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//! `xmloxide` parser adapter for the shared semantic arena.
use std::ops::Range;
use xmloxide::tree::{NodeId as XmloxNodeId, NodeKind as XmloxNodeKind};
use super::{
Document, LexicalPreflight, ParseError, ParsingOptions, XmlBackendImplementation,
preflight::{PositionCursor, SourceKind},
tree::{AttributeData, NamespaceData, NodeId, NodeKind, TreeBuilder},
};
pub(super) struct XmloxideBackend;
impl XmlBackendImplementation for XmloxideBackend {
fn parse<'input>(
input: &'input str,
options: ParsingOptions,
preflight: &LexicalPreflight,
) -> Result<Document<'input>, ParseError> {
let parsed = xmloxide::parser::parse_str_with_options(input, &backend_options()).map_err(
|error| ParseError::Backend {
backend: "xmloxide",
message: error.to_string(),
},
)?;
let mut projector = Projector {
source: &parsed,
target: TreeBuilder::new(input, parsed.node_count()),
positions: preflight.positions(),
nodes_limit: options.nodes_limit,
};
let root = projector.target.push(None, NodeKind::Root, 0..input.len());
projector.project_children(parsed.root(), root)?;
projector.positions.finish()?;
projector.target.finish_subtree(root);
Ok(projector.target.finish())
}
}
fn backend_options() -> xmloxide::parser::ParseOptions {
// The shared preflight owns the backend-neutral contract. These absolute
// limits are defense in depth against a backend regression allocating
// expanded entity data before returning control to the projector.
xmloxide::parser::ParseOptions::default()
.max_depth(
u32::try_from(crate::hard_limits::XML_DOCUMENT_DEPTH_CEILING)
.expect("XML depth ceiling fits into u32"),
)
.max_attributes(u32::MAX)
.max_attribute_length(usize::MAX)
.max_text_length(crate::hard_limits::XML_ENTITY_EXPANSION_WORK_BYTE_CEILING)
.max_name_length(usize::MAX)
.max_entity_expansions(crate::hard_limits::XML_ENTITY_EXPANSION_CEILING)
}
struct Projector<'source, 'input, 'positions> {
source: &'source xmloxide::Document,
target: TreeBuilder<'input>,
positions: PositionCursor<'positions>,
nodes_limit: u32,
}
enum ProjectionFrame {
Enter {
source: XmloxNodeId,
parent: NodeId,
namespace_owner: Option<NodeId>,
inherited_range: Option<Range<usize>>,
range_actionable: bool,
},
Exit(NodeId),
}
impl Projector<'_, '_, '_> {
fn project_children(&mut self, source: XmloxNodeId, parent: NodeId) -> Result<(), ParseError> {
let mut stack = Vec::new();
self.push_children(&mut stack, source, parent, None, None, true);
while let Some(frame) = stack.pop() {
match frame {
ProjectionFrame::Exit(node) => self.target.finish_subtree(node),
ProjectionFrame::Enter {
source,
parent,
namespace_owner,
inherited_range,
range_actionable,
} => {
let source_node = self.source.node(source);
match &source_node.kind {
XmloxNodeKind::Document | XmloxNodeKind::DocumentType { .. } => {
self.push_children(
&mut stack,
source,
parent,
namespace_owner,
inherited_range,
range_actionable,
);
}
XmloxNodeKind::Element {
name,
prefix,
namespace,
attributes,
} => {
let range = match inherited_range.clone() {
Some(range) => range,
None => self.positions.take(SourceKind::Element)?,
};
let mut namespaces = namespace_owner
.and_then(|owner| self.target.namespaces(owner))
.unwrap_or_default()
.to_vec();
let mut semantic_attributes = Vec::with_capacity(attributes.len());
for attribute in attributes {
if attribute.prefix.as_deref() == Some("xmlns") {
set_namespace(
&mut namespaces,
Some(attribute.name.clone()),
attribute.value.clone(),
);
} else if attribute.prefix.is_none() && attribute.name == "xmlns" {
set_namespace(&mut namespaces, None, attribute.value.clone());
} else {
semantic_attributes.push(AttributeData {
name: attribute.name.clone(),
namespace: attribute.namespace.clone(),
prefix: attribute.prefix.clone(),
value: attribute.value.clone(),
});
}
}
let node = self.target.push_with_actionability(
Some(parent),
NodeKind::Element {
name: name.clone(),
namespace: namespace
.as_deref()
.filter(|uri| !uri.is_empty())
.map(str::to_owned),
prefix: prefix.clone(),
attributes: semantic_attributes,
namespaces,
},
range,
range_actionable,
);
self.enforce_node_limit()?;
stack.push(ProjectionFrame::Exit(node));
self.push_children(
&mut stack,
source,
node,
Some(node),
inherited_range,
range_actionable,
);
}
XmloxNodeKind::Text { content } => {
if self.source.parent(source) == Some(self.source.root())
&& content.chars().all(char::is_whitespace)
{
continue;
}
let range = match inherited_range {
Some(range) => range,
None => self.positions.take(SourceKind::Text)?,
};
self.target
.append_text(parent, content, range, range_actionable);
self.enforce_node_limit()?;
}
XmloxNodeKind::CData { content } => {
let range = match inherited_range {
Some(range) => range,
None => self.positions.take(SourceKind::CData)?,
};
self.target
.append_text(parent, content, range, range_actionable);
self.enforce_node_limit()?;
}
XmloxNodeKind::Comment { content } => {
let range = match inherited_range {
Some(range) => range,
None => self.positions.take(SourceKind::Comment)?,
};
self.target.push_with_actionability(
Some(parent),
NodeKind::Comment(content.clone()),
range,
range_actionable,
);
self.enforce_node_limit()?;
}
XmloxNodeKind::ProcessingInstruction {
target: pi_target,
data,
} => {
let range = match inherited_range {
Some(range) => range,
None => self.positions.take(SourceKind::Pi)?,
};
self.target.push_with_actionability(
Some(parent),
NodeKind::PI {
target: pi_target.clone(),
value: data.clone(),
},
range,
range_actionable,
);
self.enforce_node_limit()?;
}
XmloxNodeKind::EntityRef { value, .. } => {
let range = match inherited_range {
Some(range) => range,
None => self.positions.take(SourceKind::EntityRef)?,
};
if self.source.children(source).next().is_some() {
self.push_children(
&mut stack,
source,
parent,
namespace_owner,
Some(range),
false,
);
} else if let Some(value) = value {
self.target.append_text(parent, value, range, false);
self.enforce_node_limit()?;
}
}
}
}
}
}
Ok(())
}
fn push_children(
&self,
stack: &mut Vec<ProjectionFrame>,
source: XmloxNodeId,
parent: NodeId,
namespace_owner: Option<NodeId>,
inherited_range: Option<Range<usize>>,
range_actionable: bool,
) {
let children = self.source.children(source).collect::<Vec<_>>();
for child in children.into_iter().rev() {
stack.push(ProjectionFrame::Enter {
source: child,
parent,
namespace_owner,
inherited_range: inherited_range.clone(),
range_actionable,
});
}
}
fn enforce_node_limit(&self) -> Result<(), ParseError> {
if self.target.len() > self.nodes_limit as usize {
Err(ParseError::NodesLimitReached)
} else {
Ok(())
}
}
}
fn set_namespace(namespaces: &mut Vec<NamespaceData>, prefix: Option<String>, uri: String) {
if let Some(existing) = namespaces.iter_mut().find(|item| item.prefix == prefix) {
existing.uri = uri;
} else {
namespaces.push(NamespaceData { prefix, uri });
}
}