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|
//! Contains functions for performing XML special characters escaping.
use std::{borrow::Cow, marker::PhantomData, fmt::{Display, Result, Formatter}};
pub(crate) trait Escapes {
fn escape(c: u8) -> Option<&'static str>;
fn byte_needs_escaping(c: u8) -> bool {
Self::escape(c).is_some()
}
fn str_needs_escaping(s: &str) -> bool {
s.bytes().any(|c| Self::escape(c).is_some())
}
}
pub(crate) struct Escaped<'a, E: Escapes> {
_escape_phantom: PhantomData<E>,
to_escape: &'a str,
}
impl<'a, E: Escapes> Escaped<'a, E> {
pub fn new(s: &'a str) -> Self {
Escaped {
_escape_phantom: PhantomData,
to_escape: s,
}
}
}
impl<'a, E: Escapes> Display for Escaped<'a, E> {
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
let mut total_remaining = self.to_escape;
// find the next occurence
while let Some(n) = total_remaining
.bytes()
.position(E::byte_needs_escaping)
{
let (start, remaining) = total_remaining.split_at(n);
f.write_str(start)?;
// unwrap is safe because we checked is_some for position n earlier
let next_byte = remaining.bytes().next().unwrap();
let replacement = E::escape(next_byte).unwrap();
f.write_str(replacement)?;
total_remaining = &remaining[1..];
}
f.write_str(total_remaining)
}
}
fn escape_str<E: Escapes>(s: &str) -> Cow<'_, str> {
if E::str_needs_escaping(s) {
Cow::Owned(format!("{}", Escaped::<E>::new(s)))
} else {
Cow::Borrowed(s)
}
}
macro_rules! escapes {
{
$name: ident,
$($k: expr => $v: expr),* $(,)?
} => {
pub(crate) struct $name;
impl Escapes for $name {
fn escape(c: u8) -> Option<&'static str> {
match c {
$( $k => Some($v),)*
_ => None
}
}
}
};
}
escapes!(
AttributeEscapes,
b'<' => "<",
b'>' => ">",
b'"' => """,
b'\'' => "'",
b'&' => "&",
b'\n' => "
",
b'\r' => "
",
);
escapes!(
PcDataEscapes,
b'<' => "<",
b'&' => "&",
);
/// Performs escaping of common XML characters inside an attribute value.
///
/// This function replaces several important markup characters with their
/// entity equivalents:
///
/// * `<` → `<`
/// * `>` → `>`
/// * `"` → `"`
/// * `'` → `'`
/// * `&` → `&`
///
/// The following characters are escaped so that attributes are printed on
/// a single line:
/// * `\n` → `
`
/// * `\r` → `
`
///
/// The resulting string is safe to use inside XML attribute values or in PCDATA sections.
///
/// Does not perform allocations if the given string does not contain escapable characters.
#[inline]
#[must_use]
pub fn escape_str_attribute(s: &str) -> Cow<'_, str> {
escape_str::<AttributeEscapes>(s)
}
/// Performs escaping of common XML characters inside PCDATA.
///
/// This function replaces several important markup characters with their
/// entity equivalents:
///
/// * `<` → `<`
/// * `&` → `&`
///
/// The resulting string is safe to use inside PCDATA sections but NOT inside attribute values.
///
/// Does not perform allocations if the given string does not contain escapable characters.
#[inline]
#[must_use]
pub fn escape_str_pcdata(s: &str) -> Cow<'_, str> {
escape_str::<PcDataEscapes>(s)
}
#[cfg(test)]
mod tests {
use super::{escape_str_attribute, escape_str_pcdata};
#[test]
fn test_escape_str_attribute() {
assert_eq!(escape_str_attribute("<>'\"&\n\r"), "<>'"&

");
assert_eq!(escape_str_attribute("no_escapes"), "no_escapes");
}
#[test]
fn test_escape_str_pcdata() {
assert_eq!(escape_str_pcdata("<&"), "<&");
assert_eq!(escape_str_pcdata("no_escapes"), "no_escapes");
}
#[test]
fn test_escape_multibyte_code_points() {
assert_eq!(escape_str_attribute("☃<"), "☃<");
assert_eq!(escape_str_pcdata("☃<"), "☃<");
}
}
|
