1 files changed, 121 insertions, 0 deletions
diff --git a/user/forkman.c b/user/forkman.c
new file mode 100644
index 0000000..fb5ae5f
--- /dev/null
+++ b/user/forkman.c
@@ -0,0 +1,121 @@
+/*
+ * FORKMAN: a platformer game with IPC
+ *
+ * This executable will fork. One process is responsible for writing to the
+ * screen and getting user input, the other is responsible for game logic.
+ *
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define GAME_WIDTH 480
+#define GAME_HEIGHT 360
+#define SHARED_PAGES 10
+#define PAGE_SIZE 4096
+
+typedef struct {
+	uint32_t *mapped_memory;
+	int width;
+	int height;
+	int bpp;
+	int scale;
+	size_t size;
+} framebuffer;
+
+typedef struct {
+	volatile size_t frame;
+	volatile size_t dummy_counter;
+	volatile int lock;
+	volatile uint8_t mem[PAGE_SIZE * (SHARED_PAGES - 1)];
+} sharedmem;
+
+static int display_server_entry(sharedmem *);
+static int client_entry(sharedmem *);
+
+int main(void)
+{
+	uint8_t *current_break = sbrk(0);
+	if (!current_break) {
+		fprintf(stderr, "sbrk failure\n");
+		return 1;
+	}
+
+	printf("ABOUT TO FORK\n");
+
+	int child = fork();
+	if (child < 0) {
+		fprintf(stderr, "fork failed!\n");
+		return 1;
+	}
+
+	if (child) {
+		printf("FORK GOOD, CHILD IS %d\n", child);
+		sharedmem *shared = allocshared(SHARED_PAGES, child);
+		if (!shared) {
+			fprintf(stderr, "memory share failure\n");
+			return 1;
+		}
+
+		return display_server_entry(shared);
+	} else {
+		printf("FORK GOOD, WE ARE CHILD\n");
+
+		sharedmem *shared;
+
+		while (!(shared = popsharedmem()))
+			sleep(1);
+
+		return client_entry(shared);
+	}
+}
+
+static void set_pixel(framebuffer *fb, size_t x, size_t y,
+					  int state) // state is 0 or 1
+{
+	fb->mapped_memory[x + y * fb->width] = state * (0x00010101);
+}
+
+static int display_server_entry(sharedmem *shared)
+{
+	framebuffer fb;
+	if (drm((void **)&fb.mapped_memory, &fb.width, &fb.height, &fb.bpp)) {
+		fprintf(stderr, "Unable to map framebuffer, display server failing\n");
+		return 1;
+	}
+
+	fb.size = (fb.width * fb.height * fb.bpp) / 8;
+
+	size_t last_frame = 1;
+
+	while (1) {
+		if (shared->frame == last_frame) {
+			continue;
+		}
+
+		printf("server writing frame %zu\n", last_frame);
+
+		last_frame += 1;
+		shared->frame = last_frame;
+	}
+
+	return 0;
+}
+
+static int client_entry(sharedmem *shared)
+{
+	size_t last_frame = shared->frame;
+	do {
+		if (last_frame == shared->frame)
+			continue;
+
+		printf("client writing frame %zu\n", last_frame);
+
+		last_frame += 1;
+		shared->frame = last_frame;
+	} while (1);
+
+	return 0;
+}