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
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! UTF-8 and UTF-16 decoding iterators

use fmt;
use iter::FusedIterator;
use super::from_u32_unchecked;

/// An iterator over an iterator of bytes of the characters the bytes represent
/// as UTF-8
#[unstable(feature = "decode_utf8", issue = "33906")]
#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
#[derive(Clone, Debug)]
#[allow(deprecated)]
pub struct DecodeUtf8<I: Iterator<Item = u8>>(::iter::Peekable<I>);

/// Decodes an `Iterator` of bytes as UTF-8.
#[unstable(feature = "decode_utf8", issue = "33906")]
#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
#[allow(deprecated)]
#[inline]
pub fn decode_utf8<I: IntoIterator<Item = u8>>(i: I) -> DecodeUtf8<I::IntoIter> {
    DecodeUtf8(i.into_iter().peekable())
}

/// `<DecodeUtf8 as Iterator>::next` returns this for an invalid input sequence.
#[unstable(feature = "decode_utf8", issue = "33906")]
#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
#[derive(PartialEq, Eq, Debug)]
#[allow(deprecated)]
pub struct InvalidSequence(());

#[unstable(feature = "decode_utf8", issue = "33906")]
#[allow(deprecated)]
impl<I: Iterator<Item = u8>> Iterator for DecodeUtf8<I> {
    type Item = Result<char, InvalidSequence>;
    #[inline]

    fn next(&mut self) -> Option<Result<char, InvalidSequence>> {
        self.0.next().map(|first_byte| {
            // Emit InvalidSequence according to
            // Unicode §5.22 Best Practice for U+FFFD Substitution
            // http://www.unicode.org/versions/Unicode9.0.0/ch05.pdf#G40630

            // Roughly: consume at least one byte,
            // then validate one byte at a time and stop before the first unexpected byte
            // (which might be the valid start of the next byte sequence).

            let mut code_point;
            macro_rules! first_byte {
                ($mask: expr) => {
                    code_point = u32::from(first_byte & $mask)
                }
            }
            macro_rules! continuation_byte {
                () => { continuation_byte!(0x80..=0xBF) };
                ($range: pat) => {
                    match self.0.peek() {
                        Some(&byte @ $range) => {
                            code_point = (code_point << 6) | u32::from(byte & 0b0011_1111);
                            self.0.next();
                        }
                        _ => return Err(InvalidSequence(()))
                    }
                }
            }

            match first_byte {
                0x00..=0x7F => {
                    first_byte!(0b1111_1111);
                }
                0xC2..=0xDF => {
                    first_byte!(0b0001_1111);
                    continuation_byte!();
                }
                0xE0 => {
                    first_byte!(0b0000_1111);
                    continuation_byte!(0xA0..=0xBF);  // 0x80..=0x9F here are overlong
                    continuation_byte!();
                }
                0xE1..=0xEC | 0xEE..=0xEF => {
                    first_byte!(0b0000_1111);
                    continuation_byte!();
                    continuation_byte!();
                }
                0xED => {
                    first_byte!(0b0000_1111);
                    continuation_byte!(0x80..=0x9F);  // 0xA0..0xBF here are surrogates
                    continuation_byte!();
                }
                0xF0 => {
                    first_byte!(0b0000_0111);
                    continuation_byte!(0x90..=0xBF);  // 0x80..0x8F here are overlong
                    continuation_byte!();
                    continuation_byte!();
                }
                0xF1..=0xF3 => {
                    first_byte!(0b0000_0111);
                    continuation_byte!();
                    continuation_byte!();
                    continuation_byte!();
                }
                0xF4 => {
                    first_byte!(0b0000_0111);
                    continuation_byte!(0x80..=0x8F);  // 0x90..0xBF here are beyond char::MAX
                    continuation_byte!();
                    continuation_byte!();
                }
                _ => return Err(InvalidSequence(()))  // Illegal first byte, overlong, or beyond MAX
            }
            unsafe {
                Ok(from_u32_unchecked(code_point))
            }
        })
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        let (lower, upper) = self.0.size_hint();

        // A code point is at most 4 bytes long.
        let min_code_points = lower / 4;

        (min_code_points, upper)
    }
}

#[unstable(feature = "decode_utf8", issue = "33906")]
#[allow(deprecated)]
impl<I: FusedIterator<Item = u8>> FusedIterator for DecodeUtf8<I> {}

/// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s.
#[stable(feature = "decode_utf16", since = "1.9.0")]
#[derive(Clone, Debug)]
pub struct DecodeUtf16<I>
    where I: Iterator<Item = u16>
{
    iter: I,
    buf: Option<u16>,
}

/// An error that can be returned when decoding UTF-16 code points.
#[stable(feature = "decode_utf16", since = "1.9.0")]
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct DecodeUtf16Error {
    code: u16,
}

/// Create an iterator over the UTF-16 encoded code points in `iter`,
/// returning unpaired surrogates as `Err`s.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::char::decode_utf16;
///
/// fn main() {
///     // 𝄞mus<invalid>ic<invalid>
///     let v = [0xD834, 0xDD1E, 0x006d, 0x0075,
///              0x0073, 0xDD1E, 0x0069, 0x0063,
///              0xD834];
///
///     assert_eq!(decode_utf16(v.iter().cloned())
///                            .map(|r| r.map_err(|e| e.unpaired_surrogate()))
///                            .collect::<Vec<_>>(),
///                vec![Ok('𝄞'),
///                     Ok('m'), Ok('u'), Ok('s'),
///                     Err(0xDD1E),
///                     Ok('i'), Ok('c'),
///                     Err(0xD834)]);
/// }
/// ```
///
/// A lossy decoder can be obtained by replacing `Err` results with the replacement character:
///
/// ```
/// use std::char::{decode_utf16, REPLACEMENT_CHARACTER};
///
/// fn main() {
///     // 𝄞mus<invalid>ic<invalid>
///     let v = [0xD834, 0xDD1E, 0x006d, 0x0075,
///              0x0073, 0xDD1E, 0x0069, 0x0063,
///              0xD834];
///
///     assert_eq!(decode_utf16(v.iter().cloned())
///                    .map(|r| r.unwrap_or(REPLACEMENT_CHARACTER))
///                    .collect::<String>(),
///                "𝄞mus�ic�");
/// }
/// ```
#[stable(feature = "decode_utf16", since = "1.9.0")]
#[inline]
pub fn decode_utf16<I: IntoIterator<Item = u16>>(iter: I) -> DecodeUtf16<I::IntoIter> {
    DecodeUtf16 {
        iter: iter.into_iter(),
        buf: None,
    }
}

#[stable(feature = "decode_utf16", since = "1.9.0")]
impl<I: Iterator<Item = u16>> Iterator for DecodeUtf16<I> {
    type Item = Result<char, DecodeUtf16Error>;

    fn next(&mut self) -> Option<Result<char, DecodeUtf16Error>> {
        let u = match self.buf.take() {
            Some(buf) => buf,
            None => self.iter.next()?
        };

        if u < 0xD800 || 0xDFFF < u {
            // not a surrogate
            Some(Ok(unsafe { from_u32_unchecked(u as u32) }))
        } else if u >= 0xDC00 {
            // a trailing surrogate
            Some(Err(DecodeUtf16Error { code: u }))
        } else {
            let u2 = match self.iter.next() {
                Some(u2) => u2,
                // eof
                None => return Some(Err(DecodeUtf16Error { code: u })),
            };
            if u2 < 0xDC00 || u2 > 0xDFFF {
                // not a trailing surrogate so we're not a valid
                // surrogate pair, so rewind to redecode u2 next time.
                self.buf = Some(u2);
                return Some(Err(DecodeUtf16Error { code: u }));
            }

            // all ok, so lets decode it.
            let c = (((u - 0xD800) as u32) << 10 | (u2 - 0xDC00) as u32) + 0x1_0000;
            Some(Ok(unsafe { from_u32_unchecked(c) }))
        }
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        let (low, high) = self.iter.size_hint();
        // we could be entirely valid surrogates (2 elements per
        // char), or entirely non-surrogates (1 element per char)
        (low / 2, high)
    }
}

impl DecodeUtf16Error {
    /// Returns the unpaired surrogate which caused this error.
    #[stable(feature = "decode_utf16", since = "1.9.0")]
    pub fn unpaired_surrogate(&self) -> u16 {
        self.code
    }
}

#[stable(feature = "decode_utf16", since = "1.9.0")]
impl fmt::Display for DecodeUtf16Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "unpaired surrogate found: {:x}", self.code)
    }
}