fix analyzer warnings, made it possible to load credentials by byte stream.

lib/src/internal/byte_utils.dart

@@ -1,4 +1,3 @@
-import 'dart:ffi';
 import 'dart:io';
 import 'dart:math';
 import 'dart:typed_data';

lib/src/kdbx_format.dart

@@ -20,11 +20,22 @@ import 'kdbx_object.dart';
 
 final _logger = Logger('kdbx.format');
 
-class Credentials {
-  Credentials(this._password);
+abstract class Credentials {
+  factory Credentials(ProtectedValue password) => PasswordCredentials(password);
+
+  Credentials._();
+
+  factory Credentials.fromHash(Uint8List hash) => HashCredentials(hash);
+
+  Uint8List getHash();
+}
+
+class PasswordCredentials implements Credentials {
+  PasswordCredentials(this._password);
 
   final ProtectedValue _password;
 
+  @override
   Uint8List getHash() {
     final output = convert.AccumulatorSink<crypto.Digest>();
     final input = crypto.sha256.startChunkedConversion(output);
@@ -34,6 +45,15 @@ class Credentials {
   }
 }
 
+class HashCredentials implements Credentials {
+  HashCredentials(this.hash);
+
+  final Uint8List hash;
+
+  @override
+  Uint8List getHash() => hash;
+}
+
 class KdbxFile {
   KdbxFile(this.credentials, this.header, this.body) {
     for (final obj in _allObjects) {

lib/src/kdbx_group.dart

@@ -1,5 +1,4 @@
 import 'package:kdbx/kdbx.dart';
-import 'package:kdbx/src/internal/async_utils.dart';
 import 'package:kdbx/src/kdbx_consts.dart';
 import 'package:kdbx/src/kdbx_entry.dart';
 import 'package:kdbx/src/kdbx_xml.dart';
@@ -27,8 +26,6 @@ class KdbxGroup extends KdbxObject {
         .forEach(_entries.add);
   }
 
-  final StreamSubscriptions _subscriptions = StreamSubscriptions();
-
   @override
   XmlElement toXml() {
     final el = super.toXml();

test/kdbx_test.dart

@@ -4,7 +4,6 @@ import 'dart:typed_data';
 import 'package:kdbx/kdbx.dart';
 import 'package:kdbx/src/crypto/protected_salt_generator.dart';
 import 'package:kdbx/src/crypto/protected_value.dart';
-import 'package:kdbx/src/internal/byte_utils.dart';
 import 'package:kdbx/src/kdbx_format.dart';
 import 'package:logging/logging.dart';
 import 'package:logging_appenders/logging_appenders.dart';