Add get_storage_keys_paged (#403)

* add storage keys paged

* add storage fetch

examples/examples/get_storage.rs

@@ -56,4 +56,20 @@ async fn main() {
 	let signer = AccountKeyring::Alice.pair();
 	api.set_signer(signer);
 	println!("[+] Alice's Account Nonce is {}", api.get_nonce().unwrap());
+
+	// Get an vector of storage keys, numbering up to the given max keys and that start with the (optionally) given storage key prefix.
+	let storage_key_prefix = api.get_storage_map_key_prefix("System", "Account").unwrap();
+	let max_keys = 3;
+	let storage_keys = api
+		.get_storage_keys_paged(Some(storage_key_prefix), max_keys, None, None)
+		.unwrap();
+	assert_eq!(storage_keys.len() as u32, max_keys);
+	// Get the storage values that belong to the retrieved storage keys.
+	for storage_key in storage_keys.iter() {
+		println!("Retrieving value for key {:?}", storage_key);
+		// We're expecting account info as return value because we fetch added a prefix of "System" + "Account".
+		let storage_data: AccountInfo =
+			api.get_storage_by_key_hash(storage_key.clone(), None).unwrap().unwrap();
+		println!("Retrieved data {:?}", storage_data);
+	}
 }

src/api/rpc_api/state.rs

@@ -62,6 +62,17 @@ pub trait GetStorage<Hash> {
 		at_block: Option<Hash>,
 	) -> Result<Option<V>>;
 
+	/// Returns the keys with prefix with pagination support.
+	/// Up to `count` keys will be returned.
+	/// If `start_key` is passed, return next keys in storage in lexicographic order.
+	fn get_storage_keys_paged(
+		&self,
+		prefix: Option<StorageKey>,
+		count: u32,
+		start_key: Option<StorageKey>,
+		at_block: Option<Hash>,
+	) -> Result<Vec<StorageKey>>;
+
 	fn get_opaque_storage_by_key_hash(
 		&self,
 		key: StorageKey,
@@ -175,6 +186,19 @@ where
 		}
 	}
 
+	fn get_storage_keys_paged(
+		&self,
+		prefix: Option<StorageKey>,
+		count: u32,
+		start_key: Option<StorageKey>,
+		at_block: Option<Runtime::Hash>,
+	) -> Result<Vec<StorageKey>> {
+		let storage = self
+			.client()
+			.request("state_getKeysPaged", rpc_params![prefix, count, start_key, at_block])?;
+		Ok(storage)
+	}
+
 	fn get_opaque_storage_by_key_hash(
 		&self,
 		key: StorageKey,

testing/examples/state_tests.rs

@@ -90,4 +90,14 @@ async fn main() {
 		api.get_storage_proof_by_keys(vec![storage_key.clone()], None).unwrap().unwrap();
 	let _keys = api.get_keys(storage_key, None).unwrap().unwrap();
 	let _constants: Balance = api.get_constant("Balances", "ExistentialDeposit").unwrap();
+
+	let max_keys = 3;
+	let storage_keys = api
+		.get_storage_keys_paged(Some(storage_key_prefix), max_keys, None, None)
+		.unwrap();
+	assert_eq!(storage_keys.len() as u32, max_keys);
+
+	let max_keys = 20;
+	let storage_keys = api.get_storage_keys_paged(None, max_keys, None, None).unwrap();
+	assert_eq!(storage_keys.len() as u32, max_keys);
 }