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//! Contains namespace manipulation types and functions.
use std::iter::{Map, Rev};
use std::collections::btree_map::{BTreeMap, Entry};
use std::collections::btree_map::Iter as Entries;
use std::collections::HashSet;
use std::slice::Iter;
/// Designates prefix for namespace definitions.
///
/// See [Namespaces in XML][namespace] spec for more information.
///
pub const NS_XMLNS_PREFIX: &'static str = "xmlns";
/// Designates the standard URI for `xmlns` prefix.
///
/// See [A Namespace Name for xmlns Attributes][1] for more information.
///
/// Designates prefix for a namespace containing several special predefined attributes.
///
/// See [2.10 White Space handling][1], [2.1 Language Identification][2],
/// [XML Base specification][3] and [xml:id specification][4] for more information.
///
pub const NS_XML_PREFIX: &'static str = "xml";
/// Designates the standard URI for `xml` prefix.
///
/// See `NS_XML_PREFIX` documentation for more information.
/// Designates the absence of prefix in a qualified name.
///
/// This constant should be used to define or query default namespace which should be used
/// for element or attribute names without prefix. For example, if a namespace mapping
/// at a particular point in the document contains correspondence like
///
/// ```none
/// NS_NO_PREFIX --> urn:some:namespace
/// ```
///
/// then all names declared without an explicit prefix `urn:some:namespace` is assumed as
/// a namespace URI.
///
/// By default empty prefix corresponds to absence of namespace, but this can change either
/// when writing an XML document (manually) or when reading an XML document (based on namespace
/// declarations).
pub const NS_NO_PREFIX: &'static str = "";
/// Designates an empty namespace URI, which is equivalent to absence of namespace.
///
/// This constant should not usually be used directly; it is used to designate that
/// empty prefix corresponds to absent namespace in `NamespaceStack` instances created with
/// `NamespaceStack::default()`. Therefore, it can be used to restore `NS_NO_PREFIX` mapping
/// in a namespace back to its default value.
pub const NS_EMPTY_URI: &'static str = "";
/// Namespace is a map from prefixes to namespace URIs.
///
/// No prefix (i.e. default namespace) is designated by `NS_NO_PREFIX` constant.
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct Namespace(pub BTreeMap<String, String>);
impl Namespace {
/// Returns an empty namespace.
#[inline]
pub fn empty() -> Namespace { Namespace(BTreeMap::new()) }
/// Checks whether this namespace is empty.
#[inline]
pub fn is_empty(&self) -> bool {
self.0.is_empty()
}
/// Checks whether this namespace is essentially empty, that is, it does not contain
/// anything but default mappings.
pub fn is_essentially_empty(&self) -> bool {
// a shortcut for a namespace which is definitely not empty
if self.0.len() > 3 { return false; }
self.0.iter().all(|(k, v)| match (&**k, &**v) {
(NS_NO_PREFIX, NS_EMPTY_URI) => true,
(NS_XMLNS_PREFIX, NS_XMLNS_URI) => true,
(NS_XML_PREFIX, NS_XML_URI) => true,
_ => false
})
}
/// Checks whether this namespace mapping contains the given prefix.
///
/// # Parameters
/// * `prefix` --- namespace prefix.
///
/// # Return value
/// `true` if this namespace contains the given prefix, `false` otherwise.
#[inline]
pub fn contains<P: ?Sized+AsRef<str>>(&self, prefix: &P) -> bool {
self.0.contains_key(prefix.as_ref())
}
/// Puts a mapping into this namespace.
///
/// This method does not override any already existing mappings.
///
/// Returns a boolean flag indicating whether the map already contained
/// the given prefix.
///
/// # Parameters
/// * `prefix` --- namespace prefix;
/// * `uri` --- namespace URI.
