From e7eaae9b6ce9536dcb14a71257769352d6faa53d Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Sun, 9 Feb 2025 18:57:36 +0100
Subject: [PATCH] Reduce memory usage of Cartridge::Mbc1

Precomputing one Proc per possible address amount of 8MiB of memory
and almost 100k objects the GC as to scan etc.

This can be reduced to just 24 objects with only an extra
bitshit on access.
---
 lib/rubyboy/cartridge/mbc1.rb | 38 +++++++++++++++++------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/lib/rubyboy/cartridge/mbc1.rb b/lib/rubyboy/cartridge/mbc1.rb
index 833eeee..47c0e09 100644
--- a/lib/rubyboy/cartridge/mbc1.rb
+++ b/lib/rubyboy/cartridge/mbc1.rb
@@ -18,13 +18,13 @@ def initialize(rom, ram)
       end
 
       def set_methods
-        0xc000.times do |addr|
-          @read_methods[addr] =
-            case addr
-            when 0x0000..0x3fff then -> { @rom.data[addr] }
-            when 0x4000..0x7fff then -> { @rom.data[addr + (@rom_bank - 1) * 0x4000] }
-            when 0xa000..0xbfff
-              lambda do
+        0xc.times do |prefix|
+          @read_methods[prefix] =
+            case prefix
+            when 0x0..0x3 then ->(addr) { @rom.data[addr] }
+            when 0x4..0x7 then ->(addr) { @rom.data[addr + (@rom_bank - 1) * 0x4000] }
+            when 0xa..0xb
+              lambda do |addr|
                 if @ram_enable
                   if @ram_banking_mode
                     @ram.eram[addr - 0xa000 + @ram_bank * 0x800]
@@ -38,19 +38,19 @@ def set_methods
             end
         end
 
-        0xc000.times do |addr|
-          @write_methods[addr] =
-            case addr
-            when 0x0000..0x1fff then ->(value) { @ram_enable = value & 0x0f == 0x0a }
-            when 0x2000..0x3fff
-              lambda do |value|
+        0xc.times do |prefix|
+          @write_methods[prefix] =
+            case prefix
+            when 0x0..0x1 then ->(_addr, value) { @ram_enable = value & 0x0f == 0x0a }
+            when 0x2..0x3
+              lambda do |_addr, value|
                 @rom_bank = value & 0x1f
                 @rom_bank = 1 if @rom_bank == 0
               end
-            when 0x4000..0x5fff then ->(value) { @ram_bank = value & 0x03 }
-            when 0x6000..0x7fff then ->(value) { @ram_banking_mode = value & 0x01 == 0x01 }
-            when 0xa000..0xbfff
-              lambda do |value|
+            when 0x4..0x5 then ->(_addr, value) { @ram_bank = value & 0x03 }
+            when 0x6..0x7 then ->(_addr, value) { @ram_banking_mode = value & 0x01 == 0x01 }
+            when 0xa..0xb
+              lambda do |addr, value|
                 if @ram_enable
                   if @ram_banking_mode
                     @ram.eram[addr - 0xa000 + @ram_bank * 0x800] = value
@@ -64,11 +64,11 @@ def set_methods
       end
 
       def read_byte(addr)
-        @read_methods[addr].call
+        @read_methods[addr >> 12].call(addr)
       end
 
       def write_byte(addr, value)
-        @write_methods[addr].call(value)
+        @write_methods[addr >> 12].call(addr, value)
       end
     end
   end