From 9f58ed0fea4e7b1f8f69846d8f72bec19390d7ed Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Sun, 2 Jun 2019 15:38:00 +0200
Subject: [PATCH] ui: add version to OpBlock to track invalidated blocks

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 ui/internal/ops/ops.go |  2 +-
 ui/ops.go              | 15 ++++++++++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/ui/internal/ops/ops.go b/ui/internal/ops/ops.go
index cc214b64..d3843a3f 100644
--- a/ui/internal/ops/ops.go
+++ b/ui/internal/ops/ops.go
@@ -24,7 +24,7 @@ const (
 
 const (
 	TypeBlockDefLen       = 1 + 4 + 4
-	TypeBlockLen          = 1 + 4 + 4
+	TypeBlockLen          = 1 + 4 + 4 + 4
 	TypeTransformLen      = 1 + 4*2
 	TypeLayerLen          = 1
 	TypeRedrawLen         = 1 + 8
diff --git a/ui/ops.go b/ui/ops.go
index d84e6953..40b84dfa 100644
--- a/ui/ops.go
+++ b/ui/ops.go
@@ -14,6 +14,7 @@ type Ops struct {
 }
 
 type opsData struct {
+	version int
 	// Serialized ops.
 	data []byte
 	// Op references.
@@ -76,8 +77,9 @@ type OpPush struct{}
 type OpPop struct{}
 
 type OpBlock struct {
-	ops *Ops
-	pc  pc
+	ops     *Ops
+	version int
+	pc      pc
 }
 
 type opBlockDef struct {
@@ -126,7 +128,7 @@ func (o *Ops) End() OpBlock {
 	bo := binary.LittleEndian
 	bo.PutUint32(data[1:], uint32(pc.data))
 	bo.PutUint32(data[5:], uint32(pc.refs))
-	return OpBlock{ops: o, pc: start}
+	return OpBlock{ops: o, pc: start, version: o.ops.version}
 }
 
 // Reset clears the Ops.
@@ -138,6 +140,7 @@ func (o *Ops) Reset() {
 func (d *opsData) reset() {
 	d.data = d.data[:0]
 	d.refs = d.refs[:0]
+	d.version++
 }
 
 func (d *opsData) write(op []byte, refs []interface{}) {
@@ -160,12 +163,14 @@ func (b *OpBlock) decode(data []byte, refs []interface{}) {
 	bo := binary.LittleEndian
 	dataIdx := int(bo.Uint32(data[1:]))
 	refsIdx := int(bo.Uint32(data[5:]))
+	version := int(bo.Uint32(data[9:]))
 	*b = OpBlock{
 		ops: refs[0].(*Ops),
 		pc: pc{
 			data: dataIdx,
 			refs: refsIdx,
 		},
+		version: version,
 	}
 }
 
@@ -175,6 +180,7 @@ func (b OpBlock) Add(o *Ops) {
 	bo := binary.LittleEndian
 	bo.PutUint32(data[1:], uint32(b.pc.data))
 	bo.PutUint32(data[5:], uint32(b.pc.refs))
+	bo.PutUint32(data[9:], uint32(b.version))
 	o.Write(data, []interface{}{b.ops})
 }
 
@@ -212,6 +218,9 @@ func (r *OpsReader) Decode() ([]byte, []interface{}, bool) {
 			if ops.OpType(blockOps.data[op.pc.data]) != ops.TypeBlockDef {
 				panic("invalid block reference")
 			}
+			if op.version != r.ops.version {
+				panic("invalid OpBlock reference to reset Ops")
+			}
 			var opDef opBlockDef
 			opDef.decode(blockOps.data[op.pc.data : op.pc.data+ops.TypeBlockDefLen])
 			retPC := r.pc