mirror of https://github.com/JakubMelka/PDF4QT.git
570 lines
19 KiB
C++
570 lines
19 KiB
C++
// Copyright (C) 2020-2022 Jakub Melka
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//
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// This file is part of PDF4QT.
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//
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// PDF4QT is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// with the written consent of the copyright owner, any later version.
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//
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// PDF4QT is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with PDF4QT. If not, see <https://www.gnu.org/licenses/>.
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#include "pdfoptimizer.h"
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#include "pdfvisitor.h"
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#include "pdfexecutionpolicy.h"
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#include "pdfobjectutils.h"
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#include "pdfutils.h"
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#include "pdfconstants.h"
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#include "pdfdocumentbuilder.h"
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#include "pdfstreamfilters.h"
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#include "pdfdbgheap.h"
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namespace pdf
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{
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class PDFUpdateObjectVisitor : public PDFAbstractVisitor
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{
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public:
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explicit inline PDFUpdateObjectVisitor(const PDFObjectStorage* storage) :
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m_storage(storage)
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{
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m_objectStack.reserve(32);
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}
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virtual void visitNull() override;
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virtual void visitBool(bool value) override;
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virtual void visitInt(PDFInteger value) override;
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virtual void visitReal(PDFReal value) override;
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virtual void visitString(PDFStringRef string) override;
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virtual void visitName(PDFStringRef name) override;
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virtual void visitArray(const PDFArray* array) override;
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virtual void visitDictionary(const PDFDictionary* dictionary) override;
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virtual void visitStream(const PDFStream* stream) override;
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virtual void visitReference(const PDFObjectReference reference) override;
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PDFObject getObject();
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protected:
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const PDFObjectStorage* m_storage;
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std::vector<PDFObject> m_objectStack;
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};
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void PDFUpdateObjectVisitor::visitNull()
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{
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m_objectStack.push_back(PDFObject::createNull());
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}
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void PDFUpdateObjectVisitor::visitBool(bool value)
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{
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m_objectStack.push_back(PDFObject::createBool(value));
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}
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void PDFUpdateObjectVisitor::visitInt(PDFInteger value)
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{
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m_objectStack.push_back(PDFObject::createInteger(value));
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}
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void PDFUpdateObjectVisitor::visitReal(PDFReal value)
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{
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m_objectStack.push_back(PDFObject::createReal(value));
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}
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void PDFUpdateObjectVisitor::visitString(PDFStringRef string)
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{
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m_objectStack.push_back(PDFObject::createString(string));
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}
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void PDFUpdateObjectVisitor::visitName(PDFStringRef name)
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{
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m_objectStack.push_back(PDFObject::createName(name));
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}
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void PDFUpdateObjectVisitor::visitArray(const PDFArray* array)
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{
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acceptArray(array);
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// We have all objects on the stack
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Q_ASSERT(array->getCount() <= m_objectStack.size());
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auto it = std::next(m_objectStack.cbegin(), m_objectStack.size() - array->getCount());
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std::vector<PDFObject> objects(it, m_objectStack.cend());
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PDFObject object = PDFObject::createArray(std::make_shared<PDFArray>(qMove(objects)));
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m_objectStack.erase(it, m_objectStack.cend());
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m_objectStack.push_back(object);
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}
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void PDFUpdateObjectVisitor::visitDictionary(const PDFDictionary* dictionary)
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{
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Q_ASSERT(dictionary);
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std::vector<PDFDictionary::DictionaryEntry> entries;
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entries.reserve(dictionary->getCount());
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for (size_t i = 0, count = dictionary->getCount(); i < count; ++i)
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{
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dictionary->getValue(i).accept(this);
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Q_ASSERT(!m_objectStack.empty());
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entries.emplace_back(dictionary->getKey(i), m_objectStack.back());
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m_objectStack.pop_back();
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}
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m_objectStack.push_back(PDFObject::createDictionary(std::make_shared<PDFDictionary>(qMove(entries))));
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}
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void PDFUpdateObjectVisitor::visitStream(const PDFStream* stream)
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{
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const PDFDictionary* dictionary = stream->getDictionary();
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visitDictionary(dictionary);
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Q_ASSERT(!m_objectStack.empty());
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PDFObject dictionaryObject = m_objectStack.back();
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m_objectStack.pop_back();
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PDFDictionary newDictionary(*dictionaryObject.getDictionary());
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m_objectStack.push_back(PDFObject::createStream(std::make_shared<PDFStream>(qMove(newDictionary), QByteArray(*stream->getContent()))));
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}
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void PDFUpdateObjectVisitor::visitReference(const PDFObjectReference reference)
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{
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m_objectStack.push_back(PDFObject::createReference(reference));
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}
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PDFObject PDFUpdateObjectVisitor::getObject()
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{
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Q_ASSERT(m_objectStack.size() == 1);
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return qMove(m_objectStack.back());
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}
