Move the underlying Cpu ops methods to their own file.

.rubocop.yml

@@ -5,11 +5,12 @@ AllCops:
   NewCops: enable
 
 # Set a slightly bigger default, and ignore ABC failures in the tests.
-# Also ignore in the CPU instructions file, which is unavoidably big.
+# Also ignore in the CPU instructions files, which are unavoidably big.
 Metrics/AbcSize:
   Max: 25
   Exclude:
     - 'lib/mos6502/cpu_instructions.rb'
+    - 'lib/mos6502/cpu_ops.rb'
     - 'test/**/*.rb'
 
 # Ignore block length failures in the tests.
@@ -33,10 +34,11 @@ Metrics/CyclomaticComplexity:
     - 'lib/mos6502/cpu_instructions.rb'
 
 # Ignore method length failures in the tests.
-# Also ignore in the CPU instructions file, which is unavoidably big.
+# Also ignore in the CPU instructions files, which are unavoidably big.
 Metrics/MethodLength:
   Exclude:
     - 'lib/mos6502/cpu_instructions.rb'
+    - 'lib/mos6502/cpu_ops.rb'
     - 'test/**/*.rb'
 
 # Ignore module length failures in the tests.

lib/mos6502/cpu_instructions.rb

@@ -4,99 +4,12 @@
 #
 # Licensed under the BSD License. See LICENCE for details.
 
+require_relative 'cpu_ops'
+
 module Mos6502
   class Cpu
     private
 
-    def branch(offset)
-      if offset > 0x7f
-        @pc - (0x100 - offset)
-      else
-        @pc + offset
-      end
-    end
-
-    def compare(register, value)
-      @status.carry = register >= value
-      set_nz_flags(register - value)
-    end
-
-    def adc(value)
-      carry = @status.carry? ? 1 : 0
-
-      if @status.decimal_mode?
-        result = (@a & 0x0f) + (value & 0x0f) + carry
-        result = 0x10 | ((result + 0x06) & 0x0f) if result >= 0x0a
-        result += (@a & 0xf0) + (value & 0xf0)
-
-        if result >= 0xa0
-          result += 0x60
-          @status.carry = true
-          @status.overflow = ((@a ^ value) & 0x80).zero? && (result >= 0x0180)
-        else
-          @status.carry = false
-          @status.overflow = !((@a ^ value) & 0x80).zero? && (result < 0x80)
-        end
-      else
-        result = @a + value + carry
-        @status.overflow =
-          (((@a & 0x7f) + (value & 0x7f) + carry) >> 7) ^ (result >> 8)
-        @status.carry = result > 0xff
-      end
-
-      @a = result & 0xff
-      set_nz_flags(@a)
-    end
-
-    def sbc(value)
-      if @status.decimal_mode?
-        carry = @status.carry? ? 1 : 0
-        ones = 0x0f + (@a & 0x0f) - (value & 0x0f) + carry
-        tens = 0xf0 + (@a & 0xf0) - (value & 0xf0)
-
-        if ones < 0x10
-          ones -= 6
-        else
-          tens += 0x10
-          ones -= 0x10
-        end
-
-        if tens < 0x100
-          tens -= 0x60
-          @status.carry = false
-          @status.overflow = !((@a ^ value) & 0x80).zero? && (tens < 0x80)
-        else
-          @status.carry = true
-          @status.overflow = !((@a ^ value) & 0x80).zero? && (tens < 0x0180)
-        end
-
-        @a = (ones + tens) & 0xff
-        set_nz_flags(@a)
-      else
-        adc(value ^ 0xff)
-      end
-    end
-
-    def asl(value)
-      set_carry(value, 7)
-      value = value << 1
-      set_nz_flags(value)
-      value
-    end
-
-    def lsr(value)
-      set_carry(value, 0)
-      value = value >> 1
-      set_nz_flags(value)
-      value
-    end
-
-    def bit(value)
-      @status.zero = (@a & value).zero?
-      @status.overflow = value & 0x40
-      @status.negative = value & 0x80
-    end
-
     def instructions
       {
         # BRK

lib/mos6502/cpu_ops.rb

@@ -0,0 +1,100 @@
+# frozen_string_literal: true
+
+# Copyright (c) 2020, Robert Haines.
+#
+# Licensed under the BSD License. See LICENCE for details.
+
+module Mos6502
+  class Cpu
+    private
+
+    def adc(value)
+      carry = @status.carry? ? 1 : 0
+
+      if @status.decimal_mode?
+        result = (@a & 0x0f) + (value & 0x0f) + carry
+        result = 0x10 | ((result + 0x06) & 0x0f) if result >= 0x0a
+        result += (@a & 0xf0) + (value & 0xf0)
+
+        if result >= 0xa0
+          result += 0x60
+          @status.carry = true
+          @status.overflow = ((@a ^ value) & 0x80).zero? && (result >= 0x0180)
+        else
+          @status.carry = false
+          @status.overflow = !((@a ^ value) & 0x80).zero? && (result < 0x80)
+        end
+      else
+        result = @a + value + carry
+        @status.overflow =
+          (((@a & 0x7f) + (value & 0x7f) + carry) >> 7) ^ (result >> 8)
+        @status.carry = result > 0xff
+      end
+
+      @a = result & 0xff
+      set_nz_flags(@a)
+    end
+
+    def asl(value)
+      set_carry(value, 7)
+      value = value << 1
+      set_nz_flags(value)
+      value
+    end
+
+    def bit(value)
+      @status.zero = (@a & value).zero?
+      @status.overflow = value & 0x40
+      @status.negative = value & 0x80
+    end
+
+    def branch(offset)
+      if offset > 0x7f
+        @pc - (0x100 - offset)
+      else
+        @pc + offset
+      end
+    end
+
+    def compare(register, value)
+      @status.carry = register >= value
+      set_nz_flags(register - value)
+    end
+
+    def lsr(value)
+      set_carry(value, 0)
+      value = value >> 1
+      set_nz_flags(value)
+      value
+    end
+
+    def sbc(value)
+      if @status.decimal_mode?
+        carry = @status.carry? ? 1 : 0
+        ones = 0x0f + (@a & 0x0f) - (value & 0x0f) + carry
+        tens = 0xf0 + (@a & 0xf0) - (value & 0xf0)
+
+        if ones < 0x10
+          ones -= 6
+        else
+          tens += 0x10
+          ones -= 0x10
+        end
+
+        if tens < 0x100
+          tens -= 0x60
+          @status.carry = false
+          @status.overflow = !((@a ^ value) & 0x80).zero? && (tens < 0x80)
+        else
+          @status.carry = true
+          @status.overflow = !((@a ^ value) & 0x80).zero? && (tens < 0x0180)
+        end
+
+        @a = (ones + tens) & 0xff
+        set_nz_flags(@a)
+      else
+        adc(value ^ 0xff)
+      end
+    end
+  end
+end