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use core::fmt;
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
escape::unescape,
parse::check_suffix,
};
/// A (single) byte literal, e.g. `b'k'` or `b'!'`.
///
/// See [the reference][ref] for more information.
///
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ByteLit<B: Buffer> {
raw: B,
/// Start index of the suffix or `raw.len()` if there is no suffix.
start_suffix: usize,
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));
}
let (value, start_suffix) = parse_impl(&input)?;
Ok(Self { raw: input, value, start_suffix })
}
/// Returns the byte value that this literal represents.
pub fn value(&self) -> u8 {
self.value
}
/// The optional suffix. Returns `""` if the suffix is empty/does not exist.
pub fn suffix(&self) -> &str {
&(*self.raw)[self.start_suffix..]
}
/// Returns the raw input that was passed to `parse`.
pub fn raw_input(&self) -> &str {
&self.raw
}
/// Returns the raw input that was passed to `parse`, potentially owned.
pub fn into_raw_input(self) -> B {
self.raw
}
}
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(),
start_suffix: self.start_suffix,
value: self.value,
}
}
}
impl<B: Buffer> fmt::Display for ByteLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(&self.raw)
}
}
/// Precondition: must start with `b'`.
#[inline(never)]
pub(crate) fn parse_impl(input: &str) -> Result<(u8, usize), ParseError> {
let input_bytes = input.as_bytes();
let first = input_bytes.get(2).ok_or(perr(None, UnterminatedByteLiteral))?;
let (c, len) = match first {
b'\'' if input_bytes.get(3) == Some(&b'\'') => return Err(perr(2, UnescapedSingleQuote)),
b'\'' => return Err(perr(None, EmptyByteLiteral)),
b'\n' | b'\t' | b'\r' => return Err(perr(2, UnescapedSpecialWhitespace)),
b'\\' => unescape::<u8>(&input[2..], 2)?,
other if other.is_ascii() => (*other, 1),
_ => return Err(perr(2, NonAsciiInByteLiteral)),
};
match input[2 + len..].find('\'') {
Some(0) => {}
Some(_) => return Err(perr(None, OverlongByteLiteral)),
None => return Err(perr(None, UnterminatedByteLiteral)),
}
let start_suffix = 2 + len + 1;
let suffix = &input[start_suffix..];
check_suffix(suffix).map_err(|kind| perr(start_suffix, kind))?;
Ok((c, start_suffix))
}
#[cfg(test)]
mod tests;