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class PDFRemoveSimpleObjectsVisitor : public PDFUpdateObjectVisitor
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{
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public:
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explicit inline PDFRemoveSimpleObjectsVisitor(const PDFObjectStorage* storage, std::atomic<PDFInteger>* counter) :
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PDFUpdateObjectVisitor(storage),
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m_counter(counter)
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{
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}
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virtual void visitReference(const PDFObjectReference reference) override;
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private:
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std::atomic<PDFInteger>* m_counter;
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};
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void PDFRemoveSimpleObjectsVisitor::visitReference(const PDFObjectReference reference)
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{
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PDFObject object = m_storage->getObjectByReference(reference);
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switch (object.getType())
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{
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case PDFObject::Type::Null:
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case PDFObject::Type::Bool:
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case PDFObject::Type::Int:
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case PDFObject::Type::Real:
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case PDFObject::Type::String:
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case PDFObject::Type::Name:
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++*m_counter;
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m_objectStack.push_back(qMove(object));
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break;
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default:
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m_objectStack.push_back(PDFObject::createReference(reference));
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break;
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}
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}
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class PDFRemoveNullDictionaryEntriesVisitor : public PDFUpdateObjectVisitor
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{
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public:
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explicit PDFRemoveNullDictionaryEntriesVisitor(const PDFObjectStorage* storage, std::atomic<PDFInteger>* counter) :
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PDFUpdateObjectVisitor(storage),
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m_counter(counter)
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{
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}
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virtual void visitDictionary(const PDFDictionary* dictionary) override;
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private:
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std::atomic<PDFInteger>* m_counter;
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};
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void PDFRemoveNullDictionaryEntriesVisitor::visitDictionary(const PDFDictionary* dictionary)
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{
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Q_ASSERT(dictionary);
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std::vector<PDFDictionary::DictionaryEntry> entries;
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entries.reserve(dictionary->getCount());
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for (size_t i = 0, count = dictionary->getCount(); i < count; ++i)
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{
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dictionary->getValue(i).accept(this);
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Q_ASSERT(!m_objectStack.empty());
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if (!m_objectStack.back().isNull())
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{
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entries.emplace_back(dictionary->getKey(i), m_objectStack.back());
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}
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else
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{
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++*m_counter;
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}
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m_objectStack.pop_back();
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}
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m_objectStack.push_back(PDFObject::createDictionary(std::make_shared<PDFDictionary>(qMove(entries))));
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}
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PDFOptimizer::PDFOptimizer(OptimizationFlags flags, QObject* parent) :
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QObject(parent),
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m_flags(flags)
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{
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}
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void PDFOptimizer::optimize()
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{
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// Jakub Melka: We divide optimization into stages, each
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// stage can consist from multiple passes.
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constexpr OptimizationFlags stages[] = { OptimizationFlags(DereferenceSimpleObjects),
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OptimizationFlags(RemoveNullObjects),
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OptimizationFlags(RemoveUnusedObjects | MergeIdenticalObjects),
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OptimizationFlags(ShrinkObjectStorage),
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OptimizationFlags(RecompressFlateStreams) };
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int stage = 1;
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emit optimizationStarted();
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for (OptimizationFlags flags : stages)
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{
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emit optimizationProgress(tr("Stage %1").arg(stage++));
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OptimizationFlags currentSteps = flags & m_flags;
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int passIndex = 1;
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bool pass = true;
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while (pass)
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{
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emit optimizationProgress(tr("Pass %1").arg(passIndex++));
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pass = false;
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if (currentSteps.testFlag(DereferenceSimpleObjects))
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{
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pass = performDereferenceSimpleObjects() || pass;
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}
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if (currentSteps.testFlag(RemoveNullObjects))
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{
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pass = performRemoveNullObjects() || pass;
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}
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if (currentSteps.testFlag(RemoveUnusedObjects))
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{
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pass = performRemoveUnusedObjects() || pass;
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}
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if (currentSteps.testFlag(MergeIdenticalObjects))
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{
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pass = performMergeIdenticalObjects() || pass;
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}
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if (currentSteps.testFlag(ShrinkObjectStorage))
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{
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pass = performShrinkObjectStorage() || pass;
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}
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if (currentSteps.testFlag(RecompressFlateStreams))
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{
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pass = performRecompressFlateStreams() || pass;
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}
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}
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}
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emit optimizationFinished();
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}
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PDFOptimizer::OptimizationFlags PDFOptimizer::getFlags() const
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{
