WebCore/html/HTMLParserScheduler.cpp

/*
 * Copyright (C) 2010 Google, Inc. All Rights Reserved.
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#include "config.h"
#include "HTMLParserScheduler.h"

#include "FrameView.h" // Only for isLayoutTimerActive
#include "HTMLDocumentParser.h"
#include "Document.h"

// defaultParserChunkSize is used to define how many tokens the parser will
// process before checking against parserTimeLimit and possibly yielding.
// This is a performance optimization to prevent checking after every token.
static const int defaultParserChunkSize = 4096;

// defaultParserTimeLimit is the seconds the parser will run in one write() call
// before yielding.  Inline <script> execution can cause it to excede the limit.
// FIXME: We would like this value to be 0.2.
static const double defaultParserTimeLimit = 0.500;

namespace WebCore {

static double parserTimeLimit(Page* page)
{
    // We're using the poorly named customHTMLTokenizerTimeDelay setting.
    if (page && page->hasCustomHTMLTokenizerTimeDelay())
        return page->customHTMLTokenizerTimeDelay();
    return defaultParserTimeLimit;
}

static int parserChunkSize(Page* page)
{
    // FIXME: We may need to divide the value from customHTMLTokenizerChunkSize
    // by some constant to translate from the "character" based behavior of the
    // old LegacyHTMLDocumentParser to the token-based behavior of this parser.
    if (page && page->hasCustomHTMLTokenizerChunkSize())
        return page->customHTMLTokenizerChunkSize();
    return defaultParserChunkSize;
}

HTMLParserScheduler::HTMLParserScheduler(HTMLDocumentParser* parser)
    : m_parser(parser)
    , m_parserTimeLimit(parserTimeLimit(m_parser->document()->page()))
    , m_parserChunkSize(parserChunkSize(m_parser->document()->page()))
    , m_continueNextChunkTimer(this, &HTMLParserScheduler::continueNextChunkTimerFired)
{
}

HTMLParserScheduler::~HTMLParserScheduler()
{
    m_continueNextChunkTimer.stop();
}

// FIXME: This belongs on Document.
static bool isLayoutTimerActive(Document* doc)
{
    ASSERT(doc);
    return doc->view() && doc->view()->layoutPending() && !doc->minimumLayoutDelay();
}

void HTMLParserScheduler::continueNextChunkTimerFired(Timer<HTMLParserScheduler>* timer)
{
    ASSERT_UNUSED(timer, timer == &m_continueNextChunkTimer);
    // FIXME: The timer class should handle timer priorities instead of this code.
    // If a layout is scheduled, wait again to let the layout timer run first.
    if (isLayoutTimerActive(m_parser->document())) {
        m_continueNextChunkTimer.startOneShot(0);
        return;
    }
    m_parser->resumeParsingAfterYield();
}

}