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
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
|
// Copyright Mozilla Foundation
//
// Licensed under the Apache License (Version 2.0), or the MIT license,
// (the "Licenses") at your option. You may not use this file except in
// compliance with one of the Licenses. You may obtain copies of the
// Licenses at:
//
// https://www.apache.org/licenses/LICENSE-2.0
// https://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Licenses is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the Licenses for the specific language governing permissions and
// limitations under the Licenses.
#![no_std]
//! Provides iteration by `char` over `&[u8]` containing potentially-invalid
//! UTF-8 such that errors are handled according to the [WHATWG Encoding
//! Standard](https://encoding.spec.whatwg.org/#utf-8-decoder) (i.e. the same
//! way as in `String::from_utf8_lossy`).
//!
//! The trait `Utf8CharsEx` provides the convenience method `chars()` on
//! byte slices themselves instead of having to use the more verbose
//! `Utf8Chars::new(slice)`.
//!
//! ```rust
//! use utf8_iter::Utf8CharsEx;
//! let data = b"\xFF\xC2\xE2\xE2\x98\xF0\xF0\x9F\xF0\x9F\x92\xE2\x98\x83";
//! let from_iter: String = data.chars().collect();
//! let from_std = String::from_utf8_lossy(data);
//! assert_eq!(from_iter, from_std);
//! ```
mod indices;
pub use crate::indices::Utf8CharIndices;
use core::iter::FusedIterator;
#[repr(align(64))] // Align to cache lines
struct Utf8Data {
pub table: [u8; 384],
}
// This is generated code copied and pasted from utf_8.rs of encoding_rs.
// Please don't edit by hand but instead regenerate as instructed in that
// file.
static UTF8_DATA: Utf8Data = Utf8Data {
table: [
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 84, 148, 148, 148,
148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 164, 164, 164, 164, 164,
164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164,
164, 164, 164, 164, 164, 164, 164, 164, 164, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
252, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 16, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 32, 8, 8, 64, 8, 8, 8, 128, 4,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
],
};
// End manually copypasted generated code.
#[inline(always)]
fn in_inclusive_range8(i: u8, start: u8, end: u8) -> bool {
i.wrapping_sub(start) <= (end - start)
}
/// Iterator by `char` over `&[u8]` that contains
/// potentially-invalid UTF-8. See the crate documentation.
#[derive(Debug, Clone)]
pub struct Utf8Chars<'a> {
remaining: &'a [u8],
}
impl<'a> Utf8Chars<'a> {
#[inline(always)]
/// Creates the iterator from a byte slice.
pub fn new(bytes: &'a [u8]) -> Self {
Utf8Chars::<'a> { remaining: bytes }
}
/// Views the current remaining data in the iterator as a subslice
/// of the original slice.
#[inline(always)]
pub fn as_slice(&self) -> &'a [u8] {
self.remaining
}
#[inline(never)]
fn next_fallback(&mut self) -> Option<char> {
if self.remaining.is_empty() {
return None;
}
let first = self.remaining[0];
if first < 0x80 {
self.remaining = &self.remaining[1..];
return Some(char::from(first));
}
if !in_inclusive_range8(first, 0xC2, 0xF4) || self.remaining.len() == 1 {
self.remaining = &self.remaining[1..];
return Some('\u{FFFD}');
}
let second = self.remaining[1];
let (lower_bound, upper_bound) = match first {
0xE0 => (0xA0, 0xBF),
0xED => (0x80, 0x9F),
0xF0 => (0x90, 0xBF),
0xF4 => (0x80, 0x8F),
_ => (0x80, 0xBF),
};
if !in_inclusive_range8(second, lower_bound, upper_bound) {
self.remaining = &self.remaining[1..];
return Some('\u{FFFD}');
}
if first < 0xE0 {
self.remaining = &self.remaining[2..];
let point = ((u32::from(first) & 0x1F) << 6) | (u32::from(second) & 0x3F);
return Some(unsafe { char::from_u32_unchecked(point) });
}
if self.remaining.len() == 2 {
self.remaining = &self.remaining[2..];
return Some('\u{FFFD}');
}
let third = self.remaining[2];
if !in_inclusive_range8(third, 0x80, 0xBF) {
self.remaining = &self.remaining[2..];
return Some('\u{FFFD}');
}
if first < 0xF0 {
self.remaining = &self.remaining[3..];
let point = ((u32::from(first) & 0xF) << 12)
| ((u32::from(second) & 0x3F) << 6)
| (u32::from(third) & 0x3F);
return Some(unsafe { char::from_u32_unchecked(point) });
}
// At this point, we have a valid 3-byte prefix of a
// four-byte sequence that has to be incomplete, because
// otherwise `next()` would have succeeded.
