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// # << NEORV32 - Conway's Game of Life >>                                                         #

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// # BSD 3-Clause License                                                                          #

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// # Copyright (c) 2022, Stephan Nolting. All rights reserved.                                     #

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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

// #################################################################################################

/**********************************************************************//**

 * @file game_of_life/main.c

 * @author Stephan Nolting

 * @brief Conway's game of life in a UART terminal.

 **************************************************************************/

#include <neorv32.h>

/**********************************************************************//**

 * @name User configuration

 **************************************************************************/

/**@{*/

/** UART BAUD rate */

#define BAUD_RATE     19200

/** Universe x size (has to be a multiple of 8) */

#define NUM_CELLS_X   160

/** Universe y size */

#define NUM_CELLS_Y   40

/** Delay between generations in ms */

#define GEN_DELAY     500

/** Symbol for dead cell */

#define CELL_DEAD  (' ')

/** Symbol for alive cell */

#define CELL_ALIVE ('#')

/**@}*/

/**********************************************************************//**

 * The universe

 **************************************************************************/

uint8_t universe[2][NUM_CELLS_X/8][NUM_CELLS_Y];

// Prototypes

void clear_universe(int u);

void set_cell(int u, int x, int y);

int get_cell(int u, int x, int y);

int get_neighborhood(int u, int x, int y);

void print_universe(int u);

int pop_count(int u);

uint32_t xorshift32(void);

/**********************************************************************//**

 * Conway's Game of Life.

 *

 * @note This program requires the UART to be synthesized (the TRNG is optional).

 *

 * @return 0 if execution was successful

 **************************************************************************/

int main(void) {

  // check if UART unit is implemented at all

  if (neorv32_uart0_available() == 0) {

    return 1;

  }

  // capture all exceptions and give debug info via UART

  // this is not required, but keeps us safe

  neorv32_rte_setup();

  // init UART at default baud rate, no parity bits, ho hw flow control

  neorv32_uart0_setup(BAUD_RATE, PARITY_NONE, FLOW_CONTROL_NONE);

  // check available hardware extensions and compare with compiler flags

  neorv32_rte_check_isa(0); // silent = 0 -> show message if isa mismatch

  while (1) {

    int u = 0, cell = 0, n = 0;

    int x, y;

    int trng_available = 0;

    uint8_t trng_data;

    // initialize universe

    uint32_t generation = 0;

    clear_universe(0);

    clear_universe(1);

    // intro

    neorv32_uart0_printf("\n\n<<< Conways's Game of Life >>>\n\n");

    neorv32_uart0_printf("This program requires a terminal resolution of at least %ux%u characters.\n", NUM_CELLS_X+2, NUM_CELLS_Y+3);

    neorv32_uart0_printf("Press any key to start a random-initialized torus-style universe of %ux%u cells.\n", NUM_CELLS_X, NUM_CELLS_Y);

    neorv32_uart0_printf("You can pause/restart the simulation by pressing any key.\n");

    // check if TRNG was synthesized

    if (neorv32_trng_available()) {

      neorv32_uart0_printf("\nTRNG detected. Using TRNG for universe initialization.\n");

      neorv32_trng_enable();

      trng_available = 1;

    }

    // randomize until key pressed

    while (neorv32_uart0_char_received() == 0) {

      xorshift32();

    }

    // initialize universe using random data

    for (x=0; x<NUM_CELLS_X/8; x++) {

      for (y=0; y<NUM_CELLS_Y; y++) {

        if (trng_available) {

          while (1) {

            int err = neorv32_trng_get(&trng_data);

            if (err) {

              neorv32_uart0_printf("TRNG error (%i)! Restarting TRNG...\n", err);

              continue;

            }

            else {

              break;

            }

          }

          universe[0][x][y] = trng_data; // use data from TRNG

        }

        else {

          universe[0][x][y] = (uint8_t)xorshift32(); // use data from PRNG

        }

      }

    }

    while(1) {

      // user abort?

      if (neorv32_uart0_char_received()) {

        neorv32_uart0_printf("\nRestart (y/n)?");

        if (neorv32_uart0_getc() == 'y') {

          break;

        }

      }

      // print generation, population count and the current universe

      neorv32_uart0_printf("\n\nGeneration %u: %u/%u living cells\n", (uint32_t)generation, (uint32_t)pop_count(u), NUM_CELLS_X*NUM_CELLS_Y);

      print_universe(u);

      // compute next generation

      clear_universe((u + 1) & 1);

      for (x=0; x<NUM_CELLS_X; x++) {

        for (y=0; y<NUM_CELLS_Y; y++) {

          cell = get_cell(u, x, y); // state of current cell

          n = get_neighborhood(u, x, y); // number of living neighbor cells

          // -- classic rule set --

          // if center cell is dead -> cell comes to life when there are exactly 3 living cells around

          // if center cell is alive -> stay alive if there are 2 or three living cells around

          // else -> cell is/becomes dead

          if (((cell == 0) && (n == 3)) || ((cell != 0) && ((n == 2) || (n == 3)))) {

            set_cell((u + 1) & 1, x, y);

          }

        } // y

      } // x

      u = (u + 1) & 1; // switch universe

      generation++;

      // wait GEN_DELAY ms

      neorv32_cpu_delay_ms(GEN_DELAY);

    }

  }

  return 0;

}

/**********************************************************************//**

 * Print universe via UARt.

