apps: Add a Game of Life implementation

apps/CMakeLists.txt

@@ -41,3 +41,4 @@ luna_app(sysfuzz.cpp sysfuzz)
 luna_app(pivot_root.cpp pivot_root)
 luna_app(cp.cpp cp)
 luna_app(kill.cpp kill)
+luna_app(gol.cpp gol)

apps/gol.cpp

@@ -0,0 +1,166 @@
+#include <alloca.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <luna/Heap.h>
+#include <os/ArgumentParser.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <time.h>
+#include <unistd.h>
+
+struct Cell
+{
+    bool state;
+    bool new_state;
+};
+
+static int g_num_rows = 76;
+static int g_num_columns = 102;
+
+static int g_fb_width;
+static int g_fb_height;
+
+static int g_fd;
+
+static Cell* g_cells;
+
+static Result<void> fill_cells()
+{
+    g_cells = (Cell*)TRY(calloc_impl(g_num_rows, g_num_columns * sizeof(Cell), false));
+
+    for (isize i = 0; i < (g_num_rows * g_num_columns); i++)
+    {
+        auto value = rand() % 2;
+        g_cells[i].state = g_cells[i].new_state = value;
+    }
+
+    return {};
+}
+
+static Cell& find_cell(int row, int column)
+{
+    assert(row < g_num_rows);
+    assert(column < g_num_columns);
+    return g_cells[row * g_num_columns + column];
+}
+
+static constexpr int BYTES_PER_PIXEL = 4;
+
+static char* g_buf;
+
+static void draw_cells()
+{
+    lseek(g_fd, 0, SEEK_SET);
+
+    const int CELL_WIDTH = g_fb_width / g_num_columns;
+    const int CELL_HEIGHT = g_fb_height / g_num_rows;
+
+    for (int i = 0; i < g_num_rows; i++)
+    {
+        memset(g_buf, 0, g_fb_width * BYTES_PER_PIXEL);
+
+        for (int j = 0; j < g_num_columns; j++)
+        {
+            auto& cell = find_cell(i, j);
+            if (cell.state) memset(g_buf + (j * CELL_WIDTH * BYTES_PER_PIXEL), 0xff, CELL_WIDTH * BYTES_PER_PIXEL);
+        }
+
+        for (int j = 0; j < CELL_HEIGHT; j++) { write(g_fd, g_buf, g_fb_width * BYTES_PER_PIXEL); }
+    }
+}
+
+static int find_neighbors(int row, int column)
+{
+    int sum = 0;
+
+    if (row > 0 && column > 0) sum += find_cell(row - 1, column - 1).state;
+    if (row > 0) sum += find_cell(row - 1, column).state;
+    if (row > 0 && (column + 1) < g_num_columns) sum += find_cell(row - 1, column + 1).state;
+    if (column > 0) sum += find_cell(row, column - 1).state;
+    if ((column + 1) < g_num_columns) sum += find_cell(row, column + 1).state;
+    if ((row + 1) < g_num_rows && column > 0) sum += find_cell(row + 1, column - 1).state;
+    if ((row + 1) < g_num_rows) sum += find_cell(row + 1, column).state;
+    if ((row + 1) < g_num_rows && (column + 1) < g_num_columns) sum += find_cell(row + 1, column + 1).state;
+
+    return sum;
+}
+
+static void next_generation()
+{
+    for (int i = 0; i < g_num_rows; i++)
+    {
+        for (int j = 0; j < g_num_columns; j++)
+        {
+            auto& cell = find_cell(i, j);
+            int neighbors = find_neighbors(i, j);
+            if (!cell.state && neighbors == 3) cell.new_state = true;
+            else if (cell.state && (neighbors < 2 || neighbors > 3))
+                cell.new_state = false;
+        }
+    }
+
+    for (isize i = 0; i < (g_num_rows * g_num_columns); i++) g_cells[i].state = g_cells[i].new_state;
+}
+
+Result<int> luna_main(int argc, char** argv)
+{
+    u64 delay_between_iterations = 250;
+    u64 delay_at_end = 3000;
+    u64 num_iterations = 100;
+
+    StringView columns;
+    StringView rows;
+    StringView delay;
+    StringView end_delay;
+    StringView iterations;
+    StringView seed;
+
+    os::ArgumentParser parser;
+    parser.add_description("A framebuffer-based implementation for Conway's Game of Life.");
+    parser.add_system_program_info("gol"_sv);
+    parser.add_positional_argument(rows, "rows"_sv, "76"_sv);
+    parser.add_positional_argument(columns, "columns"_sv, "102"_sv);
+    parser.add_value_argument(delay, 'd', "delay"_sv, "the delay between generations (in ms)");
+    parser.add_value_argument(end_delay, 'e', "end-delay"_sv,
+                              "after finishing, how much to wait before returning to the shell (in ms)");
+    parser.add_value_argument(iterations, 'i', "iterations"_sv, "how many generations to show (default: 100)");
+    parser.add_value_argument(seed, 's', "seed"_sv, "the seed for the random number generator");
+    parser.parse(argc, argv);
+
+    g_num_columns = (int)TRY(columns.to_uint());
+    g_num_rows = (int)TRY(rows.to_uint());
+    if (!delay.is_empty()) delay_between_iterations = TRY(delay.to_uint());
+    if (!end_delay.is_empty()) delay_at_end = TRY(end_delay.to_uint());
+    if (!iterations.is_empty()) num_iterations = TRY(iterations.to_uint());
+    if (!seed.is_empty()) srand((unsigned)TRY(seed.to_uint()));
+    else
+        srand((unsigned)time(NULL));
+
+    g_fd = open("/dev/fb0", O_WRONLY);
+    if (g_fd < 0)
+    {
+        perror("gol: cannot open framebuffer for writing");
+        return 1;
+    }
+
+    g_fb_height = ioctl(g_fd, FB_GET_HEIGHT);
+    g_fb_width = ioctl(g_fd, FB_GET_WIDTH);
+
+    TRY(fill_cells());
+
+    g_buf = (char*)TRY(calloc_impl(g_fb_width, BYTES_PER_PIXEL));
+
+    draw_cells();
+
+    while (num_iterations--)
+    {
+        usleep(delay_between_iterations * 1000);
+        next_generation();
+        draw_cells();
+    }
+
+    usleep(delay_at_end * 1000);
+
+    return 0;
+}