moved save mirroring to each save impl

src/crab/bus.cr

@@ -23,7 +23,7 @@ class Bus
     when 0x8, 0x9,
          0xA, 0xB,
          0xC, 0xD then @gba.cartridge.rom[index & 0x01FFFFFF]
-    when 0xE, 0xF then @gba.storage[index & 0xFFFF]
+    when 0xE, 0xF then @gba.storage[index]
     else               abort "Unmapped read: #{hex_str index.to_u32}"
     end
   end
@@ -123,7 +123,7 @@ class Bus
     when 0x8, 0x9,
          0xA, 0xB,
          0xC, 0xD then log "Writing to cart - #{hex_str index.to_u32}: #{hex_str value}"
-    when 0xE then @gba.storage[index & 0xFFFF] = value
+    when 0xE then @gba.storage[index] = value
     else          abort "Unmapped write: #{hex_str index.to_u32}"
     end
   end

src/crab/storage/flash.cr

@@ -32,6 +32,7 @@ class Flash < Storage
   end
 
   def [](index : Int) : Byte
+    index &= 0xFFFF
     if @state.includes?(State::IDENTIFICATION) && 0 <= index <= 1
       (@id >> (8 * index) & 0xFF).to_u8!
     else
@@ -40,6 +41,7 @@ class Flash < Storage
   end
 
   def []=(index : Int, value : Byte) : Nil
+    index &= 0xFFFF
     case @state
     when .includes? State::PREPARE_WRITE
       @memory[0x10000 * @bank + index] &= value

src/crab/storage/sram.cr

@@ -2,13 +2,11 @@ class SRAM < Storage
   @memory = Bytes.new(Type::SRAM.bytes, 0xFF)
 
   def [](index : Int) : Byte
-    index < @memory.size ? @memory[index] : 0_u8
+    @memory[index & 0x7FFF]
   end
 
   def []=(index : Int, value : Byte) : Nil
-    if index < @memory.size
-      @memory[index] = value
-      @dirty = true
-    end
+    @memory[index & 0x7FFF] = value
+    @dirty = true
   end
 end