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#[derive(Clone, Copy, Eq, PartialEq)]
enum State {
/// The state after seeing a `\`.
Escape,
/// The state after seeing a `\x`.
HexFirst,
/// The state after seeing a `\x[0-9A-Fa-f]`.
HexSecond(char),
/// Default state.
Literal,
}
pub fn unescape(s: &str) -> Vec<u8> {
use self::State::*;
let mut bytes = vec![];
let mut state = Literal;
for c in s.chars() {
match state {
Escape => {
match c {
'\\' => { bytes.push(b'\\'); state = Literal; }
'n' => { bytes.push(b'\n'); state = Literal; }
'r' => { bytes.push(b'\r'); state = Literal; }
't' => { bytes.push(b'\t'); state = Literal; }
'x' => { state = HexFirst; }
c => {
bytes.extend(format!(r"\{}", c).into_bytes());
state = Literal;
}
}
}
HexFirst => {
match c {
'0'...'9' | 'A'...'F' | 'a'...'f' => {
state = HexSecond(c);
}
c => {
bytes.extend(format!(r"\x{}", c).into_bytes());
state = Literal;
}
}
}
HexSecond(first) => {
match c {
'0'...'9' | 'A'...'F' | 'a'...'f' => {
let ordinal = format!("{}{}", first, c);
let byte = u8::from_str_radix(&ordinal, 16).unwrap();
bytes.push(byte);
state = Literal;
}
c => {
let original = format!(r"\x{}{}", first, c);
bytes.extend(original.into_bytes());
state = Literal;
}
}
}
Literal => {
match c {
'\\' => { state = Escape; }
c => { bytes.extend(c.to_string().as_bytes()); }
}
}
}
}
match state {
Escape => bytes.push(b'\\'),
HexFirst => bytes.extend(b"\\x"),
HexSecond(c) => bytes.extend(format!("\\x{}", c).into_bytes()),
Literal => {}
}
bytes
}