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//! This module contains extensions for generalized RDF / RDF-star.
//! Its elements are re-exported by `model` and `parser`, respectively.
/// Data structures for generalized [RDF 1.1 Concepts](https://www.w3.org/TR/rdf11-concepts/),
/// allowing variables, and any kind of node in any Triple/Quad position.
pub mod model {
use std::convert::TryFrom;
use std::error::Error;
use std::fmt;
pub use crate::model::*;
/// A SPARQL [variable](https://www.w3.org/TR/sparql11-query/#QSynVariables).
///
/// The default string formatter is returning a SPARQL compatible representation.
///
/// ```
/// use rio_api::model::Variable;
///
/// assert_eq!(
/// "?foobar",
/// Variable { name: "foobar" }.to_string()
/// )
/// ```
///
/// Using it requires to enable the `generalized` feature.
#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Copy, Hash)]
pub struct Variable<'a> {
/// The name of the [variable](https://www.w3.org/TR/sparql11-query/#QSynVariables) itself.
pub name: &'a str,
}
impl<'a> fmt::Display for Variable<'a> {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "?{}", self.name)
}
}
//
/// A generalized RDF [term](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-term).
///
/// It is the union of
/// * [IRI](https://www.w3.org/TR/rdf11-concepts/#dfn-iri) references (absolute *or relative*),
/// * [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node)
/// * [literals](https://www.w3.org/TR/rdf11-concepts/#dfn-literal) and
/// * [variables](https://www.w3.org/TR/sparql11-query/#QSynVariables).
/// * [quoted triples](https://www.w3.org/2021/12/rdf-star.html#dfn-quoted)
///
/// The default string formatter is returning an N-Triples, Turtle and SPARQL compatible representation.
///
/// Using it requires to enable the `generalized` feature.
#[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
pub enum GeneralizedTerm<'a> {
NamedNode(NamedNode<'a>),
BlankNode(BlankNode<'a>),
Literal(Literal<'a>),
Variable(Variable<'a>),
Triple(&'a [GeneralizedTerm<'a>; 3]),
}
impl<'a> From<NamedNode<'a>> for GeneralizedTerm<'a> {
#[inline]
fn from(other: NamedNode<'a>) -> GeneralizedTerm<'a> {
GeneralizedTerm::NamedNode(other)
}
}
impl<'a> From<BlankNode<'a>> for GeneralizedTerm<'a> {
#[inline]
fn from(other: BlankNode<'a>) -> GeneralizedTerm<'a> {
GeneralizedTerm::BlankNode(other)
}
}
impl<'a> From<Literal<'a>> for GeneralizedTerm<'a> {
#[inline]
fn from(other: Literal<'a>) -> GeneralizedTerm<'a> {
GeneralizedTerm::Literal(other)
}
}
impl<'a> From<Variable<'a>> for GeneralizedTerm<'a> {
#[inline]
fn from(other: Variable<'a>) -> GeneralizedTerm<'a> {
GeneralizedTerm::Variable(other)
}
}
impl<'a> From<GraphName<'a>> for GeneralizedTerm<'a> {
#[inline]
fn from(other: GraphName<'a>) -> GeneralizedTerm<'a> {
match other {
GraphName::NamedNode(inner) => GeneralizedTerm::NamedNode(inner),
GraphName::BlankNode(inner) => GeneralizedTerm::BlankNode(inner),
}
}
}
impl<'a> TryFrom<GeneralizedTerm<'a>> for NamedNode<'a> {
type Error = StrictRdfError;
#[inline]
fn try_from(other: GeneralizedTerm<'a>) -> Result<NamedNode<'a>, StrictRdfError> {
match other {
GeneralizedTerm::NamedNode(inner) => Ok(inner),
GeneralizedTerm::BlankNode(_) => Err(StrictRdfError {
message: "Blank node cannot be used as predicate",
}),
GeneralizedTerm::Literal(_) => Err(StrictRdfError {
message: "Literal cannot be used as predicate",
}),
GeneralizedTerm::Variable(_) => Err(StrictRdfError {
message: "Variable cannot be converted to Term",
}),
GeneralizedTerm::Triple(_) => Err(StrictRdfError {
message: "Triple cannot be used as predicate",
}),
}
}
}
impl<'a> TryFrom<GeneralizedTerm<'a>> for GraphName<'a> {
type Error = StrictRdfError;
#[inline]
fn try_from(other: GeneralizedTerm<'a>) -> Result<GraphName<'a>, StrictRdfError> {
match other {
GeneralizedTerm::NamedNode(inner) => Ok(GraphName::NamedNode(inner)),
GeneralizedTerm::BlankNode(inner) => Ok(GraphName::BlankNode(inner)),
GeneralizedTerm::Literal(_) => Err(StrictRdfError {
message: "Literal cannot be used a graph name",
}),
GeneralizedTerm::Variable(_) => Err(StrictRdfError {
message: "Variable cannot be converted to Term",
}),
GeneralizedTerm::Triple(_) => Err(StrictRdfError {
message: "Triple cannot be used as a graph name",
}),
}
}
}
impl<'a> fmt::Display for GeneralizedTerm<'a> {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
GeneralizedTerm::NamedNode(node) => node.fmt(f),
GeneralizedTerm::BlankNode(node) => node.fmt(f),
GeneralizedTerm::Literal(literal) => literal.fmt(f),
GeneralizedTerm::Variable(variable) => variable.fmt(f),
GeneralizedTerm::Triple(triple) => {
write!(f, "<< {} {} {} >>", triple[0], triple[1], triple[2])
}
}
}
}
//
/// A generalized [RDF triple](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple) in a [RDF dataset](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-dataset).
