1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef AAPT_XML_PULL_PARSER_H
18 #define AAPT_XML_PULL_PARSER_H
19 
20 #include <algorithm>
21 #include <ostream>
22 #include <string>
23 #include <vector>
24 
25 #include "StringPiece.h"
26 
27 namespace aapt {
28 
29 class XmlPullParser {
30 public:
31     enum class Event {
32         kBadDocument,
33         kStartDocument,
34         kEndDocument,
35 
36         kStartNamespace,
37         kEndNamespace,
38         kStartElement,
39         kEndElement,
40         kText,
41         kComment,
42     };
43 
44     static void skipCurrentElement(XmlPullParser* parser);
45     static bool isGoodEvent(Event event);
46 
~XmlPullParser()47     virtual ~XmlPullParser() {}
48 
49     /**
50      * Returns the current event that is being processed.
51      */
52     virtual Event getEvent() const = 0;
53 
54     virtual const std::string& getLastError() const = 0;
55 
56     /**
57      * Note, unlike XmlPullParser, the first call to next() will return
58      * StartElement of the first element.
59      */
60     virtual Event next() = 0;
61 
62     //
63     // These are available for all nodes.
64     //
65 
66     virtual const std::u16string& getComment() const = 0;
67     virtual size_t getLineNumber() const = 0;
68     virtual size_t getDepth() const = 0;
69 
70     /**
71      * Returns the character data for a Text event.
72      */
73     virtual const std::u16string& getText() const = 0;
74 
75     //
76     // Namespace prefix and URI are available for StartNamespace and EndNamespace.
77     //
78 
79     virtual const std::u16string& getNamespacePrefix() const = 0;
80     virtual const std::u16string& getNamespaceUri() const = 0;
81 
82     /*
83      * Uses the current stack of namespaces to resolve the package. Eg:
84      * xmlns:app = "http://schemas.android.com/apk/res/com.android.app"
85      * ...
86      * android:text="@app:string/message"
87      *
88      * In this case, 'app' will be converted to 'com.android.app'.
89      *
90      * If xmlns:app="http://schemas.android.com/apk/res-auto", then
91      * 'package' will be set to 'defaultPackage'.
92      */
93     virtual bool applyPackageAlias(std::u16string* package,
94                                    const std::u16string& defaultPackage) const = 0;
95 
96     //
97     // These are available for StartElement and EndElement.
98     //
99 
100     virtual const std::u16string& getElementNamespace() const = 0;
101     virtual const std::u16string& getElementName() const = 0;
102 
103     //
104     // Remaining methods are for retrieving information about attributes
105     // associated with a StartElement.
106     //
107     // Attributes must be in sorted order (according to the less than operator
108     // of struct Attribute).
109     //
110 
111     struct Attribute {
112         std::u16string namespaceUri;
113         std::u16string name;
114         std::u16string value;
115 
116         int compare(const Attribute& rhs) const;
117         bool operator<(const Attribute& rhs) const;
118         bool operator==(const Attribute& rhs) const;
119         bool operator!=(const Attribute& rhs) const;
120     };
121 
122     using const_iterator = std::vector<Attribute>::const_iterator;
123 
124     virtual const_iterator beginAttributes() const = 0;
125     virtual const_iterator endAttributes() const = 0;
126     virtual size_t getAttributeCount() const = 0;
127     const_iterator findAttribute(StringPiece16 namespaceUri, StringPiece16 name) const;
128 };
129 
130 //
131 // Implementation
132 //
133 
134 inline ::std::ostream& operator<<(::std::ostream& out, XmlPullParser::Event event) {
135     switch (event) {
136         case XmlPullParser::Event::kBadDocument: return out << "BadDocument";
137         case XmlPullParser::Event::kStartDocument: return out << "StartDocument";
138         case XmlPullParser::Event::kEndDocument: return out << "EndDocument";
139         case XmlPullParser::Event::kStartNamespace: return out << "StartNamespace";
140         case XmlPullParser::Event::kEndNamespace: return out << "EndNamespace";
141         case XmlPullParser::Event::kStartElement: return out << "StartElement";
142         case XmlPullParser::Event::kEndElement: return out << "EndElement";
143         case XmlPullParser::Event::kText: return out << "Text";
144         case XmlPullParser::Event::kComment: return out << "Comment";
145     }
146     return out;
147 }
148 
skipCurrentElement(XmlPullParser * parser)149 inline void XmlPullParser::skipCurrentElement(XmlPullParser* parser) {
150     int depth = 1;
151     while (depth > 0) {
152         switch (parser->next()) {
153             case Event::kEndDocument:
154             case Event::kBadDocument:
155                 return;
156             case Event::kStartElement:
157                 depth++;
158                 break;
159             case Event::kEndElement:
160                 depth--;
161                 break;
162             default:
163                 break;
164         }
165     }
166 }
167 
isGoodEvent(XmlPullParser::Event event)168 inline bool XmlPullParser::isGoodEvent(XmlPullParser::Event event) {
169     return event != Event::kBadDocument && event != Event::kEndDocument;
170 }
171 
compare(const Attribute & rhs)172 inline int XmlPullParser::Attribute::compare(const Attribute& rhs) const {
173     int cmp = namespaceUri.compare(rhs.namespaceUri);
174     if (cmp != 0) return cmp;
175     return name.compare(rhs.name);
176 }
177 
178 inline bool XmlPullParser::Attribute::operator<(const Attribute& rhs) const {
179     return compare(rhs) < 0;
180 }
181 
182 inline bool XmlPullParser::Attribute::operator==(const Attribute& rhs) const {
183     return compare(rhs) == 0;
184 }
185 
186 inline bool XmlPullParser::Attribute::operator!=(const Attribute& rhs) const {
187     return compare(rhs) != 0;
188 }
189 
findAttribute(StringPiece16 namespaceUri,StringPiece16 name)190 inline XmlPullParser::const_iterator XmlPullParser::findAttribute(StringPiece16 namespaceUri,
191                                                                   StringPiece16 name) const {
192     const auto endIter = endAttributes();
193     const auto iter = std::lower_bound(beginAttributes(), endIter,
194             std::pair<StringPiece16, StringPiece16>(namespaceUri, name),
195             [](const Attribute& attr, const std::pair<StringPiece16, StringPiece16>& rhs) -> bool {
196                 int cmp = attr.namespaceUri.compare(0, attr.namespaceUri.size(),
197                         rhs.first.data(), rhs.first.size());
198                 if (cmp < 0) return true;
199                 if (cmp > 0) return false;
200                 cmp = attr.name.compare(0, attr.name.size(), rhs.second.data(), rhs.second.size());
201                 if (cmp < 0) return true;
202                 return false;
203             }
204     );
205 
206     if (iter != endIter && namespaceUri == iter->namespaceUri && name == iter->name) {
207         return iter;
208     }
209     return endIter;
210 }
211 
212 } // namespace aapt
213 
214 #endif // AAPT_XML_PULL_PARSER_H
215