GCC Code Coverage Report

Directory: gridformat/
File: gridformat/xml/parser.hpp
Date: 2026-10-12 17:50:57
Exec Total Coverage
Lines: 130 140 92.9%
Functions: 14 14 100.0%
Branches: 145 289 50.2%
Line Branch Exec Source
1 // SPDX-FileCopyrightText: 2022-2023 Dennis Gläser <dennis.glaeser@iws.uni-stuttgart.de>
2 // SPDX-License-Identifier: MIT
3 /*!
4 * \ingroup XML
5 * \copydoc GridFormat::XMLParser
6 */
7 #ifndef GRIDFORMAT_XML_PARSER_HPP_
8 #define GRIDFORMAT_XML_PARSER_HPP_
9
10 #include <cmath>
11 #include <string>
12 #include <memory>
13 #include <istream>
14 #include <fstream>
15 #include <type_traits>
16 #include <unordered_map>
17 #include <functional>
18 #include <optional>
19 #include <concepts>
20 #include <limits>
21
22 #include <gridformat/common/exceptions.hpp>
23 #include <gridformat/common/istream_helper.hpp>
24 #include <gridformat/xml/element.hpp>
25 #include <gridformat/xml/tag.hpp>
26
27 namespace GridFormat {
28
29
30 /*!
31 * \ingroup XML
32 * \brief Parses an XML file into an XMLElement.
33 * \note Discards any comments.
34 * \note Creates a single root element in which the parsed elements are placed.
35 * \note The XML element contents are not read. Instead, their bounds within the input stream
36 * are stored separately and the content can be retrieved via get_content(const XMLElement&).
37 * \note Content inside XML elements is assumed to be either before or after child elements. If multiple
38 pieces of content are intermingled with child elements, only the first piece of content will be detected.
39 * \note This implementation is not a fully-fleshed XML parser, but suffices for our requirements.
40 * It is likely to fail when textual content that can be mistaken for xml is inside the elements.
41 */
42 class XMLParser {
43 public:
44 using ContentSkipFunction = std::function<bool(const XMLElement&)>;
45
46 struct StreamBounds {
47 std::streamsize begin_pos;
48 std::streamsize end_pos;
49 };
50
51 /*!
52 * \brief Parse an xml tree from the data in the file with the given name.
53 * \param filename The name of the xml file.
54 * \param root_name The name of the root element in which to place the read xml (default: "ROOT")
55 * \param skip_content_parsing A function that takes an xml element and returns true if the content
56 * of that element should not be parsed for child nodes. This is useful
57 * if the content of an element is very large and potentially invalid xml.
58 */
59 1941 explicit XMLParser(const std::string& filename,
60 const std::string& root_name = "ROOT",
61 const ContentSkipFunction& skip_content_parsing = [] (const XMLElement&) { return false; })
62 1941 : _owned{std::make_unique<std::ifstream>()}
63 3882 , _helper{*_owned}
64
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 1941 , _element{root_name}
65
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 1941 , _skip_content{skip_content_parsing} {
66
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 1941 _owned->open(filename);
67
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 9705 while (_parse_next_element(_element)) {}
68 1941 }
69
70 //! Overload for reading from an existing stream
71 3 explicit XMLParser(std::istream& stream,
72 const std::string& root_name = "ROOT",
73 5 const ContentSkipFunction& skip_content_parsing = [] (const XMLElement&) { return false; })
74 3 : _owned{}
75 6 , _helper{stream}
76
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 3 , _element{root_name}
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 3 , _skip_content{skip_content_parsing} {
78
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 15 while (_parse_next_element(_element)) {}
79 3 }
80
81 //! Return a reference the read xml representation
82 111215 const XMLElement& get_xml() const & {
83 111215 return _element;
84 }
85
86 //! Return the read xml representation as an rvalue
87 XMLElement&& get_xml() && {
88 return std::move(_element);
89 }
90
91 //! Return true if a content was read for the given xml element
92 8 bool has_content(const XMLElement& e) const {
93
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 8 return _content_bounds.contains(&e);
94 }
95
96 //! Return the stream bounds for the content of the given xml element
97 11520 const StreamBounds& get_content_bounds(const XMLElement& e) const {
98
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 11520 return _content_bounds.at(&e);
99 }
100
101 //! Read and return the content of the given xml element
102 8 std::string read_content_for(const XMLElement& e, const std::optional<std::size_t> max_chars = {}) {
103
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 8 const auto& bounds = _content_bounds.at(&e);
