From 7f074a775e5d5b3c49a63ecad49431f1e13182c7 Mon Sep 17 00:00:00 2001
From: Alex Vanin <alexey@nspcc.ru>
Date: Mon, 6 Sep 2021 15:43:30 +0300
Subject: [PATCH] [#798] util/state: Implement persistent storage for
 application state

Signed-off-by: Alex Vanin <alexey@nspcc.ru>
---
 pkg/util/state/storage.go      | 71 ++++++++++++++++++++++++++++++++++
 pkg/util/state/storage_test.go | 26 +++++++++++++
 2 files changed, 97 insertions(+)
 create mode 100644 pkg/util/state/storage.go
 create mode 100644 pkg/util/state/storage_test.go

diff --git a/pkg/util/state/storage.go b/pkg/util/state/storage.go
new file mode 100644
index 000000000..f09f6b70e
--- /dev/null
+++ b/pkg/util/state/storage.go
@@ -0,0 +1,71 @@
+package state
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+
+	"go.etcd.io/bbolt"
+)
+
+// PersistentStorage is a wrapper around persistent K:V db that
+// provides thread safe functions to set and fetch state variables
+// of the Inner Ring and Storage applications.
+type PersistentStorage struct {
+	db *bbolt.DB
+}
+
+var stateBucket = []byte("state")
+
+// NewPersistentStorage creates new instance of a storage with 0600 rights.
+func NewPersistentStorage(path string) (*PersistentStorage, error) {
+	db, err := bbolt.Open(path, 0600, nil)
+	if err != nil {
+		return nil, fmt.Errorf("can't open bbolt at %s: %w", path, err)
+	}
+
+	return &PersistentStorage{db: db}, nil
+}
+
+// SetUInt32 sets uint32 value in the storage.
+func (p PersistentStorage) SetUInt32(key []byte, value uint32) error {
+	return p.db.Update(func(tx *bbolt.Tx) error {
+		b, err := tx.CreateBucketIfNotExists(stateBucket)
+		if err != nil {
+			return fmt.Errorf("can't create state bucket in state persistent storage: %w", err)
+		}
+
+		buf := make([]byte, 8)
+		binary.LittleEndian.PutUint64(buf, uint64(value))
+
+		return b.Put(key, buf)
+	})
+}
+
+// UInt32 returns uint32 value from persistent storage. If value is not exists,
+// returns 0.
+func (p PersistentStorage) UInt32(key []byte) (n uint32, err error) {
+	err = p.db.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(stateBucket)
+		if b == nil {
+			return nil // if bucket not exists yet, return default n = 0
+		}
+
+		buf := b.Get(key)
+		if len(buf) != 8 {
+			return fmt.Errorf("persistent storage does not store uint data in %s", hex.EncodeToString(key))
+		}
+
+		u64 := binary.LittleEndian.Uint64(buf)
+		n = uint32(u64)
+
+		return nil
+	})
+
+	return
+}
+
+// Close closes persistent database instance.
+func (p PersistentStorage) Close() error {
+	return p.db.Close()
+}
diff --git a/pkg/util/state/storage_test.go b/pkg/util/state/storage_test.go
new file mode 100644
index 000000000..528b57984
--- /dev/null
+++ b/pkg/util/state/storage_test.go
@@ -0,0 +1,26 @@
+package state_test
+
+import (
+	"path"
+	"testing"
+
+	"github.com/nspcc-dev/neofs-node/pkg/util/state"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPersistentStorage_UInt32(t *testing.T) {
+	storage, err := state.NewPersistentStorage(path.Join(t.TempDir(), ".storage"))
+	require.NoError(t, err)
+	defer storage.Close()
+
+	n, err := storage.UInt32([]byte("unset-value"))
+	require.NoError(t, err)
+	require.EqualValues(t, 0, n)
+
+	err = storage.SetUInt32([]byte("foo"), 10)
+	require.NoError(t, err)
+
+	n, err = storage.UInt32([]byte("foo"))
+	require.NoError(t, err)
+	require.EqualValues(t, 10, n)
+}