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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 library dart.codec; | |
6 | |
7 import 'dart:convert'; | |
8 | |
9 part 'encoding.dart'; | |
10 part 'json.dart'; | |
11 | |
12 /** | |
13 * A [Codec] encodes and (if supported) decodes data. | |
14 * | |
15 * Codecs can be fused. For example fusing [JSON] and [UTF8] produces | |
16 * an encoder that can convert Json objects directly to bytes, or can decode | |
17 * bytes directly to json objects. | |
18 * | |
19 * Fused codecs generally attempt to optimize the operations and can be faster | |
20 * than executing each step of an encoding separately. | |
21 * | |
22 * *Codecs are still experimental and are subject to change without notice.* | |
23 */ | |
24 abstract class Codec<S, T> { | |
25 const Codec(); | |
26 | |
27 T encode(S input) => encoder.convert(input); | |
28 S decode(T encoded) => decoder.convert(encoded); | |
29 | |
30 /** | |
31 * Returns the encoder from [S] to [T]. | |
32 * | |
33 * It may be stateful and should not be reused. | |
34 */ | |
35 Converter<S, T> get encoder; | |
36 /** | |
37 * Returns the decoder of `this`, converting from [T] to [S]. | |
38 * | |
39 * It may be stateful an should not be reused. | |
40 */ | |
41 Converter<T, S> get decoder; | |
42 | |
43 /** | |
44 * Fuses `this` with `other`. | |
45 * | |
46 * When encoding, the resulting codec encodes with `this` before | |
47 * encoding with [other]. | |
48 * | |
49 * When decoding, the resulting codec decodes with [other] before decoding | |
50 * with `this`. | |
51 * | |
52 * In some cases one needs to use the [inverted] codecs to be able to fuse | |
53 * them correctly. That is, the output type of `this` ([T]) must match the | |
54 * input type of the second codec [other]. | |
55 * | |
56 * Examples: | |
57 * | |
58 * final JSON_TO_BYTES = JSON.fuse(UTF8); | |
59 * List<int> bytes = JSON_TO_BYTES.encode(["json-object"]); | |
60 * var decoded = JSON_TO_BYTES.decode(bytes); | |
61 * assert(decoded is List && decoded[0] == "json-object"); | |
62 * | |
63 * var inverted = JSON.inverted; | |
64 * var jsonIdentity = JSON.fuse(inverted); | |
65 * var jsonObject = jsonIdentity.encode(["1", 2]); | |
66 * assert(jsonObject is List && jsonObject[0] == "1" && jsonObject[1] == 2
); | |
67 */ | |
68 // TODO(floitsch): use better example with line-splitter once that one is | |
69 // in this library. | |
70 Codec<S, dynamic> fuse(Codec<T, dynamic> other) { | |
71 return new _FusedCodec<S, T, dynamic>(this, other); | |
72 } | |
73 | |
74 /** | |
75 * Inverts `this`. | |
76 * | |
77 * The [encoder] and [decoder] of the resulting codec are swapped. | |
78 */ | |
79 Codec<T, S> get inverted => new _InvertedCodec<T, S>(this); | |
80 } | |
81 | |
82 /** | |
83 * Fuses the given codecs. | |
84 * | |
85 * In the non-chunked conversion simply invokes the non-chunked conversions in | |
86 * sequence. | |
87 */ | |
88 class _FusedCodec<S, M, T> extends Codec<S, T> { | |
89 final Codec<S, M> _first; | |
90 final Codec<M, T> _second; | |
91 | |
92 Converter<S, T> get encoder => _first.encoder.fuse(_second.encoder); | |
93 Converter<T, S> get decoder => _second.decoder.fuse(_first.decoder); | |
94 | |
95 _FusedCodec(this._first, this._second); | |
96 } | |
97 | |
98 class _InvertedCodec<T, S> extends Codec<T, S> { | |
99 final Codec<S, T> _codec; | |
100 | |
101 _InvertedCodec(Codec<S, T> codec) : _codec = codec; | |
102 | |
103 Converter<T, S> get encoder => _codec.decoder; | |
104 Converter<S, T> get decoder => _codec.encoder; | |
105 | |
106 Codec<S, T> get inverted => _codec; | |
107 } | |
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