1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
use Result;
use reader::rdf_parser::RdfParser;
use graph::Graph;
use error::{Error, ErrorType};
use triple::Triple;
use reader::lexer::n_triples_lexer::NTriplesLexer;
use reader::lexer::rdf_lexer::RdfLexer;
use node::Node;
use reader::lexer::token::Token;
use std::io::Read;
use uri::Uri;
use std::io::Cursor;
/// RDF parser to generate an RDF graph from N-Triples syntax.
pub struct NTriplesParser<R: Read> {
lexer: NTriplesLexer<R>,
}
impl<R: Read> RdfParser for NTriplesParser<R> {
/// Generates an RDF graph from a string containing N-Triples syntax.
///
/// Returns an error in case invalid N-Triples syntax is provided.
///
/// # Examples
///
/// ```
/// use rdf::reader::n_triples_parser::NTriplesParser;
/// use rdf::reader::rdf_parser::RdfParser;
///
/// let input = "<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://xmlns.com/foaf/0.1/maker> _:art .
/// _:art <http://xmlns.com/foaf/0.1/name> \"Art Barstow\" .";
///
/// let mut reader = NTriplesParser::from_string(input.to_string());
///
/// match reader.decode() {
/// Ok(graph) => assert_eq!(graph.count(), 2),
/// Err(_) => assert!(false)
/// }
/// ```
///
/// # Failures
///
/// - Invalid input that does not conform with NTriples standard.
/// - Invalid node type for triple segment.
///
fn decode(&mut self) -> Result<Graph> {
let mut graph = Graph::new(None);
loop {
match self.lexer.peek_next_token()? {
Token::Comment(_) => {
// ignore comments
let _ = self.lexer.get_next_token();
continue;
}
Token::EndOfInput => return Ok(graph),
_ => {}
}
match self.read_triple() {
Ok(triple) => graph.add_triple(&triple),
Err(err) => match *err.error_type() {
ErrorType::EndOfInput(_) => return Ok(graph),
_ => {
println!("Error: {}", err.to_string());
return Err(Error::new(
ErrorType::InvalidReaderInput,
"Error while parsing NTriples syntax.",
));
}
},
}
}
}
}
impl NTriplesParser<Cursor<Vec<u8>>> {
/// Constructor of `NTriplesParser` from input string.
///
/// # Examples
///
/// ```
/// use rdf::reader::n_triples_parser::NTriplesParser;
/// use rdf::reader::rdf_parser::RdfParser;
///
/// let input = "<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://xmlns.com/foaf/0.1/maker> _:art .
/// _:art <http://xmlns.com/foaf/0.1/name> \"Art Barstow\" .";
///
/// let reader = NTriplesParser::from_string(input.to_string());
/// ```
pub fn from_string<S>(input: S) -> NTriplesParser<Cursor<Vec<u8>>>
where
S: Into<String>,
{
NTriplesParser::from_reader(Cursor::new(input.into().into_bytes()))
}
}
impl<R: Read> NTriplesParser<R> {
/// Constructor of `NTriplesParser` from input reader.
///
/// # Examples
///
/// ```
/// use rdf::reader::n_triples_parser::NTriplesParser;
/// use rdf::reader::rdf_parser::RdfParser;
///
/// let input = "<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://xmlns.com/foaf/0.1/maker> _:art .
/// _:art <http://xmlns.com/foaf/0.1/name> \"Art Barstow\" .";
///
/// let reader = NTriplesParser::from_reader(input.as_bytes());
/// ```
pub fn from_reader(input: R) -> NTriplesParser<R> {
NTriplesParser {
lexer: NTriplesLexer::new(input),
}
}
/// Creates a triple from the parsed tokens.
fn read_triple(&mut self) -> Result<Triple> {
let subject = self.read_subject()?;
let predicate = self.read_predicate()?;
let object = self.read_object()?;
match self.lexer.get_next_token() {
Ok(Token::TripleDelimiter) => {}
_ => {
return Err(Error::new(
ErrorType::InvalidReaderInput,
"Expected triple delimiter.",
))
}
}
Ok(Triple::new(&subject, &predicate, &object))
}
/// Get the next token and check if it is a valid subject and create a new subject node.
fn read_subject(&mut self) -> Result<Node> {
match self.lexer.get_next_token() {
Ok(Token::BlankNode(id)) => Ok(Node::BlankNode { id }),
Ok(Token::Uri(uri)) => Ok(Node::UriNode { uri: Uri::new(uri) }),
_ => Err(Error::new(
ErrorType::InvalidToken,
"Invalid token for NTriples subject.",
)),
}
}
/// Get the next token and check if it is a valid predicate and create a new predicate node.
fn read_predicate(&mut self) -> Result<Node> {
match self.lexer.get_next_token() {
Ok(Token::Uri(uri)) => Ok(Node::UriNode { uri: Uri::new(uri) }),
_ => Err(Error::new(
ErrorType::InvalidToken,
"Invalid token for NTriples predicate.",
)),
}
}
/// Get the next token and check if it is a valid object and create a new object node.
fn read_object(&mut self) -> Result<Node> {
match self.lexer.get_next_token()? {
Token::BlankNode(id) => Ok(Node::BlankNode { id }),
Token::Uri(uri) => Ok(Node::UriNode { uri: Uri::new(uri) }),
Token::LiteralWithLanguageSpecification(literal, lang) => Ok(Node::LiteralNode {
literal,
data_type: None,
language: Some(lang),
}),
Token::LiteralWithUrlDatatype(literal, datatype) => Ok(Node::LiteralNode {
literal,
data_type: Some(Uri::new(datatype)),
language: None,
}),
Token::Literal(literal) => Ok(Node::LiteralNode {
literal,
data_type: None,
language: None,
}),
_ => Err(Error::new(
ErrorType::InvalidToken,
"Invalid token for NTriples object.",
)),
}
}
}
#[cfg(test)]
mod tests {
use reader::n_triples_parser::NTriplesParser;
use reader::rdf_parser::RdfParser;
#[test]
fn test_read_n_triples_from_string() {
let input = "<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Document> .
<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://purl.org/dc/terms/title> \"N-Triples\"@en-US .
<http://www.w3.org/2001/sw/RDFCore/ntriples/> <http://xmlns.com/foaf/0.1/maker> _:art .
_:art <http://xmlns.com/foaf/0.1/name> \"Art Barstow\" .";
let mut reader = NTriplesParser::from_string(input.to_string());
match reader.decode() {
Ok(graph) => assert_eq!(graph.count(), 4),
Err(e) => {
println!("Err {}", e.to_string());
assert!(false)
}
}
}
}