HTMLPreloadScanner.cpp   [plain text]

/*
 * Copyright (C) 2008, 2014 Apple Inc. All Rights Reserved.
 * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
 * Copyright (C) 2010 Google Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 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
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"
#include "HTMLPreloadScanner.h"

#include "HTMLNames.h"
#include "HTMLParserIdioms.h"
#include "HTMLSrcsetParser.h"
#include "HTMLTokenizer.h"
#include "InputTypeNames.h"
#include "LinkRelAttribute.h"
#include "SourceSizeList.h"
#include <wtf/MainThread.h>

namespace WebCore {

using namespace HTMLNames;

TokenPreloadScanner::TagId TokenPreloadScanner::tagIdFor(const HTMLToken::DataVector& data)
{
    AtomicString tagName(data);
    if (tagName == imgTag)
        return TagId::Img;
    if (tagName == inputTag)
        return TagId::Input;
    if (tagName == linkTag)
        return TagId::Link;
    if (tagName == scriptTag)
        return TagId::Script;
    if (tagName == styleTag)
        return TagId::Style;
    if (tagName == baseTag)
        return TagId::Base;
    if (tagName == templateTag)
        return TagId::Template;
    return TagId::Unknown;
}

String TokenPreloadScanner::initiatorFor(TagId tagId)
{
    switch (tagId) {
    case TagId::Img:
        return "img";
    case TagId::Input:
        return "input";
    case TagId::Link:
        return "link";
    case TagId::Script:
        return "script";
    case TagId::Unknown:
    case TagId::Style:
    case TagId::Base:
    case TagId::Template:
        ASSERT_NOT_REACHED();
        return "unknown";
    }
    ASSERT_NOT_REACHED();
    return "unknown";
}

class TokenPreloadScanner::StartTagScanner {
public:
    explicit StartTagScanner(TagId tagId, float deviceScaleFactor = 1.0)
        : m_tagId(tagId)
        , m_linkIsStyleSheet(false)
        , m_inputIsImage(false)
        , m_deviceScaleFactor(deviceScaleFactor)
    {
    }

    void processAttributes(const HTMLToken::AttributeList& attributes
#if ENABLE(PICTURE_SIZES)
        , RenderView* view, Frame* frame
#endif
        )
    {
        ASSERT(isMainThread());
        if (m_tagId >= TagId::Unknown)
            return;
        for (HTMLToken::AttributeList::const_iterator iter = attributes.begin(); iter != attributes.end(); ++iter) {
            AtomicString attributeName(iter->name);
            String attributeValue = StringImpl::create8BitIfPossible(iter->value);
            processAttribute(attributeName, attributeValue);
        }

        // Resolve between src and srcSet if we have them.
        if (!m_srcSetAttribute.isEmpty()) {
            ImageCandidate imageCandidate = bestFitSourceForImageAttributes(m_deviceScaleFactor, m_urlToLoad, m_srcSetAttribute
#if ENABLE(PICTURE_SIZES)
                , SourceSizeList::parseSizesAttribute(m_sizesAttribute, view, frame)
#endif
                );
            setUrlToLoad(imageCandidate.string.toString(), true);
        }
    }

    std::unique_ptr<PreloadRequest> createPreloadRequest(const URL& predictedBaseURL)
    {
        if (!shouldPreload())
            return nullptr;

        auto request = std::make_unique<PreloadRequest>(initiatorFor(m_tagId), m_urlToLoad, predictedBaseURL, resourceType(), m_mediaAttribute);

        request->setCrossOriginModeAllowsCookies(crossOriginModeAllowsCookies());
        request->setCharset(charset());
        return request;
    }

    static bool match(const AtomicString& name, const QualifiedName& qName)
    {
        ASSERT(isMainThread());
        return qName.localName() == name;
    }

private:
    template<typename NameType>
    void processAttribute(const NameType& attributeName, const String& attributeValue)
    {
        if (match(attributeName, charsetAttr))
            m_charset = attributeValue;

