2 files changed, 65 insertions, 3 deletions

diff --git a/pkg/lang/vm/code/builder.go b/pkg/lang/vm/code/builder.go
new file mode 100644
index 0000000..3aa6b6b
--- /dev/null
+++ b/pkg/lang/vm/code/builder.go
@@ -0,0 +1,60 @@
+package code
+
+import (
+	"encoding/binary"
+	"math"
+)
+
+type Builder struct {
+	code      []byte
+	debugInfo DebugInfo
+}
+
+func NewBuilder() Builder {
+	return Builder{
+		code:      make([]byte, 0, 64),
+		debugInfo: NewDebugInfo("unknown file"),
+	}
+}
+
+func (b *Builder) AppendOp(op Op) {
+	b.code = append(b.code, byte(op))
+}
+
+func (b *Builder) AppendInt(x int64) {
+	b.code = append(b.code, make([]byte, 8)...)
+	binary.LittleEndian.PutUint64(b.code[len(b.code)-8:], uint64(x))
+}
+
+func (b *Builder) AppendFloat(x float64) {
+	b.AppendInt(int64(math.Float64bits(x)))
+}
+
+func (b *Builder) AppendString(s string) {
+	b.code = append(b.code, []byte(s)...)
+	b.code = append(b.code, 0)
+}
+
+func (b *Builder) AppendRaw(raw Raw) {
+	b.code = append(b.code, raw...)
+}
+
+func (b *Builder) AppendLine(line int) {
+	b.debugInfo.AppendLine(len(b.code)-1, line)
+}
+
+func (b *Builder) SetInt(at int, x int64) {
+	binary.LittleEndian.PutUint64(b.code[at:], uint64(x))
+}
+
+func (b *Builder) Code() Raw {
+	return Raw(b.code)
+}
+
+func (b *Builder) Len() int {
+	return len(b.code)
+}
+
+func (b *Builder) Build() Code {
+	return New(b.code, b.debugInfo)
+}
diff --git a/pkg/lang/vm/code/code.go b/pkg/lang/vm/code/code.go
index 38bbcf5..94fd612 100644
--- a/pkg/lang/vm/code/code.go
+++ b/pkg/lang/vm/code/code.go
@@ -7,12 +7,14 @@ import (
 	"strings"
 )
 
+type Raw []byte
+
 type Code struct {
-	code      []byte
+	code      Raw
 	debugInfo DebugInfo
 }
 
-func New(code []byte, info DebugInfo) Code {
+func New(code Raw, info DebugInfo) Code {
 	return Code{
 		code:      code,
 		debugInfo: info,
@@ -23,7 +25,7 @@ func (c *Code) Len() int {
 	return len(c.code)
 }
 
-func (c *Code) Code() []byte {
+func (c *Code) Code() Raw {
 	return c.code
 }