ethdb: add NewBatch

Author: fjl

ethdb/database.go

@@ -268,3 +268,23 @@ func (self *LDBDatabase) meter(refresh time.Duration) {
 		}
 	}
 }
+
+// TODO: remove this stuff and expose leveldb directly
+
+func (db *LDBDatabase) NewBatch() Batch {
+	return &ldbBatch{db: db.db, b: new(leveldb.Batch)}
+}
+
+type ldbBatch struct {
+	db *leveldb.DB
+	b  *leveldb.Batch
+}
+
+func (b *ldbBatch) Put(key, value []byte) error {
+	b.b.Put(key, value)
+	return nil
+}
+
+func (b *ldbBatch) Write() error {
+	return b.db.Write(b.b, nil)
+}

ethdb/interface.go

@@ -22,4 +22,10 @@ type Database interface {
 	Delete(key []byte) error
 	Close()
 	Flush() error
+	NewBatch() Batch
+}
+
+type Batch interface {
+	Put(key, value []byte) error
+	Write() error
 }

ethdb/memory_database.go

@@ -95,3 +95,26 @@ func (db *MemDatabase) LastKnownTD() []byte {
 func (db *MemDatabase) Flush() error {
 	return nil
 }
+
+func (db *MemDatabase) NewBatch() Batch {
+	return &memBatch{db: db}
+}
+
+type kv struct{ k, v []byte }
+
+type memBatch struct {
+	db     *MemDatabase
+	writes []kv
+}
+
+func (w *memBatch) Put(key, value []byte) error {
+	w.writes = append(w.writes, kv{key, common.CopyBytes(value)})
+	return nil
+}
+
+func (w *memBatch) Write() error {
+	for _, kv := range w.writes {
+		w.db.db[string(kv.k)] = kv.v
+	}
+	return nil
+}