///
/// The default string formatter is returning a SPARQL representation.
///
/// ```
/// use rio_api::model::{GeneralizedQuad, Variable};
///
/// assert_eq!(
/// "?s ?p ?o .",
/// GeneralizedQuad {
/// subject: Variable { name: "s" }.into(),
/// predicate: Variable { name: "p" }.into(),
/// object: Variable { name: "o" }.into(),
/// graph_name: None,
/// }.to_string()
/// );
///
/// assert_eq!(
/// "GRAPH ?g { ?s ?p ?o .}",
/// GeneralizedQuad {
/// subject: Variable { name: "s" }.into(),
/// predicate: Variable { name: "p" }.into(),
/// object: Variable { name: "o" }.into(),
/// graph_name: Some(Variable { name: "g" }.into()),
/// }.to_string()
/// );
/// ```
///
/// Using it requires to enable the `generalized` feature.
#[derive(Eq, PartialEq, Debug, Clone, Hash)]
pub struct GeneralizedQuad<'a> {
pub subject: GeneralizedTerm<'a>,
pub predicate: GeneralizedTerm<'a>,
pub object: GeneralizedTerm<'a>,
pub graph_name: Option<GeneralizedTerm<'a>>,
}
impl<'a> fmt::Display for GeneralizedQuad<'a> {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let Some(graph_name) = &self.graph_name {
write!(f, "GRAPH {} {{ ", graph_name)?;
}
write!(f, "{} {} {} .", self.subject, self.predicate, self.object)?;
if self.graph_name.is_some() {
write!(f, "}}")?;
}
Ok(())
}
}
//
/// An error raised when generalized RDF cannot be converted to strict RDF.
#[derive(Debug, Clone, Copy)]
pub struct StrictRdfError {
pub message: &'static str,
}
impl fmt::Display for StrictRdfError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.message.fmt(f)
}
}
impl Error for StrictRdfError {}
}
/// Interface for generalized RDF parsers.
pub mod parser {
use super::model::GeneralizedQuad;
use std::error::Error;
/// A parser returning generalized [`Quad`](super::model::Quad).
///
/// Using it requires to enable the `generalized` feature.
pub trait GeneralizedQuadsParser {
type Error: Error;
/// Parses the complete file and calls `on_quad` each time a new quad is read.
///
/// May fails on errors caused by the parser itself or by the callback function `on_quad`.
fn parse_all<E: From<Self::Error>>(
&mut self,
on_quad: &mut impl FnMut(GeneralizedQuad<'_>) -> Result<(), E>,
) -> Result<(), E> {
while !self.is_end() {
self.parse_step(on_quad)?
}
Ok(())
}
/// Parses a small chunk of the file and calls `on_quad` each time a new quad is read.
/// (A "small chunk" could be a line for an N-Quads parser.)
///
/// This method should be called as long as [`is_end`](GeneralizedQuadsParser::is_end) returns false.
///
/// May fails on errors caused by the parser itself or by the callback function `on_quad`.
fn parse_step<E: From<Self::Error>>(
&mut self,
on_quad: &mut impl FnMut(GeneralizedQuad<'_>) -> Result<(), E>,
) -> Result<(), E>;
/// Returns `true` if the file has been completely consumed by the parser.
fn is_end(&self) -> bool;
/// Converts the parser into a `Result<T, E>` iterator.
///
/// `convert_quad` is a function converting Rio [`GeneralizedQuad`]s to `T`.
fn into_iter<T, E, F>(
self,
convert_quad: F,
) -> GeneralizedQuadsParserIterator<T, E, F, Self>
where
E: From<Self::Error>,
F: FnMut(GeneralizedQuad<'_>) -> Result<T, E>,
Self: Sized,
{
GeneralizedQuadsParserIterator {
parser: self,
buffer: Vec::default(),
convert_quad,
}
}
}
/// Created with the method [`into_iter`](GeneralizedQuadsParser::into_iter()).
///
/// Using it requires to enable the `generalized` feature.
pub struct GeneralizedQuadsParserIterator<
T,
E: From<P::Error>,
F: FnMut(GeneralizedQuad<'_>) -> Result<T, E>,
P: GeneralizedQuadsParser,
> {
parser: P,
buffer: Vec<T>,
convert_quad: F,
}
impl<T, E, F, P> Iterator for GeneralizedQuadsParserIterator<T, E, F, P>
where
E: From<P::Error>,
F: FnMut(GeneralizedQuad<'_>) -> Result<T, E>,
P: GeneralizedQuadsParser + Sized,
{
type Item = Result<T, E>;
fn next(&mut self) -> Option<Result<T, E>> {
loop {
if let Some(r) = self.buffer.pop() {
return Some(Ok(r));
}
if self.parser.is_end() {
return None;
}
let buffer = &mut self.buffer;
let convert_quad = &mut self.convert_quad;
if let Err(e) = self
.parser
.parse_step(&mut |q| convert_quad(q).map(|q| buffer.push(q)))
{
return Some(Err(e));
}
}
}
}
}