HTMLParserScheduler.cpp   [plain text]

/*
 * Copyright (C) 2010 Google, Inc. All Rights Reserved.
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 INC. 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, DATA, OR
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#include "config.h"
#include "HTMLParserScheduler.h"

#include "Document.h"
#include "FrameView.h"
#include "HTMLDocumentParser.h"
#include "Page.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)
    , m_isSuspendedWithActiveTimer(false)
{
}

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

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 (m_parser->document()->isLayoutTimerActive()) {
        m_continueNextChunkTimer.startOneShot(0);
        return;
    }
    m_parser->resumeParsingAfterYield();
}

void HTMLParserScheduler::checkForYieldBeforeScript(PumpSession& session)
{
    // If we've never painted before and a layout is pending, yield prior to running
    // scripts to give the page a chance to paint earlier.
    Document* document = m_parser->document();
    bool needsFirstPaint = document->view() && !document->view()->hasEverPainted();
    if (needsFirstPaint && document->isLayoutTimerActive())
        session.needsYield = true;
}

void HTMLParserScheduler::scheduleForResume()
{
    m_continueNextChunkTimer.startOneShot(0);
}


void HTMLParserScheduler::suspend()
{
    ASSERT(!m_isSuspendedWithActiveTimer);
    if (!m_continueNextChunkTimer.isActive())
        return;
    m_isSuspendedWithActiveTimer = true;
    m_continueNextChunkTimer.stop();
}

void HTMLParserScheduler::resume()
{
    ASSERT(!m_continueNextChunkTimer.isActive());
    if (!m_isSuspendedWithActiveTimer)
        return;
    m_isSuspendedWithActiveTimer = false;
    m_continueNextChunkTimer.startOneShot(0);
}

}