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 <expat.h>
21
22#include <algorithm>
23#include <istream>
24#include <ostream>
25#include <queue>
26#include <stack>
27#include <string>
28#include <vector>
29
30#include "android-base/macros.h"
31#include "androidfw/StringPiece.h"
32
33#include "Resource.h"
34#include "process/IResourceTableConsumer.h"
35#include "util/Maybe.h"
36#include "xml/XmlUtil.h"
37
38namespace aapt {
39namespace xml {
40
41class XmlPullParser : public IPackageDeclStack {
42 public:
43  enum class Event {
44    kBadDocument,
45    kStartDocument,
46    kEndDocument,
47
48    kStartNamespace,
49    kEndNamespace,
50    kStartElement,
51    kEndElement,
52    kText,
53    kComment,
54  };
55
56  /**
57   * Skips to the next direct descendant node of the given start_depth,
58   * skipping namespace nodes.
59   *
60   * When NextChildNode() returns true, you can expect Comments, Text, and
61   * StartElement events.
62   */
63  static bool NextChildNode(XmlPullParser* parser, size_t start_depth);
64  static bool SkipCurrentElement(XmlPullParser* parser);
65  static bool IsGoodEvent(Event event);
66
67  explicit XmlPullParser(std::istream& in);
68  ~XmlPullParser();
69
70  /**
71   * Returns the current event that is being processed.
72   */
73  Event event() const;
74
75  const std::string& error() const;
76
77  /**
78   * Note, unlike XmlPullParser, the first call to next() will return
79   * StartElement of the first element.
80   */
81  Event Next();
82
83  //
84  // These are available for all nodes.
85  //
86
87  const std::string& comment() const;
88  size_t line_number() const;
89  size_t depth() const;
90
91  /**
92   * Returns the character data for a Text event.
93   */
94  const std::string& text() const;
95
96  //
97  // Namespace prefix and URI are available for StartNamespace and EndNamespace.
98  //
99
100  const std::string& namespace_prefix() const;
101  const std::string& namespace_uri() const;
102
103  //
104  // These are available for StartElement and EndElement.
105  //
106
107  const std::string& element_namespace() const;
108  const std::string& element_name() const;
109
110  /*
111   * Uses the current stack of namespaces to resolve the package. Eg:
112   * xmlns:app = "http://schemas.android.com/apk/res/com.android.app"
113   * ...
114   * android:text="@app:string/message"
115   *
116   * In this case, 'app' will be converted to 'com.android.app'.
117   *
118   * If xmlns:app="http://schemas.android.com/apk/res-auto", then
119   * 'package' will be set to 'defaultPackage'.
120   */
121  Maybe<ExtractedPackage> TransformPackageAlias(
122      const android::StringPiece& alias, const android::StringPiece& local_package) const override;
123
124  //
125  // Remaining methods are for retrieving information about attributes
126  // associated with a StartElement.
127  //
128  // Attributes must be in sorted order (according to the less than operator
129  // of struct Attribute).
130  //
131
132  struct Attribute {
133    std::string namespace_uri;
134    std::string name;
135    std::string value;
136
137    int compare(const Attribute& rhs) const;
138    bool operator<(const Attribute& rhs) const;
139    bool operator==(const Attribute& rhs) const;
140    bool operator!=(const Attribute& rhs) const;
141  };
142
143  using const_iterator = std::vector<Attribute>::const_iterator;
144
145  const_iterator begin_attributes() const;
146  const_iterator end_attributes() const;
147  size_t attribute_count() const;
148  const_iterator FindAttribute(android::StringPiece namespace_uri, android::StringPiece name) const;
149
150 private:
151  DISALLOW_COPY_AND_ASSIGN(XmlPullParser);
152
153  static void XMLCALL StartNamespaceHandler(void* user_data, const char* prefix,
154                                            const char* uri);
155  static void XMLCALL StartElementHandler(void* user_data, const char* name,
156                                          const char** attrs);
157  static void XMLCALL CharacterDataHandler(void* user_data, const char* s,
158                                           int len);
159  static void XMLCALL EndElementHandler(void* user_data, const char* name);
160  static void XMLCALL EndNamespaceHandler(void* user_data, const char* prefix);
161  static void XMLCALL CommentDataHandler(void* user_data, const char* comment);
162
163  struct EventData {
164    Event event;
165    size_t line_number;
166    size_t depth;
167    std::string data1;
168    std::string data2;
169    std::vector<Attribute> attributes;
170  };
171
172  std::istream& in_;
173  XML_Parser parser_;
174  char buffer_[16384];
175  std::queue<EventData> event_queue_;
176  std::string error_;
177  const std::string empty_;
178  size_t depth_;
179  std::stack<std::string> namespace_uris_;
180
181  struct PackageDecl {
182    std::string prefix;
183    ExtractedPackage package;
184  };
185  std::vector<PackageDecl> package_aliases_;
186};
187
188/**
189 * Finds the attribute in the current element within the global namespace.
