Add db package

Add own db (storage) package with db.Storage interface, with Memory & Leveldb
implementations, and with tests.

Adapted with several changes from
https://github.com/iden3/go-iden3-core/tree/v0.0.8/db

db/memory/memory.go

@@ -0,0 +1,129 @@
+package memory
+
+import (
+	"bytes"
+	"sort"
+
+	"github.com/iden3/go-merkletree/db"
+)
+
+// MemoryStorage implements the db.Storage interface
+type MemoryStorage struct {
+	prefix []byte
+	kv     db.KvMap
+}
+
+// MemoryStorageTx implements the db.Tx interface
+type MemoryStorageTx struct {
+	s  *MemoryStorage
+	kv db.KvMap
+}
+
+// NewMemoryStorage returns a new MemoryStorage
+func NewMemoryStorage() *MemoryStorage {
+	kvmap := make(db.KvMap)
+	return &MemoryStorage{[]byte{}, kvmap}
+}
+
+// Info implements the method Info of the interface db.Storage
+func (l *MemoryStorage) Info() string {
+	return "in-memory"
+}
+
+// WithPrefix implements the method WithPrefix of the interface db.Storage
+func (m *MemoryStorage) WithPrefix(prefix []byte) db.Storage {
+	return &MemoryStorage{db.Concat(m.prefix, prefix), m.kv}
+}
+
+// NewTx implements the method NewTx of the interface db.Storage
+func (m *MemoryStorage) NewTx() (db.Tx, error) {
+	return &MemoryStorageTx{m, make(db.KvMap)}, nil
+}
+
+// Get retreives a value from a key in the db.Storage
+func (l *MemoryStorage) Get(key []byte) ([]byte, error) {
+	if v, ok := l.kv.Get(db.Concat(l.prefix, key[:])); ok {
+		return v, nil
+	}
+	return nil, db.ErrNotFound
+}
+
+// Iterate implements the method Iterate of the interface db.Storage
+func (l *MemoryStorage) Iterate(f func([]byte, []byte) (bool, error)) error {
+	kvs := make([]db.KV, 0)
+	for _, v := range l.kv {
+		if len(v.K) < len(l.prefix) || !bytes.Equal(v.K[:len(l.prefix)], l.prefix) {
+			continue
+		}
+		localkey := v.K[len(l.prefix):]
+		kvs = append(kvs, db.KV{K: localkey, V: v.V})
+
+	}
+	sort.SliceStable(kvs, func(i, j int) bool { return bytes.Compare(kvs[i].K, kvs[j].K) < 0 })
+
+	for _, kv := range kvs {
+		if cont, err := f(kv.K, kv.V); err != nil {
+			return err
+		} else if !cont {
+			break
+		}
+	}
+	return nil
+}
+
+// Get implements the method Get of the interface db.Tx
+func (tx *MemoryStorageTx) Get(key []byte) ([]byte, error) {
+
+	if v, ok := tx.kv.Get(db.Concat(tx.s.prefix, key)); ok {
+		return v, nil
+	}
+	if v, ok := tx.s.kv.Get(db.Concat(tx.s.prefix, key)); ok {
+		return v, nil
+	}
+
+	return nil, db.ErrNotFound
+}
+
+// Put implements the method Put of the interface db.Tx
+func (tx *MemoryStorageTx) Put(k, v []byte) {
+	tx.kv.Put(db.Concat(tx.s.prefix, k), v)
+}
+
+// Commit implements the method Commit of the interface db.Tx
+func (tx *MemoryStorageTx) Commit() error {
+	for _, v := range tx.kv {
+		tx.s.kv.Put(v.K, v.V)
+	}
+	tx.kv = nil
+	return nil
+}
+
+// Add implements the method Add of the interface db.Tx
+func (tx *MemoryStorageTx) Add(atx db.Tx) {
+	mstx := atx.(*MemoryStorageTx)
+	for _, v := range mstx.kv {
+		tx.kv.Put(v.K, v.V)
+	}
+}
+
+// Close implements the method Close of the interface db.Tx
+func (tx *MemoryStorageTx) Close() {
+	tx.kv = nil
+}
+
+// Close implements the method Close of the interface db.Storage
+func (m *MemoryStorage) Close() {
+}
+
+// List implements the method List of the interface db.Storage
+func (l *MemoryStorage) List(limit int) ([]db.KV, error) {
+	ret := []db.KV{}
+	err := l.Iterate(func(key []byte, value []byte) (bool, error) {
+		ret = append(ret, db.KV{K: db.Clone(key), V: db.Clone(value)})
+		if len(ret) == limit {
+			return false, nil
+		}
+		return true, nil
+	})
+	return ret, err
+}

db/memory/memory_test.go

@@ -0,0 +1,25 @@
+package memory
+
+import (
+	"testing"
+
+	"github.com/iden3/go-merkletree/db"
+	"github.com/iden3/go-merkletree/db/test"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMemoryStorageInterface(t *testing.T) {
+	var db db.Storage //nolint:gosimple
+
+	db = NewMemoryStorage()
+	require.NotNil(t, db)
+}
+
+func TestMemory(t *testing.T) {
+	test.TestReturnKnownErrIfNotExists(t, NewMemoryStorage())
+	test.TestStorageInsertGet(t, NewMemoryStorage())
+	test.TestStorageWithPrefix(t, NewMemoryStorage())
+	test.TestConcatTx(t, NewMemoryStorage())
+	test.TestList(t, NewMemoryStorage())
+	test.TestIterate(t, NewMemoryStorage())
+}