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use core::fmt;
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
escape::unescape,
};
/// A (single) byte literal, e.g. `b'k'` or `b'!'`.
///
/// See [the reference][ref] for more information.
///
/// [ref]: https://doc.rust-lang.org/reference/tokens.html#byte-literals
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ByteLit<B: Buffer> {
raw: B,
value: u8,
}
impl<B: Buffer> ByteLit<B> {
/// Parses the input as a byte literal. Returns an error if the input is
/// invalid or represents a different kind of literal.
pub fn parse(input: B) -> Result<Self, ParseError> {
if input.is_empty() {
return Err(perr(None, Empty));
}
if !input.starts_with("b'") {
return Err(perr(None, InvalidByteLiteralStart));
}
Self::parse_impl(input)
}
/// Returns the byte value that this literal represents.
pub fn value(&self) -> u8 {
self.value
}
/// Precondition: must start with `b'`.
pub(crate) fn parse_impl(input: B) -> Result<Self, ParseError> {
if input.len() == 2 {
return Err(perr(None, UnterminatedByteLiteral));
}
if *input.as_bytes().last().unwrap() != b'\'' {
return Err(perr(None, UnterminatedByteLiteral));
}
let inner = &input[2..input.len() - 1];
let first = inner.as_bytes().get(0).ok_or(perr(None, EmptyByteLiteral))?;
let (c, len) = match first {
b'\'' => return Err(perr(2, UnescapedSingleQuote)),
b'\n' | b'\t' | b'\r'
=> return Err(perr(2, UnescapedSpecialWhitespace)),
b'\\' => unescape::<u8>(inner, 2)?,
other if other.is_ascii() => (*other, 1),
_ => return Err(perr(2, NonAsciiInByteLiteral)),
};
let rest = &inner[len..];
if !rest.is_empty() {
return Err(perr(len + 2..input.len() - 1, OverlongByteLiteral));
}
Ok(Self {
raw: input,
value: c,
})
}
}
impl ByteLit<&str> {
/// Makes a copy of the underlying buffer and returns the owned version of
/// `Self`.
pub fn to_owned(&self) -> ByteLit<String> {
ByteLit {
raw: self.raw.to_owned(),
value: self.value,
}
}
}
impl<B: Buffer> fmt::Display for ByteLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(&self.raw)
}
}
#[cfg(test)]
mod tests;
|
