vm: implement custom port handlers

cmd/retro/main.go

@@ -27,21 +27,35 @@ import (
 	"github.com/pkg/errors"
 )
 
+var fileName = flag.String("image", "retroImage", "Use `filename` as the image to load")
+var withFile = flag.String("with", "", "Add `filename` to the input stack")
+var shrink = flag.Bool("shrink", true, "When saving, don't save unused cells")
+var size = flag.Int("size", 50000, "image size in cells")
+var debug = flag.Bool("debug", false, "enable debug diagnostics")
+
 func main() {
 	// check exit condition
 	var err error
+	var proc *vm.Instance
 	defer func() {
-		if err != nil {
-			err = errors.Cause(err)
-			fmt.Fprintf(os.Stderr, "%+v\n", err)
+		if err == nil {
+			return
+		}
+		if !*debug {
+			fmt.Fprintf(os.Stderr, "\n%v\n", err)
 			os.Exit(1)
 		}
+		fmt.Fprintf(os.Stderr, "\n%+#v\n", err)
+		if proc != nil {
+			if proc.PC < len(proc.Image) {
+				fmt.Fprintf(os.Stderr, "PC: %v (%v), Stack: %v, Ret: %v\n", proc.PC, proc.Image[proc.PC], proc.Data(), proc.Address())
+			} else {
+				fmt.Fprintf(os.Stderr, "PC: %v, Stack: %v\nRet:  %v\n", proc.PC, proc.Data(), proc.Address())
+			}
+		}
+		os.Exit(1)
 	}()
 
-	var fileName = flag.String("image", "retroImage", "Use `filename` as the image to load")
-	var withFile = flag.String("with", "", "Add `filename` to the input stack")
-	var shrink = flag.Bool("shrink", true, "When saving, don't save unused cells")
-	var size = flag.Int("size", 50000, "image size in cells")
 	flag.Parse()
 
 	var interactive bool
@@ -52,10 +66,16 @@ func main() {
 	}
 
 	// default options
+	output := bufio.NewWriter(os.Stdout)
 	var opts = []vm.Option{
 		vm.Shrink(*shrink),
 		// buffered io is faster
-		vm.Output(bufio.NewWriter(os.Stdout)),
+		vm.Output(output),
+		// handle Flush events
+		vm.OutHandler(3, func(vm.Cell) (vm.Cell, error) {
+			output.Flush()
+			return 0, nil
+		}),
 	}
 
 	// buffer input if not interactive
@@ -79,7 +99,7 @@ func main() {
 	if err != nil {
 		return
 	}
-	proc, err := vm.New(img, *fileName, opts...)
+	proc, err = vm.New(img, *fileName, opts...)
 	if err != nil {
 		return
 	}

vm/core.go

@@ -18,6 +18,43 @@ package vm
 
 import "github.com/pkg/errors"
 
+type opcode Cell
+
+// ngaro Virtual Machine Opcodes.
+const (
+	OpNop opcode = iota
+	OpLit
+	OpDup
+	OpDrop
+	OpSwap
+	OpPush
+	OpPop
+	OpLoop
+	OpJump
+	OpReturn
+	OpGtJump
+	OpLtJump
+	OpNeJump
+	OpEqJump
+	OpFetch
+	OpStore
+	OpAdd
+	OpSub
+	OpMul
+	OpDimod
+	OpAnd
+	OpOr
+	OpXor
+	OpShl
+	OpShr
+	OpZeroExit
+	OpInc
+	OpDec
+	OpIn
+	OpOut
+	OpWait
+)
+
 // Push pushes the argument on top of the data stack.
 func (i *Instance) Push(v Cell) {
 	i.sp++
@@ -53,7 +90,11 @@ func (i *Instance) Rpop() Cell {
 func (i *Instance) Run(toPC int) (err error) {
 	defer func() {
 		if e := recover(); e != nil {
-			err = errors.Errorf("%v", e)
+			var ok bool
+			if err, ok = e.(error); !ok {
+				panic(e)
+			}
+			err = errors.Wrap(err, "VM abort")
 		}
 	}()
 	i.insCount = 0
@@ -186,26 +227,33 @@ func (i *Instance) Run(toPC int) (err error) {
 			i.PC++
 		case OpIn:
 			port := i.data[i.sp]
-			i.data[i.sp], i.ports[port] = i.ports[port], 0
+			v := i.ports[port]
+			if h := i.inH[int(port)]; h != nil {
+				v, err = h(v)
+				if err != nil {
+					return err
+				}
+			}
+			i.data[i.sp], i.ports[port] = v, 0
 			i.PC++
 		case OpOut:
 			port := i.data[i.sp]
-			i.ports[port] = i.data[i.sp-1]
-			i.sp -= 2
-			if port == 3 {
-				if o, ok := i.output.(Flusher); ok {
-					o.Flush()
+			v := i.data[i.sp-1]
+			if h := i.outH[int(port)]; h != nil {
+				v, err = h(v)
+				if err != nil {
+					return err
 				}
 			}
+			i.ports[port] = v
+			i.sp -= 2
 			i.PC++
 		case OpWait:
 			err = i.ioWait()
-			switch err.(type) {
-			case nil:
-				i.PC++
-			default:
+			if err != nil {
 				return err
 			}
+			i.PC++
 		default:
 			i.rsp++
 			i.address[i.rsp], i.PC = Cell(i.PC), int(op)