1 use core::fmt;
2
3 use crate::{
4 Buffer, ParseError,
5 err::{perr, ParseErrorKind::*},
6 escape::unescape,
7 parse::check_suffix,
8 };
9
10
11 /// A (single) byte literal, e.g. `b'k'` or `b'!'`.
12 ///
13 /// See [the reference][ref] for more information.
14 ///
15 /// [ref]: https://doc.rust-lang.org/reference/tokens.html#byte-literals
16 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
17 pub struct ByteLit<B: Buffer> {
18 raw: B,
19 /// Start index of the suffix or `raw.len()` if there is no suffix.
20 start_suffix: usize,
21 value: u8,
22 }
23
24 impl<B: Buffer> ByteLit<B> {
25 /// Parses the input as a byte literal. Returns an error if the input is
26 /// invalid or represents a different kind of literal.
parse(input: B) -> Result<Self, ParseError>27 pub fn parse(input: B) -> Result<Self, ParseError> {
28 if input.is_empty() {
29 return Err(perr(None, Empty));
30 }
31 if !input.starts_with("b'") {
32 return Err(perr(None, InvalidByteLiteralStart));
33 }
34
35 let (value, start_suffix) = parse_impl(&input)?;
36 Ok(Self { raw: input, value, start_suffix })
37 }
38
39 /// Returns the byte value that this literal represents.
value(&self) -> u840 pub fn value(&self) -> u8 {
41 self.value
42 }
43
44 /// The optional suffix. Returns `""` if the suffix is empty/does not exist.
suffix(&self) -> &str45 pub fn suffix(&self) -> &str {
46 &(*self.raw)[self.start_suffix..]
47 }
48
49 /// Returns the raw input that was passed to `parse`.
raw_input(&self) -> &str50 pub fn raw_input(&self) -> &str {
51 &self.raw
52 }
53
54 /// Returns the raw input that was passed to `parse`, potentially owned.
into_raw_input(self) -> B55 pub fn into_raw_input(self) -> B {
56 self.raw
57 }
58
59 }
60
61 impl ByteLit<&str> {
62 /// Makes a copy of the underlying buffer and returns the owned version of
63 /// `Self`.
to_owned(&self) -> ByteLit<String>64 pub fn to_owned(&self) -> ByteLit<String> {
65 ByteLit {
66 raw: self.raw.to_owned(),
67 start_suffix: self.start_suffix,
68 value: self.value,
69 }
70 }
71 }
72
73 impl<B: Buffer> fmt::Display for ByteLit<B> {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result74 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
75 f.pad(&self.raw)
76 }
77 }
78
79 /// Precondition: must start with `b'`.
80 #[inline(never)]
parse_impl(input: &str) -> Result<(u8, usize), ParseError>81 pub(crate) fn parse_impl(input: &str) -> Result<(u8, usize), ParseError> {
82 let input_bytes = input.as_bytes();
83 let first = input_bytes.get(2).ok_or(perr(None, UnterminatedByteLiteral))?;
84 let (c, len) = match first {
85 b'\'' if input_bytes.get(3) == Some(&b'\'') => return Err(perr(2, UnescapedSingleQuote)),
86 b'\'' => return Err(perr(None, EmptyByteLiteral)),
87 b'\n' | b'\t' | b'\r' => return Err(perr(2, UnescapedSpecialWhitespace)),
88 b'\\' => unescape::<u8>(&input[2..], 2)?,
89 other if other.is_ascii() => (*other, 1),
90 _ => return Err(perr(2, NonAsciiInByteLiteral)),
91 };
92
93 match input[2 + len..].find('\'') {
94 Some(0) => {}
95 Some(_) => return Err(perr(None, OverlongByteLiteral)),
96 None => return Err(perr(None, UnterminatedByteLiteral)),
97 }
98
99 let start_suffix = 2 + len + 1;
100 let suffix = &input[start_suffix..];
101 check_suffix(suffix).map_err(|kind| perr(start_suffix, kind))?;
102
103 Ok((c, start_suffix))
104 }
105
106 #[cfg(test)]
107 mod tests;
108