storage: add Delete method for Batch and Store

It's gonna be used by Storage and Contract interops, both can delete their
data.

pkg/core/storage/boltdb_store.go

@@ -71,6 +71,14 @@ func (s *BoltDBStore) Get(key []byte) (val []byte, err error) {
 	return
 }
 
+// Delete implements the Store interface.
+func (s *BoltDBStore) Delete(key []byte) error {
+	return s.db.Update(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(Bucket)
+		return b.Delete(key)
+	})
+}
+
 // PutBatch implements the Store interface.
 func (s *BoltDBStore) PutBatch(batch Batch) error {
 	return s.db.Batch(func(tx *bbolt.Tx) error {
@@ -81,6 +89,12 @@ func (s *BoltDBStore) PutBatch(batch Batch) error {
 				return err
 			}
 		}
+		for k := range batch.(*MemoryBatch).del {
+			err := b.Delete([]byte(k))
+			if err != nil {
+				return err
+			}
+		}
 		return nil
 	})
 }

pkg/core/storage/leveldb_store.go

@@ -48,6 +48,11 @@ func (s *LevelDBStore) Get(key []byte) ([]byte, error) {
 	return value, err
 }
 
+// Delete implements the Store interface.
+func (s *LevelDBStore) Delete(key []byte) error {
+	return s.db.Delete(key, nil)
+}
+
 // PutBatch implements the Store interface.
 func (s *LevelDBStore) PutBatch(batch Batch) error {
 	lvldbBatch := batch.(*leveldb.Batch)

pkg/core/storage/memory_store.go

@@ -10,11 +10,15 @@ import (
 type MemoryStore struct {
 	mut sync.RWMutex
 	mem map[string][]byte
+	// A map, not a slice, to avoid duplicates.
+	del map[string]bool
 }
 
 // MemoryBatch a in-memory batch compatible with MemoryStore.
 type MemoryBatch struct {
 	m map[string][]byte
+	// A map, not a slice, to avoid duplicates.
+	del map[string]bool
 }
 
 // Put implements the Batch interface.
@@ -23,6 +27,14 @@ func (b *MemoryBatch) Put(k, v []byte) {
 	copy(vcopy, v)
 	kcopy := string(k)
 	b.m[kcopy] = vcopy
+	delete(b.del, kcopy)
+}
+
+// Delete implements Batch interface.
+func (b *MemoryBatch) Delete(k []byte) {
+	kcopy := string(k)
+	delete(b.m, kcopy)
+	b.del[kcopy] = true
 }
 
 // Len implements the Batch interface.
@@ -34,6 +46,7 @@ func (b *MemoryBatch) Len() int {
 func NewMemoryStore() *MemoryStore {
 	return &MemoryStore{
 		mem: make(map[string][]byte),
+		del: make(map[string]bool),
 	}
 }
 
@@ -50,7 +63,19 @@ func (s *MemoryStore) Get(key []byte) ([]byte, error) {
 // Put implements the Store interface. Never returns an error.
 func (s *MemoryStore) Put(key, value []byte) error {
 	s.mut.Lock()
-	s.mem[string(key)] = value
+	newKey := string(key)
+	s.mem[newKey] = value
+	delete(s.del, newKey)
+	s.mut.Unlock()
+	return nil
+}
+
+// Delete implements Store interface. Never returns an error.
+func (s *MemoryStore) Delete(key []byte) error {
+	s.mut.Lock()
+	newKey := string(key)
+	s.del[newKey] = true
+	delete(s.mem, newKey)
 	s.mut.Unlock()
 	return nil
 }
@@ -58,6 +83,9 @@ func (s *MemoryStore) Put(key, value []byte) error {
 // PutBatch implements the Store interface. Never returns an error.
 func (s *MemoryStore) PutBatch(batch Batch) error {
 	b := batch.(*MemoryBatch)
+	for k := range b.del {
+		_ = s.Delete([]byte(k))
+	}
 	for k, v := range b.m {
 		_ = s.Put([]byte(k), v)
 	}
@@ -82,6 +110,7 @@ func (s *MemoryStore) Batch() Batch {
 func newMemoryBatch() *MemoryBatch {
 	return &MemoryBatch{
 		m:   make(map[string][]byte),
+		del: make(map[string]bool),
 	}
 }
 
@@ -91,17 +120,22 @@ func (s *MemoryStore) Persist(ps Store) (int, error) {
 	s.mut.Lock()
 	defer s.mut.Unlock()
 	batch := ps.Batch()
-	keys := 0
+	keys, dkeys := 0, 0
 	for k, v := range s.mem {
 		batch.Put([]byte(k), v)
 		keys++
 	}
+	for k := range s.del {
+		batch.Delete([]byte(k))
+		dkeys++
+	}
 	var err error
-	if keys != 0 {
+	if keys != 0 || dkeys != 0 {
 		err = ps.PutBatch(batch)
 	}
 	if err == nil {
 		s.mem = make(map[string][]byte)
+		s.del = make(map[string]bool)
 	}
 	return keys, err
 }
@@ -110,6 +144,7 @@ func (s *MemoryStore) Persist(ps Store) (int, error) {
 // error.
 func (s *MemoryStore) Close() error {
 	s.mut.Lock()
+	s.del = nil
 	s.mem = nil
 	s.mut.Unlock()
 	return nil

pkg/core/storage/memory_store_test.go

@@ -125,4 +125,16 @@ func TestMemoryStorePersist(t *testing.T) {
 	c, err = ts.Persist(ps)
 	assert.Equal(t, nil, err)
 	assert.Equal(t, 0, c)
+	// test persisting deletions
+	err = ts.Delete([]byte("key"))
+	assert.Equal(t, nil, err)
+	c, err = ts.Persist(ps)
+	assert.Equal(t, nil, err)
+	assert.Equal(t, 0, c)
+	v, err = ps.Get([]byte("key"))
+	assert.Equal(t, ErrKeyNotFound, err)
+	assert.Equal(t, []byte(nil), v)
+	v, err = ps.Get([]byte("key2"))
+	assert.Equal(t, nil, err)
+	assert.Equal(t, []byte("value2"), v)
 }

pkg/core/storage/redis_store.go

@@ -48,6 +48,12 @@ func (s *RedisStore) Get(k []byte) ([]byte, error) {
 	return []byte(val), nil
 }
 
+// Delete implements the Store interface.
+func (s *RedisStore) Delete(k []byte) error {
+	s.client.Del(string(k))
+	return nil
+}
+
 // Put implements the Store interface.
 func (s *RedisStore) Put(k, v []byte) error {
 	s.client.Set(string(k), string(v), 0)
@@ -60,6 +66,9 @@ func (s *RedisStore) PutBatch(b Batch) error {
 	for k, v := range b.(*MemoryBatch).m {
 		pipe.Set(k, v, 0)
 	}
+	for k := range b.(*MemoryBatch).del {
+		pipe.Del(k)
+	}
 	_, err := pipe.Exec()
 	return err
 }

pkg/core/storage/store.go

@@ -32,6 +32,7 @@ type (
 	// information.
 	Store interface {
 		Batch() Batch
+		Delete(k []byte) error
 		Get([]byte) ([]byte, error)
 		Put(k, v []byte) error
 		PutBatch(Batch) error
@@ -43,6 +44,7 @@ type (
 	// Each Store implementation is responsible of casting a Batch
 	// to its appropriate type.
 	Batch interface {
+		Delete(k []byte)
 		Put(k, v []byte)
 		Len() int
 	}