///
/// # Return value
/// `true` if `prefix` has been inserted successfully; `false` if the `prefix`
/// was already present in the namespace.
pub fn put<P, U>(&mut self, prefix: P, uri: U) -> bool
where P: Into<String>, U: Into<String>
{
match self.0.entry(prefix.into()) {
Entry::Occupied(_) => false,
Entry::Vacant(ve) => {
ve.insert(uri.into());
true
}
}
}
/// Puts a mapping into this namespace forcefully.
///
/// This method, unlike `put()`, does replace an already existing mapping.
///
/// Returns previous URI which was assigned to the given prefix, if it is present.
///
/// # Parameters
/// * `prefix` --- namespace prefix;
/// * `uri` --- namespace URI.
///
/// # Return value
/// `Some(uri)` with `uri` being a previous URI assigned to the `prefix`, or
/// `None` if such prefix was not present in the namespace before.
pub fn force_put<P, U>(&mut self, prefix: P, uri: U) -> Option<String>
where P: Into<String>, U: Into<String>
{
self.0.insert(prefix.into(), uri.into())
}
/// Queries the namespace for the given prefix.
///
/// # Parameters
/// * `prefix` --- namespace prefix.
///
/// # Return value
/// Namespace URI corresponding to the given prefix, if it is present.
pub fn get<'a, P: ?Sized+AsRef<str>>(&'a self, prefix: &P) -> Option<&'a str> {
self.0.get(prefix.as_ref()).map(|s| &**s)
}
}
/// An alias for iterator type for namespace mappings contained in a namespace.
pub type NamespaceMappings<'a> = Map<
Entries<'a, String, String>,
for<'b> fn((&'b String, &'b String)) -> UriMapping<'b>
>;
impl<'a> IntoIterator for &'a Namespace {
type Item = UriMapping<'a>;
type IntoIter = NamespaceMappings<'a>;
fn into_iter(self) -> Self::IntoIter {
fn mapper<'a>((prefix, uri): (&'a String, &'a String)) -> UriMapping<'a> {
(&*prefix, &*uri)
}
self.0.iter().map(mapper)
}
}
/// Namespace stack is a sequence of namespaces.
///
/// Namespace stack is used to represent cumulative namespace consisting of
/// combined namespaces from nested elements.
#[derive(Clone, Eq, PartialEq, Debug)]
pub struct NamespaceStack(pub Vec<Namespace>);
impl NamespaceStack {
/// Returns an empty namespace stack.
#[inline]
pub fn empty() -> NamespaceStack { NamespaceStack(Vec::with_capacity(2)) }
/// Returns a namespace stack with default items in it.
///
/// Default items are the following:
///
#[inline]
pub fn default() -> NamespaceStack {
let mut nst = NamespaceStack::empty();
nst.push_empty();
// xml namespace
nst.put(NS_XML_PREFIX, NS_XML_URI);
// xmlns namespace
nst.put(NS_XMLNS_PREFIX, NS_XMLNS_URI);
// empty namespace
nst.put(NS_NO_PREFIX, NS_EMPTY_URI);
nst
}
/// Adds an empty namespace to the top of this stack.
#[inline]
pub fn push_empty(&mut self) -> &mut NamespaceStack {
self.0.push(Namespace::empty());
self
}
/// Removes the topmost namespace in this stack.
///
/// Panics if the stack is empty.
#[inline]
pub fn pop(&mut self) -> Namespace {
self.0.pop().unwrap()
}
/// Removes the topmost namespace in this stack.
///
/// Returns `Some(namespace)` if this stack is not empty and `None` otherwise.
#[inline]
pub fn try_pop(&mut self) -> Option<Namespace> {
self.0.pop()
}
/// Borrows the topmost namespace mutably, leaving the stack intact.
///
/// Panics if the stack is empty.
#[inline]
pub fn peek_mut(&mut self) -> &mut Namespace {
self.0.last_mut().unwrap()
}
/// Borrows the topmost namespace immutably, leaving the stack intact.
///
/// Panics if the stack is empty.
