From d1ac3b5e930a83b78c5ad871a97e13242983df96 Mon Sep 17 00:00:00 2001
From: Tristan Morgan <tristanmorgan@users.noreply.github.com>
Date: Mon, 25 Mar 2024 09:53:57 +1100
Subject: [PATCH] Implement opSkip.

---
 parser/execute.go          | 4 ++++
 parser/execute_test.go     | 5 +++--
 parser/instruction.go      | 2 ++
 parser/instruction_test.go | 1 +
 parser/tokenise.go         | 5 +++++
 parser/tokenise_test.go    | 8 ++++++++
 6 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/parser/execute.go b/parser/execute.go
index c92c207..266f87a 100644
--- a/parser/execute.go
+++ b/parser/execute.go
@@ -41,6 +41,10 @@ func Execute(program []Instruction, reader io.ByteReader, writer *bufio.Writer)
 			} else if err != nil {
 				break
 			}
+		case opSkip:
+			for data[dataPtr] != 0 {
+				dataPtr = (operand + dataPtr) & dataMask
+			}
 		case opJmpZ:
 			if data[dataPtr] == 0 {
 				pc = operand
diff --git a/parser/execute_test.go b/parser/execute_test.go
index 84321e1..ef1e8e1 100644
--- a/parser/execute_test.go
+++ b/parser/execute_test.go
@@ -29,7 +29,8 @@ func TestExecuteSmall(t *testing.T) {
 
 func TestTokeniseExecuteSmall(t *testing.T) {
 	program, _ := Tokenise(bufio.NewReader(strings.NewReader(
-		`+> >+> >+> >+> >
+		`>>>>>>>>>>
+<+< <+< <+< <+ [>>]
 >++++++++
 [
   <
@@ -40,7 +41,7 @@ func TestTokeniseExecuteSmall(t *testing.T) {
 	outputBuf := bufio.NewWriter(os.Stdout)
 	inputBuf := bufio.NewReader(strings.NewReader("no input."))
 	data := Execute(program, inputBuf, outputBuf)[:10]
-	want := []int{170, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	want := []int{0, 0, 0, 170, 0, 0, 0, 0, 0, 0}
 
 	if !reflect.DeepEqual(data, want) {
 		t.Errorf("got %v want %v", data, want)
diff --git a/parser/instruction.go b/parser/instruction.go
index c107309..14ccb1e 100644
--- a/parser/instruction.go
+++ b/parser/instruction.go
@@ -23,6 +23,7 @@ const (
 	opJmpZ
 	opJmpNz
 	opMove
+	opSkip
 )
 
 // String representation of Instruction
@@ -37,6 +38,7 @@ func (inst Instruction) String() string {
 		"jmpz",
 		"jmpnz",
 		"mov",
+		"skip",
 	}
 	return fmt.Sprintf("%s:%v", opName[inst.operator], inst.operand)
 }
diff --git a/parser/instruction_test.go b/parser/instruction_test.go
index 147204e..99e85e7 100644
--- a/parser/instruction_test.go
+++ b/parser/instruction_test.go
@@ -43,6 +43,7 @@ func TestSameOp(t *testing.T) {
 		opJmpZ,
 		opJmpNz,
 		opMove,
+		opSkip,
 	}
 
 	for row, rval := range opsList {
diff --git a/parser/tokenise.go b/parser/tokenise.go
index 4ccf695..c896f28 100644
--- a/parser/tokenise.go
+++ b/parser/tokenise.go
@@ -57,6 +57,11 @@ func Tokenise(input io.ByteReader) (program []Instruction, err error) {
 				pc = jmpPc
 				program = program[:pc]
 				program = append(program, Instruction{opSetVal, 0})
+			} else if pc-jmpPc == 2 && program[pc-1].operator == opAddDp {
+				offset := program[pc-1].operand
+				pc = jmpPc
+				program = program[:pc]
+				program = append(program, Instruction{opSkip, offset})
 			} else if pc-jmpPc == 5 &&
 				program[pc-4].Complement(program[pc-2]) &&
 				program[pc-3].Complement(program[pc-1]) {
diff --git a/parser/tokenise_test.go b/parser/tokenise_test.go
index fdf8baf..5010dd3 100644
--- a/parser/tokenise_test.go
+++ b/parser/tokenise_test.go
@@ -43,6 +43,14 @@ func TestTokenise(t *testing.T) {
 				Instruction{opAddVal, -4},
 			},
 		},
+		{
+			"op_skip",
+			"[>>>>>]",
+			[]Instruction{
+				Instruction{opNoop, 0},
+				Instruction{opSkip, 5},
+			},
+		},
 		{
 			"op_move",
 			"[->>+<<][<<<+>>>-]",