190 */
191Maybe<android::StringPiece> FindAttribute(const XmlPullParser* parser,
192                                          const android::StringPiece& name);
193
194/**
195 * Finds the attribute in the current element within the global namespace. The
196 * attribute's value
197 * must not be the empty string.
198 */
199Maybe<android::StringPiece> FindNonEmptyAttribute(const XmlPullParser* parser,
200                                                  const android::StringPiece& name);
201
202//
203// Implementation
204//
205
206inline ::std::ostream& operator<<(::std::ostream& out,
207                                  XmlPullParser::Event event) {
208  switch (event) {
209    case XmlPullParser::Event::kBadDocument:
210      return out << "BadDocument";
211    case XmlPullParser::Event::kStartDocument:
212      return out << "StartDocument";
213    case XmlPullParser::Event::kEndDocument:
214      return out << "EndDocument";
215    case XmlPullParser::Event::kStartNamespace:
216      return out << "StartNamespace";
217    case XmlPullParser::Event::kEndNamespace:
218      return out << "EndNamespace";
219    case XmlPullParser::Event::kStartElement:
220      return out << "StartElement";
221    case XmlPullParser::Event::kEndElement:
222      return out << "EndElement";
223    case XmlPullParser::Event::kText:
224      return out << "Text";
225    case XmlPullParser::Event::kComment:
226      return out << "Comment";
227  }
228  return out;
229}
230
231inline bool XmlPullParser::NextChildNode(XmlPullParser* parser,
232                                         size_t start_depth) {
233  Event event;
234
235  // First get back to the start depth.
236  while (IsGoodEvent(event = parser->Next()) &&
237         parser->depth() > start_depth + 1) {
238  }
239
240  // Now look for the first good node.
241  while ((event != Event::kEndElement || parser->depth() > start_depth) &&
242         IsGoodEvent(event)) {
243    switch (event) {
244      case Event::kText:
245      case Event::kComment:
246      case Event::kStartElement:
247        return true;
248      default:
249        break;
250    }
251    event = parser->Next();
252  }
253  return false;
254}
255
256inline bool XmlPullParser::SkipCurrentElement(XmlPullParser* parser) {
257  int depth = 1;
258  while (depth > 0) {
259    switch (parser->Next()) {
260      case Event::kEndDocument:
261        return true;
262      case Event::kBadDocument:
263        return false;
264      case Event::kStartElement:
265        depth++;
266        break;
267      case Event::kEndElement:
268        depth--;
269        break;
270      default:
271        break;
272    }
273  }
274  return true;
275}
276
277inline bool XmlPullParser::IsGoodEvent(XmlPullParser::Event event) {
278  return event != Event::kBadDocument && event != Event::kEndDocument;
279}
280
281inline int XmlPullParser::Attribute::compare(const Attribute& rhs) const {
282  int cmp = namespace_uri.compare(rhs.namespace_uri);
283  if (cmp != 0) return cmp;
284  return name.compare(rhs.name);
285}
286
287inline bool XmlPullParser::Attribute::operator<(const Attribute& rhs) const {
288  return compare(rhs) < 0;
289}
290
291inline bool XmlPullParser::Attribute::operator==(const Attribute& rhs) const {
292  return compare(rhs) == 0;
293}
294
295inline bool XmlPullParser::Attribute::operator!=(const Attribute& rhs) const {
296  return compare(rhs) != 0;
297}
298
299inline XmlPullParser::const_iterator XmlPullParser::FindAttribute(
300    android::StringPiece namespace_uri, android::StringPiece name) const {
301  const auto end_iter = end_attributes();
302  const auto iter = std::lower_bound(
303      begin_attributes(), end_iter,
304      std::pair<android::StringPiece, android::StringPiece>(namespace_uri, name),
305      [](const Attribute& attr,
306         const std::pair<android::StringPiece, android::StringPiece>& rhs) -> bool {
307        int cmp = attr.namespace_uri.compare(
308            0, attr.namespace_uri.size(), rhs.first.data(), rhs.first.size());
309        if (cmp < 0) return true;
310        if (cmp > 0) return false;
311        cmp = attr.name.compare(0, attr.name.size(), rhs.second.data(),
312                                rhs.second.size());
313        if (cmp < 0) return true;
314        return false;
315      });
316
317  if (iter != end_iter && namespace_uri == iter->namespace_uri &&
318      name == iter->name) {
319    return iter;
320  }
321  return end_iter;
322}
323
324}  // namespace xml
325}  // namespace aapt
326
327#endif  // AAPT_XML_PULL_PARSER_H
328