#[inline]
pub fn peek(&self) -> &Namespace {
self.0.last().unwrap()
}
/// Puts a mapping into the topmost namespace if this stack does not already contain one.
///
/// Returns a boolean flag indicating whether the insertion has completed successfully.
/// Note that both key and value are matched and the mapping is inserted if either
/// namespace prefix is not already mapped, or if it is mapped, but to a different URI.
///
/// # Parameters
/// * `prefix` --- namespace prefix;
/// * `uri` --- namespace URI.
///
/// # Return value
/// `true` if `prefix` has been inserted successfully; `false` if the `prefix`
/// was already present in the namespace stack.
pub fn put_checked<P, U>(&mut self, prefix: P, uri: U) -> bool
where P: Into<String> + AsRef<str>,
U: Into<String> + AsRef<str>
{
if self.0.iter().any(|ns| ns.get(&prefix) == Some(uri.as_ref())) {
false
} else {
self.put(prefix, uri);
true
}
}
/// Puts a mapping into the topmost namespace in this stack.
///
/// This method does not override a mapping in the topmost namespace if it is
/// already present, however, it does not depend on other namespaces in the stack,
/// so it is possible to put a mapping which is present in lower namespaces.
///
/// Returns a boolean flag indicating whether the insertion has completed successfully.
///
/// # Parameters
/// * `prefix` --- namespace prefix;
/// * `uri` --- namespace URI.
///
/// # Return value
/// `true` if `prefix` has been inserted successfully; `false` if the `prefix`
/// was already present in the namespace.
#[inline]
pub fn put<P, U>(&mut self, prefix: P, uri: U) -> bool
where P: Into<String>, U: Into<String>
{
self.0.last_mut().unwrap().put(prefix, uri)
}
/// Performs a search for the given prefix in the whole stack.
///
/// This method walks the stack from top to bottom, querying each namespace
/// in order for the given prefix. If none of the namespaces contains the prefix,
/// `None` is returned.
///
/// # Parameters
/// * `prefix` --- namespace prefix.
#[inline]
pub fn get<'a, P: ?Sized+AsRef<str>>(&'a self, prefix: &P) -> Option<&'a str> {
let prefix = prefix.as_ref();
for ns in self.0.iter().rev() {
match ns.get(prefix) {
None => {},
r => return r,
}
}
None
}
/// Combines this stack of namespaces into a single namespace.
///
/// Namespaces are combined in left-to-right order, that is, rightmost namespace
/// elements take priority over leftmost ones.
pub fn squash(&self) -> Namespace {
let mut result = BTreeMap::new();
for ns in self.0.iter() {
result.extend(ns.0.iter().map(|(k, v)| (k.clone(), v.clone())));
}
Namespace(result)
}
/// Returns an object which implements `Extend` using `put_checked()` instead of `put()`.
///
/// See `CheckedTarget` for more information.
#[inline]
pub fn checked_target(&mut self) -> CheckedTarget {
CheckedTarget(self)
}
/// Returns an iterator over all mappings in this namespace stack.
#[inline]
pub fn iter(&self) -> NamespaceStackMappings {
self.into_iter()
}
}
/// An iterator over mappings from prefixes to URIs in a namespace stack.
