// g2o - General Graph Optimization
// Copyright (C) 2011 R. Kuemmerle, G. Grisetti, W. Burgard
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the
//   documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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#ifndef G2O_MATRIX_STRUCTURE_H
#define G2O_MATRIX_STRUCTURE_H

#include <string_view>

#include "g2o_core_api.h"

namespace g2o {

/**
 * \brief representing the structure of a matrix in column compressed structure
 * (only the upper triangular part of the matrix)
 */
class G2O_CORE_API MatrixStructure {
 public:
  MatrixStructure();
  ~MatrixStructure();
  /**
   * allocate space for the Matrix Structure. You may call this on an already
   * allocated struct, it will then reallocate the memory + additional space
   * (double the required space).
   */
  void alloc(int n_, int nz);

  void free();

  /**
   * Write the matrix pattern to a file. File is also loadable by octave, e.g.,
   * then use spy(matrix)
   */
  bool write(std::string_view filename) const;

  int n;     ///< A is m-by-n.  n must be >= 0.
  int m;     ///< A is m-by-n.  m must be >= 0.
  int* Ap;   ///< column pointers for A, of size n+1
  int* Aii;  ///< row indices of A, of size nz = Ap [n]

  //! max number of non-zeros blocks
  int nzMax() const { return maxNz; }

 protected:
  int maxN;   ///< size of the allocated memory
  int maxNz;  ///< size of the allocated memory
};

}  // namespace g2o

#endif