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return m_flags;
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}
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void PDFOptimizer::setFlags(OptimizationFlags flags)
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{
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m_flags = flags;
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}
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bool PDFOptimizer::performDereferenceSimpleObjects()
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{
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std::atomic<PDFInteger> counter = 0;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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auto processEntry = [this, &counter](PDFObjectStorage::Entry& entry)
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{
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PDFRemoveSimpleObjectsVisitor visitor(&m_storage, &counter);
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entry.object.accept(&visitor);
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entry.object = visitor.getObject();
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};
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PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Unknown, objects.begin(), objects.end(), processEntry);
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m_storage.setObjects(qMove(objects));
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emit optimizationProgress(tr("Simple objects dereferenced and embedded: %1").arg(counter));
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return false;
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}
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bool PDFOptimizer::performRemoveNullObjects()
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{
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std::atomic<PDFInteger> counter = 0;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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auto processEntry = [this, &counter](PDFObjectStorage::Entry& entry)
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{
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PDFRemoveNullDictionaryEntriesVisitor visitor(&m_storage, &counter);
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entry.object.accept(&visitor);
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entry.object = visitor.getObject();
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};
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PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Unknown, objects.begin(), objects.end(), processEntry);
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m_storage.setObjects(qMove(objects));
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emit optimizationProgress(tr("Null objects entries from dictionaries removed: %1").arg(counter));
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return false;
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}
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bool PDFOptimizer::performRemoveUnusedObjects()
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{
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std::atomic<PDFInteger> counter = 0;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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std::set<PDFObjectReference> references = PDFObjectUtils::getReferences({ m_storage.getTrailerDictionary() }, m_storage);
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PDFIntegerRange<size_t> range(0, objects.size());
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auto processEntry = [&counter, &objects, &references](size_t index)
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{
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PDFObjectStorage::Entry& entry = objects[index];
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PDFObjectReference reference(PDFInteger(index), entry.generation);
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if (!references.count(reference) && !entry.object.isNull())
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{
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entry.object = PDFObject();
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++counter;
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}
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};
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PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Unknown, range.begin(), range.end(), processEntry);
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m_storage.setObjects(qMove(objects));
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emit optimizationProgress(tr("Unused objects removed: %1").arg(counter));
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return counter > 0;
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}
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bool PDFOptimizer::performMergeIdenticalObjects()
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{
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std::atomic<PDFInteger> counter = 0;
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std::map<PDFObjectReference, PDFObjectReference> replacementMap;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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// Find same objects
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QMutex mutex;
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PDFIntegerRange<size_t> range(0, objects.size());
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auto processEntry = [this, &counter, &objects, &mutex, &replacementMap](size_t index)
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{
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const PDFObjectStorage::Entry& entry = objects[index];
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// We do not merge special objects, such as pages
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if (const PDFDictionary* dictionary = m_storage.getDictionaryFromObject(entry.object))
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{
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PDFObject nameObject = m_storage.getObject(dictionary->get("Type"));
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if (nameObject.isName())
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{
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if (nameObject.getString() == "Page")
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{
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return;
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}
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}
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}
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for (size_t i = 0; i < index; ++i)
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{
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if (objects[i].object.isNull())
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{
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// Jakub Melka: we do not merge null objects, they are just removed
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continue;
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}
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if (objects[i].object == entry.object)
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{
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QMutexLocker lock(&mutex);
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PDFObjectReference oldReference = PDFObjectReference(PDFInteger(index), objects[index].generation);
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PDFObjectReference newReference = PDFObjectReference(PDFInteger(i), objects[i].generation);
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replacementMap[oldReference] = newReference;
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++counter;
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break;
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}
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}
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};
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PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Unknown, range.begin(), range.end(), processEntry);
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// Replace objects
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if (!replacementMap.empty())
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{
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for (size_t i = 0; i < objects.size(); ++i)
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{
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objects[i].object = PDFObjectUtils::replaceReferences(objects[i].object, replacementMap);
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}
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PDFObject trailerDictionary = PDFObjectUtils::replaceReferences(m_storage.getTrailerDictionary(), replacementMap);
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m_storage.setTrailerDictionary(trailerDictionary);
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}
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m_storage.setObjects(qMove(objects));
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emit optimizationProgress(tr("Identical objects merged: %1").arg(counter));
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return counter > 0;
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}