///
/// # Example
/// ```
/// # use xml::namespace::NamespaceStack;
/// let mut nst = NamespaceStack::empty();
/// nst.push_empty();
/// nst.put("a", "urn:A");
/// nst.put("b", "urn:B");
/// nst.push_empty();
/// nst.put("c", "urn:C");
///
/// assert_eq!(vec![("c", "urn:C"), ("a", "urn:A"), ("b", "urn:B")], nst.iter().collect::<Vec<_>>());
/// ```
pub struct NamespaceStackMappings<'a> {
namespaces: Rev<Iter<'a, Namespace>>,
current_namespace: Option<NamespaceMappings<'a>>,
used_keys: HashSet<&'a str>
}
impl<'a> NamespaceStackMappings<'a> {
fn go_to_next_namespace(&mut self) -> bool {
self.current_namespace = self.namespaces.next().map(|ns| ns.into_iter());
self.current_namespace.is_some()
}
}
impl<'a> Iterator for NamespaceStackMappings<'a> {
type Item = UriMapping<'a>;
fn next(&mut self) -> Option<UriMapping<'a>> {
// If there is no current namespace and no next namespace, we're finished
if self.current_namespace.is_none() && !self.go_to_next_namespace() {
return None;
}
let next_item = self.current_namespace.as_mut().unwrap().next();
match next_item {
// There is an element in the current namespace
Some((k, v)) => if self.used_keys.contains(&k) {
// If the current key is used, go to the next one
self.next()
} else {
// Otherwise insert the current key to the set of used keys and
// return the mapping
self.used_keys.insert(k);
Some((k, v))
},
// Current namespace is exhausted
None => if self.go_to_next_namespace() {
// If there is next namespace, continue from it
self.next()
} else {
// No next namespace, exiting
None
}
}
}
}
impl<'a> IntoIterator for &'a NamespaceStack {
type Item = UriMapping<'a>;
type IntoIter = NamespaceStackMappings<'a>;
fn into_iter(self) -> Self::IntoIter {
NamespaceStackMappings {
namespaces: self.0.iter().rev(),
current_namespace: None,
used_keys: HashSet::new()
}
}
}
/// A type alias for a pair of `(prefix, uri)` values returned by namespace iterators.
pub type UriMapping<'a> = (&'a str, &'a str);
impl<'a> Extend<UriMapping<'a>> for Namespace {
fn extend<T>(&mut self, iterable: T) where T: IntoIterator<Item=UriMapping<'a>> {
for (prefix, uri) in iterable {
self.put(prefix, uri);
}
}
}
impl<'a> Extend<UriMapping<'a>> for NamespaceStack {
fn extend<T>(&mut self, iterable: T) where T: IntoIterator<Item=UriMapping<'a>> {
for (prefix, uri) in iterable {
self.put(prefix, uri);
}
}
}
/// A wrapper around `NamespaceStack` which implements `Extend` using `put_checked()`.
///
/// # Example
///
/// ```
/// # use xml::namespace::NamespaceStack;
///
/// let mut nst = NamespaceStack::empty();
/// nst.push_empty();
/// nst.put("a", "urn:A");
/// nst.put("b", "urn:B");
/// nst.push_empty();
/// nst.put("c", "urn:C");
///
/// nst.checked_target().extend(vec![("a", "urn:Z"), ("b", "urn:B"), ("c", "urn:Y"), ("d", "urn:D")]);
/// assert_eq!(
/// vec![("a", "urn:Z"), ("c", "urn:C"), ("d", "urn:D"), ("b", "urn:B")],
/// nst.iter().collect::<Vec<_>>()
/// );
/// ```
///
/// Compare:
///
/// ```
/// # use xml::namespace::NamespaceStack;
/// # let mut nst = NamespaceStack::empty();
/// # nst.push_empty();
/// # nst.put("a", "urn:A");
/// # nst.put("b", "urn:B");
/// # nst.push_empty();
/// # nst.put("c", "urn:C");
///
/// nst.extend(vec![("a", "urn:Z"), ("b", "urn:B"), ("c", "urn:Y"), ("d", "urn:D")]);
/// assert_eq!(
/// vec![("a", "urn:Z"), ("b", "urn:B"), ("c", "urn:C"), ("d", "urn:D")],
/// nst.iter().collect::<Vec<_>>()
/// );
/// ```
pub struct CheckedTarget<'a>(&'a mut NamespaceStack);
impl<'a, 'b> Extend<UriMapping<'b>> for CheckedTarget<'a> {
fn extend<T>(&mut self, iterable: T) where T: IntoIterator<Item=UriMapping<'b>> {
for (prefix, uri) in iterable {
self.0.put_checked(prefix, uri);
}
}
}