1use crate::{
2 BoolLit,
3 Buffer,
4 ByteLit,
5 ByteStringLit,
6 CharLit,
7 ParseError,
8 FloatLit,
9 IntegerLit,
10 Literal,
11 StringLit,
12 err::{perr, ParseErrorKind::{*, self}},
13};
14
15
16pub fn parse<B: Buffer>(input: B) -> Result<Literal<B>, ParseError> {
17 let (first, rest) = input.as_bytes().split_first().ok_or(perr(None, Empty))?;
18 let second = input.as_bytes().get(1).copied();
19
20 match first {
21 b'f' if &*input == "false" => Ok(Literal::Bool(BoolLit::False)),
22 b't' if &*input == "true" => Ok(Literal::Bool(BoolLit::True)),
23
24 // A number literal (integer or float).
25 b'0'..=b'9' => {
26 // To figure out whether this is a float or integer, we do some
27 // quick inspection here. Yes, this is technically duplicate
28 // work with what is happening in the integer/float parse
29 // methods, but it makes the code way easier for now and won't
30 // be a huge performance loss.
31 //
32 // The first non-decimal char in a float literal must
33 // be '.', 'e' or 'E'.
34 match input.as_bytes().get(1 + end_dec_digits(rest)) {
35 Some(b'.') | Some(b'e') | Some(b'E')
36 => FloatLit::parse(input).map(Literal::Float),
37
38 _ => IntegerLit::parse(input).map(Literal::Integer),
39 }
40 },
41
42 b'\'' => CharLit::parse(input).map(Literal::Char),
43 b'"' | b'r' => StringLit::parse(input).map(Literal::String),
44
45 b'b' if second == Some(b'\'') => ByteLit::parse(input).map(Literal::Byte),
46 b'b' if second == Some(b'r') || second == Some(b'"')
47 => ByteStringLit::parse(input).map(Literal::ByteString),
48
49 _ => Err(perr(None, InvalidLiteral)),
50 }
51}
52
53
54pub(crate) fn first_byte_or_empty(s: &str) -> Result<u8, ParseError> {
55 s.as_bytes().get(0).copied().ok_or(err:perr(span:None, kind:Empty))
56}
57
58/// Returns the index of the first non-underscore, non-decimal digit in `input`,
59/// or the `input.len()` if all characters are decimal digits.
60pub(crate) fn end_dec_digits(input: &[u8]) -> usize {
61 input.iter()
62 .position(|b| !matches!(b, b'_' | b'0'..=b'9'))
63 .unwrap_or(default:input.len())
64}
65
66pub(crate) fn hex_digit_value(digit: u8) -> Option<u8> {
67 match digit {
68 b'0'..=b'9' => Some(digit - b'0'),
69 b'a'..=b'f' => Some(digit - b'a' + 10),
70 b'A'..=b'F' => Some(digit - b'A' + 10),
71 _ => None,
72 }
73}
74
75/// Makes sure that `s` is a valid literal suffix.
76pub(crate) fn check_suffix(s: &str) -> Result<(), ParseErrorKind> {
77 if s.is_empty() {
78 return Ok(());
79 }
80
81 let mut chars = s.chars();
82 let first = chars.next().unwrap();
83 let rest = chars.as_str();
84 if first == '_' && rest.is_empty() {
85 return Err(InvalidSuffix);
86 }
87
88 // This is just an extra check to improve the error message. If the first
89 // character of the "suffix" is already some invalid ASCII
90 // char, "unexpected character" seems like the more fitting error.
91 if first.is_ascii() && !(first.is_ascii_alphabetic() || first == '_') {
92 return Err(UnexpectedChar);
93 }
94
95 // Proper check is optional as it's not really necessary in proc macro
96 // context.
97 #[cfg(feature = "check_suffix")]
98 fn is_valid_suffix(first: char, rest: &str) -> bool {
99 use unicode_xid::UnicodeXID;
100
101 (first == '_' || first.is_xid_start())
102 && rest.chars().all(|c| c.is_xid_continue())
103 }
104
105 // When avoiding the dependency on `unicode_xid`, we just do a best effort
106 // to catch the most common errors.
107 #[cfg(not(feature = "check_suffix"))]
108 fn is_valid_suffix(first: char, rest: &str) -> bool {
109 if first.is_ascii() && !(first.is_ascii_alphabetic() || first == '_') {
110 return false;
111 }
112 for c in rest.chars() {
113 if c.is_ascii() && !(c.is_ascii_alphanumeric() || c == '_') {
114 return false;
115 }
116 }
117 true
118 }
119
120 if is_valid_suffix(first, rest) {
121 Ok(())
122 } else {
123 Err(InvalidSuffix)
124 }
125}
126