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1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file | 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 | 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. | 3 // BSD-style license that can be found in the LICENSE file. |
4 | 4 |
5 library barback.utils.file_pool; | 5 library barback.utils.file_pool; |
6 | 6 |
7 import 'dart:async'; | 7 import 'dart:async'; |
8 import 'dart:convert'; | 8 import 'dart:convert'; |
9 import 'dart:io'; | 9 import 'dart:io'; |
10 | 10 |
11 import 'package:pool/pool.dart'; | 11 import 'package:pool/pool.dart'; |
12 import 'package:stack_trace/stack_trace.dart'; | |
13 | 12 |
14 import '../utils.dart'; | 13 import '../utils.dart'; |
15 | 14 |
16 /// Manages a pool of files that are opened for reading to cope with maximum | 15 /// Manages a pool of files that are opened for reading to cope with maximum |
17 /// file descriptor limits. | 16 /// file descriptor limits. |
18 /// | 17 /// |
19 /// If a file cannot be opened because too many files are already open, this | 18 /// If a file cannot be opened because too many files are already open, this |
20 /// will defer the open until a previously opened file is closed and then try | 19 /// will defer the open until a previously opened file is closed and then try |
21 /// again. If this doesn't succeed after a certain amount of time, the open | 20 /// again. If this doesn't succeed after a certain amount of time, the open |
22 /// will fail and the original "too many files" exception will be thrown. | 21 /// will fail and the original "too many files" exception will be thrown. |
23 class FilePool { | 22 class FilePool { |
24 /// The underlying pool. | 23 /// The underlying pool. |
25 /// | 24 /// |
26 /// The maximum number of allocated descriptors is based on empirical tests | 25 /// The maximum number of allocated descriptors is based on empirical tests |
27 /// that indicate that beyond 32, additional file reads don't provide | 26 /// that indicate that beyond 32, additional file reads don't provide |
28 /// substantial additional throughput. | 27 /// substantial additional throughput. |
29 final Pool _pool = new Pool(32, timeout: new Duration(seconds: 60)); | 28 final Pool _pool = new Pool(32, timeout: new Duration(seconds: 60)); |
30 | 29 |
31 /// Opens the file at [path] for reading. | 30 /// Opens the file at [path] for reading. |
32 /// | 31 /// |
33 /// When the returned stream is listened to, if there are too many files | 32 /// When the returned stream is listened to, if there are too many files |
34 /// open, this will wait for a previously opened file to be closed and then | 33 /// open, this will wait for a previously opened file to be closed and then |
35 /// try again. | 34 /// try again. |
36 Stream<List<int>> openRead(String path) { | 35 Stream<List<int>> openRead(String path) { |
37 return futureStream(_pool.request().then((resource) { | 36 return futureStream(_pool.request().then((resource) { |
38 return Chain.track(new File(path).openRead()).transform( | 37 return new File(path).openRead().transform( |
39 new StreamTransformer.fromHandlers(handleDone: (sink) { | 38 new StreamTransformer.fromHandlers(handleDone: (sink) { |
40 sink.close(); | 39 sink.close(); |
41 resource.release(); | 40 resource.release(); |
42 })); | 41 })); |
43 })); | 42 })); |
44 } | 43 } |
45 | 44 |
46 /// Reads [path] as a string using [encoding]. | 45 /// Reads [path] as a string using [encoding]. |
47 /// | 46 /// |
48 /// If there are too many files open and the read fails, this will wait for | 47 /// If there are too many files open and the read fails, this will wait for |
49 /// a previously opened file to be closed and then try again. | 48 /// a previously opened file to be closed and then try again. |
50 Future<String> readAsString(String path, Encoding encoding) { | 49 Future<String> readAsString(String path, Encoding encoding) { |
51 return _readAsBytes(path).then(encoding.decode); | 50 return _readAsBytes(path).then(encoding.decode); |
52 } | 51 } |
53 | 52 |
54 /// Reads [path] as a list of bytes, using [openRead] to retry if there are | 53 /// Reads [path] as a list of bytes, using [openRead] to retry if there are |
55 /// failures. | 54 /// failures. |
56 Future<List<int>> _readAsBytes(String path) { | 55 Future<List<int>> _readAsBytes(String path) { |
57 var completer = new Completer<List<int>>(); | 56 var completer = new Completer<List<int>>(); |
58 var builder = new BytesBuilder(); | 57 var builder = new BytesBuilder(); |
59 | 58 |
60 openRead(path).listen(builder.add, onDone: () { | 59 openRead(path).listen(builder.add, onDone: () { |
61 completer.complete(builder.takeBytes()); | 60 completer.complete(builder.takeBytes()); |
62 }, onError: completer.completeError, cancelOnError: true); | 61 }, onError: completer.completeError, cancelOnError: true); |
63 | 62 |
64 return completer.future; | 63 return completer.future; |
65 } | 64 } |
66 } | 65 } |
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