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      1 /*
      2  * Copyright (C) 2010 Google, Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #include "config.h"
     27 #include "core/html/parser/HTMLParserScheduler.h"
     28 
     29 #include "core/dom/Document.h"
     30 #include "core/html/parser/HTMLDocumentParser.h"
     31 #include "core/frame/FrameView.h"
     32 
     33 namespace WebCore {
     34 
     35 // parserChunkSize is used to define how many tokens the parser will
     36 // process before checking against parserTimeLimit and possibly yielding.
     37 // This is a performance optimization to prevent checking after every token.
     38 const int HTMLParserScheduler::parserChunkSize = 4096;
     39 
     40 // parserTimeLimit is the seconds the parser will run in one write() call
     41 // before yielding. Inline <script> execution can cause it to exceed the limit.
     42 const double HTMLParserScheduler::parserTimeLimit = 0.2;
     43 
     44 ActiveParserSession::ActiveParserSession(Document* document)
     45     : m_document(document)
     46 {
     47     if (!m_document)
     48         return;
     49     m_document->incrementActiveParserCount();
     50 }
     51 
     52 ActiveParserSession::~ActiveParserSession()
     53 {
     54     if (!m_document)
     55         return;
     56     m_document->decrementActiveParserCount();
     57 }
     58 
     59 PumpSession::PumpSession(unsigned& nestingLevel, Document* document)
     60     : NestingLevelIncrementer(nestingLevel)
     61     , ActiveParserSession(document)
     62     // Setting processedTokens to INT_MAX causes us to check for yields
     63     // after any token during any parse where yielding is allowed.
     64     // At that time we'll initialize startTime.
     65     , processedTokens(INT_MAX)
     66     , startTime(0)
     67     , needsYield(false)
     68     , didSeeScript(false)
     69 {
     70 }
     71 
     72 PumpSession::~PumpSession()
     73 {
     74 }
     75 
     76 HTMLParserScheduler::HTMLParserScheduler(HTMLDocumentParser* parser)
     77     : m_parser(parser)
     78     , m_continueNextChunkTimer(this, &HTMLParserScheduler::continueNextChunkTimerFired)
     79     , m_isSuspendedWithActiveTimer(false)
     80 {
     81 }
     82 
     83 HTMLParserScheduler::~HTMLParserScheduler()
     84 {
     85     m_continueNextChunkTimer.stop();
     86 }
     87 
     88 void HTMLParserScheduler::continueNextChunkTimerFired(Timer<HTMLParserScheduler>* timer)
     89 {
     90     ASSERT_UNUSED(timer, timer == &m_continueNextChunkTimer);
     91     // FIXME: The timer class should handle timer priorities instead of this code.
     92     // If a layout is scheduled, wait again to let the layout timer run first.
     93     // FIXME: We should fix this by reducing the max-parse-time instead of
     94     // artificially forcing the parser to yield agressively before first layout.
     95     if (m_parser->document()->shouldParserYieldAgressivelyBeforeScriptExecution()) {
     96         m_continueNextChunkTimer.startOneShot(0);
     97         return;
     98     }
     99     m_parser->resumeParsingAfterYield();
    100 }
    101 
    102 void HTMLParserScheduler::checkForYieldBeforeScript(PumpSession& session)
    103 {
    104     // If we've never painted before and a layout is pending, yield prior to running
    105     // scripts to give the page a chance to paint earlier.
    106     Document* document = m_parser->document();
    107     bool needsFirstPaint = document->view() && !document->view()->hasEverPainted();
    108     if (needsFirstPaint && document->shouldParserYieldAgressivelyBeforeScriptExecution())
    109         session.needsYield = true;
    110     session.didSeeScript = true;
    111 }
    112 
    113 void HTMLParserScheduler::scheduleForResume()
    114 {
    115     m_continueNextChunkTimer.startOneShot(0);
    116 }
    117 
    118 
    119 void HTMLParserScheduler::suspend()
    120 {
    121     ASSERT(!m_isSuspendedWithActiveTimer);
    122     if (!m_continueNextChunkTimer.isActive())
    123         return;
    124     m_isSuspendedWithActiveTimer = true;
    125     m_continueNextChunkTimer.stop();
    126 }
    127 
    128 void HTMLParserScheduler::resume()
    129 {
    130     ASSERT(!m_continueNextChunkTimer.isActive());
    131     if (!m_isSuspendedWithActiveTimer)
    132         return;
    133     m_isSuspendedWithActiveTimer = false;
    134     m_continueNextChunkTimer.startOneShot(0);
    135 }
    136 
    137 }
    138