pkg/analyzer_cli/lib/src/message_grouper.dart - Issue 1885073002: update to use bazel_worker package

Side by Side Diff: pkg/analyzer_cli/lib/src/message_grouper.dart

Issue 1885073002: update to use bazel_worker package (Closed) Base URL: https://github.com/dart-lang/sdk.git@master

Patch Set: Created 4 years, 8 months ago

Use n/p to move between diff chunks; N/P to move between comments. Draft comments are only viewable by you.

Jump to:

OLD	NEW
	(Empty)
1 // Copyright (c) 2016, 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 import 'dart:io';

6 import 'dart:typed_data';

7

8 /// Groups stdin input into messages by interpreting it as

9 /// base-128 encoded lengths interleaved with raw data.

10 ///

11 /// The base-128 encoding is in little-endian order, with the high bit set on

12 /// all bytes but the last. This was chosen since it's the same as the

13 /// base-128 encoding used by protobufs, so it allows a modest amount of code

14 /// reuse at the other end of the protocol.

15 ///

16 /// Possible future improvements to consider (should a debugging need arise):

17 /// - Put a magic number at the beginning of the stream.

18 /// - Use a guard byte between messages to sanity check that the encoder and

19 /// decoder agree on the encoding of lengths.

20 class MessageGrouper {

21 final _state = new _MessageGrouperState();

22 final Stdin _stdin;

23

24 MessageGrouper(this._stdin);

25

26 /// Blocks until the next full message is received, and then returns it.

27 ///

28 /// Returns null at end of file.

29 List<int> get next {

30 var message;

31 while (message == null) {

32 var nextByte = _stdin.readByteSync();

33 if (nextByte == -1) return null;

34 message = _state.handleInput(nextByte);

35 }

36 return message;

37 }

38 }

39

40 /// State held by the [MessageGrouper] while waiting for additional data to

41 /// arrive.

42 class _MessageGrouperState {

43 /// `true` means we are waiting to receive bytes of base-128 encoded length.

44 /// Some bytes of length may have been received already.

45 ///

46 /// `false` means we are waiting to receive more bytes of message data. Some

47 /// bytes of message data may have been received already.

48 bool waitingForLength = true;

49

50 /// If [waitingForLength] is `true`, the decoded value of the length bytes

51 /// received so far (if any). If [waitingForLength] is `false`, the decoded

52 /// length that was most recently received.

53 int length = 0;

54

55 /// If [waitingForLength] is `true`, the amount by which the next received

56 /// length byte must be left-shifted; otherwise undefined.

57 int lengthShift = 0;

58

59 /// If [waitingForLength] is `false`, a [Uint8List] which is ready to receive

60 /// message data. Otherwise null.

61 Uint8List message;

62

63 /// If [waitingForLength] is `false`, the number of message bytes that have

64 /// been received so far. Otherwise zero.

65 int numMessageBytesReceived;

66

67 _MessageGrouperState() {

68 reset();

69 }

70

71 /// Handle one byte at a time.

72 ///

73 /// Returns a [List<int>] of message bytes if [byte] was the last byte in a

74 /// message, otherwise returns [null].

75 List<int> handleInput(int byte) {

76 if (waitingForLength) {

77 length \|= (byte & 0x7f) << lengthShift;

78 if ((byte & 0x80) == 0) {

79 waitingForLength = false;

80 message = new Uint8List(length);

81 if (length == 0) {

82 // There is no message data to wait for, so just go ahead and deliver the

83 // empty message.

84 var messageToReturn = message;

85 reset();

86 return messageToReturn;

87 }

88 } else {

89 lengthShift += 7;

90 }

91 } else {

92 message[numMessageBytesReceived] = byte;

93 numMessageBytesReceived++;

94 if (numMessageBytesReceived == length) {

95 var messageToReturn = message;

96 reset();

97 return messageToReturn;

98 }

99 }

100 return null;

101 }

102

103 /// Reset the state so that we are ready to receive the next base-128 encoded

104 /// length.

105 void reset() {

106 waitingForLength = true;

107 length = 0;

108 lengthShift = 0;

109 message = null;

110 numMessageBytesReceived = 0;

111 }

112 }

OLD	NEW

« no previous file with comments | « pkg/analyzer_cli/lib/src/driver.dart ('k') | pkg/analyzer_cli/lib/src/worker_protocol.pb.dart » ('j') | no next file with comments »