From c6a953d722b1fdc27a9db6f78f00c52fe43a7222 Mon Sep 17 00:00:00 2001
From: James Barnett <noreply@jamesbarnett.xyz>
Date: Sat, 21 Jul 2018 19:46:20 +0100
Subject: Add ability to step through CPU execution of boot rom

---
 src/main/kotlin/cpu/Cpu.kt               |  61 +++++++++++++++++++++++++++++++
 src/main/kotlin/gui/CpuRegisterWindow.kt |   2 +-
 src/main/kotlin/gui/RunControlWindow.kt  |  46 +++++++++++++++++++++++
 src/main/kotlin/gui/WindowContainer.kt   |   6 +++
 src/main/kotlin/ram/Ram.kt               |   7 ++++
 src/main/resources/roms/boot-rom.gb      | Bin 0 -> 256 bytes
 6 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 src/main/kotlin/gui/RunControlWindow.kt
 create mode 100644 src/main/resources/roms/boot-rom.gb

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]!!
+    }
+  }
+
 }
\ No newline at end of file
diff --git a/src/main/kotlin/gui/CpuRegisterWindow.kt b/src/main/kotlin/gui/CpuRegisterWindow.kt
index 0de7ad6..618d298 100644
--- a/src/main/kotlin/gui/CpuRegisterWindow.kt
+++ b/src/main/kotlin/gui/CpuRegisterWindow.kt
@@ -7,7 +7,7 @@ import imgui.ImGui
 
 fun paintCpuRegisterWindow(registers: Registers) {
   with(ImGui) {
-    setNextWindowSize(Vec2(200, 300), Cond.FirstUseEver)
+    setNextWindowSize(Vec2(200, 250), Cond.FirstUseEver)
     setNextWindowPos(Vec2(20, 150), Cond.FirstUseEver)
     begin("CPU state")
 
diff --git a/src/main/kotlin/gui/RunControlWindow.kt b/src/main/kotlin/gui/RunControlWindow.kt
new file mode 100644
index 0000000..8ffc764
--- /dev/null
+++ b/src/main/kotlin/gui/RunControlWindow.kt
@@ -0,0 +1,46 @@
+package gui
+
+import cpu.Cpu
+import glm_.vec2.Vec2
+import imgui.Cond
+import imgui.ImGui
+
+fun paintRunControlWindow(cpu: Cpu) {
+  with(ImGui) {
+
+    setNextWindowPos(Vec2(20, 410), Cond.FirstUseEver)
+    begin("Run control")
+
+    text("Current op:")
+    separator()
+    if(cpu.currentOp != null) {
+      text(cpu.currentOp!!.name)
+    }
+    else {
+      text("None")
+    }
+
+    newLine()
+
+    text("Next op:")
+    separator()
+    if(cpu.nextOp != null) {
+      text(cpu.nextOp!!.name)
+    }
+    else {
+      text("None")
+    }
+
+    newLine()
+
+    text("Control:")
+    separator()
+
+
+    if(button("Step")) {
+      cpu.executeNextInstruction()
+    }
+
+    end()
+  }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/gui/WindowContainer.kt b/src/main/kotlin/gui/WindowContainer.kt
index 5e101b7..4d58c18 100644
--- a/src/main/kotlin/gui/WindowContainer.kt
+++ b/src/main/kotlin/gui/WindowContainer.kt
@@ -10,6 +10,7 @@ import imgui.impl.LwjglGL3
 import org.lwjgl.opengl.GL11
 import uno.glfw.GlfwWindow
 import uno.glfw.glfw
+import java.io.File
 
 class WindowContainer {
 
@@ -18,6 +19,10 @@ class WindowContainer {
   init {
     glfw.init("3.2")
     cpu = Cpu()
+    val file = File("src/main/resources/roms/boot-rom.gb")
+    val rom = file.readBytes()
+    cpu.loadRom(rom)
+    //cpu.run()
   }
 
   val window = GlfwWindow(1280, 720, "KGB - KotlinGameBoy").apply {
@@ -52,6 +57,7 @@ class WindowContainer {
       paintDebugWindow()
       paintEmulationOutputWindow()
       paintCpuRegisterWindow(cpu.registers)
+      paintRunControlWindow(cpu)
     }
 
     gln.glViewport(window.framebufferSize)
diff --git a/src/main/kotlin/ram/Ram.kt b/src/main/kotlin/ram/Ram.kt
index 93336a7..7614040 100644
--- a/src/main/kotlin/ram/Ram.kt
+++ b/src/main/kotlin/ram/Ram.kt
@@ -13,4 +13,11 @@ class Ram {
     ram[address] = data
   }
 
+  fun load(rom: ByteArray) {
+
+    rom.forEachIndexed{i, b ->
+      ram[i] = b.toInt() and 0xFF
+    }
+  }
+
 }
\ No newline at end of file
diff --git a/src/main/resources/roms/boot-rom.gb b/src/main/resources/roms/boot-rom.gb
new file mode 100644
index 0000000..afa0ee4
Binary files /dev/null and b/src/main/resources/roms/boot-rom.gb differ
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