client(consensus/grandpa): implement grandpaDb and environment types (#…

…3383)

client/api/backend.go

@@ -0,0 +1,26 @@
+// Copyright 2023 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package api
+
+type Key []byte
+
+type KeyValue struct {
+	Key   Key
+	Value []byte
+}
+
+// AuxStore is part of the substrate backend.
+// Provides access to an auxiliary database.
+//
+// This is a simple global database not aware of forks. Can be used for storing auxiliary
+// information like total block weight/difficulty for fork resolution purposes as a common use
+// case.
+type AuxStore interface {
+	// Insert auxiliary data into key-Value store.
+	//
+	// Deletions occur after insertions.
+	Insert(insert []KeyValue, delete []Key) error
+	// Get Query auxiliary data from key-Value store.
+	Get(key Key) (*[]byte, error)
+}