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1 // Copyright (c) 2015, 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 library convert.hex.decoder; | |
6 | |
7 import 'dart:convert'; | |
8 import 'dart:typed_data'; | |
9 | |
10 import 'package:charcode/ascii.dart'; | |
11 | |
12 /// The canonical instance of [HexDecoder]. | |
13 const hexDecoder = const HexDecoder._(); | |
14 | |
15 /// A converter that decodes hexadecimal strings into byte arrays. | |
16 /// | |
17 /// Because two hexadecimal digits correspond to a single byte, this will throw | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Maybe mention that this is RFC 4648 base-16 encodi
nweiz
2015/09/23 22:04:20
Done, in the HexCodec documentation.
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18 /// a [FormatException] if given an odd-length string. It will also throw a | |
19 /// [FormatException] if given a string containing non-hexadecimal code units. | |
20 class HexDecoder extends Converter<String, List<int>> { | |
21 const HexDecoder._(); | |
22 | |
23 List<int> convert(String string) { | |
24 if (!string.length.isEven) { | |
25 throw new FormatException("Expected an even-length hexadecimal string, " | |
26 "was odd."); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Add ", string, string.length" as arguments to Form
nweiz
2015/09/23 22:04:21
Done.
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27 } | |
28 | |
29 var bytes = new Uint8List(string.length ~/ 2); | |
30 _decode(string.runes, bytes, 0); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Use string.codeUnits instead. It's more efficient
nweiz
2015/09/23 22:04:20
Done.
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31 return bytes; | |
32 } | |
33 | |
34 StringConversionSink startChunkedConversion(Sink<List<int>> sink) => | |
35 new _HexDecoderSink(sink); | |
36 } | |
37 | |
38 /// A sink for chunked hexadecimal decoding. | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
A conversion sink for ...
("A sink" is too generic
nweiz
2015/09/23 22:04:21
Done.
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39 class _HexDecoderSink extends StringConversionSinkBase { | |
40 /// The underlying sink to which decoded byte arrays will be passed. | |
41 final Sink<List<int>> _sink; | |
42 | |
43 /// The trailing digit from the previous string. | |
44 /// | |
45 /// This will be non-`null` if the most recent string had an odd number of | |
46 /// hexadecimal digits. Since it's the most significant digit, it's always a | |
47 /// multiple of 16. | |
48 int _lastDigit; | |
49 | |
50 _HexDecoderSink(this._sink); | |
51 | |
52 void addSlice(String string, int start, int end, bool isLast) { | |
Lasse Reichstein Nielsen
2015/09/23 08:32:03
Maybe use:
end = RangeError.checkValidRange(star
nweiz
2015/09/23 22:04:21
Done, although I'm not checking for null explicitl
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53 if (start > end) { | |
54 throw new ArgumentError( | |
55 "start $start must be less than or equal to end $end."); | |
56 } | |
57 | |
58 var bytes; | |
59 var bytesStart; | |
60 if (_lastDigit == null) { | |
Lasse Reichstein Nielsen
2015/09/23 08:32:03
dart2js would probably prefer if the variable alwa
nweiz
2015/09/23 22:04:20
I really don't like using magic numbers to indicat
Lasse Reichstein Nielsen
2015/09/24 08:07:01
True. This is definitely speculative, so keep it a
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61 bytes = new Uint8List((end - start) ~/ 2); | |
62 bytesStart = 0; | |
63 } else { | |
64 start++; | |
65 bytes = new Uint8List(1 + (end - start) ~/ 2); | |
66 bytes[0] = _lastDigit + _digitForCodeUnit(string.codeUnitAt(start - 1)); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Slightly confusing to increment start first and th
nweiz
2015/09/23 22:04:20
Done.
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67 bytesStart = 1; | |
68 } | |
69 | |
70 var runes = string.runes.skip(start).take(end); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:03
Should have be either .take(end).skip(start) or .s
nweiz
2015/09/23 22:04:21
Changed to use codeUnits, although I'm still using
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71 _lastDigit = _decode(runes, bytes, bytesStart); | |
72 | |
73 _sink.add(bytes); | |
74 if (isLast) close(); | |
75 } | |
76 | |
77 void close() { | |
78 if (_lastDigit != null) { | |
79 throw new FormatException("Expected an even-length hexadecimal string, " | |
80 "was odd."); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:03
Same message as above (if you changed it there).
nweiz
2015/09/23 22:04:20
Done.
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81 } | |
82 | |
83 _sink.close(); | |
84 } | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Consider extending with asUtf8Sink because you can
nweiz
2015/09/23 22:04:20
Done.
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85 } | |
86 | |
87 /// Decodes [runes] and writes the result into [destination]. | |
88 /// | |
89 /// This begins writing into destination at the index [start]. | |
90 int _decode(Iterable<int> runes, List<int> destination, int start) { | |
Lasse Reichstein Nielsen
2015/09/23 08:32:03
Make it: _decode(List<int> codeUnits, int start, i
nweiz
2015/09/23 22:04:21
Is that going to be substantially more efficient?
Lasse Reichstein Nielsen
2015/09/24 08:07:01
Most likely yes.
This is the inner loop of the tra
nweiz
2015/09/24 23:23:42
Done.
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91 var iterator = runes.iterator; | |
92 for (var i = start; true; i++) { | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
remove the "true". An omitted condition in a for s
nweiz
2015/09/23 22:04:21
Done.
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93 if (!iterator.moveNext()) return null; | |
94 var firstDigit = _digitForCodeUnit(iterator.current) * 16; | |
95 | |
96 if (!iterator.moveNext()) return firstDigit; | |
97 var secondDigit = _digitForCodeUnit(iterator.current); | |
98 | |
99 destination[i] = firstDigit + secondDigit; | |
100 } | |
101 } | |
102 | |
103 /// Returns the digit (0 through 15) corresponding to the hexadecimal code unit | |
104 /// [codeUnit]. | |
105 /// | |
106 /// If [codeUnit] isn't a valid hexadecimal code unit, throws a | |
107 /// [FormatException]. | |
108 int _digitForCodeUnit(int codeUnit) { | |
109 if (codeUnit >= $0 && codeUnit <= $9) return codeUnit - $0; | |
110 if (codeUnit >= $a && codeUnit <= $f) return codeUnit - $a + 10; | |
111 if (codeUnit >= $A && codeUnit <= $F) return codeUnit - $A + 10; | |
112 | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
Consider optimizing this to:
int digit = codeUnit
nweiz
2015/09/23 22:04:21
If this is worth heavily optimizing, would it be b
Lasse Reichstein Nielsen
2015/09/24 08:07:01
It's executed twice in the inner loop of the trans
nweiz
2015/09/24 23:23:41
Done.
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113 throw new FormatException("Invalid hexadecimal code point " | |
114 "U+${codeUnit.toRadixString(16)}."); | |
Lasse Reichstein Nielsen
2015/09/23 08:32:04
code point -> code unit
add: .padLeft(4, '0') so t
nweiz
2015/09/23 22:04:21
Done.
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115 } | |
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