From a26a17028485480af2f769169a22b0577aecccbd Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Fri, 26 Feb 2021 21:39:49 -0800
Subject: [PATCH] sram word and halfword reads

---
 src/crab/bus.cr     | 4 ++--
 src/crab/storage.cr | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/crab/bus.cr b/src/crab/bus.cr
index 20147a1..2249623 100644
--- a/src/crab/bus.cr
+++ b/src/crab/bus.cr
@@ -43,7 +43,7 @@ class Bus
     when 0x8, 0x9,
          0xA, 0xB,
          0xC, 0xD then (@gba.cartridge.rom.to_unsafe + (index & 0x01FFFFFF)).as(HalfWord*).value
-    when 0xE, 0xF then read_half_slow(index)
+    when 0xE, 0xF then @gba.storage.read_half(index)
     else               abort "Unmapped read: #{hex_str index.to_u32}"
     end
   end
@@ -81,7 +81,7 @@ class Bus
     when 0x8, 0x9,
          0xA, 0xB,
          0xC, 0xD then (@gba.cartridge.rom.to_unsafe + (index & 0x01FFFFFF)).as(Word*).value
-    when 0xE, 0xF then read_word_slow(index)
+    when 0xE, 0xF then @gba.storage.read_word(index)
     else               abort "Unmapped read: #{hex_str index.to_u32}"
     end
   end
diff --git a/src/crab/storage.cr b/src/crab/storage.cr
index 88a5677..e3a30b3 100644
--- a/src/crab/storage.cr
+++ b/src/crab/storage.cr
@@ -49,6 +49,14 @@ abstract class Storage
 
   abstract def [](index : Int) : Byte
 
+  def read_half(index : Int) : HalfWord
+    0x0101_u16 * self[index & ~1]
+  end
+
+  def read_word(index : Int) : Word
+    0x01010101_u32 * self[index & ~3]
+  end
+
   abstract def []=(index : Int, value : Byte) : Nil
 
   private def self.find_type(file : File) : Type?