self.remaining = &self.remaining[3..];
Some('\u{FFFD}')
}
}
impl<'a> Iterator for Utf8Chars<'a> {
type Item = char;
#[inline]
fn next(&mut self) -> Option<char> {
// This loop is only broken out of as goto forward
#[allow(clippy::never_loop)]
loop {
if self.remaining.len() < 4 {
break;
}
let first = self.remaining[0];
if first < 0x80 {
self.remaining = &self.remaining[1..];
return Some(char::from(first));
}
let second = self.remaining[1];
if in_inclusive_range8(first, 0xC2, 0xDF) {
if !in_inclusive_range8(second, 0x80, 0xBF) {
break;
}
let point = ((u32::from(first) & 0x1F) << 6) | (u32::from(second) & 0x3F);
self.remaining = &self.remaining[2..];
return Some(unsafe { char::from_u32_unchecked(point) });
}
// This table-based formulation was benchmark-based in encoding_rs,
// but it hasn't been re-benchmarked in this iterator context.
let third = self.remaining[2];
if first < 0xF0 {
if ((UTF8_DATA.table[usize::from(second)]
& UTF8_DATA.table[usize::from(first) + 0x80])
| (third >> 6))
!= 2
{
break;
}
let point = ((u32::from(first) & 0xF) << 12)
| ((u32::from(second) & 0x3F) << 6)
| (u32::from(third) & 0x3F);
self.remaining = &self.remaining[3..];
return Some(unsafe { char::from_u32_unchecked(point) });
}
let fourth = self.remaining[3];
if (u16::from(
UTF8_DATA.table[usize::from(second)] & UTF8_DATA.table[usize::from(first) + 0x80],
) | u16::from(third >> 6)
| (u16::from(fourth & 0xC0) << 2))
!= 0x202
{
break;
}
let point = ((u32::from(first) & 0x7) << 18)
| ((u32::from(second) & 0x3F) << 12)
| ((u32::from(third) & 0x3F) << 6)
| (u32::from(fourth) & 0x3F);
self.remaining = &self.remaining[4..];
return Some(unsafe { char::from_u32_unchecked(point) });
}
self.next_fallback()
}
}
impl<'a> DoubleEndedIterator for Utf8Chars<'a> {
#[inline]
fn next_back(&mut self) -> Option<char> {
if self.remaining.is_empty() {
return None;
}
let mut attempt = 1;
for b in self.remaining.iter().rev() {
if b & 0xC0 != 0x80 {
let (head, tail) = self.remaining.split_at(self.remaining.len() - attempt);
let mut inner = Utf8Chars::new(tail);
let candidate = inner.next();
if inner.as_slice().is_empty() {
self.remaining = head;
return candidate;
}
break;
}
if attempt == 4 {
break;
}
attempt += 1;
}
self.remaining = &self.remaining[..self.remaining.len() - 1];
Some('\u{FFFD}')
}
}
impl FusedIterator for Utf8Chars<'_> {}
/// Convenience trait that adds `chars()` and `char_indices()` methods
/// similar to the ones on string slices to byte slices.
pub trait Utf8CharsEx {
fn chars(&self) -> Utf8Chars<'_>;
fn char_indices(&self) -> Utf8CharIndices<'_>;
}
impl Utf8CharsEx for [u8] {
/// Convenience method for creating an UTF-8 iterator
/// for the slice.
#[inline]
fn chars(&self) -> Utf8Chars<'_> {
Utf8Chars::new(self)
}
/// Convenience method for creating a byte index and
/// UTF-8 iterator for the slice.
#[inline]
fn char_indices(&self) -> Utf8CharIndices<'_> {
Utf8CharIndices::new(self)
}
}
// No manually-written tests for forward-iteration, because the code passed multiple
// days of fuzzing comparing with known-good behavior.
|
