Merge pull request #5 from maxfierke/mf-debugger

Implement a basic interactive debugger

README.md

@@ -8,6 +8,7 @@ a gameboy emulator for funsies
 - [X] Implement timer
 - [X] Pass Blargg's `cpu_instrs`/`02-interrupts.gb` ROM (manually verified)
 - [X] Pass Blargg's `instr_timing.gb` ROM (manually verified)
+- [X] Implement a basic interactive debugger
 - [ ] Pass Blargg's `mem_timing.gb` ROM (manually verified)
 - [ ] Implement LCD
 - [ ] Implement PPU, VRAM, OAM, etc.

cpu/cpu.go

@@ -43,7 +43,7 @@ func (cpu *CPU) Step(mmu *mem.MMU) (uint8, error) {
 		return 4, nil
 	}
 
-	inst, err := cpu.fetchAndDecode(mmu)
+	inst, err := cpu.FetchAndDecode(mmu, cpu.PC.Read())
 	if err != nil {
 		return 0, err
 	}
@@ -54,9 +54,8 @@ func (cpu *CPU) Step(mmu *mem.MMU) (uint8, error) {
 	return cycles, err
 }
 
-func (cpu *CPU) fetchAndDecode(mmu *mem.MMU) (*isa.Instruction, error) {
+func (cpu *CPU) FetchAndDecode(mmu *mem.MMU, addr uint16) (*isa.Instruction, error) {
 	// Fetch :)
-	addr := cpu.PC.Read()
 	opcodeByte := mmu.Read8(addr)
 	prefixed := opcodeByte == 0xCB
 

cpu/isa/opcodes.go

@@ -43,8 +43,7 @@ func (operand *Operand) String() string {
 type Opcode struct {
 	Addr       uint8
 	CbPrefixed bool
-	Mnemonic   string `json:"mnemonic"`
-	Comment    string
+	Mnemonic   string       `json:"mnemonic"`
 	Bytes      int          `json:"bytes"`
 	Cycles     []int        `json:"cycles"`
 	Operands   []Operand    `json:"operands"`
@@ -60,18 +59,11 @@ func (opcode *Opcode) String() string {
 		operands = append(operands, operandText)
 	}
 
-	var comment string
-
-	if opcode.Comment != "" {
-		comment = fmt.Sprintf("; %s", opcode.Comment)
-	}
-
 	return fmt.Sprintf(
-		"0x%02X %s %s %s",
+		"0x%02X %s %s",
 		opcode.Addr,
 		opcode.Mnemonic,
 		strings.Join(operands, ", "),
-		comment,
 	)
 }
 

debug/debugger.go

@@ -20,6 +20,8 @@ func NewDebugger(name string) (Debugger, error) {
 	switch name {
 	case "gameboy-doctor":
 		return NewGBDoctorDebugger(), nil
+	case "interactive":
+		return NewInteractiveDebugger()
 	case "none":
 		return NewNullDebugger(), nil
 	default: