indexmap.h

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#ifndef ION_BASE_INDEXMAP_H_
#define ION_BASE_INDEXMAP_H_

#include "ion/base/logging.h"

namespace ion {
namespace base {

template <typename OrderedIndexType, typename UnorderedIndexType>
class IndexMap {
 public:
  IndexMap(const UnorderedIndexType unordered_indices[], size_t count)
      : unordered_indices_(unordered_indices),
        count_(count) {}

  size_t GetCount() const { return count_; }

  UnorderedIndexType GetUnorderedIndex(OrderedIndexType ordered_index) const {
    DCHECK_LE(0, static_cast<int>(ordered_index));
    DCHECK_GT(count_, static_cast<size_t>(ordered_index));
    return unordered_indices_[ordered_index];
  }

  OrderedIndexType GetOrderedIndex(UnorderedIndexType unordered_index) const {
    int ordered_index = -1;
    for (size_t i = 0; i < count_; ++i) {
      if (unordered_indices_[i] == unordered_index) {
        ordered_index = static_cast<int>(i);
        break;
      }
    }
    DCHECK_GE(ordered_index, 0) << "IndexMap: Invalid unordered index "
                                << unordered_index << " does not match any "
                                << "ordered index.";
    return static_cast<OrderedIndexType>(ordered_index);
  }

 private:
  const UnorderedIndexType* unordered_indices_;
  const size_t count_;
};

}  // namespace base
}  // namespace ion

#endif  // ION_BASE_INDEXMAP_H_