104 8 const auto content_size = bounds.end_pos - bounds.begin_pos;
105 8 const auto num_chars = std::min(static_cast<std::size_t>(content_size), max_chars.value_or(content_size));
106
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 8 _helper.seek_position(bounds.begin_pos);
107
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 16 return _helper.read_chunk(num_chars);
108 }
109
110 private:
111 // parse the content or child elements from the stream and add them to the given parent element
112 15737 void _parse_content(XMLElement& parent) {
113
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 15737 const std::string close_tag = "</" + parent.name();
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 15737 auto content_begin_pos = _helper.position();
115 15737 auto content_end_pos = content_begin_pos;
116
117
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 15737 if (_skip_content(parent)) {
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 1089 if (!_helper.shift_until_substr(close_tag))
119 ✗ throw IOError("Could not find closing tag: " + close_tag);
120
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 1089 content_end_pos = _helper.position();
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 1089 _helper.shift_by(close_tag.size());
122 } else {
123 // check for content before the first child
124
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 43944 if (!_helper.shift_until_any_of("<"))
125 ✗ throw IOError("Could not find closing tag for '" + parent.name() + "'");
126
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 14648 content_end_pos = _helper.position();
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 14648 _helper.seek_position(content_begin_pos);
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 14648 _helper.shift_whitespace();
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 14648 const bool have_read_content = _helper.position() < content_end_pos;
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 14648 _helper.seek_position(content_end_pos);
131
132 // parse all children
133 14648 std::optional<std::streamsize> position_after_last_child;
134 while (true) {
135
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 51208 auto pos = _parse_next_element(parent, close_tag);
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 51208 if (pos) position_after_last_child = pos;
137 14648 else break;
138 36560 }
139
140 // (maybe) check for content after the children
141
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 14648 if (!have_read_content && position_after_last_child.has_value()) {
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 12421 content_begin_pos = position_after_last_child.value();
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 12421 content_end_pos = _helper.position();
144 }
145
146
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 14648 if (_helper.read_chunk(close_tag.size()) != close_tag)
147 ✗ throw IOError("Could not find closing tag for '" + parent.name() + "'");
148
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 43944 if (!_helper.shift_until_any_of(">"))
149 ✗ throw IOError("Could not find closing tag for '" + parent.name() + "'");
150
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 14648 if (!_helper.is_end_of_file())
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 14648 _helper.shift_by(1);
152 }
153
154
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 15737 _content_bounds[&parent] = StreamBounds{.begin_pos = content_begin_pos, .end_pos = content_end_pos};
155 15737 }
156
157 // parse the next child element from the stream and return the position after it (or none if no child found)
158 55096 std::optional<std::streamsize> _parse_next_element(XMLElement& parent, const std::string& close_tag = "") {
159 while (true) {
160
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161
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 1518 if (!close_tag.empty())
162 ✗ throw IOError("Did not find closing tag: " + close_tag);
163 1518 return {};
164 }
165
166
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 165930 if (!_helper.shift_until_any_of("<")) {
167
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 426 if (!close_tag.empty())
168 ✗ throw IOError("Did not find closing tag: " + close_tag);
169 426 return {};
170 }
171
172
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 54884 const auto cur_pos = _helper.position();
173
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 54884 const auto chunk = _helper.read_chunk(4);
174
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 54884 if (chunk.starts_with("<?"))
