qpdf/include/qpdf/QPDFNumberTreeObjectHelper.hh

// Copyright (c) 2005-2024 Jay Berkenbilt
//
// This file is part of qpdf.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
// or implied. See the License for the specific language governing permissions and limitations under
// the License.
//
// Versions of qpdf prior to version 7 were released under the terms of version 2.0 of the Artistic
// License. At your option, you may continue to consider qpdf to be licensed under those terms.
// Please see the manual for additional information.

#ifndef QPDFNUMBERTREEOBJECTHELPER_HH
#define QPDFNUMBERTREEOBJECTHELPER_HH

#include <qpdf/QPDFObjGen.hh>
#include <qpdf/QPDFObjectHelper.hh>
#include <map>
#include <memory>

#include <qpdf/DLL.h>

// This is an object helper for number trees. See section 7.9.7 in the PDF spec (ISO 32000) for a
// description of number trees.

// See examples/pdf-name-number-tree.cc for a demonstration of using QPDFNumberTreeObjectHelper.

class NNTreeImpl;
class NNTreeIterator;
class NNTreeDetails;

class QPDF_DLL_CLASS QPDFNumberTreeObjectHelper: public QPDFObjectHelper
{
  public:
    // The qpdf object is required so that this class can issue warnings, attempt repairs, and add
    // indirect objects.
    QPDF_DLL
    QPDFNumberTreeObjectHelper(QPDFObjectHandle, QPDF&, bool auto_repair = true);

    QPDF_DLL
    ~QPDFNumberTreeObjectHelper() override;

    // Create an empty number tree
    QPDF_DLL
    static QPDFNumberTreeObjectHelper newEmpty(QPDF&, bool auto_repair = true);

    typedef long long int numtree_number;

    // Return overall minimum and maximum indices
    QPDF_DLL
    numtree_number getMin();
    QPDF_DLL
    numtree_number getMax();

    // Return whether the number tree has an explicit entry for this number.
    QPDF_DLL
    bool hasIndex(numtree_number idx);

    // Find an object with a specific index. If found, returns true and initializes oh. See also
    // find().
    QPDF_DLL
    bool findObject(numtree_number idx, QPDFObjectHandle& oh);
    // Find the object at the index or, if not found, the object whose index is the highest index
    // less than the requested index. If the requested index is less than the minimum, return false.
    // Otherwise, return true, initialize oh to the object, and set offset to the difference between
    // the requested index and the actual index. For example, if a number tree has values for 3 and
    // 6 and idx is 5, this method would return true, initialize oh to the value with index 3, and
    // set offset to 2 (5 - 3). See also find().
    QPDF_DLL
    bool findObjectAtOrBelow(numtree_number idx, QPDFObjectHandle& oh, numtree_number& offset);

    class QPDF_DLL_PRIVATE iterator
    {
        friend class QPDFNumberTreeObjectHelper;

      public:
        typedef std::pair<numtree_number, QPDFObjectHandle> T;
        using iterator_category = std::bidirectional_iterator_tag;
        using value_type = T;
        using difference_type = long;
        using pointer = T*;
        using reference = T&;

        virtual ~iterator() = default;
        QPDF_DLL
        bool valid() const;
        QPDF_DLL
        iterator& operator++();
        QPDF_DLL
        iterator
        operator++(int)
        {
            iterator t = *this;
            ++(*this);
            return t;
        }
        QPDF_DLL
        iterator& operator--();
        QPDF_DLL
        iterator
        operator--(int)
        {
            iterator t = *this;
            --(*this);
            return t;
        }
        QPDF_DLL
        reference operator*();
        QPDF_DLL
        pointer operator->();
        QPDF_DLL
        bool operator==(iterator const& other) const;
        QPDF_DLL
        bool
        operator!=(iterator const& other) const
        {
            return !operator==(other);
        }

        // DANGER: this method can create inconsistent trees if not used properly! Insert a new item
        // immediately after the current iterator and increment so that it points to the new item.
        // If the current iterator is end(), insert at the beginning. This method does not check for
        // proper ordering, so if you use it, you must ensure that the item you are inserting
        // belongs where you are putting it. The reason for this method is that it is more efficient
        // than insert() and can be used safely when you are creating a new tree and inserting items
        // in sorted order.
        QPDF_DLL
        void insertAfter(numtree_number key, QPDFObjectHandle value);

        // Remove the current item and advance the iterator to the next item.
        QPDF_DLL
        void remove();

      private:
        void updateIValue();

        iterator(std::shared_ptr<NNTreeIterator> const&);
        std::shared_ptr<NNTreeIterator> impl;
        value_type ivalue;
    };

    // The iterator looks like map iterator, so i.first is a numtree_number and i.second is a
    // QPDFObjectHandle. Incrementing end() brings you to the first item. Decrementing end() brings
    // you to the last item.
    QPDF_DLL
    iterator begin() const;
    QPDF_DLL
    iterator end() const;
    // Return a bidirectional iterator that points to the last item.
    QPDF_DLL
    iterator last() const;

    // Find the entry with the given key. If return_prev_if_not_found is true and the item is not
    // found, return the next lower item.
    QPDF_DLL
    iterator find(numtree_number key, bool return_prev_if_not_found = false);

    // Insert a new item. If the key already exists, it is replaced.
    QPDF_DLL
    iterator insert(numtree_number key, QPDFObjectHandle value);

    // Remove an item. Return true if the item was found and removed; otherwise return false. If
    // value is not nullptr, initialize it to the value that was removed.
    QPDF_DLL
    bool remove(numtree_number key, QPDFObjectHandle* value = nullptr);

    // Return the contents of the number tree as a map. Note that number trees may be very large, so
    // this may use a lot of RAM. It is more efficient to use QPDFNumberTreeObjectHelper's iterator.
    typedef std::map<numtree_number, QPDFObjectHandle> idx_map;
    QPDF_DLL
    idx_map getAsMap() const;

    // Split a node if the number of items exceeds this value. There's no real reason to ever set
    // this except for testing.
    QPDF_DLL
    void setSplitThreshold(int);

  private:
    class QPDF_DLL_PRIVATE Members
    {
        friend class QPDFNumberTreeObjectHelper;
        typedef QPDFNumberTreeObjectHelper::numtree_number numtree_number;

      public:
        QPDF_DLL
        ~Members() = default;

      private:
        Members(QPDFObjectHandle& oh, QPDF&, bool auto_repair);
        Members(Members const&) = delete;

        std::shared_ptr<NNTreeImpl> impl;
    };

    std::shared_ptr<Members> m;
};

#endif // QPDFNUMBERTREEOBJECTHELPER_HH