core: move blockdb into core package and minor change on governance interface (#110)

Since third party apps will possibly implement their only blockdb class,
it make sense for the interface to be in core.
Also add GetNumShards into the governance interface.

1 files changed, 127 insertions, 0 deletions

diff --git a/core/blockdb/level-db.go b/core/blockdb/level-db.go
new file mode 100644
index 0000000..79099c0
--- /dev/null
+++ b/core/blockdb/level-db.go
@@ -0,0 +1,127 @@
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package blockdb
+
+import (
+	"encoding/json"
+
+	"github.com/syndtr/goleveldb/leveldb"
+
+	"github.com/dexon-foundation/dexon-consensus-core/common"
+	"github.com/dexon-foundation/dexon-consensus-core/core/types"
+)
+
+// LevelDBBackedBlockDB is a leveldb backed BlockDB implementation.
+type LevelDBBackedBlockDB struct {
+	db *leveldb.DB
+}
+
+// NewLevelDBBackedBlockDB initialize a leveldb-backed block database.
+func NewLevelDBBackedBlockDB(
+	path string) (lvl *LevelDBBackedBlockDB, err error) {
+
+	db, err := leveldb.OpenFile(path, nil)
+	if err != nil {
+		return
+	}
+	lvl = &LevelDBBackedBlockDB{db: db}
+	return
+}
+
+// Close implement Closer interface, which would release allocated resource.
+func (lvl *LevelDBBackedBlockDB) Close() error {
+	return lvl.db.Close()
+}
+
+// Has implements the Reader.Has method.
+func (lvl *LevelDBBackedBlockDB) Has(hash common.Hash) bool {
+	exists, err := lvl.db.Has([]byte(hash[:]), nil)
+	if err != nil {
+		// TODO(missionliao): Modify the interface to return error.
+		panic(err)
+	}
+	return exists
+}
+
+// Get implements the Reader.Get method.
+func (lvl *LevelDBBackedBlockDB) Get(
+	hash common.Hash) (block types.Block, err error) {
+
+	queried, err := lvl.db.Get([]byte(hash[:]), nil)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			err = ErrBlockDoesNotExist
+		}
+		return
+	}
+	err = json.Unmarshal(queried, &block)
+	if err != nil {
+		return
+	}
+	return
+}
+
+// Update implements the Writer.Update method.
+func (lvl *LevelDBBackedBlockDB) Update(block types.Block) (err error) {
+	// NOTE: we didn't handle changes of block hash (and it
+	//       should not happen).
+	marshaled, err := json.Marshal(&block)
+	if err != nil {
+		return
+	}
+
+	if !lvl.Has(block.Hash) {
+		err = ErrBlockDoesNotExist
+		return
+	}
+	err = lvl.db.Put(
+		[]byte(block.Hash[:]),
+		marshaled,
+		nil)
+	if err != nil {
+		return
+	}
+	return
+}
+
+// Put implements the Writer.Put method.
+func (lvl *LevelDBBackedBlockDB) Put(block types.Block) (err error) {
+	marshaled, err := json.Marshal(&block)
+	if err != nil {
+		return
+	}
+	if lvl.Has(block.Hash) {
+		err = ErrBlockExists
+		return
+	}
+	err = lvl.db.Put(
+		[]byte(block.Hash[:]),
+		marshaled,
+		nil)
+	if err != nil {
+		return
+	}
+	return
+}
+
+// GetAll implements Reader.GetAll method, which allows callers
+// to retrieve all blocks in DB.
+func (lvl *LevelDBBackedBlockDB) GetAll() (BlockIterator, error) {
+	// TODO (mission): Implement this part via goleveldb's iterator.
+	return nil, ErrNotImplemented
+}