fix: pass none.gba and kind of sram.gba from jsmolka test suite

src/Bus.zig

@@ -14,6 +14,9 @@ const Scheduler = @import("scheduler.zig").Scheduler;
 const io = @import("bus/io.zig");
 const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.Bus);
+
+const rotr = @import("util.zig").rotr;
+
 const Self = @This();
 
 const panic_on_und_bus: bool = false;
@@ -68,6 +71,7 @@ pub fn read32(self: *const Self, addr: u32) u32 {
         0x0800_0000...0x09FF_FFFF => self.pak.read(u32, addr),
         0x0A00_0000...0x0BFF_FFFF => self.pak.read(u32, addr),
         0x0C00_0000...0x0DFF_FFFF => self.pak.read(u32, addr),
+        0x0E00_0000...0x0FFF_FFFF => @as(u32, self.pak.backup.read(addr)) * 0x01010101,
 
         else => undRead("Tried to read from 0x{X:0>8}", .{addr}),
     };
@@ -86,6 +90,10 @@ pub fn write32(self: *Self, addr: u32, word: u32) void {
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.write(u32, addr, word),
         0x0600_0000...0x06FF_FFFF => self.ppu.vram.write(u32, addr, word),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.write(u32, addr, word),
+        0x0E00_0000...0x0FFF_FFFF => {
+            const value = rotr(u32, word, 8 * (addr & 3));
+            self.pak.backup.write(addr, @truncate(u8, value));
+        },
 
         else => undWrite("Tried to write 0x{X:0>8} to 0x{X:0>8}", .{ word, addr }),
     }
@@ -108,6 +116,7 @@ pub fn read16(self: *const Self, addr: u32) u16 {
         0x0800_0000...0x09FF_FFFF => self.pak.read(u16, addr),
         0x0A00_0000...0x0BFF_FFFF => self.pak.read(u16, addr),
         0x0C00_0000...0x0DFF_FFFF => self.pak.read(u16, addr),
+        0x0E00_0000...0x0FFF_FFFF => @as(u16, self.pak.backup.read(addr)) * 0x0101,
 
         else => undRead("Tried to read from 0x{X:0>8}", .{addr}),
     };
@@ -127,6 +136,9 @@ pub fn write16(self: *Self, addr: u32, halfword: u16) void {
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.write(u16, addr, halfword),
         0x0800_00C4, 0x0800_00C6, 0x0800_00C8 => log.warn("Tried to write 0x{X:0>4} to GPIO", .{halfword}),
 
+        // External Memory (Game Pak)
+        0x0E00_0000...0x0FFF_FFFF => self.pak.backup.write(addr, @truncate(u8, rotr(u16, halfword, 8 * (addr & 1)))),
+
         else => undWrite("Tried to write 0x{X:0>4} to 0x{X:0>8}", .{ halfword, addr }),
     }
 }
@@ -148,7 +160,7 @@ pub fn read8(self: *const Self, addr: u32) u8 {
         0x0800_0000...0x09FF_FFFF => self.pak.read(u8, addr),
         0x0A00_0000...0x0BFF_FFFF => self.pak.read(u8, addr),
         0x0C00_0000...0x0DFF_FFFF => self.pak.read(u8, addr),
-        0x0E00_0000...0x0E00_FFFF => self.pak.backup.read(addr),
+        0x0E00_0000...0x0FFF_FFFF => self.pak.backup.read(addr),
 
         else => undRead("Tried to read from 0x{X:0>2}", .{addr}),
     };
@@ -163,7 +175,7 @@ pub fn write8(self: *Self, addr: u32, byte: u8) void {
         0x0400_0410 => log.info("Ignored write of 0x{X:0>2} to 0x{X:0>8}", .{ byte, addr }),
 
         // External Memory (Game Pak)
-        0x0E00_0000...0x0E00_FFFF => self.pak.backup.write(addr, byte),
+        0x0E00_0000...0x0FFF_FFFF => self.pak.backup.write(addr, byte),
         else => undWrite("Tried to write 0x{X:0>2} to 0x{X:0>8}", .{ byte, addr }),
     }
 }

src/bus/GamePak.zig

@@ -21,7 +21,7 @@ pub fn init(alloc: Allocator, rom_path: []const u8, save_path: ?[]const u8) !Sel
     defer alloc.free(file_buf);
 
     const title = parseTitle(file_buf);
-    const kind = Backup.guessKind(file_buf) orelse .Sram;
+    const kind = Backup.guessKind(file_buf) orelse .None;
 
     const buf = try alloc.alloc(u8, 0x200_0000); // 32MiB
 
@@ -40,6 +40,7 @@ pub fn init(alloc: Allocator, rom_path: []const u8, save_path: ?[]const u8) !Sel
         .backup = try Backup.init(alloc, kind, title, save_path),
     };
     pak.parseHeader();
+    log.info("Backup: {}", .{kind});
 
     return pak;
 }

src/bus/backup.zig

@@ -32,10 +32,11 @@ pub const Backup = struct {
             .Flash => 0x10000, // 64K
             .Flash1M => 0x20000, // 128K
             .Eeprom => 0x2000, // FIXME: We assume 8K here
+            .None => 0,
         };
 
         const buf = try alloc.alloc(u8, buf_len);
-        std.mem.set(u8, buf, 0);
+        std.mem.set(u8, buf, 0xFF);
 
         var backup = Self{
             .buf = buf,
@@ -80,8 +81,10 @@ pub const Backup = struct {
 
         switch (self.kind) {
             .Sram, .Flash, .Flash1M => {
+                if (self.buf.len == file_buf.len) {
                     std.mem.copy(u8, self.buf, file_buf);
                     log.info("Loaded Save from {s}", .{file_path});
+                }
             },
             else => return SaveError.UnsupportedBackupKind,
         }
@@ -139,6 +142,7 @@ pub const Backup = struct {
             },
             .Eeprom => return self.buf[addr],
             .Sram => return self.buf[addr & 0x7FFF], // 32K SRAM chip is mirrored
+            .None => return 0xFF,
         }
     }
 
@@ -171,6 +175,7 @@ pub const Backup = struct {
             },
             .Eeprom => self.buf[addr] = byte,
             .Sram => self.buf[addr & 0x7FFF] = byte,
+            .None => {},
         }
     }
 };
@@ -180,6 +185,7 @@ const BackupKind = enum {
     Sram,
     Flash,
     Flash1M,
+    None,
 };
 
 const Needle = struct {