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, 70 insertions, 0 deletions

diff --git a/core/blockdb/interfaces.go b/core/blockdb/interfaces.go
new file mode 100644
index 0000000..fd176bc
--- /dev/null
+++ b/core/blockdb/interfaces.go
@@ -0,0 +1,70 @@
+// 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 (
+	"errors"
+	"fmt"
+
+	"github.com/dexon-foundation/dexon-consensus-core/common"
+	"github.com/dexon-foundation/dexon-consensus-core/core/types"
+)
+
+var (
+	// ErrBlockExists is the error when block eixsts.
+	ErrBlockExists = errors.New("block exists")
+	// ErrBlockDoesNotExist is the error when block does not eixst.
+	ErrBlockDoesNotExist = errors.New("block does not exist")
+	// ErrIterationFinished is the error to check if the iteration is finished.
+	ErrIterationFinished = errors.New("iteration finished")
+	// ErrEmptyPath is the error when the required path is empty.
+	ErrEmptyPath = fmt.Errorf("empty path")
+	// ErrClosed is the error when using DB after it's closed.
+	ErrClosed = fmt.Errorf("db closed")
+	// ErrNotImplemented is the error that some interface is not implemented.
+	ErrNotImplemented = fmt.Errorf("not implemented")
+)
+
+// BlockDatabase is the interface for a BlockDatabase.
+type BlockDatabase interface {
+	Reader
+	Writer
+
+	// Close allows database implementation able to
+	// release resource when finishing.
+	Close() error
+}
+
+// Reader defines the interface for reading blocks into DB.
+type Reader interface {
+	Has(hash common.Hash) bool
+	Get(hash common.Hash) (types.Block, error)
+	GetAll() (BlockIterator, error)
+}
+
+// Writer defines the interface for writing blocks into DB.
+type Writer interface {
+	Update(block types.Block) error
+	Put(block types.Block) error
+}
+
+// BlockIterator defines an iterator on blocks hold
+// in a DB.
+type BlockIterator interface {
+	Next() (types.Block, error)
+}