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PdfForQtLib/sources/pdfdocumentreader.cpp

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+//    Copyright (C) 2018 Jakub Melka
+//
+//    This file is part of PdfForQt.
+//
+//    PdfForQt is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Lesser General Public License as published by
+//    the Free Software Foundation, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    PdfForQt 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 Lesser General Public License for more details.
+//
+//    You should have received a copy of the GNU Lesser General Public License
+//    along with PDFForQt.  If not, see <https://www.gnu.org/licenses/>.
+
+
+#include "pdfdocumentreader.h"
+#include "pdfparser.h"
+#include "pdfconstants.h"
+
+#include <QFile>
+
+#include <regex>
+#include <cctype>
+#include <algorithm>
+
+namespace pdf
+{
+
+PDFDocumentReader::PDFDocumentReader() :
+    m_successfull(true)
+{
+
+}
+
+PDFDocument PDFDocumentReader::readFromFile(const QString& fileName)
+{
+    QFile file(fileName);
+
+    reset();
+
+    if (file.exists())
+    {
+        if (file.open(QFile::ReadOnly))
+        {
+            PDFDocument document = readFromDevice(&file);
+            file.close();
+            return document;
+        }
+        else
+        {
+            m_successfull = false;
+            m_errorMessage = tr("File '%1' cannot be opened for reading. %1").arg(file.errorString());
+        }
+    }
+    else
+    {
+        m_successfull = false;
+        m_errorMessage = tr("File '%1' doesn't exist.").arg(fileName);
+    }
+
+    return PDFDocument();
+}
+
+PDFDocument PDFDocumentReader::readFromDevice(QIODevice* device)
+{
+    reset();
+
+    if (device->isOpen())
+    {
+        if (device->isReadable())
+        {
+            // Do not close the device, it was not opened by us.
+            return readFromBuffer(device->readAll());
+        }
+        else
+        {
+            m_successfull = false;
+            m_errorMessage = tr("Device is not opened for reading.");
+        }
+    }
+    else if (device->open(QIODevice::ReadOnly))
+    {
+        QByteArray byteArray = device->readAll();
+        device->close();
+        return readFromBuffer(byteArray);
+    }
+    else
+    {
+        m_successfull = false;
+        m_errorMessage = tr("Can't open device for reading.");
+    }
+
+    return PDFDocument();
+}
+
+PDFDocument PDFDocumentReader::readFromBuffer(const QByteArray& buffer)
+{
+    try
+    {
+        // FOOTER CHECKING
+        //  1) Check, if EOF marking is present
+        //  2) Find start of cross reference table
+        if (findFromEnd(PDF_END_OF_FILE_MARK, buffer, PDF_FOOTER_SCAN_LIMIT) == FIND_NOT_FOUND_RESULT)
+        {
+            throw PDFParserException(tr("End of file marking was not found."));
+        }
+
+        const int startXRefPosition = findFromEnd(PDF_START_OF_XREF_MARK, buffer, PDF_FOOTER_SCAN_LIMIT);
+        if (startXRefPosition == FIND_NOT_FOUND_RESULT)
+        {
+            throw PDFParserException(tr("Start of object reference table not found."));
+        }
+
+        // HEADER CHECKING
+        //  1) Check if header is present
+        //  2) Scan header version
+
+        // According to PDF Reference 1.7, Appendix H, file header can have two formats:
+        //  - %PDF-x.x
+        //  - %!PS-Adobe-y.y PDF-x.x
+        // We will search for both of these formats.
+
+        std::regex headerRegExp("(%PDF-[[:digit:]]\\.[[:digit:]])|(%!PS-Adobe-[[:digit:]]\\.[[:digit:]] PDF-[[:digit:]]\\.[[:digit:]])");
+        std::cmatch headerMatch;
+
+        auto itBegin = buffer.cbegin();
+        auto itEnd = std::next(buffer.cbegin(), qMin(buffer.size(), PDF_HEADER_SCAN_LIMIT));
+
+        if (std::regex_search(itBegin, itEnd, headerMatch, headerRegExp))
+        {
+            // Size depends on regular expression, not on the text (if regular expresion is matched)
+            Q_ASSERT(headerMatch.size() == 3);
+            Q_ASSERT(headerMatch[1].matched != headerMatch[2].matched);
+
+            for (int i : { 1, 2 })
+            {
+                if (headerMatch[i].matched)
+                {
+                    Q_ASSERT(std::distance(headerMatch[i].first, headerMatch[i].second) == 3);
+                    m_version = PDFVersion(*headerMatch[i].first - '0', *std::prev(headerMatch[i].second) - '0');
+                    break;
+                }
+            }
+        }
+        else
+        {
+            throw PDFParserException(tr("Header of PDF file was not found."));
+        }
+
+        // Check, if version is valid
+        if (!m_version.isValid())
+        {
+            throw PDFParserException(tr("Version of the PDF file is not valid."));
+        }
+
+
+    }
+    catch (PDFParserException parserException)
+    {
+        m_successfull = false;
+        m_errorMessage = parserException.getMessage();
+    }
+
+    return PDFDocument();
+}
+
+void PDFDocumentReader::reset()
+{
+    m_successfull = true;
+    m_errorMessage = QString();
+    m_version = PDFVersion();
+}
+
+int PDFDocumentReader::findFromEnd(const char* what, const QByteArray& byteArray, int limit)
+{
+    if (byteArray.isEmpty())
+    {
+        // Byte array is empty, no value found
+        return FIND_NOT_FOUND_RESULT;
+    }
+
+    const int size = byteArray.size();
+    const int adjustedLimit = qMin(byteArray.size(), limit);
+    const int whatLength = static_cast<int>(std::strlen(what));
+
+    if (adjustedLimit < whatLength)
+    {
+        // Buffer is smaller than scan string
+        return FIND_NOT_FOUND_RESULT;
+    }
+
+    auto itBegin = std::next(byteArray.cbegin(), size - adjustedLimit);
+    auto itEnd = byteArray.cend();
+    auto it = std::find_end(itBegin, itEnd, what, std::next(what, whatLength));
+
+    if (it != byteArray.cend())
+    {
+        return std::distance(byteArray.cbegin(), it);
+    }
+
+    return FIND_NOT_FOUND_RESULT;
+}
+
+}   // namespace pdf