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Unified Diff: lib/src/byte_collector.dart

Issue 2661603002: Add collectBytesCancelable function. (Closed)
Patch Set: Created 3 years, 11 months ago
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Index: lib/src/byte_collector.dart
diff --git a/lib/src/byte_collector.dart b/lib/src/byte_collector.dart
index 3b4f075034f853275ab587434e1147568c3b47e2..d85b1db2da9a3fc718cec13eabc55d95d8286198 100644
--- a/lib/src/byte_collector.dart
+++ b/lib/src/byte_collector.dart
@@ -4,6 +4,7 @@
import "dart:async";
import "dart:typed_data";
+import "cancelable_operation.dart";
/// Collects an asynchronous sequence of byte lists into a single list of bytes.
///
@@ -13,10 +14,50 @@ import "dart:typed_data";
/// If any of the input data are not valid bytes, they will be truncated to
/// an eight-bit unsigned value in the resulting list.
Future<Uint8List> collectBytes(Stream<List<int>> source) {
- var byteLists = List<List<int>>[];
Lasse Reichstein Nielsen 2017/01/27 12:20:48 The type here was actually wrong (I just moved it
+ return _collectBytes<Future<Uint8List>>(source, _futureResult);
nweiz 2017/01/27 21:56:00 I think you shouldn't need an explicit generic typ
Lasse Reichstein Nielsen 2017/01/30 15:06:33 It probably doesn't even need to be generic, I can
nweiz 2017/01/30 22:21:26 It does need to be generic in strong mode—but I be
Lasse Reichstein Nielsen 2017/01/31 11:53:54 I've removed all the explicit type declarations (e
+}
+
+/// Collects an asynchronous sequence of byte lists into a single list of bytes.
+///
+/// Returns a [CancelableOperation] that provides the result future and a way
+/// to cancel the collection early.
+///
+/// If the [source] stream emits an error event,
+/// the collection fails and the returned future completes with the same error.
+///
+/// If any of the input data are not valid bytes, they will be truncated to
+/// an eight-bit unsigned value in the resulting list.
+CancelableOperation<Uint8List> collectBytesCancelable(
+ Stream<List<int>> source) {
+ return _collectBytes<CancelableOperation<Uint8List>>(
+ source, _cancelOperationResult);
+}
+
+// Helper function for [collectBytes].
+Future<Uint8List> _futureResult(_, Completer<Uint8List> completer) =>
+ completer.future;
nweiz 2017/01/27 21:56:00 I'd make these inline—I think it reads clearer, an
Lasse Reichstein Nielsen 2017/01/30 15:06:33 Done.
+
+// Helper function for [collectBytesCancelable].
+CancelableOperation<Uint8List> _cancelOperationResult(
+ StreamSubscription<List<int>> subscription,
+ Completer<Uint8List> completer) {
+ return new CancelableOperation.fromFuture(completer.future,
+ onCancel: subscription.cancel);
+}
+
+/// Generalization over [collectBytes] and [collectBytesCancelable].
+///
+/// Performs all the same operations, but the final result is created
+/// by the [result] function, which has access to the stream subscription
+/// so it can cancel the operation.
+T _collectBytes<T>(
+ Stream<List<int>> source,
+ T result(StreamSubscription<List<int>> subscription,
+ Completer<Uint8List> completer)) {
nweiz 2017/01/27 21:56:00 I'd just pass the Future here, since that's the on
Lasse Reichstein Nielsen 2017/01/30 15:06:33 True. Might as well extract it early instead of la
+ var byteLists = <List<int>>[];
var length = 0;
var completer = new Completer<Uint8List>.sync();
- source.listen(
+ var subscription = source.listen(
(bytes) {
byteLists.add(bytes);
length += bytes.length;
@@ -26,7 +67,7 @@ Future<Uint8List> collectBytes(Stream<List<int>> source) {
completer.complete(_collect(length, byteLists));
},
cancelOnError: true);
- return completer.future;
+ return result(subscription, completer);
nweiz 2017/01/27 21:56:00 I really wish we had efficient multiple returns -_
Lasse Reichstein Nielsen 2017/01/30 15:06:33 Not sure what "multiple returns" means here, but I
nweiz 2017/01/30 22:21:26 So we could write "return subscription, completer;
Lasse Reichstein Nielsen 2017/01/31 11:53:54 Oh, I absolutely would love to have that. It's so
}
// Join a lists of bytes with a known total length into a single [Uint8List].
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