Make a start on opcodes

1 files changed, 124 insertions, 0 deletions

diff --git a/src/main/kotlin/cpu/Registers.kt b/src/main/kotlin/cpu/Registers.kt
new file mode 100644
index 0000000..6cf417e
--- /dev/null
+++ b/src/main/kotlin/cpu/Registers.kt
@@ -0,0 +1,124 @@
+package cpu
+
+class Registers {
+
+  // General purpose registers
+  var B: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var C: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var D: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var E: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var H: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var L: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+
+  // Special registers
+  var A: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var F: Int = 0
+    set(value) {
+      validateUnsigned8Bit(value)
+      field = value
+    }
+  var SP: Int = 0
+    set(value) {
+      validateUnsigned16Bit(value)
+      field = value
+    }
+  var PC: Int = 0
+    set(value) {
+      validateUnsigned16Bit(value)
+      field = value
+    }
+
+  // 16-Bit accessors
+  var AF: Int
+    get() {
+      return bytesToWord(A, F)
+    }
+    set(value) {
+      validateUnsigned16Bit(value)
+      A = getMsb(value)
+      F = getLsb(value)
+    }
+
+  var BC: Int
+    get() {
+      return bytesToWord(B, C)
+    }
+    set(value) {
+      validateUnsigned16Bit(value)
+      B = getMsb(value)
+      C = getLsb(value)
+    }
+
+  var DE: Int
+    get() {
+      return bytesToWord(D, E)
+    }
+    set(value) {
+      validateUnsigned16Bit(value)
+      D = getMsb(value)
+      E = getLsb(value)
+    }
+
+  var HL: Int
+    get() {
+      return bytesToWord(H, L)
+    }
+    set(value) {
+      validateUnsigned16Bit(value)
+      H = getMsb(value)
+      L = getLsb(value)
+    }
+
+  private fun bytesToWord(msb: Int, lsb: Int): Int {
+    return msb.shl(8) + lsb
+  }
+
+  private fun getMsb(value: Int): Int {
+    return value.shr(8)
+  }
+
+  private fun getLsb(value: Int): Int {
+    return value.and(0xFF)
+  }
+
+  private fun validateUnsigned8Bit(value: Int) {
+    if(value < 0 || value > 255) {
+      throw IllegalArgumentException("Value $value is not an unsigned 8-Bit value")
+    }
+  }
+
+  private fun validateUnsigned16Bit(value: Int) {
+    if(value < 0 || value > 65535) {
+      throw IllegalArgumentException("Value $value is not an unsigned 16-Bit value")
+    }
+  }
+
+}
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