        if (m_tagId == TagId::Script || m_tagId == TagId::Img) {
            if (match(attributeName, srcAttr))
                setUrlToLoad(attributeValue);
            else if (match(attributeName, srcsetAttr) && m_srcSetAttribute.isNull())
                m_srcSetAttribute = attributeValue;
#if ENABLE(PICTURE_SIZES)
            else if (match(attributeName, sizesAttr) && m_sizesAttribute.isNull())
                m_sizesAttribute = attributeValue;
#endif
            else if (match(attributeName, crossoriginAttr) && !attributeValue.isNull())
                m_crossOriginMode = stripLeadingAndTrailingHTMLSpaces(attributeValue);
        } else if (m_tagId == TagId::Link) {
            if (match(attributeName, hrefAttr))
                setUrlToLoad(attributeValue);
            else if (match(attributeName, relAttr))
                m_linkIsStyleSheet = relAttributeIsStyleSheet(attributeValue);
            else if (match(attributeName, mediaAttr))
                m_mediaAttribute = attributeValue;
        } else if (m_tagId == TagId::Input) {
            if (match(attributeName, srcAttr))
                setUrlToLoad(attributeValue);
            else if (match(attributeName, typeAttr))
                m_inputIsImage = equalIgnoringCase(attributeValue, InputTypeNames::image());
        }
    }

    static bool relAttributeIsStyleSheet(const String& attributeValue)
    {
        LinkRelAttribute rel(attributeValue);
        return rel.m_isStyleSheet && !rel.m_isAlternate && rel.m_iconType == InvalidIcon && !rel.m_isDNSPrefetch;
    }

    void setUrlToLoad(const String& value, bool allowReplacement = false)
    {
        // We only respect the first src/href, per HTML5:
        // http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#attribute-name-state
        if (!allowReplacement && !m_urlToLoad.isEmpty())
            return;
        String url = stripLeadingAndTrailingHTMLSpaces(value);
        if (url.isEmpty())
            return;
        m_urlToLoad = url;
    }

    const String& charset() const
    {
        // FIXME: Its not clear that this if is needed, the loader probably ignores charset for image requests anyway.
        if (m_tagId == TagId::Img)
            return emptyString();
        return m_charset;
    }

    CachedResource::Type resourceType() const
    {
        if (m_tagId == TagId::Script)
            return CachedResource::Script;
        if (m_tagId == TagId::Img || (m_tagId == TagId::Input && m_inputIsImage))
            return CachedResource::ImageResource;
        if (m_tagId == TagId::Link && m_linkIsStyleSheet)
            return CachedResource::CSSStyleSheet;
        ASSERT_NOT_REACHED();
        return CachedResource::RawResource;
    }

    bool shouldPreload()
    {
        if (m_urlToLoad.isEmpty())
            return false;

        if (m_tagId == TagId::Link && !m_linkIsStyleSheet)
            return false;

        if (m_tagId == TagId::Input && !m_inputIsImage)
            return false;

        return true;
    }

    bool crossOriginModeAllowsCookies()
    {
        return m_crossOriginMode.isNull() || equalIgnoringCase(m_crossOriginMode, "use-credentials");
    }

    TagId m_tagId;
    String m_urlToLoad;
    String m_srcSetAttribute;
#if ENABLE(PICTURE_SIZES)
    String m_sizesAttribute;
#endif
    String m_charset;
    String m_crossOriginMode;
    bool m_linkIsStyleSheet;
    String m_mediaAttribute;
    bool m_inputIsImage;
    float m_deviceScaleFactor;
};

TokenPreloadScanner::TokenPreloadScanner(const URL& documentURL, float deviceScaleFactor)
    : m_documentURL(documentURL)
    , m_inStyle(false)
    , m_deviceScaleFactor(deviceScaleFactor)
#if ENABLE(TEMPLATE_ELEMENT)
    , m_templateCount(0)
#endif
{
}

