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| 1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 /** |
| 6 * Help for combining multiple streams into a single stream. |
| 7 */ |
| 8 library dart.pkg.async.stream_zip; |
| 9 |
| 10 import "dart:async"; |
| 11 |
| 12 /** |
| 13 * A stream that combines the values of other streams. |
| 14 */ |
| 15 class StreamZip extends Stream<List> { |
| 16 final Iterable<Stream> _streams; |
| 17 StreamZip(Iterable<Stream> streams) : _streams = streams; |
| 18 |
| 19 StreamSubscription<List> listen(void onData(List data), { |
| 20 Function onError, |
| 21 void onDone(), |
| 22 bool cancelOnError}) { |
| 23 cancelOnError = identical(true, cancelOnError); |
| 24 List<StreamSubscription> subscriptions = <StreamSubscription>[]; |
| 25 StreamController controller; |
| 26 List current; |
| 27 int dataCount = 0; |
| 28 |
| 29 /// Called for each data from a subscription in [subscriptions]. |
| 30 void handleData(int index, data) { |
| 31 current[index] = data; |
| 32 dataCount++; |
| 33 if (dataCount == subscriptions.length) { |
| 34 List data = current; |
| 35 current = new List(subscriptions.length); |
| 36 dataCount = 0; |
| 37 for (int i = 0; i < subscriptions.length; i++) { |
| 38 if (i != index) subscriptions[i].resume(); |
| 39 } |
| 40 controller.add(data); |
| 41 } else { |
| 42 subscriptions[index].pause(); |
| 43 } |
| 44 } |
| 45 |
| 46 /// Called for each error from a subscription in [subscriptions]. |
| 47 /// Except if [cancelOnError] is true, in which case the function below |
| 48 /// is used instead. |
| 49 void handleError(Object error, StackTrace stackTrace) { |
| 50 controller.addError(error, stackTrace); |
| 51 } |
| 52 |
| 53 /// Called when a subscription has an error and [cancelOnError] is true. |
| 54 /// |
| 55 /// Prematurely cancels all subscriptions since we know that we won't |
| 56 /// be needing any more values. |
| 57 void handleErrorCancel(Object error, StackTrace stackTrace) { |
| 58 for (int i = 0; i < subscriptions.length; i++) { |
| 59 subscriptions[i].cancel(); |
| 60 } |
| 61 controller.addError(error, stackTrace); |
| 62 } |
| 63 |
| 64 void handleDone() { |
| 65 for (int i = 0; i < subscriptions.length; i++) { |
| 66 subscriptions[i].cancel(); |
| 67 } |
| 68 controller.close(); |
| 69 } |
| 70 |
| 71 try { |
| 72 for (Stream stream in _streams) { |
| 73 int index = subscriptions.length; |
| 74 subscriptions.add(stream.listen( |
| 75 (data) { handleData(index, data); }, |
| 76 onError: cancelOnError ? handleError : handleErrorCancel, |
| 77 onDone: handleDone, |
| 78 cancelOnError: cancelOnError)); |
| 79 } |
| 80 } catch (e) { |
| 81 for (int i = subscriptions.length - 1; i >= 0; i--) { |
| 82 subscriptions[i].cancel(); |
| 83 } |
| 84 rethrow; |
| 85 } |
| 86 |
| 87 current = new List(subscriptions.length); |
| 88 |
| 89 controller = new StreamController<List>( |
| 90 onPause: () { |
| 91 for (int i = 0; i < subscriptions.length; i++) { |
| 92 // This may pause some subscriptions more than once. |
| 93 // These will not be resumed by onResume below, but must wait for the |
| 94 // next round. |
| 95 subscriptions[i].pause(); |
| 96 } |
| 97 }, |
| 98 onResume: () { |
| 99 for (int i = 0; i < subscriptions.length; i++) { |
| 100 subscriptions[i].resume(); |
| 101 } |
| 102 }, |
| 103 onCancel: () { |
| 104 for (int i = 0; i < subscriptions.length; i++) { |
| 105 // Canceling more than once is safe. |
| 106 subscriptions[i].cancel(); |
| 107 } |
| 108 } |
| 109 ); |
| 110 |
| 111 if (subscriptions.isEmpty) { |
| 112 controller.close(); |
| 113 } |
| 114 return controller.stream.listen(onData, |
| 115 onError: onError, |
| 116 onDone: onDone, |
| 117 cancelOnError: cancelOnError); |
| 118 } |
| 119 } |
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