From 2f0cb2569ffe989cd0afcc85ed124c305f173515 Mon Sep 17 00:00:00 2001
From: Ethan Frey <ethanfrey@users.noreply.github.com>
Date: Mon, 10 Jul 2017 22:57:18 +0200
Subject: [PATCH] Add prefixStore (state space)

---
 stack/prefixstore.go | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 stack/prefixstore.go

diff --git a/stack/prefixstore.go b/stack/prefixstore.go
new file mode 100644
index 000000000..8592ba321
--- /dev/null
+++ b/stack/prefixstore.go
@@ -0,0 +1,31 @@
+package stack
+
+import "github.com/tendermint/basecoin/state"
+
+type prefixStore struct {
+	prefix []byte
+	store  state.KVStore
+}
+
+var _ state.KVStore = prefixStore{}
+
+func (p prefixStore) Set(key, value []byte) {
+	key = append(key, p.prefix...)
+	p.store.Set(key, value)
+}
+
+func (p prefixStore) Get(key []byte) (value []byte) {
+	key = append(key, p.prefix...)
+	return p.store.Get(key)
+}
+
+// stateSpace will unwrap any prefixStore and then add the prefix
+func stateSpace(store state.KVStore, app string) state.KVStore {
+	// unwrap one-level if wrapped
+	if pstore, ok := store.(prefixStore); ok {
+		store = pstore.store
+	}
+	// wrap it with the prefix
+	prefix := append([]byte(app), byte(0))
+	return prefixStore{prefix, store}
+}