1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
|
use crate::Error;
use proc_macro2::{Delimiter, Ident, Literal, Span, TokenStream, TokenTree};
use std::char;
macro_rules! unexpected_content {
() => {
"expected one of: byte string literal, string literal, identifier"
};
}
pub(crate) fn parse_input(mut input: TokenStream) -> Result<(Vec<u8>, Span), Error> {
loop {
let mut tokens = input.into_iter();
let token = match tokens.next() {
Some(token) => token,
None => {
return Err(Error(
Span::call_site(),
concat!("unexpected end of input, ", unexpected_content!()),
))
}
};
let span = token.span();
let result = match token {
// Unwrap any empty group which may be created from macro expansion.
TokenTree::Group(group) if group.delimiter() == Delimiter::None => Err(group),
TokenTree::Literal(literal) => match parse_literal(literal) {
Ok(result) => Ok(result),
Err(msg) => return Err(Error(span, msg)),
},
TokenTree::Ident(ident) => Ok(parse_ident(ident)),
_ => return Err(Error(span, unexpected_content!())),
};
if let Some(token) = tokens.next() {
return Err(Error(token.span(), "unexpected token"));
}
match result {
Ok(result) => return Ok((result, span)),
Err(group) => input = group.stream(),
}
}
}
fn parse_literal(literal: Literal) -> Result<Vec<u8>, &'static str> {
let s = literal.to_string();
let s = s.as_bytes();
match s[0] {
b'"' => Ok(parse_cooked_content(s)),
b'r' => Ok(parse_raw_content(&s[1..])),
b'b' => match s[1] {
b'"' => Ok(parse_cooked_content(&s[1..])),
b'r' => Ok(parse_raw_content(&s[2..])),
_ => Err(unexpected_content!()),
},
_ => Err(unexpected_content!()),
}
}
fn all_pounds(bytes: &[u8]) -> bool {
bytes.iter().all(|b| *b == b'#')
}
/// Parses raw string / bytes content after `r` prefix.
fn parse_raw_content(s: &[u8]) -> Vec<u8> {
let q_start = s.iter().position(|b| *b == b'"').unwrap();
let q_end = s.iter().rposition(|b| *b == b'"').unwrap();
assert!(all_pounds(&s[0..q_start]));
assert!(all_pounds(&s[q_end + 1..q_end + q_start + 1]));
Vec::from(&s[q_start + 1..q_end])
}
/// Parses the cooked string / bytes content within quotes.
fn parse_cooked_content(mut s: &[u8]) -> Vec<u8> {
s = &s[1..s.iter().rposition(|b| *b == b'"').unwrap()];
let mut result = Vec::new();
while !s.is_empty() {
match s[0] {
b'\\' => {}
b'\r' => {
assert_eq!(s[1], b'\n');
result.push(b'\n');
s = &s[2..];
continue;
}
b => {
result.push(b);
s = &s[1..];
continue;
}
}
let b = s[1];
s = &s[2..];
match b {
b'x' => {
let (b, rest) = backslash_x(s);
result.push(b);
s = rest;
}
b'u' => {
let (c, rest) = backslash_u(s);
result.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes());
s = rest;
}
b'n' => result.push(b'\n'),
b'r' => result.push(b'\r'),
b't' => result.push(b'\t'),
b'\\' => result.push(b'\\'),
b'0' => result.push(b'\0'),
b'\'' => result.push(b'\''),
b'"' => result.push(b'"'),
b'\r' | b'\n' => {
let next = s.iter().position(|b| {
let ch = char::from_u32(u32::from(*b)).unwrap();
!ch.is_whitespace()
});
match next {
Some(pos) => s = &s[pos..],
None => s = b"",
}
}
b => panic!("unexpected byte {:?} after \\", b),
}
}
result
}
fn backslash_x(s: &[u8]) -> (u8, &[u8]) {
let ch = hex_to_u8(s[0]) * 0x10 + hex_to_u8(s[1]);
(ch, &s[2..])
}
fn hex_to_u8(b: u8) -> u8 {
match b {
b'0'..=b'9' => b - b'0',
b'a'..=b'f' => b - b'a' + 10,
b'A'..=b'F' => b - b'A' + 10,
_ => unreachable!("unexpected non-hex character {:?} after \\x", b),
}
}
fn backslash_u(s: &[u8]) -> (char, &[u8]) {
assert_eq!(s[0], b'{');
let end = s[1..].iter().position(|b| *b == b'}').unwrap();
let mut ch = 0;
for b in &s[1..=end] {
ch *= 0x10;
ch += u32::from(hex_to_u8(*b));
}
(char::from_u32(ch).unwrap(), &s[end + 2..])
}
fn parse_ident(ident: Ident) -> Vec<u8> {
ident.to_string().into_bytes()
}
#[cfg(test)]
mod tests {
use super::*;
use std::str::FromStr;
// Tests below were modified from
// https://github.com/dtolnay/syn/blob/cd5fdc0f530f822446fccaf831669cd0cf4a0fc9/tests/test_lit.rs
fn lit(s: &str) -> Vec<u8> {
match TokenStream::from_str(s)
.unwrap()
.into_iter()
.next()
.unwrap()
{
TokenTree::Literal(lit) => parse_literal(lit).unwrap(),
_ => panic!(),
}
}
#[test]
fn strings() {
#[track_caller]
fn test_string(s: &str, value: &[u8]) {
assert_eq!(lit(s), value);
}
test_string("\"a\"", b"a");
test_string("\"\\n\"", b"\n");
test_string("\"\\r\"", b"\r");
test_string("\"\\t\"", b"\t");
test_string("\"🐕\"", b"\xf0\x9f\x90\x95"); // NOTE: This is an emoji
test_string("\"\\\"\"", b"\"");
test_string("\"'\"", b"'");
test_string("\"\"", b"");
test_string("\"\\u{1F415}\"", b"\xf0\x9f\x90\x95");
test_string(
"\"contains\nnewlines\\\nescaped newlines\"",
b"contains\nnewlinesescaped newlines",
);
test_string("r\"raw\nstring\\\nhere\"", b"raw\nstring\\\nhere");
test_string("\"...\"q", b"...");
test_string("r\"...\"q", b"...");
test_string("r##\"...\"##q", b"...");
}
#[test]
fn byte_strings() {
#[track_caller]
fn test_byte_string(s: &str, value: &[u8]) {
assert_eq!(lit(s), value);
}
test_byte_string("b\"a\"", b"a");
test_byte_string("b\"\\n\"", b"\n");
test_byte_string("b\"\\r\"", b"\r");
test_byte_string("b\"\\t\"", b"\t");
test_byte_string("b\"\\\"\"", b"\"");
test_byte_string("b\"'\"", b"'");
test_byte_string("b\"\"", b"");
test_byte_string(
"b\"contains\nnewlines\\\nescaped newlines\"",
b"contains\nnewlinesescaped newlines",
);
test_byte_string("br\"raw\nstring\\\nhere\"", b"raw\nstring\\\nhere");
test_byte_string("b\"...\"q", b"...");
test_byte_string("br\"...\"q", b"...");
test_byte_string("br##\"...\"##q", b"...");
}
}
|
