From 38319c5a6719e6b4c138f845792c193ed8f057a6 Mon Sep 17 00:00:00 2001
From: Sami Hiltunen <sami.hiltunen@lovoo.com>
Date: Thu, 20 Jul 2017 11:08:41 +0200
Subject: [PATCH] iterator offset key skipping

* Skips the offset key while iterating over the storage. Returning
  the offset produces errors as users only expect to receive
  objects they've stored in the storage themselves and the stored
  offset can be considered an implementation detail.
---
 storage/storage.go      | 15 ++++++++++++++-
 storage/storage_mock.go |  3 +++
 storage/storage_test.go |  3 ++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/storage/storage.go b/storage/storage.go
index 5eba2b85..27b105bf 100644
--- a/storage/storage.go
+++ b/storage/storage.go
@@ -84,6 +84,11 @@ func (i *iter) Next() bool {
 
 	// find the next non deleted snapshot value
 	for !i.snapExhausted() {
+		if string(i.Key()) == offsetKey {
+			i.current++
+			continue
+		}
+
 		if val, err := i.Value(); err != nil {
 			// TODO (franz): sure we want a panic? Not returning the error?
 			i.storage.log.Panicf("error getting snapshot value in next: %v", err)
@@ -96,6 +101,10 @@ func (i *iter) Next() bool {
 
 	// find next value in db that was not in snapshot
 	for i.iter.Next() {
+		if string(i.Key()) == offsetKey {
+			continue
+		}
+
 		if !i.snapshot.Has(string(i.Key())) {
 			return true
 		}
@@ -114,7 +123,11 @@ func (i *iter) Key() []byte {
 
 func (i *iter) Value() (interface{}, error) {
 	if i.snapExhausted() {
-		return i.storage.codec.Decode(i.iter.Value())
+		dec, err := i.storage.codec.Decode(i.iter.Value())
+		if err != nil {
+			return nil, fmt.Errorf("error decoding value (key: %s): %v", string(i.Key()), err)
+		}
+		return dec, nil
 	}
 
 	val, enc, err := i.snapshot.Get(string(i.Key()), i.storage.stateCloner(i.storage.codec))
diff --git a/storage/storage_mock.go b/storage/storage_mock.go
index 7fac1c30..1606bcb9 100644
--- a/storage/storage_mock.go
+++ b/storage/storage_mock.go
@@ -28,6 +28,9 @@ func (i *memiter) exhausted() bool {
 
 func (i *memiter) Next() bool {
 	i.current++
+	if string(i.Key()) == offsetKey {
+		i.current++
+	}
 	return !i.exhausted()
 }
 
diff --git a/storage/storage_test.go b/storage/storage_test.go
index e540821f..5b15c7c0 100644
--- a/storage/storage_test.go
+++ b/storage/storage_test.go
@@ -46,11 +46,12 @@ func TestMemIter(t *testing.T) {
 
 	found := map[string]string{}
 
+	storage.Set(offsetKey, "not-returned")
 	for k, v := range kv {
 		storage.Set(k, v)
 	}
 
-	// released iterator should be immidiately exhausted
+	// released iterator should be immediately exhausted
 	iter := storage.Iterator()
 	iter.Release()
 	ensure.False(t, iter.Next(), "released iterator had a next")