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Side by Side Diff: sdk/lib/collection_dev/to_string.dart

Issue 11938036: Hide collection-dev library. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Allow dart:_collection-dev in dartc. Other fixes. Created 7 years, 10 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.collection.dev;
6
7 /**
8 * Temporary move `toString` methods into this class.
9 */
10 class ToString {
11 // TODO(jjb): visiting list should be an identityHashSet when it exists
12
13 /**
14 * Returns a string representing the specified collection. If the
15 * collection is a [List], the returned string looks like this:
16 * [:'[element0, element1, ... elementN]':]. The value returned by its
17 * [toString] method is used to represent each element. If the specified
18 * collection is not a list, the returned string looks like this:
19 * [:{element0, element1, ... elementN}:]. In other words, the strings
20 * returned for lists are surrounded by square brackets, while the strings
21 * returned for other collections are surrounded by curly braces.
22 *
23 * If the specified collection contains a reference to itself, either
24 * directly or indirectly through other collections or maps, the contained
25 * reference is rendered as [:'[...]':] if it is a list, or [:'{...}':] if
26 * it is not. This prevents the infinite regress that would otherwise occur.
27 * So, for example, calling this method on a list whose sole element is a
28 * reference to itself would return [:'[[...]]':].
29 *
30 * A typical implementation of a collection's [toString] method will
31 * simply return the results of this method applied to the collection.
32 */
33 static String collectionToString(Collection c) {
34 var result = new StringBuffer();
35 _emitCollection(c, result, new List());
36 return result.toString();
37 }
38
39 /**
40 * Appends a string representing the specified collection to the specified
41 * string buffer. The string is formatted as per [collectionToString].
42 * The [:visiting:] list contains references to all of the enclosing
43 * collections and maps (which are currently in the process of being
44 * emitted into [:result:]). The [:visiting:] parameter allows this method to
45 * generate a [:'[...]':] or [:'{...}':] where required. In other words,
46 * it allows this method and [_emitMap] to identify recursive collections
47 * and maps.
48 */
49 static void _emitCollection(Collection c,
50 StringBuffer result,
51 List visiting) {
52 visiting.add(c);
53 bool isList = c is List;
54 result.add(isList ? '[' : '{');
55
56 bool first = true;
57 for (var e in c) {
58 if (!first) {
59 result.add(', ');
60 }
61 first = false;
62 _emitObject(e, result, visiting);
63 }
64
65 result.add(isList ? ']' : '}');
66 visiting.removeLast();
67 }
68
69 /**
70 * Appends a string representing the specified object to the specified
71 * string buffer. If the object is a [Collection] or [Map], it is formatted
72 * as per [collectionToString] or [mapToString]; otherwise, it is formatted
73 * by invoking its own [toString] method.
74 *
75 * The [:visiting:] list contains references to all of the enclosing
76 * collections and maps (which are currently in the process of being
77 * emitted into [:result:]). The [:visiting:] parameter allows this method
78 * to generate a [:'[...]':] or [:'{...}':] where required. In other words,
79 * it allows this method and [_emitCollection] to identify recursive maps
80 * and collections.
81 */
82 static void _emitObject(Object o, StringBuffer result, List visiting) {
83 if (o is Collection) {
84 if (_containsRef(visiting, o)) {
85 result.add(o is List ? '[...]' : '{...}');
86 } else {
87 _emitCollection(o, result, visiting);
88 }
89 } else if (o is Map) {
90 if (_containsRef(visiting, o)) {
91 result.add('{...}');
92 } else {
93 _emitMap(o, result, visiting);
94 }
95 } else { // o is neither a collection nor a map
96 result.add(o);
97 }
98 }
99
100 /**
101 * Returns true if the specified collection contains the specified object
102 * reference.
103 */
104 static _containsRef(Collection c, Object ref) {
105 for (var e in c) {
106 if (identical(e, ref)) return true;
107 }
108 return false;
109 }
110
111 /**
112 * Returns a string representing the specified map. The returned string
113 * looks like this: [:'{key0: value0, key1: value1, ... keyN: valueN}':].
114 * The value returned by its [toString] method is used to represent each
115 * key or value.
116 *
117 * If the map collection contains a reference to itself, either
118 * directly as a key or value, or indirectly through other collections
119 * or maps, the contained reference is rendered as [:'{...}':]. This
120 * prevents the infinite regress that would otherwise occur. So, for example,
121 * calling this method on a map whose sole entry maps the string key 'me'
122 * to a reference to the map would return [:'{me: {...}}':].
123 *
124 * A typical implementation of a map's [toString] method will
125 * simply return the results of this method applied to the collection.
126 */
127 static String mapToString(Map m) {
128 var result = new StringBuffer();
129 _emitMap(m, result, new List());
130 return result.toString();
131 }
132
133 /**
134 * Appends a string representing the specified map to the specified
135 * string buffer. The string is formatted as per [mapToString].
136 * The [:visiting:] list contains references to all of the enclosing
137 * collections and maps (which are currently in the process of being
138 * emitted into [:result:]). The [:visiting:] parameter allows this method
139 * to generate a [:'[...]':] or [:'{...}':] where required. In other words,
140 * it allows this method and [_emitCollection] to identify recursive maps
141 * and collections.
142 */
143 static void _emitMap(Map m, StringBuffer result, List visiting) {
144 visiting.add(m);
145 result.add('{');
146
147 bool first = true;
148 m.forEach((k, v) {
149 if (!first) {
150 result.add(', ');
151 }
152 first = false;
153 _emitObject(k, result, visiting);
154 result.add(': ');
155 _emitObject(v, result, visiting);
156 });
157
158 result.add('}');
159 visiting.removeLast();
160 }
161 }
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