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Side by Side Diff: sdk/lib/convert/byte_conversion.dart

Issue 19883003: Add chunked conversion to converters. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Address comments. Created 7 years, 4 months ago
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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 part of dart.convert;
6
7 /**
8 * The [ByteConversionSink] provides an interface for converters to
9 * efficiently transmit byte data.
10 *
11 * Instead of limiting the interface to one non-chunked list of bytes it
12 * accepts its input in chunks (themselves being lists of bytes).
13 */
14 abstract class ByteConversionSink extends ChunkedConversionSink<List<int>> {
15 ByteConversionSink();
16 factory ByteConversionSink.withCallback(void callback(List<int> accumulated))
17 = _ByteCallbackSink;
18 factory ByteConversionSink.from(ChunkedConversionSink<List<int>> sink)
19 = _ByteAdapterSink;
20
21 /**
22 * Adds the next [chunk] to `this`.
23 *
24 * Adds the bytes defined by [start] and [end]-exclusive to `this`.
25 *
26 * If [isLast] is `true` closes `this`.
27 *
28 * The given [chunk] is not held onto. Once the method returns, it is safe to
29 * overwrite the data in it.
30 */
31 void addSlice(List<int> chunk, int start, int end, bool isLast);
32
33 // TODO(floitsch): add more methods:
34 // - iterateBytes.
35 }
36
37 /**
38 * This class provides a base-class for converters that need to accept byte
39 * inputs.
40 */
41 abstract class ByteConversionSinkBase extends ByteConversionSink {
42
43 void add(List<int> chunk);
44 void close();
45
46 void addSlice(List<int> chunk, int start, int end, bool isLast) {
47 if (start != 0 || end != chunk.length) {
48 add(chunk.sublist(start, end));
49 } else {
50 add(chunk);
51 }
52 if (isLast) close();
53 }
54 }
55
56 /**
57 * This class adapts a simple [ChunkedConversionSink] to a [ByteConversionSink].
58 *
59 * All additional methods of the [ByteConversionSink] (compared to the
60 * ChunkedConversionSink) are redirected to the `add` method.
61 */
62 class _ByteAdapterSink extends ByteConversionSinkBase {
63 final ChunkedConversionSink<List<int>> _sink;
64
65 _ByteAdapterSink(this._sink);
66
67 void add(List<int> chunk) => _sink.add(chunk);
68 void close() => _sink.close();
69 }
70
71 /**
72 * This class accumulates all chunks into one list of bytes
73 * and invokes a callback when the sink is closed.
74 *
75 * This class can be used to terminate a chunked conversion.
76 */
77 class _ByteCallbackSink extends ByteConversionSinkBase {
78 static const _INITIAL_BUFFER_SIZE = 1024;
79
80 final _ChunkedConversionCallback<List<int>> _callback;
81 // TODO(11971, floitsch): use Uint8List instead of normal lists.
82 List<int> _buffer = new List<int>(_INITIAL_BUFFER_SIZE);
83 int _bufferIndex = 0;
84
85 _ByteCallbackSink(void callback(List<int> accumulated))
86 : this._callback = callback;
87
88 void add(Iterable<int> chunk) {
89 int freeCount = _buffer.length - _bufferIndex;
90 if (chunk.length > freeCount) {
91 // Grow the buffer.
92 int oldLength = _buffer.length;
93 int newLength = _roundToPowerOf2(chunk.length + oldLength) * 2;
94 // TODO(11971, floitsch): use Uint8List instead of normal lists.
95 List<int> grown = new List<int>(newLength);
96 grown.setRange(0, _buffer.length, _buffer);
97 _buffer = grown;
98 }
99 _buffer.setRange(_bufferIndex, _bufferIndex + chunk.length, chunk);
100 _bufferIndex += chunk.length;
101 }
102
103 static int _roundToPowerOf2(int v) {
104 assert(v > 0);
105 v--;
106 v |= v >> 1;
107 v |= v >> 2;
108 v |= v >> 4;
109 v |= v >> 8;
110 v |= v >> 16;
111 v++;
112 return v;
113 }
114
115 void close() {
116 _callback(_buffer.sublist(0, _bufferIndex));
117 }
118 }
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