3 files changed, 28 insertions, 23 deletions

diff --git a/chip8.c b/chip8.c
index b79bc3a..9c3d7eb 100644
--- a/chip8.c
+++ b/chip8.c
@@ -39,7 +39,7 @@ static u8 font[] = {
   0xF0, 0x80, 0xF0, 0x80, 0x80  // F
 };
 
-void init_vm() {
+void init_vm(void) {
   vm.PC = 0x200; // start of chip8 programs
 
   // write fonts into memory
@@ -48,9 +48,9 @@ void init_vm() {
   }
 }
 
-void load_rom(char *file_path) {
+void load_rom(char *path) {
   memset(&vm, 0, sizeof(chip8_vm));
-  int fd = open(file_path, O_RDONLY);
+  int fd = open(path, O_RDONLY);
   FILE* f = fdopen(fd, "r");
   fseek(f, 0, SEEK_END);
   off_t fsize = ftell(f);
@@ -73,7 +73,7 @@ void load_rom(char *file_path) {
   fclose(f); close(fd);
 }
 
-void vm_step() {
+void vm_step(void) {
   // read 2 bytes and convert to big-endian
   u16 in = htons(vm.ram[vm.PC + 0x1]<<8 | vm.ram[vm.PC]);
 
@@ -198,7 +198,7 @@ void vm_step() {
       for (u32 i = 0; i < (in&0xF); i++) {
         for (u32 s = 0; s < 8; s++) {
 
-          // 0x80 = 10000000
+          // 0x80 = b10000000
           u8 pix = (vm.ram[vm.I + i] & (0x80 >> s)) != 0;
 
           if (pix) {
@@ -207,12 +207,13 @@ void vm_step() {
  
             u32 byte = y * 64 + x;
 
-            // put the single 1 bit in the position
+            // put the single '1' bit in the position
             // that is relative to the pixel
-            u32 bit = 1 << (byte & 0x07);
+            u8 bit = 1 << (byte & 0x07);
 
             // byte>>3 ~ byte / 8 
-            // used to get the index of byte to xor
+            // used to get the index of the byte
+            // containing the bit to change
             if (vm.screen[byte>>3] & bit) {
               vm.Vx[0xF] = 1;
             }
diff --git a/chip8.h b/chip8.h
index ce02394..d21ae0a 100644
--- a/chip8.h
+++ b/chip8.h
@@ -2,9 +2,9 @@
 
 #include "util.h"
 
-void init_vm();
-void vm_step();
-void load_rom();
+void init_vm(void);
+void vm_step(void);
+void load_rom(char *path);
 
 typedef struct {
   u8* ram;
diff --git a/ui_sdl.c b/ui_sdl.c
index 0433d5f..7ac32ca 100644
--- a/ui_sdl.c
+++ b/ui_sdl.c
@@ -1,6 +1,7 @@
 #define SDL_MAIN_HANDLED
 
 #include <time.h>
+#include <stdbool.h>
 
 #ifdef _WIN32
 #include <SDL.h>
@@ -15,19 +16,18 @@
 
 SDL_Renderer *r;
 
-void setup() {
+void setup(void) {
   SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO);
   SDL_Window* win = SDL_CreateWindow("chip8", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, W, H, SDL_WINDOW_SHOWN);
   r = SDL_CreateRenderer(win, -1, SDL_RENDERER_PRESENTVSYNC|SDL_RENDERER_ACCELERATED);  
   SDL_RenderClear(r);
 }
 
-void draw() {
-  SDL_Rect box = (SDL_Rect){1, 0, 10, 10};
+void draw(void) {
+  SDL_Rect box = (SDL_Rect){0, 0, 10, 10};
   SDL_SetRenderDrawColor(r, 12, 5, 9, 255);
   SDL_RenderClear(r);
   SDL_SetRenderDrawColor(r, 228, 167, 104, 255);
-  //SDL_RenderFillRect(r, &box);
   for (int x = 0; x <= 0x3F; x++) {
     for (int y = 0; y <= 0x1F; y++) {
       int byte = y * 64 + x;
@@ -44,7 +44,7 @@ void draw() {
 
 int main(int argc, char* argv[]) {
   if (argc != 2) {
-    printf("%s [rom file]\n", argv[0]);
+    printf("./%s <rom file>\n", argv[0]);
     return 1;
   }
 
@@ -55,19 +55,20 @@ int main(int argc, char* argv[]) {
   setup();
 
   int last_500hz = SDL_GetTicks();
-  int last_60hz = SDL_GetTicks();
-  int last_45hz = SDL_GetTicks();
+  int last_60hz = last_500hz;
+  int last_45hz = last_500hz;
+
+  bool quit = false;
 
   SDL_Event e;
-  while (1) {
+  while (!quit) {
     SDL_PollEvent(&e);
     switch (e.type) {
+      case SDL_QUIT:
+        quit = true; break;
       case SDL_KEYDOWN:
         switch (e.key.keysym.sym) {
-          case SDLK_ESCAPE:
-            SDL_Quit();
-            exit(0);
-            break;
+          case SDLK_ESCAPE: quit = true; break;
           case '1': vm.keyboard[0x0] = 1; break;
           case '2': vm.keyboard[0x1] = 1; break;
           case '3': vm.keyboard[0x2] = 1; break;
@@ -132,6 +133,9 @@ int main(int argc, char* argv[]) {
       last_45hz = cur;
     }
   }
+
+  SDL_Quit();
+
   return 0;
 }