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bool PDFOptimizer::performShrinkObjectStorage()
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{
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std::map<PDFObjectReference, PDFObjectReference> replacementMap;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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auto isFree = [](const PDFObjectStorage::Entry& entry)
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{
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return entry.object.isNull() && entry.generation < PDF_MAX_OBJECT_GENERATION;
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};
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auto isOccupied = [](const PDFObjectStorage::Entry& entry)
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{
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return !entry.object.isNull();
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};
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// Make list of free usable indices
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std::vector<size_t> freeIndices;
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freeIndices.reserve(objects.size() / 8);
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const size_t objectCount = objects.size();
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for (size_t sourceIndex = 1; sourceIndex < objectCount; ++sourceIndex)
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{
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if (isFree(objects[sourceIndex]))
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{
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freeIndices.push_back(sourceIndex);
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}
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}
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std::reverse(freeIndices.begin(), freeIndices.end());
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// Move objects to free entries
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for (size_t sourceIndex = objectCount - 1; sourceIndex > 0; --sourceIndex)
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{
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if (freeIndices.empty())
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{
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// Jakub Melka: We have run out of free indices
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break;
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}
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PDFObjectStorage::Entry& sourceEntry = objects[sourceIndex];
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if (isOccupied(sourceEntry))
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{
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size_t targetIndex = freeIndices.back();
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freeIndices.pop_back();
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if (targetIndex >= sourceIndex)
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{
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break;
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}
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PDFObjectStorage::Entry& targetEntry = objects[targetIndex];
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Q_ASSERT(isFree(targetEntry));
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++targetEntry.generation;
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targetEntry.object = qMove(sourceEntry.object);
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sourceEntry.object = PDFObject();
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replacementMap[PDFObjectReference(PDFInteger(sourceIndex), sourceEntry.generation)] = PDFObjectReference(PDFInteger(targetIndex), targetEntry.generation);
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}
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}
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// Shrink objects array
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for (size_t sourceIndex = objectCount - 1; sourceIndex > 0; --sourceIndex)
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{
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if (isOccupied(objects[sourceIndex]))
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{
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objects.resize(sourceIndex + 1);
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break;
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}
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}
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// Update objects
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if (!replacementMap.empty())
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{
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for (size_t i = 0; i < objects.size(); ++i)
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{
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objects[i].object = PDFObjectUtils::replaceReferences(objects[i].object, replacementMap);
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}
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PDFObject trailerDictionary = PDFObjectUtils::replaceReferences(m_storage.getTrailerDictionary(), replacementMap);
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PDFObjectFactory factory;
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factory.beginDictionary();
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factory.beginDictionaryItem("Size");
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factory << PDFInteger(objects.size());
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factory.endDictionaryItem();
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factory.endDictionary();
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trailerDictionary = PDFObjectManipulator::merge(trailerDictionary, factory.takeObject(), PDFObjectManipulator::NoFlag);
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m_storage.setTrailerDictionary(trailerDictionary);
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}
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const size_t newObjectCount = objects.size();
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m_storage.setObjects(qMove(objects));
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emit optimizationProgress(tr("Object list shrinked by: %1").arg(objectCount - newObjectCount));
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return false;
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}
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bool PDFOptimizer::performRecompressFlateStreams()
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{
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std::atomic<PDFInteger> bytesSaved = 0;
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PDFObjectStorage::PDFObjects objects = m_storage.getObjects();
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auto processEntry = [this, &bytesSaved](PDFObjectStorage::Entry& entry)
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{
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if (entry.object.isStream())
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{
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const PDFStream* stream = entry.object.getStream();
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const PDFDictionary* dictionary = stream->getDictionary();
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if (dictionary->hasKey("F"))
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{
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// External file stream, we do not recompress it
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return;
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}
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PDFStreamFilterStorage::StreamFilters streamFilters = PDFStreamFilterStorage::getStreamFilters(stream, std::bind(QOverload<const PDFObject&>::of(&PDFObjectStorage::getObject), &m_storage, std::placeholders::_1));
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if (streamFilters.filterObjects.empty())
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{
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// No filters
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return;
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}
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const PDFStreamFilter* streamFilter = streamFilters.filterObjects.front();
|
|
if (dynamic_cast<const PDFFlateDecodeFilter*>(streamFilter))
|
|
{
|
|
// Try to recompress. If we end with less data, then we use recompressed stream
|
|
QByteArray recompressedData = PDFFlateDecodeFilter::recompress(*stream->getContent());
|
|
const PDFInteger currentBytesSaved = stream->getContent()->size() - recompressedData.size();
|
|
if (currentBytesSaved > 0)
|
|
{
|
|
bytesSaved += currentBytesSaved;
|
|
PDFDictionary updatedDictionary = *dictionary;
|
|
updatedDictionary.setEntry(PDFInplaceOrMemoryString("Length"), PDFObject::createInteger(recompressedData.size()));
|
|
entry.object = PDFObject::createStream(std::make_shared<PDFStream>(qMove(updatedDictionary), qMove(recompressedData)));
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Unknown, objects.begin(), objects.end(), processEntry);
|
|
m_storage.setObjects(qMove(objects));
|
|
emit optimizationProgress(tr("Bytes saved by recompressing stream: %1").arg(bytesSaved));
|
|
|
|
return false;
|
|
}
|
|
|
|
} // namespace pdf
|