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      1 /*
      2  * Copyright (C) 2013 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 GOOGLE 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 GOOGLE INC. OR
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     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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     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/BackgroundHTMLParser.h"
     28 
     29 #include "core/html/parser/HTMLDocumentParser.h"
     30 #include "core/html/parser/HTMLParserThread.h"
     31 #include "core/html/parser/XSSAuditor.h"
     32 #include "wtf/MainThread.h"
     33 #include "wtf/text/TextPosition.h"
     34 
     35 namespace WebCore {
     36 
     37 // On a network with high latency and high bandwidth, using a device
     38 // with a fast CPU, we could end up speculatively tokenizing
     39 // the whole document, well ahead of when the main-thread actually needs it.
     40 // This is a waste of memory (and potentially time if the speculation fails).
     41 // So we limit our outstanding tokens arbitrarily to 10,000.
     42 // Our maximal memory spent speculating will be approximately:
     43 // (outstandingTokenLimit + pendingTokenLimit) * sizeof(CompactToken)
     44 // We use a separate low and high water mark to avoid constantly topping
     45 // off the main thread's token buffer.
     46 // At time of writing, this is (10000 + 1000) * 28 bytes = ~308kb of memory.
     47 // These numbers have not been tuned.
     48 static const size_t outstandingTokenLimit = 10000;
     49 
     50 // We limit our chucks to 1000 tokens, to make sure the main
     51 // thread is never waiting on the parser thread for tokens.
     52 // This was tuned in https://bugs.webkit.org/show_bug.cgi?id=110408.
     53 static const size_t pendingTokenLimit = 1000;
     54 
     55 using namespace HTMLNames;
     56 
     57 #ifndef NDEBUG
     58 
     59 static void checkThatTokensAreSafeToSendToAnotherThread(const CompactHTMLTokenStream* tokens)
     60 {
     61     for (size_t i = 0; i < tokens->size(); ++i)
     62         ASSERT(tokens->at(i).isSafeToSendToAnotherThread());
     63 }
     64 
     65 static void checkThatPreloadsAreSafeToSendToAnotherThread(const PreloadRequestStream& preloads)
     66 {
     67     for (size_t i = 0; i < preloads.size(); ++i)
     68         ASSERT(preloads[i]->isSafeToSendToAnotherThread());
     69 }
     70 
     71 static void checkThatXSSInfosAreSafeToSendToAnotherThread(const XSSInfoStream& infos)
     72 {
     73     for (size_t i = 0; i < infos.size(); ++i)
     74         ASSERT(infos[i]->isSafeToSendToAnotherThread());
     75 }
     76 
     77 #endif
     78 
     79 BackgroundHTMLParser::BackgroundHTMLParser(PassRefPtr<WeakReference<BackgroundHTMLParser> > reference, PassOwnPtr<Configuration> config)
     80     : m_weakFactory(reference, this)
     81     , m_token(adoptPtr(new HTMLToken))
     82     , m_tokenizer(HTMLTokenizer::create(config->options))
     83     , m_treeBuilderSimulator(config->options)
     84     , m_options(config->options)
     85     , m_parser(config->parser)
     86     , m_pendingTokens(adoptPtr(new CompactHTMLTokenStream))
     87     , m_xssAuditor(config->xssAuditor.release())
     88     , m_preloadScanner(config->preloadScanner.release())
     89 {
     90 }
     91 
     92 void BackgroundHTMLParser::append(const String& input)
     93 {
     94     ASSERT(!m_input.current().isClosed());
     95     m_input.append(input);
     96     pumpTokenizer();
     97 }
     98 
     99 void BackgroundHTMLParser::resumeFrom(PassOwnPtr<Checkpoint> checkpoint)
    100 {
    101     m_parser = checkpoint->parser;
    102     m_token = checkpoint->token.release();
    103     m_tokenizer = checkpoint->tokenizer.release();
    104     m_treeBuilderSimulator.setState(checkpoint->treeBuilderState);
    105     m_input.rewindTo(checkpoint->inputCheckpoint, checkpoint->unparsedInput);
    106     m_preloadScanner->rewindTo(checkpoint->preloadScannerCheckpoint);
    107     pumpTokenizer();
    108 }
    109 
    110 void BackgroundHTMLParser::startedChunkWithCheckpoint(HTMLInputCheckpoint inputCheckpoint)
    111 {
    112     // Note, we should not have to worry about the index being invalid
    113     // as messages from the main thread will be processed in FIFO order.
