support null safety

Author: tmthecoder

lib/src/argon2.dart

@@ -57,7 +57,7 @@ class DArgon2 {
   /// Returns a [Future] containing a [DArgon2Result] with the hashed password,
   /// encoded hash, and various conversion options for the hash and encoded bytes.
   Future<DArgon2Result> hashPasswordString(String password,
-      {@required Salt salt,
+      {required Salt salt,
       int iterations = 32,
       int memory = 256,
       int parallelism = 2,
@@ -85,7 +85,7 @@ class DArgon2 {
   /// Returns a [Future] containing a [DArgon2Result] with the hashed password,
   /// encoded hash, and various conversion options for the hash and encoded bytes.
   Future<DArgon2Result> hashPasswordBytes(List<int> password,
-      {@required Salt salt,
+      {required Salt salt,
       int iterations = 32,
       int memory = 256,
       int parallelism = 2,
@@ -114,7 +114,7 @@ class DArgon2 {
   /// Returns a [DArgon2Result] with the hashed password, encoded hash, and various
   /// conversion options for the hash and encoded bytes.
   DArgon2Result hashPasswordStringSync(String password,
-      {@required Salt salt,
+      {required Salt salt,
       int iterations = 32,
       int memory = 256,
       int parallelism = 2,
@@ -142,14 +142,13 @@ class DArgon2 {
   /// Returns a [DArgon2Result] with the hashed password, encoded hash, and various
   /// conversion options for the hash and encoded bytes.
   DArgon2Result hashPasswordBytesSync(List<int> password,
-      {@required Salt salt,
+      {required Salt salt,
       int iterations = 32,
       int memory = 256,
       int parallelism = 2,
       int length = 32,
       Argon2Type type = Argon2Type.i,
       Argon2Version version = Argon2Version.V13}) {
-    assert(salt != null);
     //Create pointers to pass to the C method
     var passPointer = _setPtr(password);
     var saltPointer = _setPtr(salt.bytes);
@@ -265,7 +264,7 @@ class DArgon2 {
   /// Returns a [Pointer] of type [Uint8] to be used for Argon2 computations.
   Pointer<Uint8> _setPtr(Iterable<int> iterable) {
     //Allocate a pointer in memory and set the values from the given list
-    var p = malloc<Uint8>(Uint8List.fromList(iterable).length);
+    var p = malloc<Uint8>(Uint8List.fromList(iterable.toList()).length);
     p.asTypedList(iterable.length).setAll(0, iterable);
     return p;
   }

lib/src/native/loaders/dart_lib_loader.dart

@@ -33,7 +33,7 @@ class DartLibLoader implements LibLoader {
       rootPath = File.fromUri(Platform.script).parent.path;
     } else {
       final rootLibrary = 'package:dargon2/dargon2.dart';
-      rootPath = waitFor(Isolate.resolvePackageUri(Uri.parse(rootLibrary)))
+      rootPath = waitFor(Isolate.resolvePackageUri(Uri.parse(rootLibrary)))!
           .resolve('src/blobs/')
           .toFilePath(windows: Platform.isWindows);
     }

lib/src/native/local_binder.dart

@@ -124,32 +124,31 @@ typedef _Argon2ErrorMessage = Pointer<Utf8> Function(int error_code);
 /// there should be no reason to change this.
 class LocalBinder {
   /// Create an instanced class in order to allow the dylib to stay loaded through the session.
-  static LocalBinder _privateInstance;
+  static final LocalBinder _privateInstance = LocalBinder._();
 
   /// Callable method of type [_Argon2Hash] that binds to [_argon2_hash].
-  _Argon2Hash getHash;
+  late _Argon2Hash getHash;
 
   /// Callable method of type [_Argon2Verify] that binds to [_argon2_verify].
-  _Argon2Verify verifyHash;
+  late _Argon2Verify verifyHash;
 
   /// Callable method of type [_Argon2Encodedlen] that binds to [_argon2_encodedlen].
-  _Argon2Encodedlen getEncodedHashLength;
+  late _Argon2Encodedlen getEncodedHashLength;
 
   /// Callable method of type [_Argon2ErrorMessage] that binds to [_argon2_error_message].
-  _Argon2ErrorMessage getErrorMessage;
+  late _Argon2ErrorMessage getErrorMessage;
 
   /// The getter for the main instance, which returns the private instance if set correctly.
   /// If not, a new Instance is created and set as the private instance, then returned.
   static LocalBinder get instance {
-    _privateInstance ??= LocalBinder();
     return _privateInstance;
   }
 
   /// The class constructor, which handles loading the dylib and mapping each method to their
   /// respective C equivalents
   ///
   /// Opens the C library using dart's ffi and maps all of the main methods
-  LocalBinder() {
+  LocalBinder._() {
     var argon2lib = LibLoader().loadLib();
     getHash = argon2lib
         .lookup<NativeFunction<_argon2_hash>>('argon2_hash')