ethdb: add Putter interface and Has method

ethdb/database.go

@@ -109,6 +109,10 @@ func (db *LDBDatabase) Put(key []byte, value []byte) error {
 	return db.db.Put(key, value, nil)
 }
 
+func (db *LDBDatabase) Has(key []byte) (bool, error) {
+	return db.db.Has(key, nil)
+}
+
 // Get returns the given key if it's present.
 func (db *LDBDatabase) Get(key []byte) ([]byte, error) {
 	// Measure the database get latency, if requested
@@ -271,8 +275,6 @@ func (db *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)}
 }
@@ -309,6 +311,10 @@ func (dt *table) Put(key []byte, value []byte) error {
 	return dt.db.Put(append([]byte(dt.prefix), key...), value)
 }
 
+func (dt *table) Has(key []byte) (bool, error) {
+	return dt.db.Has(append([]byte(dt.prefix), key...))
+}
+
 func (dt *table) Get(key []byte) ([]byte, error) {
 	return dt.db.Get(append([]byte(dt.prefix), key...))
 }

ethdb/interface.go

@@ -16,15 +16,20 @@
 
 package ethdb
 
-type Database interface {
+type Putter interface {
 	Put(key []byte, value []byte) error
+}
+
+type Database interface {
+	Putter
 	Get(key []byte) ([]byte, error)
+	Has(key []byte) (bool, error)
 	Delete(key []byte) error
 	Close()
 	NewBatch() Batch
 }
 
 type Batch interface {
-	Put(key, value []byte) error
+	Putter
 	Write() error
 }

ethdb/memory_database.go

@@ -45,6 +45,14 @@ func (db *MemDatabase) Put(key []byte, value []byte) error {
 	return nil
 }
 
+func (db *MemDatabase) Has(key []byte) (bool, error) {
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	_, ok := db.db[string(key)]
+	return ok, nil
+}
+
 func (db *MemDatabase) Get(key []byte) ([]byte, error) {
 	db.lock.RLock()
 	defer db.lock.RUnlock()