    114     m_input.invalidateCheckpointsBefore(inputCheckpoint);
    115     pumpTokenizer();
    116 }
    117 
    118 void BackgroundHTMLParser::finish()
    119 {
    120     markEndOfFile();
    121     pumpTokenizer();
    122 }
    123 
    124 void BackgroundHTMLParser::stop()
    125 {
    126     delete this;
    127 }
    128 
    129 void BackgroundHTMLParser::forcePlaintextForTextDocument()
    130 {
    131     // This is only used by the TextDocumentParser (a subclass of HTMLDocumentParser)
    132     // to force us into the PLAINTEXT state w/o using a <plaintext> tag.
    133     // The TextDocumentParser uses a <pre> tag for historical/compatibility reasons.
    134     m_tokenizer->setState(HTMLTokenizer::PLAINTEXTState);
    135 }
    136 
    137 void BackgroundHTMLParser::markEndOfFile()
    138 {
    139     ASSERT(!m_input.current().isClosed());
    140     m_input.append(String(&kEndOfFileMarker, 1));
    141     m_input.close();
    142 }
    143 
    144 void BackgroundHTMLParser::pumpTokenizer()
    145 {
    146     // No need to start speculating until the main thread has almost caught up.
    147     if (m_input.totalCheckpointTokenCount() > outstandingTokenLimit)
    148         return;
    149 
    150     while (true) {
    151         m_sourceTracker.start(m_input.current(), m_tokenizer.get(), *m_token);
    152         if (!m_tokenizer->nextToken(m_input.current(), *m_token)) {
    153             // We've reached the end of our current input.
    154             sendTokensToMainThread();
    155             break;
    156         }
    157         m_sourceTracker.end(m_input.current(), m_tokenizer.get(), *m_token);
    158 
    159         {
    160             TextPosition position = TextPosition(m_input.current().currentLine(), m_input.current().currentColumn());
    161 
    162             if (OwnPtr<XSSInfo> xssInfo = m_xssAuditor->filterToken(FilterTokenRequest(*m_token, m_sourceTracker, m_tokenizer->shouldAllowCDATA()))) {
    163                 xssInfo->m_textPosition = position;
    164                 m_pendingXSSInfos.append(xssInfo.release());
    165             }
    166 
    167             CompactHTMLToken token(m_token.get(), TextPosition(m_input.current().currentLine(), m_input.current().currentColumn()));
    168 
    169             m_preloadScanner->scan(token, m_input.current(), m_pendingPreloads);
    170 
    171             m_pendingTokens->append(token);
    172         }
    173 
    174         m_token->clear();
    175 
    176         if (!m_treeBuilderSimulator.simulate(m_pendingTokens->last(), m_tokenizer.get()) || m_pendingTokens->size() >= pendingTokenLimit) {
    177             sendTokensToMainThread();
    178             // If we're far ahead of the main thread, yield for a bit to avoid consuming too much memory.
    179             if (m_input.totalCheckpointTokenCount() > outstandingTokenLimit)
    180                 break;
    181         }
    182     }
    183 }
    184 
    185 void BackgroundHTMLParser::sendTokensToMainThread()
    186 {
    187     if (m_pendingTokens->isEmpty())
    188         return;
    189 
    190 #ifndef NDEBUG
    191     checkThatTokensAreSafeToSendToAnotherThread(m_pendingTokens.get());
    192     checkThatPreloadsAreSafeToSendToAnotherThread(m_pendingPreloads);
    193     checkThatXSSInfosAreSafeToSendToAnotherThread(m_pendingXSSInfos);
    194 #endif
    195 
    196     OwnPtr<HTMLDocumentParser::ParsedChunk> chunk = adoptPtr(new HTMLDocumentParser::ParsedChunk);
    197     chunk->preloads.swap(m_pendingPreloads);
    198     chunk->xssInfos.swap(m_pendingXSSInfos);
    199     chunk->tokenizerState = m_tokenizer->state();
    200     chunk->treeBuilderState = m_treeBuilderSimulator.state();
    201     chunk->inputCheckpoint = m_input.createCheckpoint(m_pendingTokens->size());
    202     chunk->preloadScannerCheckpoint = m_preloadScanner->createCheckpoint();
    203     chunk->tokens = m_pendingTokens.release();
    204     callOnMainThread(bind(&HTMLDocumentParser::didReceiveParsedChunkFromBackgroundParser, m_parser, chunk.release()));
    205 
    206     m_pendingTokens = adoptPtr(new CompactHTMLTokenStream);
    207 }
    208 
    209 }
    210