 *

 * @param[in] u Universe select (0 or 1).

 **************************************************************************/

void print_universe(int u){

  int16_t x, y;

  neorv32_uart0_putc('+');

  for (x=0; x<NUM_CELLS_X; x++) {

    neorv32_uart0_putc('-');

  }

  neorv32_uart0_putc('+');

  neorv32_uart0_putc('\r');

  neorv32_uart0_putc('\n');

  for (y=0; y<NUM_CELLS_Y; y++) {

    neorv32_uart0_putc('|');

    for (x=0; x<NUM_CELLS_X; x++) {

      if (get_cell(u, x, y))

        neorv32_uart0_putc((char)CELL_ALIVE);

      else

        neorv32_uart0_putc((char)CELL_DEAD);

    }

    // end of line

    neorv32_uart0_putc('|');

    neorv32_uart0_putc('\r');

    neorv32_uart0_putc('\n');

  }

  neorv32_uart0_putc('+');

  for (x=0; x<NUM_CELLS_X; x++) {

    neorv32_uart0_putc('-');

  }

  neorv32_uart0_putc('+');

}

/**********************************************************************//**

 * Kill all cells in universe.

 *

 * @param[in] u Universe select (0 or 1).

 **************************************************************************/

void clear_universe(int u){

  uint16_t x, y;

  for (x=0; x<NUM_CELLS_X/8; x++) {

    for (y=0; y<NUM_CELLS_Y; y++) {

      universe[u][x][y] = 0;

    }

  }

}

/**********************************************************************//**

 * Make cell alive.

 *

 * @param[in] u Universe select (0 or 1).

 * @param[in] x X coordinate of cell.

 * @param[in] y Y coordinate of cell.

 **************************************************************************/

void set_cell(int u, int x, int y){

  if ((x >= NUM_CELLS_X) || (y >= NUM_CELLS_Y))

    return; // out of range

  universe[u][x>>3][y] |= (uint8_t)(1 << (7 - (x & 7)));

}

/**********************************************************************//**

 * Get state of cell.

 *

 * @param[in] u Universe select (0 or 1).

 * @param[in] x X coordinate of cell.

 * @param[in] y Y coordinate of cell.

 * @return Cell is dead when 0, cell is alive when 1.

 **************************************************************************/

int get_cell(int u, int x, int y){

  // range check: wrap around -> torus-style universe

  if (x < 0)

    x = NUM_CELLS_X-1;

  if (x > NUM_CELLS_X-1)

    x = 0;

  if (y < 0)

    y = NUM_CELLS_Y-1;

  if (y > NUM_CELLS_Y-1)

    y = 0;

  // check bit according to cell

  uint8_t tmp = universe[u][x>>3][y];

  tmp &= 1 << (7 - (x & 7));

  if (tmp == 0)

    return 0; // DEAD

  else

    return 1; // ALIVE

}

/**********************************************************************//**

 * Get number of living cells in neighborhood.

 *

 * @param[in] u Universe select (0 or 1).

 * @param[in] x X coordinate of the neighborhood's center cell.

 * @param[in] y Y coordinate of the neighborhood's center cell.

 * @return Number of living cells in neighborhood (0..9).

 **************************************************************************/

int get_neighborhood(int u, int x, int y){

// Cell index layout:

// 012

// 3#4

// 567

  int num = 0;

  num += get_cell(u, x-1, y-1); // 0

  num += get_cell(u, x,   y-1); // 1

  num += get_cell(u, x+1, y-1); // 2

  num += get_cell(u, x-1, y);   // 3

  num += get_cell(u, x+1, y);   // 4

  num += get_cell(u, x-1, y+1); // 5

  num += get_cell(u, x,   y+1); // 6

  num += get_cell(u, x+1, y+1); // 7

  return num;

}

/**********************************************************************//**

 * Count living cells in universe.

 *

 * @param[in] u Universe select (0 or 1).

 * @return Number of living cells.

 **************************************************************************/

int pop_count(int u) {

  int x, y, cnt;

  cnt = 0;

  for (x=0; x<NUM_CELLS_X; x++) {

    for (y=0; y<NUM_CELLS_Y; y++) {

      cnt += (int)get_cell(u, x, y);

    }

  }

  return cnt;

}

/**********************************************************************//**

 * Simple pseudo random number generator.

 *

 * @return Random number.

 **************************************************************************/

uint32_t xorshift32(void) {

  static uint32_t x32 = 314159265;

  x32 ^= x32 << 13;

  x32 ^= x32 >> 17;

  x32 ^= x32 << 5;

  return x32;

}