TokenPreloadScanner::~TokenPreloadScanner()
{
}

TokenPreloadScannerCheckpoint TokenPreloadScanner::createCheckpoint()
{
    TokenPreloadScannerCheckpoint checkpoint = m_checkpoints.size();
    m_checkpoints.append(Checkpoint(m_predictedBaseElementURL, m_inStyle
#if ENABLE(TEMPLATE_ELEMENT)
                                    , m_templateCount
#endif
                                    ));
    return checkpoint;
}

void TokenPreloadScanner::rewindTo(TokenPreloadScannerCheckpoint checkpointIndex)
{
    ASSERT(checkpointIndex < m_checkpoints.size()); // If this ASSERT fires, checkpointIndex is invalid.
    const Checkpoint& checkpoint = m_checkpoints[checkpointIndex];
    m_predictedBaseElementURL = checkpoint.predictedBaseElementURL;
    m_inStyle = checkpoint.inStyle;
#if ENABLE(TEMPLATE_ELEMENT)
    m_templateCount = checkpoint.templateCount;
#endif
    m_cssScanner.reset();
    m_checkpoints.clear();
}

void TokenPreloadScanner::scan(const HTMLToken& token, Vector<std::unique_ptr<PreloadRequest>>& requests
#if ENABLE(PICTURE_SIZES)
        , RenderView* view, Frame* frame
#endif
        )
{
    switch (token.type()) {
    case HTMLToken::Character:
        if (!m_inStyle)
            return;
        m_cssScanner.scan(token.data(), requests);
        return;

    case HTMLToken::EndTag: {
        TagId tagId = tagIdFor(token.data());
#if ENABLE(TEMPLATE_ELEMENT)
        if (tagId == TagId::Template) {
            if (m_templateCount)
                --m_templateCount;
            return;
        }
#endif
        if (tagId == TagId::Style) {
            if (m_inStyle)
                m_cssScanner.reset();
            m_inStyle = false;
        }
        return;
    }

    case HTMLToken::StartTag: {
#if ENABLE(TEMPLATE_ELEMENT)
        if (m_templateCount)
            return;
#endif
        TagId tagId = tagIdFor(token.data());
#if ENABLE(TEMPLATE_ELEMENT)
        if (tagId == TagId::Template) {
            ++m_templateCount;
            return;
        }
#endif
        if (tagId == TagId::Style) {
            m_inStyle = true;
            return;
        }
        if (tagId == TagId::Base) {
            // The first <base> element is the one that wins.
            if (!m_predictedBaseElementURL.isEmpty())
                return;
            updatePredictedBaseURL(token);
            return;
        }

        StartTagScanner scanner(tagId, m_deviceScaleFactor);
        scanner.processAttributes(token.attributes()
#if ENABLE(PICTURE_SIZES)
            , view, frame
#endif
            );
        if (auto request = scanner.createPreloadRequest(m_predictedBaseElementURL))
            requests.append(WTF::move(request));
        return;
    }

    default:
        return;
    }
}

template<typename Token>
void TokenPreloadScanner::updatePredictedBaseURL(const Token& token)
{
    ASSERT(m_predictedBaseElementURL.isEmpty());
    if (const typename Token::Attribute* hrefAttribute = token.getAttributeItem(hrefAttr))
        m_predictedBaseElementURL = URL(m_documentURL, stripLeadingAndTrailingHTMLSpaces(hrefAttribute->value)).copy();
}

HTMLPreloadScanner::HTMLPreloadScanner(const HTMLParserOptions& options, const URL& documentURL, float deviceScaleFactor)
    : m_scanner(documentURL, deviceScaleFactor)
    , m_tokenizer(std::make_unique<HTMLTokenizer>(options))
{
}

HTMLPreloadScanner::~HTMLPreloadScanner()
{
}

void HTMLPreloadScanner::appendToEnd(const SegmentedString& source)
{
    m_source.append(source);
}

void HTMLPreloadScanner::scan(HTMLResourcePreloader* preloader, const URL& startingBaseElementURL
#if ENABLE(PICTURE_SIZES)
        , RenderView* view, Frame* frame
#endif
        )
{
    ASSERT(isMainThread()); // HTMLTokenizer::updateStateFor only works on the main thread.

    // When we start scanning, our best prediction of the baseElementURL is the real one!
    if (!startingBaseElementURL.isEmpty())
        m_scanner.setPredictedBaseElementURL(startingBaseElementURL);

    PreloadRequestStream requests;

    while (m_tokenizer->nextToken(m_source, m_token)) {
        if (m_token.type() == HTMLToken::StartTag)
            m_tokenizer->updateStateFor(AtomicString(m_token.name()));
        m_scanner.scan(m_token, requests
#if ENABLE(PICTURE_SIZES)
            , view, frame
#endif
            );
        m_token.clear();
    }

    preloader->preload(WTF::move(requests));
}

}