Better handling of images

PdfForQtLib/sources/pdfutils.cpp

@@ -0,0 +1,72 @@
+//    Copyright (C) 2019 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 "pdfutils.h"
+#include "pdfexception.h"
+
+namespace pdf
+{
+
+PDFBitReader::PDFBitReader(QDataStream* stream, Value bitsPerComponent) :
+    m_stream(stream),
+    m_bitsPerComponent(bitsPerComponent),
+    m_maximalValue((static_cast<Value>(1) << m_bitsPerComponent) - static_cast<Value>(1)),
+    m_buffer(0),
+    m_bitsInBuffer(0)
+{
+    // We need reserve, so we allow number of length of component as 1-56 bits.
+    Q_ASSERT(bitsPerComponent > 0);
+    Q_ASSERT(bitsPerComponent < 56);
+}
+
+PDFBitReader::Value PDFBitReader::read()
+{
+    while (m_bitsInBuffer < m_bitsPerComponent)
+    {
+        if (!m_stream->atEnd())
+        {
+            uint8_t currentByte = 0;
+            (*m_stream) >> currentByte;
+            m_buffer = (m_buffer << 8) | currentByte;
+            m_bitsInBuffer += 8;
+        }
+        else
+        {
+            throw PDFParserException(PDFTranslationContext::tr("Not enough data to read %1-bit value.").arg(m_bitsPerComponent));
+        }
+    }
+
+    // Now we have enough bits to read the data
+    Value value = (m_buffer >> (m_bitsInBuffer - m_bitsPerComponent)) & m_maximalValue;
+    m_bitsInBuffer -= m_bitsPerComponent;
+    return value;
+}
+
+void PDFBitReader::seek(qint64 position)
+{
+    if (m_stream->device()->seek(position))
+    {
+        m_buffer = 0;
+        m_bitsInBuffer = 0;
+    }
+    else
+    {
+        throw PDFParserException(PDFTranslationContext::tr("Can't seek to position %1.").arg(position));
+    }
+}
+
+}   // namespace pdf