From c3ff2ed6c16b58eddb16143c434b7aa1d03c6f93 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Fri, 21 Oct 2022 05:12:13 -0300
Subject: [PATCH] feat: parse cartridge header

---
 src/bus/GamePak.zig | 36 +++++++++++++++++++++++++++++++++---
 src/main.zig        | 11 +++++++----
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/src/bus/GamePak.zig b/src/bus/GamePak.zig
index 979ce37..f7dd515 100644
--- a/src/bus/GamePak.zig
+++ b/src/bus/GamePak.zig
@@ -3,18 +3,48 @@ const std = @import("std");
 const Allocator = std.mem.Allocator;
 const Self = @This();
 
+title: [12]u8,
 buf: []u8,
 alloc: Allocator,
 
+const log = std.log.scoped(.GamePak);
+
 pub fn init(alloc: Allocator, path: []const u8) !Self {
     const file = try std.fs.cwd().openFile(path, .{});
     defer file.close();
 
     const len = try file.getEndPos();
+    const buf = try file.readToEndAlloc(alloc, len);
+    const title = parseTitle(buf);
 
-    return Self{
-        .buf = try file.readToEndAlloc(alloc, len),
-        .alloc = alloc,
+    const pak = Self{ .buf = buf, .alloc = alloc, .title = title };
+    pak.parseHeader();
+
+    return pak;
+}
+
+fn parseHeader(self: *const Self) void {
+    const title = parseTitle(self.buf);
+    const code = self.buf[0xAC..0xB0];
+    const maker = self.buf[0xB0..0xB2];
+    const version = self.buf[0xBC];
+
+    log.info("Title: {s}", .{title});
+    if (version != 0) log.info("Version: {}", .{version});
+    log.info("Game Code: {s}", .{code});
+    if (lookupMaker(maker)) |c| log.info("Maker Code: {s}", .{c}) else log.info("Maker: {s}", .{maker});
+}
+
+fn parseTitle(buf: []u8) [12]u8 {
+    return buf[0xA0..0xAC].*;
+}
+
+fn lookupMaker(slice: *const [2]u8) ?[]const u8 {
+    const num = @as(u16, slice[1]) << 8 | @as(u16, slice[0]);
+
+    return switch (num) {
+        0x3130 => "Nintendo",
+        else => null,
     };
 }
 
diff --git a/src/main.zig b/src/main.zig
index 0fcb3e8..1095985 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -94,8 +94,11 @@ pub fn main() anyerror!void {
     if (status < 0) sdlPanic();
     defer SDL.SDL_Quit();
 
+    var title_buf: [0x20]u8 = [_]u8{0x00} ** 0x20;
+    const title = try std.fmt.bufPrint(&title_buf, "ZBA | {s}", .{bus.pak.title});
+
     var window = SDL.SDL_CreateWindow(
-        "ZBA",
+        title.ptr,
         SDL.SDL_WINDOWPOS_CENTERED,
         SDL.SDL_WINDOWPOS_CENTERED,
         gba_width * window_scale,
@@ -111,8 +114,8 @@ pub fn main() anyerror!void {
     defer SDL.SDL_DestroyTexture(texture);
 
     // Init FPS Timer
+    // var fps_buf: [0x100]u8 = [_]u8{0x00} ** 0x100;
     // var timer = Timer.start() catch unreachable;
-    // var title_buf: [0x30]u8 = [_]u8{0x00} ** 0x30;
 
     emu_loop: while (true) {
         var event: SDL.SDL_Event = undefined;
@@ -167,8 +170,8 @@ pub fn main() anyerror!void {
         SDL.SDL_RenderPresent(renderer);
 
         // const fps = std.time.ns_per_s / timer.lap();
-        // const title = std.fmt.bufPrint(&title_buf, "ZBA FPS: {d}", .{fps}) catch unreachable;
-        // SDL.SDL_SetWindowTitle(window, title.ptr);
+        // const fps_title = std.fmt.bufPrint(&fps_buf, "{s} [FPS: {d}]", .{ title, fps }) catch unreachable;
+        // SDL.SDL_SetWindowTitle(window, fps_title.ptr);
 
         pause.store(false, .Unordered);
     }