175 1729 continue;
176
177
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 53155 if (chunk.starts_with("<!--")) {
178
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 3 _helper.seek_position(cur_pos);
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 3 _skip_comment();
180 3 continue;
181 }
182
183
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 53152 _helper.seek_position(cur_pos);
184
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 53152 if (!close_tag.empty()) {
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 51208 if (_helper.read_chunk(close_tag.size()) == close_tag) {
186
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 14648 _helper.seek_position(cur_pos);
187 14648 return {};
188 }
189
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 36560 _helper.seek_position(cur_pos);
190 }
191
192
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 38504 if (_parse_element(parent))
193
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 38504 return {_helper.position()};
194
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 56616 }
195 }
196
197 // skip beyond an xml comment in the input stream
198 3 void _skip_comment() {
199 static constexpr auto comment_begin = "<!--";
200 static constexpr auto comment_end = "-->";
201 3 std::string comment_chunk;
202
203 7 const auto append_until_closing_brace = [&] () -> void {
204
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 14 comment_chunk += _helper.read_until_any_of(">");
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 7 if (!_helper.is_end_of_file())
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 7 comment_chunk += _helper.read_chunk(1); // read the actual ">"
207 7 };
208
209 6 const auto count = [&] (const std::string& substr) {
210 6 std::size_t count = 0;
211 6 auto found_pos = comment_chunk.find(substr);
212
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 12 while (found_pos != std::string::npos) {
213 6 found_pos = comment_chunk.find(substr, found_pos + 1);
214 6 count++;
215 }
216 6 return count;
217 3 };
218
219
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 3 append_until_closing_brace();
220
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 3 if (!comment_chunk.starts_with(comment_begin))
221 ✗ throw ValueError("Stream is not at a comment start position");
222
223
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 19 while (!comment_chunk.ends_with(comment_end) || count(comment_begin) != count(comment_end))
224
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 4 append_until_closing_brace();
225 3 }
226
227 // try to parse a single element and return true/false if succeeded
228 38504 bool _parse_element(XMLElement& parent) {
229
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 38504 const auto begin_pos = _helper.position();
230
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 38504 if (!_helper.read_chunk(1).starts_with("<")) {
231 ✗ _helper.seek_position(begin_pos);
232 ✗ return false;
233 }
234
235
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 38504 _helper.seek_position(begin_pos);
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 38504 _helper.shift_by(1);
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 77008 std::string name = _helper.read_until_any_of(" />");
238
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 38504 auto& element = parent.add_child(std::move(name));
239
240 while (true) {
241
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 350518 _helper.shift_until_not_any_of(" \n");
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 175259 const auto cur_pos = _helper.position();
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 175259 if (_helper.read_chunk(2) == "/>")
244 22767 break;
245
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 152492 _helper.seek_position(cur_pos);
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 152492 if (_helper.read_chunk(1) == ">") {
248
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 15737 _parse_content(element);
249 15737 break;
250 }
251
252
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 136755 _helper.seek_position(cur_pos);
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 136755 auto [name, value] = _read_attribute();
254
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 136755 element.set_attribute(std::move(name), std::move(value));
255 136755 }
256
257 38504 return true;
258 38504 }
259
260 136755 std::pair<std::string, std::string> _read_attribute() {
261
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 273510 std::string attr_name = _helper.read_until_any_of("= ");
262
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 136755 if (attr_name.empty())
263 ✗ throw IOError("Could not parse attribute name");
264
265
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 273510 _helper.shift_until_any_of("\"");
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 136755 _helper.shift_by(1);
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 273510 std::string attr_value = XML::Detail::unescaped(_helper.read_until_any_of("\""));
268
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 136755 _helper.shift_by(1);
269
270 273510 return std::make_pair(std::move(attr_name), std::move(attr_value));
271 136755 }
272
273 std::unique_ptr<std::ifstream> _owned;
274 InputStreamHelper _helper;
275 XMLElement _element;
276 ContentSkipFunction _skip_content;
277 std::unordered_map<const XMLElement*, StreamBounds> _content_bounds;
278 };
279
280 } // end namespace GridFormat
281
282 #endif // GRIDFORMAT_XML_PARSER_HPP_
283