Add ability to step through CPU execution of boot rom

1 files changed, 61 insertions, 0 deletions

diff --git a/src/main/kotlin/cpu/Cpu.kt b/src/main/kotlin/cpu/Cpu.kt
index 91150c4..f474dbb 100644
--- a/src/main/kotlin/cpu/Cpu.kt
+++ b/src/main/kotlin/cpu/Cpu.kt
@@ -2,12 +2,16 @@ package cpu
 
 import cpu.opcodes.*
 import ram.Ram
+import kotlin.concurrent.thread
 
 class Cpu {
 
   val registers = Registers()
   val ram = Ram()
 
+  var currentOp: Operation? = null
+  var nextOp: Operation? = null
+
   var standardOpcodes: Map<Int, Operation>
   var extendedOpcodes: Map<Int, Operation>
   init {
@@ -33,4 +37,61 @@ class Cpu {
 
   }
 
+  fun loadRom(rom: ByteArray) {
+    ram.load(rom)
+  }
+
+  fun executeNextInstruction() {
+
+    val (op, opArgs) = getNextOp()
+    op.command.invoke(registers, ram, opArgs)
+
+    currentOp = op
+    nextOp = peekNextOp()
+  }
+
+  fun run() {
+    thread {
+      while(true) {
+        executeNextInstruction()
+      }
+    }
+
+  }
+
+  private fun getNextOp(): Pair<Operation, IntArray> {
+
+    var addr = registers.PC
+    val startByte = ram.readByte(addr)
+    val op: Operation
+
+    op = if(startByte == 0xCB) {
+      extendedOpcodes[ram.readByte(++addr)]!!
+    } else {
+      standardOpcodes[startByte]!!
+    }
+
+    val opLength = op.length
+    val opArgs = IntArray(opLength)
+
+    IntRange(0, opLength -1).forEach {i ->
+      opArgs[i] = ram.readByte(++addr)
+    }
+
+    registers.PC = ++addr
+
+    return Pair(op, opArgs)
+  }
+
+
+  private fun peekNextOp(): Operation {
+
+    val startByte = ram.readByte(registers.PC)
+    return if(startByte == 0xCB) {
+      extendedOpcodes[ram.readByte(registers.PC + 1)]!!
+    } else {
+      standardOpcodes[startByte]!!
+    }
+  }
+
 }
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