firstTextBox();
        bool needSpace = m_lastTextNodeEndedWithCollapsedSpace
            || (m_textBox == firstTextBox && textBoxStart == runStart && runStart > 0);
        if (needSpace && !isCollapsibleWhitespace(m_lastCharacter) && m_lastCharacter) {
            if (m_lastTextNode == m_node && runStart > 0 && str[runStart - 1] == ' ') {
                unsigned spaceRunStart = runStart - 1;
                while (spaceRunStart > 0 && str[spaceRunStart - 1] == ' ')
                    --spaceRunStart;
                emitText(m_node, renderer, spaceRunStart, spaceRunStart + 1);
            } else
                emitCharacter(' ', m_node, 0, runStart, runStart);
            return;
        }
        unsigned textBoxEnd = textBoxStart + m_textBox->len();
        unsigned runEnd = min(textBoxEnd, end);
        
        InlineTextBox* nextTextBox = 0;
        if (renderer->containsReversedText()) {
            if (m_sortedTextBoxesPosition + 1 < m_sortedTextBoxes.size())
                nextTextBox = m_sortedTextBoxes[m_sortedTextBoxesPosition + 1];
        } else 
            nextTextBox = m_textBox->nextTextBox();
        ASSERT(!nextTextBox || nextTextBox->renderer() == renderer);

        if (runStart < runEnd) {
            if (str[runStart] == '\n') {
                emitCharacter(' ', m_node, 0, runStart, runStart + 1);
                m_offset = runStart + 1;
            } else {
                size_t subrunEnd = str.find('\n', runStart);
                if (subrunEnd == notFound || subrunEnd > runEnd)
                    subrunEnd = runEnd;
    
                m_offset = subrunEnd;
                emitText(m_node, renderer, runStart, subrunEnd);
            }

            if (static_cast<unsigned>(m_positionEndOffset) < textBoxEnd)
                return;

            unsigned nextRunStart = nextTextBox ? nextTextBox->start() : str.length();
            if (nextRunStart > runEnd)
                m_lastTextNodeEndedWithCollapsedSpace = true; // collapsed space between runs or at the end
            m_textBox = nextTextBox;
            if (renderer->containsReversedText())
                ++m_sortedTextBoxesPosition;
            return;
        }
        m_textBox = nextTextBox;
        if (renderer->containsReversedText())
            ++m_sortedTextBoxesPosition;
    }
    if (!m_textBox && m_remainingTextBox) {
        m_textBox = m_remainingTextBox;
        m_remainingTextBox = 0;
        m_firstLetterText = 0;
        m_offset = 0;
        handleTextBox();
    }
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.