iterator.h

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/* Copyright (c) 2021, 2024, Oracle and/or its affiliates.
 
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   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef ITERATOR_INCLUDED
#define ITERATOR_INCLUDED
 
#include "cache.h" /* Datacache */
 
namespace keyring_common::iterator {
 
template <typename Data_extension>
class Iterator {
 public:
  /** Constructor */
  Iterator() : it_(), end_(), version_(0), valid_(false), cached_(false) {}
  Iterator(const cache::Datacache<Data_extension> &datacache,
           const meta::Metadata &metadata)
      : it_(datacache.at(metadata)),
        end_(datacache.end()),
        version_(datacache.version()),
        valid_(it_ != end_),
        cached_(false) {}
 
  Iterator(const cache::Datacache<Data_extension> &datacache, bool cached)
      : it_(datacache.begin()),
        end_(datacache.end()),
        version_(datacache.version()),
        valid_(true),
        cached_(cached) {
    if (cached_) {
      for (std::pair<meta::Metadata, Data_extension> element : datacache)
        metadata_.store(element.first, element.second);
 
      it_ = metadata_.begin();
      end_ = metadata_.end();
    }
  }
 
  /** Destructor */
  ~Iterator() { metadata_.clear(); }
 
  /** Get iterator */
  typename cache::Cache<Data_extension>::const_iterator get_iterator() const {
    return it_;
  }
 
  /** Move iterator forward */
  bool next(size_t version) {
    if (!iterator_valid(version)) {
      it_ = end_;
      valid_ = false;
      return false;
    }
    it_++;
    return true;
  }
 
  bool metadata(size_t version, meta::Metadata &metadata) {
    if (!iterator_valid(version)) {
      it_ = end_;
      valid_ = false;
      return false;
    }
    metadata = it_->first;
    return true;
  }
 
  bool data(size_t version, Data_extension &data) {
    if (!iterator_valid(version)) {
      it_ = end_;
      valid_ = false;
      return false;
    }
    data = it_->second;
    return true;
  }
 
  bool valid(size_t version) {
    valid_ = iterator_valid(version);
    return valid_;
  }
 
 private:
  /** Internal validity checker */
  inline bool iterator_valid(size_t version) {
    if (cached_) {
      return valid_ && (it_ != end_);
    }
    return valid_ && (version == version_) && (it_ != end_);
  }
 
 private:
  /** Const Iterator */
  typename cache::Cache<Data_extension>::const_iterator it_;
  /** End */
  typename cache::Cache<Data_extension>::const_iterator end_;
  /** Iterator version */
  size_t version_;
  /** validity of the iterator */
  bool valid_;
  /** Iterator type */
  bool cached_;
  /** Local copy */
  typename cache::Datacache<Data_extension> metadata_;
};
 
}  // namespace keyring_common::iterator
 
#endif  // !ITERATOR_INCLUDED