1 files changed, 30 insertions, 0 deletions
diff --git a/cart/mapper.go b/cart/mapper.go
new file mode 100644
index 0000000..7ddd8a9
--- /dev/null
+++ b/cart/mapper.go
@@ -0,0 +1,30 @@
+package cart
+
+import "fmt"
+
+type Mirroring uint8
+
+const (
+	Horizontal Mirroring = iota
+	Vertical
+	FourScreen
+	SingleScreenLower
+	SingleScreenUpper
+)
+
+type Mapper interface {
+	CPURead(addr uint16) uint8
+	CPUWrite(addr uint16, v uint8)
+	PPURead(addr uint16) uint8
+	PPUWrite(addr uint16, v uint8)
+	Mirroring() Mirroring
+}
+
+func newMapper(c *Cartridge) (Mapper, error) {
+	switch c.MapperID {
+	case 0:
+		return newNROM(c), nil
+	default:
+		return nil, fmt.Errorf("cart: unsupported mapper %d", c.MapperID)
+	}
+}