PDF4QT/Pdf4QtLib/sources/pdfnumbertreeloader.h

98 lines
3.4 KiB
C++

// Copyright (C) 2018-2021 Jakub Melka
//
// This file is part of Pdf4Qt.
//
// Pdf4Qt 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
// with the written consent of the copyright owner, any later version.
//
// Pdf4Qt 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 Pdf4Qt. If not, see <https://www.gnu.org/licenses/>.
#ifndef PDFNUMBERTREELOADER_H
#define PDFNUMBERTREELOADER_H
#include "pdfdocument.h"
#include <vector>
namespace pdf
{
/// This class can load a number tree into the array
template<typename Type>
class PDFNumberTreeLoader
{
public:
explicit PDFNumberTreeLoader() = delete;
using Objects = std::vector<Type>;
/// Parses the number tree and loads its items into the array. Some errors are ignored,
/// e.g. when kid is null. Type must contain methods to load object array.
static Objects parse(const PDFObjectStorage* storage, const PDFObject& root)
{
Objects result;
// First, try to load items from the tree into the array
parseImpl(result, storage, root);
// Array may not be sorted. Sort it using comparison operator for Type.
std::stable_sort(result.begin(), result.end());
return result;
}
private:
static void parseImpl(Objects& objects, const PDFObjectStorage* storage, const PDFObject& root)
{
if (const PDFDictionary* dictionary = storage->getDictionaryFromObject(root))
{
// First, load the objects into the array
const PDFObject& numberedItems = storage->getObject(dictionary->get("Nums"));
if (numberedItems.isArray())
{
const PDFArray* numberedItemsArray = numberedItems.getArray();
const size_t count = numberedItemsArray->getCount() / 2;
objects.reserve(objects.size() + count);
for (size_t i = 0; i < count; ++i)
{
const size_t numberIndex = 2 * i;
const size_t valueIndex = 2 * i + 1;
const PDFObject& number = storage->getObject(numberedItemsArray->getItem(numberIndex));
if (!number.isInt())
{
continue;
}
objects.emplace_back(Type::parse(number.getInteger(), storage, numberedItemsArray->getItem(valueIndex)));
}
}
// Then, follow the kids
const PDFObject& kids = storage->getObject(dictionary->get("Kids"));
if (kids.isArray())
{
const PDFArray* kidsArray = kids.getArray();
const size_t count = kidsArray->getCount();
for (size_t i = 0; i < count; ++i)
{
parseImpl(objects, storage, kidsArray->getItem(i));
}
}
}
}
};
} // namespace pdf
#endif // PDFNUMBERTREELOADER_H