Use specific types for enums.

asm/disasm.go

@@ -25,7 +25,7 @@ func bytesString(byte0, byte1, byte2 byte, length int) string {
 
 // addrString returns the address part of a 6502 assembly language
 // instruction.
-func addrString(pc uint16, byte1, byte2 byte, length int, mode int) string {
+func addrString(pc uint16, byte1, byte2 byte, length int, mode opcodes.AddressingMode) string {
 	addr16 := uint16(byte1) + uint16(byte2)<<8
 	addrRel := uint16(int32(pc+2) + int32(int8(byte1)))
 	switch mode {

cpu/cpu.go

@@ -11,8 +11,10 @@ import (
 )
 
 // Chip versions.
+type CpuVersion int
+
 const (
-	VERSION_6502 = iota
+	VERSION_6502 CpuVersion = iota
 	VERSION_65C02
 )
 
@@ -76,11 +78,11 @@ type cpu struct {
 	t       Ticker
 	r       registers
 	oldPC   uint16
-	version int
+	version CpuVersion
 }
 
 // Create and return a new Cpu object with the given memory, ticker, and of the given version.
-func NewCPU(memory Memory, ticker Ticker, version int) Cpu {
+func NewCPU(memory Memory, ticker Ticker, version CpuVersion) Cpu {
 	c := cpu{m: memory, t: ticker, version: version}
 	c.r.P |= FLAG_UNUSED // Set unused flag to 1
 	return &c

opcodes/opcodes.go

@@ -6,8 +6,10 @@ function tables.
 package opcodes
 
 // Opcode addressing modes.
+type AddressingMode int
+
 const (
-	MODE_IMPLIED = iota
+	MODE_IMPLIED AddressingMode = iota
 	MODE_ABSOLUTE
 	MODE_INDIRECT
 	MODE_RELATIVE
@@ -22,16 +24,20 @@ const (
 	MODE_A
 )
 
-// Opcode read/write semantics
+// Opcode read/write semantics: does the opcode read, write, or
+// rmw. Useful to distinguish between instructions further than just
+// addressing mode.
+type ReadWrite int
+
 const (
-	MEM_NONE = 0
-	MEM_R    = 1
-	MEM_W    = 2
-	MEM_RMW  = 3
+	RW_X   ReadWrite = 0 // Don't care
+	RW_R   ReadWrite = 1
+	RW_W   ReadWrite = 2
+	RW_RMW ReadWrite = 3
 )
 
 // Lengths of instructions for each addressing mode.
-var ModeLengths = map[int]int{
+var ModeLengths = map[AddressingMode]int{
 	MODE_IMPLIED:    1,
 	MODE_ABSOLUTE:   3,
 	MODE_INDIRECT:   3,
@@ -47,18 +53,11 @@ var ModeLengths = map[int]int{
 	MODE_A:          1,
 }
 
-const (
-	RW_X   = 0 // Don't care
-	RW_R   = 1
-	RW_W   = 2
-	RW_RMW = 3
-)
-
 // Opcode stores information about instructions.
 type Opcode struct {
 	Name string
-	Mode int
-	RW   int
+	Mode AddressingMode
+	RW   ReadWrite
 }
 
 // Fake NoOp instruction used when disassembling.