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 /*
     SPDX-FileCopyrightText: 2010 Christoph Cullmann <cullmann@kde.org>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
 #ifndef KATE_TEXTLOADER_H
 #define KATE_TEXTLOADER_H
 
 #include <QCryptographicHash>
 #include <QFile>
 #include <QMimeDatabase>
 #include <QString>
 
 // on the fly compression
 #include <KCompressionDevice>
 
 namespace Kate
 {
 /**
  * loader block size, load 256 kb at once per default
  * if file size is smaller, fall back to file size
  * must be a multiple of 2
  */
 static const qint64 KATE_FILE_LOADER_BS = 256 * 1024;
 
 /**
  * File Loader, will handle reading of files + detecting encoding
  */
 class TextLoader
 {
 public:
     /**
      * Construct file loader for given file.
      * @param filename file to open
      * @param proberType prober type
      */
     TextLoader(const QString &filename, KEncodingProber::ProberType proberType)
         : m_codec(nullptr)
         , m_eof(false) // default to not eof
         , m_lastWasEndOfLine(true) // at start of file, we had a virtual newline
         , m_lastWasR(false) // we have not found a \r as last char
         , m_position(0)
         , m_lastLineStart(0)
         , m_eol(TextBuffer::eolUnknown) // no eol type detected atm
         , m_buffer(KATE_FILE_LOADER_BS, 0)
         , m_digest(QCryptographicHash::Sha1)
         , m_converterState(nullptr)
         , m_bomFound(false)
         , m_firstRead(true)
         , m_proberType(proberType)
         , m_fileSize(0)
     {
         // try to get mimetype for on the fly decompression, don't rely on filename!
         QFile testMime(filename);
         if (testMime.open(QIODevice::ReadOnly)) {
             m_fileSize = testMime.size();
         }
         m_mimeType = QMimeDatabase().mimeTypeForFileNameAndData(filename, &testMime).name();
 
         // construct filter device
         KCompressionDevice::CompressionType compressionType = KCompressionDevice::compressionTypeForMimeType(m_mimeType);
         m_file = new KCompressionDevice(filename, compressionType);
     }
 
     /**
      * Destructor
      */
     ~TextLoader()
     {
         delete m_file;
         delete m_converterState;
     }
 
     /**
      * open file with given codec
      * @param codec codec to use, if 0, will do some auto-detect or fallback
      * @return success
      */
     bool open(QTextCodec *codec)
     {
         m_codec = codec;
         m_eof = false;
         m_lastWasEndOfLine = true;
         m_lastWasR = false;
         m_position = 0;
         m_lastLineStart = 0;
         m_eol = TextBuffer::eolUnknown;
         m_text.clear();
         delete m_converterState;
         m_converterState = new QTextCodec::ConverterState(QTextCodec::DefaultConversion);
         m_bomFound = false;
         m_firstRead = true;
 
         // init the hash with the git header
         const QString header = QStringLiteral("blob %1").arg(m_fileSize);
         m_digest.reset();
         m_digest.addData(QByteArray(header.toLatin1() + '\0'));
 
         // if already opened, close the file...
         if (m_file->isOpen()) {
             m_file->close();
         }
 
         return m_file->open(QIODevice::ReadOnly);
     }
 
     /**
      * end of file reached?
      * @return end of file reached
      */
     bool eof() const
     {
         return m_eof && !m_lastWasEndOfLine && (m_lastLineStart == m_text.length());
     }
 
     /**
      * Detected end of line mode for this file.
      * Detected during reading, is valid after complete file is read.
      * @return eol mode of this file
      */
     TextBuffer::EndOfLineMode eol() const
     {
         return m_eol;
     }
 
     /**
      * BOM found?
      * @return byte order mark found?
      */
     bool byteOrderMarkFound() const
     {
         return m_bomFound;
     }
 
     /**
      * mime type used to create filter dev
      * @return mime-type of filter device
      */
     const QString &mimeTypeForFilterDev() const
     {
         return m_mimeType;
     }
 
     /**
      * internal Unicode data array
      * @return internal Unicode data
      */
     const QChar *unicode() const
     {
         return m_text.unicode();
     }
 
     /**
      * Get codec for this loader
      * @return currently in use codec of this loader
      */
     QTextCodec *textCodec() const
     {
         return m_codec;
     }
 
     /**
      * read a line, return length + offset in Unicode data
      * @param offset offset into internal Unicode data for read line
      * @param length length of read line
      * @return true if no encoding errors occurred
      */
     bool readLine(int &offset, int &length)
     {
         length = 0;
         offset = 0;
         bool encodingError = false;
 
         static const QLatin1Char cr(QLatin1Char('\r'));
         static const QLatin1Char lf(QLatin1Char('\n'));
 
         /**
          * did we read two time but got no stuff? encoding error
          * fixes problem with one character latin-1 files, which lead to crash otherwise!
          * bug 272579
          */
         bool failedToConvertOnce = false;
         /**
          * keep track if we have found BOM so that failedToConvertOnce is not erroneously set to true
          * BUG: 440359
          */
         bool bomPreviouslyFound = m_bomFound;
 
         /**
          * reading loop
          */
         while (m_position <= m_text.length()) {
             if (m_position == m_text.length()) {
                 // try to load more text if something is around
                 if (!m_eof) {
                     // kill the old lines...
                     m_text.remove(0, m_lastLineStart);
 
                     // try to read new data
                     const int c = m_file->read(m_buffer.data(), m_buffer.size());
 
                     // if any text is there, append it....
                     if (c > 0) {
                         // update hash sum
                         m_digest.addData(m_buffer.data(), c);
 
                         // detect byte order marks & codec for byte order marks on first read
                         int bomBytes = 0;
                         if (m_firstRead) {
                             // use first 16 bytes max to allow BOM detection of codec
                             QByteArray bom(m_buffer.data(), qMin(16, c));
                             QTextCodec *codecForByteOrderMark = QTextCodec::codecForUtfText(bom, nullptr);
 
                             // if codecForByteOrderMark != null, we found a BOM!
                             // BUT we only capture BOM if no codec was set, or the BOM encodes the same codec as m_codec.
                             // These additional checks are necessary so that the (coincidentally matching) BOM characters won't be eaten for non-UTF encodings
                             // TODO: support BOMs for other encodings? (see e.g. https://en.wikipedia.org/wiki/Byte_order_mark#Byte_order_marks_by_encoding)
                             if (codecForByteOrderMark && (!m_codec || codecForByteOrderMark->mibEnum() == m_codec->mibEnum())) {
                                 m_bomFound = true;
 
                                 // eat away the different boms!
                                 const int mib = codecForByteOrderMark->mibEnum();
                                 if (mib == 106) { // utf8
                                     bomBytes = 3;
                                 } else if (mib == 1013 || mib == 1014 || mib == 1015) { // utf16
                                     bomBytes = 2;
                                 } else if (mib == 1017 || mib == 1018 || mib == 1019) { // utf32
                                     bomBytes = 4;
                                 }
                             }
 
                             /**
                              * if no codec given, do autodetection
                              */
                             if (!m_codec) {
                                 /**
                                  * byte order said something about encoding?
                                  */
                                 if (codecForByteOrderMark) {
                                     m_codec = codecForByteOrderMark;
                                 } else {
                                     /**
                                      * no Unicode BOM found, trigger prober
                                      */
 
                                     /**
                                      * first: try to get HTML header encoding
                                      */
                                     if (QTextCodec *codecForHtml = QTextCodec::codecForHtml(m_buffer, nullptr)) {
                                         m_codec = codecForHtml;
                                     }
 
                                     /**
                                      * else: use KEncodingProber
                                      */
                                     else {
                                         KEncodingProber prober(m_proberType);
                                         prober.feed(m_buffer.constData(), c);
 
