third_party/WebKit/Source/core/html/parser/TextResourceDecoder.h

/*
    Copyright (C) 1999 Lars Knoll (knoll@mpi-hd.mpg.de)
    Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
    Copyright (C) 2006, 2008 Apple Inc. All rights reserved.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.

*/

#ifndef TextResourceDecoder_h
#define TextResourceDecoder_h

#include "core/CoreExport.h"
#include "wtf/PtrUtil.h"
#include "wtf/text/TextEncoding.h"
#include <memory>

namespace blink {

class HTMLMetaCharsetParser;

class CORE_EXPORT TextResourceDecoder {
    USING_FAST_MALLOC(TextResourceDecoder);
    WTF_MAKE_NONCOPYABLE(TextResourceDecoder);
public:
    enum EncodingSource {
        DefaultEncoding,
        AutoDetectedEncoding,
        EncodingFromContentSniffing,
        EncodingFromXMLHeader,
        EncodingFromMetaTag,
        EncodingFromCSSCharset,
        EncodingFromHTTPHeader,
        EncodingFromParentFrame
    };

    static std::unique_ptr<TextResourceDecoder> create(const String& mimeType, const WTF::TextEncoding& defaultEncoding = WTF::TextEncoding(), bool usesEncodingDetector = false)
    {
        return wrapUnique(new TextResourceDecoder(mimeType, defaultEncoding, usesEncodingDetector ? UseAllAutoDetection : UseContentAndBOMBasedDetection));
    }
    // Corresponds to utf-8 decode in Encoding spec:
    // https://encoding.spec.whatwg.org/#utf-8-decode.
    static std::unique_ptr<TextResourceDecoder> createAlwaysUseUTF8ForText()
    {
        return wrapUnique(new TextResourceDecoder("plain/text", UTF8Encoding(), AlwaysUseUTF8ForText));
    }
    ~TextResourceDecoder();

    void setEncoding(const WTF::TextEncoding&, EncodingSource);
    const WTF::TextEncoding& encoding() const { return m_encoding; }
    bool encodingWasDetectedHeuristically() const
    {
        return m_source == AutoDetectedEncoding
            || m_source == EncodingFromContentSniffing;
    }

    String decode(const char* data, size_t length);
    String flush();

    void setHintEncoding(const WTF::TextEncoding& encoding)
    {
        m_hintEncoding = encoding.name();
    }

    void useLenientXMLDecoding() { m_useLenientXMLDecoding = true; }
    bool sawError() const { return m_sawError; }
    size_t checkForBOM(const char*, size_t);

private:

    // TextResourceDecoder does three kind of encoding detection:
    // 1. By BOM,
    // 2. By Content if |m_contentType| is not |PlainTextContext|
    //    (e.g. <meta> tag for HTML), and
    // 3. By detectTextEncoding().
    enum EncodingDetectionOption {
        // Use 1. + 2. + 3.
        UseAllAutoDetection,

        // Use 1. + 2.
        UseContentAndBOMBasedDetection,

        // Use None of them.
        // |m_contentType| must be |PlainTextContent| and
        // |m_encoding| must be UTF8Encoding.
        // This doesn't change encoding based on BOMs, but still processes
        // utf-8 BOMs so that utf-8 BOMs don't appear in the decoded result.
        AlwaysUseUTF8ForText
    };

    TextResourceDecoder(const String& mimeType, const WTF::TextEncoding& defaultEncoding, EncodingDetectionOption);

    enum ContentType { PlainTextContent, HTMLContent, XMLContent, CSSContent }; // PlainText only checks for BOM.
    static ContentType determineContentType(const String& mimeType);
    static const WTF::TextEncoding& defaultEncoding(ContentType, const WTF::TextEncoding& defaultEncoding);

    bool checkForCSSCharset(const char*, size_t, bool& movedDataToBuffer);
    bool checkForXMLCharset(const char*, size_t, bool& movedDataToBuffer);
    void checkForMetaCharset(const char*, size_t);
    bool shouldAutoDetect() const;

    ContentType m_contentType;
    WTF::TextEncoding m_encoding;
    std::unique_ptr<TextCodec> m_codec;
    EncodingSource m_source;
    const char* m_hintEncoding;
    Vector<char> m_buffer;
    bool m_checkedForBOM;
    bool m_checkedForCSSCharset;
    bool m_checkedForXMLCharset;
    bool m_checkedForMetaCharset;
    bool m_useLenientXMLDecoding; // Don't stop on XML decoding errors.
    bool m_sawError;
    EncodingDetectionOption m_encodingDetectionOption;

    std::unique_ptr<HTMLMetaCharsetParser> m_charsetParser;
};

} // namespace blink

#endif