alex

/* *****************************************************************************
 * A.L.E (Arcade Learning Environment)
 * Copyright (c) 2009-2013 by Yavar Naddaf, Joel Veness, Marc G. Bellemare and
 *   the Reinforcement Learning and Artificial Intelligence Laboratory
 * Released under the GNU General Public License; see License.txt for details.
 *
 * Based on: Stella  --  "An Atari 2600 VCS Emulator"
 * Copyright (c) 1995-2007 by Bradford W. Mott and the Stella team
 *
 * *****************************************************************************
 *  ale_screen.hpp
 *
 *  A class that encapsulates an Atari 2600 screen. Code is provided inline for
 *   efficiency reasons.
 *
 **************************************************************************** */

#ifndef __ALE_SCREEN_HPP__
#define __ALE_SCREEN_HPP__

#include <cassert>
#include <cstddef>
#include <cstring>
#include <memory>
#include <vector>

namespace ale {

using pixel_t = unsigned char;

/** A simple wrapper around an Atari screen. */
class ALEScreen {
 public:
  ALEScreen(int h, int w);
  ALEScreen(const ALEScreen& rhs);

  ALEScreen& operator=(const ALEScreen& rhs);

  /** pixel accessors, (row, column)-ordered */
  pixel_t get(int r, int c) const;
  pixel_t* pixel(int r, int c);

  /** Access a whole row */
  pixel_t* getRow(int r) const;

  /** Access the whole array */
  pixel_t* getArray() const { return const_cast<pixel_t*>(&m_pixels[0]); }

  /** Dimensionality information */
  size_t height() const { return m_rows; }
  size_t width() const { return m_columns; }

  /** Returns the size of the underlying array */
  size_t arraySize() const { return m_rows * m_columns * sizeof(pixel_t); }

  /** Returns whether two screens are equal */
  bool equals(const ALEScreen& rhs) const;

 protected:
  int m_rows;
  int m_columns;

  std::vector<pixel_t> m_pixels;
};

inline ALEScreen::ALEScreen(int h, int w)
    : m_rows(h), m_columns(w),
      // Create a pixel array of the requisite size
      m_pixels(m_rows * m_columns) {}

inline ALEScreen::ALEScreen(const ALEScreen& rhs)
    : m_rows(rhs.m_rows), m_columns(rhs.m_columns), m_pixels(rhs.m_pixels) {}

inline ALEScreen& ALEScreen::operator=(const ALEScreen& rhs) {
  m_rows = rhs.m_rows;
  m_columns = rhs.m_columns;

  // We rely here on the std::vector constructor doing something sensible (i.e. not wasteful)
  // inside its assignment operator
  m_pixels = rhs.m_pixels;

  return *this;
}

inline bool ALEScreen::equals(const ALEScreen& rhs) const {
  return (m_rows == rhs.m_rows && m_columns == rhs.m_columns &&
          (memcmp(&m_pixels[0], &rhs.m_pixels[0], arraySize()) == 0));
}

// pixel accessors, (row, column)-ordered
inline pixel_t ALEScreen::get(int r, int c) const {
  // Perform some bounds-checking
  assert(r >= 0 && r < m_rows && c >= 0 && c < m_columns);
  return m_pixels[r * m_columns + c];
}

inline pixel_t* ALEScreen::pixel(int r, int c) {
  // Perform some bounds-checking
  assert(r >= 0 && r < m_rows && c >= 0 && c < m_columns);
  return &m_pixels[r * m_columns + c];
}

// Access a whole row
inline pixel_t* ALEScreen::getRow(int r) const {
  assert(r >= 0 && r < m_rows);
  return const_cast<pixel_t*>(&m_pixels[r * m_columns]);
}

}  // namespace ale

#endif  // __ALE_SCREEN_HPP__