src/core/Bus.zig

@@ -128,6 +128,21 @@ pub fn reset(self: *Self) void {
     self.io.reset();
 }
 
+pub fn replaceGamepak(self: *Self, file_path: []const u8) !void {
+    // Note: `save_path` isn't owned by `Backup`
+    const save_path = self.pak.backup.save_path;
+    self.pak.deinit();
+
+    self.pak = try GamePak.init(self.allocator, self.cpu, file_path, save_path);
+
+    const read_ptr: *[table_len]?*const anyopaque = @constCast(self.read_table);
+    const write_ptrs: [2]*[table_len]?*anyopaque = .{ @constCast(self.write_tables[0]), @constCast(self.write_tables[1]) };
+
+    self.fillReadTable(read_ptr);
+    self.fillWriteTable(u32, write_ptrs[0]);
+    self.fillWriteTable(u8, write_ptrs[1]);
+}
+
 fn fillReadTable(self: *Self, table: *[table_len]?*const anyopaque) void {
     const vramMirror = @import("ppu/Vram.zig").mirror;
 

src/core/emu.zig

@@ -249,3 +249,8 @@ pub fn reset(cpu: *Arm7tdmi) void {
     cpu.bus.reset();
     cpu.reset();
 }
+
+pub fn replaceGamepak(cpu: *Arm7tdmi, file_path: []const u8) !void {
+    try cpu.bus.replaceGamepak(file_path);
+    reset(cpu);
+}

src/imgui.zig

@@ -70,7 +70,10 @@ pub fn draw(state: *State, tex_id: GLuint, cpu: *Arm7tdmi) void {
                     defer nfd.freePath(file_path);
                     log.info("user chose: \"{s}\"", .{file_path});
 
-                    // emu.loadRom(cpu, file_path);
+                    emu.replaceGamepak(cpu, file_path) catch |e| {
+                        log.err("failed to replace GamePak: {}", .{e});
+                        break :blk;
+                    };
                 }
             }
         }