GCC Code Coverage Report

Directory: gridformat/
File: gridformat/xml/parser.hpp
Date: 2026-10-18 00:09:19
Exec Total Coverage
Lines: 135 146 92.5%
Functions: 14 14 100.0%
Branches: 174 335 51.9%
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 1948 explicit XMLParser(const std::string& filename,
60 const std::string& root_name = "ROOT",
61 const ContentSkipFunction& skip_content_parsing = [] (const XMLElement&) { return false; })
62 1948 : _owned{std::make_unique<std::ifstream>()}
63 3896 , _helper{*_owned}
64
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 1948 , _element{root_name}
65
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 1948 , _skip_content{skip_content_parsing} {
66
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 1948 _owned->open(filename);
67
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 9740 while (_parse_next_element(_element)) {}
68 1948 }
69
70 //! Overload for reading from an existing stream
71 9 explicit XMLParser(std::istream& stream,
72 const std::string& root_name = "ROOT",
73 6 const ContentSkipFunction& skip_content_parsing = [] (const XMLElement&) { return false; })
74 9 : _owned{}
75 18 , _helper{stream}
76
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 9 , _element{root_name}
77
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 9 , _skip_content{skip_content_parsing} {
78
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 37 while (_parse_next_element(_element)) {}
79 25 }
80
81 //! Return a reference the read xml representation
82 111298 const XMLElement& get_xml() const & {
83 111298 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 11527 const StreamBounds& get_content_bounds(const XMLElement& e) const {
98
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 11527 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 15803 void _parse_content(XMLElement& parent) {
113
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 15803 const std::string close_tag = "</" + parent.name();
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 15803 auto content_begin_pos = _helper.position();
115 15803 auto content_end_pos = content_begin_pos;
116
117
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 15803 if (_skip_content(parent)) {
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 1092 if (!_helper.shift_until_substr(close_tag))
119 ✗ throw IOError("Could not find closing tag: " + close_tag);
120
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 1092 content_end_pos = _helper.position();
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 1092 _helper.shift_by(close_tag.size());
122 } else {
123 // check for content before the first child
124
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 44133 if (!_helper.shift_until_any_of("<"))
125 ✗ throw IOError("Could not find closing tag for '" + parent.name() + "'");
126
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 14711 content_end_pos = _helper.position();
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 14711 _helper.seek_position(content_begin_pos);
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 14711 _helper.shift_whitespace();
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 14711 const bool have_read_content = _helper.position() < content_end_pos;
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 14711 _helper.seek_position(content_end_pos);
131
132 // parse all children
133 14711 std::optional<std::streamsize> position_after_last_child;
134 while (true) {
135
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 51345 auto pos = _parse_next_element(parent, close_tag);
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 51345 if (pos) position_after_last_child = pos;
137 14711 else break;
138 36634 }
139
140 // (maybe) check for content after the children
141
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 14711 if (!have_read_content && position_after_last_child.has_value()) {
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 12464 content_begin_pos = position_after_last_child.value();
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 12464 content_end_pos = _helper.position();
144 }
145
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 14711 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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 44133 if (!_helper.shift_until_any_of(">"))
149 ✗ throw IOError("Could not find closing tag for '" + parent.name() + "'");
150
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 14711 if (!_helper.is_end_of_file())
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 14711 _helper.shift_by(1);
152 }
153
154
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 15803 _content_bounds[&parent] = StreamBounds{.begin_pos = content_begin_pos, .end_pos = content_end_pos};
155 15803 }
156
157 // parse the next child element from the stream and return the position after it (or none if no child found)
158 55255 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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 1527 if (!close_tag.empty())
162 ✗ throw IOError("Did not find closing tag: " + close_tag);
163 1527 return {};
164 }
165
166
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 166392 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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 55038 const auto cur_pos = _helper.position();
173
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 55038 const auto chunk = _helper.read_chunk(4);
174
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 55038 if (chunk.starts_with("<?"))
175 1733 continue;
176
177
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 53305 if (chunk.starts_with("<!--")) {
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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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 53302 _helper.seek_position(cur_pos);
184
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 53302 if (!close_tag.empty()) {
185
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 51345 if (_helper.read_chunk(close_tag.size()) == close_tag) {
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 14711 _helper.seek_position(cur_pos);
187 14711 return {};
188 }
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 36634 _helper.seek_position(cur_pos);
190 }
191
192
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 38591 if (_parse_element(parent))
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 38587 return {_helper.position()};
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 56774 }
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 38591 bool _parse_element(XMLElement& parent) {
229
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 38591 const auto begin_pos = _helper.position();
230
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 38591 if (!_helper.read_chunk(1).starts_with("<")) {
231 ✗ _helper.seek_position(begin_pos);
232 ✗ return false;
233 }
234
235
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 38591 _helper.seek_position(begin_pos);
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 38591 _helper.shift_by(1);
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 77182 std::string name = _helper.read_until_any_of(std::string{InputStreamHelper::default_whitespace_chars} + "/>");
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 38591 auto& element = parent.add_child(std::move(name));
239
240 while (true) {
241
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 175564 _helper.shift_whitespace();
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 175564 const auto cur_pos = _helper.position();
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 175564 if (_helper.read_chunk(2) == "/>")
244 22784 break;
245
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 152780 _helper.seek_position(cur_pos);
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 152780 if (_helper.read_chunk(1) == ">") {
248
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 15803 _parse_content(element);
249 15803 break;
250 }
251
252
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 136977 _helper.seek_position(cur_pos);
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 136977 auto [name, value] = _read_attribute();
254
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 136973 element.set_attribute(std::move(name), std::move(value));
255 136973 }
256
257 38587 return true;
258 38591 }
259
260 136977 std::pair<std::string, std::string> _read_attribute() {
261
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 273954 std::string attr_name = _helper.read_until_any_of(std::string{InputStreamHelper::default_whitespace_chars} + "=");
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 136977 if (attr_name.empty())
263 ✗ throw IOError("Could not parse attribute name");
264
265
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 136977 _helper.shift_whitespace();
266
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 136976 if (_helper.read_chunk(1) != "=")
267 ✗ throw IOError("Expected '=' after attribute '" + attr_name + "'");
268
269 // values may be enclosed in double or single quotes
270
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 136976 _helper.shift_whitespace();
271
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 136976 const std::string quote = _helper.read_chunk(1);
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 136976 if (quote != "\"" && quote != "'")
273
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 1 throw IOError("Expected quoted value for attribute '" + attr_name + "'");
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 136975 std::string attr_value = XML::Detail::unescaped(_helper.read_until_any_of(quote));
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 136975 if (_helper.is_end_of_file() || _helper.read_chunk(1) != quote)
276
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 2 throw IOError("Missing closing quote for attribute '" + attr_name + "'");
277
278 273946 return std::make_pair(std::move(attr_name), std::move(attr_value));
279 136982 }
280
281 std::unique_ptr<std::ifstream> _owned;
282 InputStreamHelper _helper;
283 XMLElement _element;
284 ContentSkipFunction _skip_content;
285 std::unordered_map<const XMLElement*, StreamBounds> _content_bounds;
286 };
287
288 } // end namespace GridFormat
289
290 #endif // GRIDFORMAT_XML_PARSER_HPP_
291