Issue #118: First part of splitting

Pdf4QtLibCore/sources/pdfnumbertreeloader.h

@@ -0,0 +1,97 @@
+//    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