oxigraph::sparql

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Utilities to read and write RDF results formats using sparesults.

It supports SPARQL Query Results XML Format (Second Edition), SPARQL 1.1 Query Results JSON Format and SPARQL 1.1 Query Results CSV and TSV Formats.

Usage example converting a JSON result file into a TSV result file:

use oxigraph::sparql::results::{QueryResultsFormat, QueryResultsParser, ReaderQueryResultsParserOutput, QueryResultsSerializer};
use std::io::Result;

fn convert_json_to_tsv(json_file: &[u8]) -> Result<Vec<u8>> {
    let json_parser = QueryResultsParser::from_format(QueryResultsFormat::Json);
    let tsv_serializer = QueryResultsSerializer::from_format(QueryResultsFormat::Tsv);
    // We start to read the JSON file and see which kind of results it is
    match json_parser.for_reader(json_file)? {
        ReaderQueryResultsParserOutput::Boolean(value) => {
            // it's a boolean result, we copy it in TSV to the output buffer
            tsv_serializer.serialize_boolean_to_writer(Vec::new(), value)
        }
        ReaderQueryResultsParserOutput::Solutions(solutions_reader) => {
            // it's a set of solutions, we create a writer and we write to it while reading in streaming from the JSON file
            let mut tsv_solutions_serializer = tsv_serializer.serialize_solutions_to_writer(Vec::new(), solutions_reader.variables().to_vec())?;
            for solution in solutions_reader {
                tsv_solutions_serializer.serialize(&solution?)?;
            }
            tsv_solutions_serializer.finish()
        }
    }
}

// Let's test with a boolean
assert_eq!(
    convert_json_to_tsv(br#"{"boolean":true}"#.as_slice()).unwrap(),
    b"true"
);

// And with a set of solutions
assert_eq!(
    convert_json_to_tsv(br#"{"head":{"vars":["foo","bar"]},"results":{"bindings":[{"foo":{"type":"literal","value":"test"}}]}}"#.as_slice()).unwrap(),
    b"?foo\t?bar\n\"test\"\t\n"
);

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