Add force option to mailbox.put

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.3.0
+
+- Add `force` option to `Mailbox`'s `put` method.
+
 ## 0.2.0
 
 - Lower SDK lower bound to 3.0.0.

lib/mailbox.dart

@@ -67,12 +67,19 @@ class Mailbox {
 
   /// Place a message into the mailbox if has space for it.
   ///
-  /// If mailbox already contains a message then [put] will throw.
-  void put(Uint8List message) {
+  /// If mailbox already contains a message then [put] will throw, unless
+  /// [force] is set to `true`.
+  void put(Uint8List message, {bool force = false}) {
     final buffer = message.isEmpty ? nullptr : _toBuffer(message);
     _mutex.runLocked(() {
       if (_mailbox.ref.state != _stateEmpty) {
-        throw StateError('Mailbox is full');
+        if (!force) {
+          throw StateError('Mailbox is full');
+        }
+
+        if (_mailbox.ref.bufferLength > 0) {
+          malloc.free(_mailbox.ref.buffer);
+        }
       }
 
       _mailbox.ref.state = _stateFull;

pubspec.yaml

@@ -1,6 +1,6 @@
 name: native_synchronization
 description: Low level synchronization primitives built on dart:ffi.
-version: 0.2.0
+version: 0.3.0
 repository: https://github.com/dart-lang/native_synchronization
 
 environment:

test/mailbox_test.dart

@@ -29,4 +29,14 @@ void main() {
     expect(value[41], equals(42));
     expect(await helperResult, equals('success'));
   });
+
+  test('mailbox throws', () {
+    final mailbox = Mailbox();
+    mailbox.put(Uint8List(42)..[41] = 42);
+    expect(() => mailbox.put(Uint8List(0)), throwsA(TypeMatcher<StateError>()));
+    mailbox.put(Uint8List(0), force: true);
+    final value = mailbox.take();
+    expect(value, isA<Uint8List>());
+    expect(value.length, equals(0));
+  });
 }