feat(ui): add the option to choose the BIOS

src/core/bus/Bios.zig

@@ -63,18 +63,23 @@ pub fn write(_: *Self, comptime T: type, addr: u32, value: T) void {
 
 pub fn init(allocator: Allocator, maybe_path: ?[]const u8) !Self {
     if (maybe_path == null) return .{ .buf = null, .allocator = allocator };
-    const path = maybe_path.?;
+    const file_path = maybe_path.?;
 
     const buf = try allocator.alloc(u8, Self.size);
     errdefer allocator.free(buf);
 
-    const file = try std.fs.cwd().openFile(path, .{});
+    var self: Self = .{ .buf = buf, .allocator = allocator };
+    try self.load(file_path);
+
+    return self;
+}
+
+pub fn load(self: *Self, file_path: []const u8) !void {
+    const file = try std.fs.cwd().openFile(file_path, .{});
     defer file.close();
 
-    const file_len = try file.readAll(buf);
-    if (file_len != Self.size) log.err("Expected BIOS to be {}B, was {}B", .{ Self.size, file_len });
-
-    return Self{ .buf = buf, .allocator = allocator };
+    const len = try file.readAll(self.buf orelse return error.UnallocatedBuffer);
+    if (len != Self.size) log.err("Expected BIOS to be {}B, was {}B", .{ Self.size, len });
 }
 
 pub fn reset(self: *Self) void {

src/core/emu.zig

@@ -253,3 +253,11 @@ pub fn replaceGamepak(cpu: *Arm7tdmi, file_path: []const u8) !void {
     try cpu.bus.replaceGamepak(file_path);
     reset(cpu);
 }
+
+pub fn replaceBios(cpu: *Arm7tdmi, file_path: []const u8) !void {
+    const allocator = cpu.bus.bios.allocator;
+    const bios_len = 0x4000;
+
+    cpu.bus.bios.buf = try allocator.alloc(u8, bios_len);
+    try cpu.bus.bios.load(file_path);
+}

src/imgui.zig

@@ -103,6 +103,25 @@ pub fn draw(state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *Arm7tdmi)
                 state.title = handleTitle(&cpu.bus.pak.title);
                 state.emulation = .{ .Transition = .Active };
             }
+
+            if (zgui.menuItem("Load BIOS", .{})) blk: {
+                const maybe_path = nfd.openFileDialog("bin", null) catch |e| {
+                    log.err("failed to open file dialog: {}", .{e});
+                    break :blk;
+                };
+
+                const file_path = maybe_path orelse {
+                    log.warn("did not receive a file path", .{});
+                    break :blk;
+                };
+                defer nfd.freePath(file_path);
+
+                log.info("user chose: \"{s}\"", .{file_path});
+                emu.replaceBios(cpu, file_path) catch |e| {
+                    log.err("failed to replace BIOS: {}", .{e});
+                    break :blk;
+                };
+            }
         }
 
         if (zgui.beginMenu("Emulation", true)) {