                                         // we found codec with some confidence?
                                         if (prober.confidence() > 0.5) {
                                             m_codec = QTextCodec::codecForName(prober.encoding());
                                         }
                                     }
 
                                     // no codec, no chance, encoding error
                                     if (!m_codec) {
                                         return false;
                                     }
                                 }
                             }
 
                             m_firstRead = false;
                         }
 
                         // detect broken encoding, we did before use QTextCodec::ConvertInvalidToNull and check for 0 chars
                         // this lead to issues with files containing 0 chars, therefore use the invalidChars field of the state
                         Q_ASSERT(m_codec);
                         QString unicode = m_codec->toUnicode(m_buffer.constData() + bomBytes, c - bomBytes, m_converterState);
                         encodingError = encodingError || m_converterState->invalidChars;
                         m_text.append(unicode);
                     }
 
                     // is file completely read ?
                     m_eof = (c == -1) || (c == 0);
 
                     // recalc current pos and last pos
                     m_position -= m_lastLineStart;
                     m_lastLineStart = 0;
                 }
 
                 // oh oh, end of file, escape !
                 if (m_eof && (m_position == m_text.length())) {
                     m_lastWasEndOfLine = false;
 
                     // line data
                     offset = m_lastLineStart;
                     length = m_position - m_lastLineStart;
 
                     m_lastLineStart = m_position;
 
                     return !encodingError && !failedToConvertOnce;
                 }
 
                 // empty? try again
                 if (m_position == m_text.length()) {
                     if (!bomPreviouslyFound && m_bomFound) {
                         // BOM was processed above, so we didn't fail to convert
                         bomPreviouslyFound = true;
                     } else {
                         failedToConvertOnce = true;
                     }
                     continue;
                 }
             }
 
             QChar current_char = m_text.at(m_position);
             if (current_char == lf) {
                 m_lastWasEndOfLine = true;
 
                 if (m_lastWasR) {
                     m_lastLineStart++;
                     m_lastWasR = false;
                     m_eol = TextBuffer::eolDos;
                 } else {
                     // line data
                     offset = m_lastLineStart;
                     length = m_position - m_lastLineStart;
 
                     m_lastLineStart = m_position + 1;
                     m_position++;
 
                     // only win, if not dos!
                     if (m_eol != TextBuffer::eolDos) {
                         m_eol = TextBuffer::eolUnix;
                     }
 
                     return !encodingError;
                 }
             } else if (current_char == cr) {
                 m_lastWasEndOfLine = true;
                 m_lastWasR = true;
 
                 // line data
                 offset = m_lastLineStart;
                 length = m_position - m_lastLineStart;
 
                 m_lastLineStart = m_position + 1;
                 m_position++;
 
                 // should only win of first time!
                 if (m_eol == TextBuffer::eolUnknown) {
                     m_eol = TextBuffer::eolMac;
                 }
 
                 return !encodingError;
             } else if (current_char == QChar::LineSeparator) {
                 m_lastWasEndOfLine = true;
 
                 // line data
                 offset = m_lastLineStart;
                 length = m_position - m_lastLineStart;
 
                 m_lastLineStart = m_position + 1;
                 m_position++;
 
                 return !encodingError;
             } else {
                 m_lastWasEndOfLine = false;
                 m_lastWasR = false;
             }
 
             m_position++;
         }
 
         return !encodingError;
     }
 
     QByteArray digest()
     {
         return m_digest.result();
     }
 
 private:
     QTextCodec *m_codec;
     bool m_eof;
     bool m_lastWasEndOfLine;
     bool m_lastWasR;
     int m_position;
     int m_lastLineStart;
     TextBuffer::EndOfLineMode m_eol;
     QString m_mimeType;
     QIODevice *m_file;
     QByteArray m_buffer;
     QCryptographicHash m_digest;
     QString m_text;
     QTextCodec::ConverterState *m_converterState;
     bool m_bomFound;
     bool m_firstRead;
     KEncodingProber::ProberType m_proberType;
     quint64 m_fileSize;
 };
 
 }
 
 #endif