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
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
/* Copyright 2016 The encode_unicode Developers
 *
 * Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
 * http://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.
 */

use utf8_char::Utf8Char;
use errors::EmptyStrError;
extern crate core;
use self::core::{mem, u32, u64};
use self::core::ops::Not;
use self::core::fmt;
use self::core::borrow::Borrow;
#[cfg(feature="std")]
use std::io::{Read, Error as ioError};



/// Read or iterate over the bytes of the UTF-8 representation of a codepoint.
#[derive(Clone)]
pub struct Utf8Iterator (u32);

impl From<Utf8Char> for Utf8Iterator {
    fn from(uc: Utf8Char) -> Self {
        let used = u32::from_le(unsafe{ mem::transmute(uc.to_array().0) });
        // uses u64 because shifting an u32 by 32 bits is a no-op.
        let unused_set = (u64::MAX  <<  uc.len() as u64*8) as u32;
        Utf8Iterator(used | unused_set)
    }
}
impl From<char> for Utf8Iterator {
    fn from(c: char) -> Self {
        Self::from(Utf8Char::from(c))
    }
}
impl Iterator for Utf8Iterator {
    type Item=u8;
    fn next(&mut self) -> Option<u8> {
        let next = self.0 as u8;
        if next == 0xff {
            None
        } else {
            self.0 = (self.0 >> 8)  |  0xff_00_00_00;
            Some(next)
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.len(),  Some(self.len()))
    }
}
impl ExactSizeIterator for Utf8Iterator {
    fn len(&self) -> usize {// not straightforward, but possible
        let unused_bytes = self.0.not().leading_zeros() / 8;
        4 - unused_bytes as usize
    }
}
#[cfg(feature="std")]
impl Read for Utf8Iterator {
    /// Always returns Ok
    fn read(&mut self,  buf: &mut[u8]) -> Result<usize, ioError> {
        // Cannot call self.next() until I know I can write the result.
        for (i, dst) in buf.iter_mut().enumerate() {
            match self.next() {
                Some(b) => *dst = b,
                None    => return Ok(i),
            }
        }
        Ok(buf.len())
    }
}
impl fmt::Debug for Utf8Iterator {
    fn fmt(&self,  fmtr: &mut fmt::Formatter) -> fmt::Result {
        let mut content = [0; 4];
        let mut i = 0;
        for b in self.clone() {
            content[i] = b;
            i += 1;
        }
        write!(fmtr, "{:?}", &content[..i])
    }
}



/// Converts an iterator of `Utf8Char` (or `&Utf8Char`)
/// to an iterator of `u8`s.  
/// Is equivalent to calling `.flat_map()` on the original iterator,
/// but the returned iterator is ~40% faster.
///
/// The iterator also implements `Read` (if the `std` feature isn't disabled).
/// Reading will never produce an error, and calls to `.read()` and `.next()`
/// can be mixed.
///
/// The exact number of bytes cannot be known in advance, but `size_hint()`
/// gives the possible range.
/// (min: all remaining characters are ASCII, max: all require four bytes)
///
/// # Examples
///
/// From iterator of values:
///
/// ```
/// use encode_unicode::{iter_bytes, CharExt};
///
/// let iterator = "foo".chars().map(|c| c.to_utf8() );
/// let mut bytes = [0; 4];
/// for (u,dst) in iter_bytes(iterator).zip(&mut bytes) {*dst=u;}
/// assert_eq!(&bytes, b"foo\0");
/// ```
///
/// From iterator of references:
///
#[cfg_attr(feature="std", doc=" ```")]
#[cfg_attr(not(feature="std"), doc=" ```no_compile")]
/// use encode_unicode::{iter_bytes, CharExt, Utf8Char};
///
/// let chars: Vec<Utf8Char> = "💣 bomb 💣".chars().map(|c| c.to_utf8() ).collect();
/// let bytes: Vec<u8> = iter_bytes(&chars).collect();
/// let flat_map: Vec<u8> = chars.iter().flat_map(|u8c| *u8c ).collect();
/// assert_eq!(bytes, flat_map);
/// ```
///
/// `Read`ing from it:
///
#[cfg_attr(feature="std", doc=" ```")]
#[cfg_attr(not(feature="std"), doc=" ```no_compile")]
/// use encode_unicode::{iter_bytes, CharExt};
/// use std::io::Read;
///
/// let s = "Ååh‽";
/// assert_eq!(s.len(), 8);
/// let mut buf = [b'E'; 9];
/// let mut reader = iter_bytes(s.chars().map(|c| c.to_utf8() ));
/// assert_eq!(reader.read(&mut buf[..]).unwrap(), 8);
/// assert_eq!(reader.read(&mut buf[..]).unwrap(), 0);
/// assert_eq!(&buf[..8], s.as_bytes());
/// assert_eq!(buf[8], b'E');
/// ```
pub fn iter_bytes<U:Borrow<Utf8Char>, I:IntoIterator<Item=U>>
(iterable: I) -> Utf8CharSplitter<U, I::IntoIter> {
    Utf8CharSplitter{ inner: iterable.into_iter(),  prev: 0 }
}

/// The iterator type returned by `iter_bytes()`
///
/// See its documentation for details.
#[derive(Clone)]
pub struct Utf8CharSplitter<U:Borrow<Utf8Char>, I:Iterator<Item=U>> {
    inner: I,
    prev: u32,
}
impl<I:Iterator<Item=Utf8Char>> From<I> for Utf8CharSplitter<Utf8Char,I> {
    /// A less generic constructor than `iter_bytes()`
    fn from(iter: I) -> Self {
        iter_bytes(iter)
    }
}
impl<U:Borrow<Utf8Char>, I:Iterator<Item=U>> Utf8CharSplitter<U,I> {
    /// Extracts the source iterator.
    ///
    /// Note that `iter_bytes(iter.into_inner())` is not a no-op:  
    /// If the last returned byte from `next()` was not an ASCII by,
    /// the remaining bytes of that codepoint is lost.
    pub fn into_inner(self) -> I {
        self.inner
    }
}
impl<U:Borrow<Utf8Char>, I:Iterator<Item=U>> Iterator for Utf8CharSplitter<U,I> {
    type Item = u8;
    fn next(&mut self) -> Option<Self::Item> {
        if self.prev == 0 {
            self.inner.next().map(|u8c| {
                let array = u8c.borrow().to_array().0;
                self.prev = unsafe{ u32::from_le(mem::transmute(array)) } >> 8;
                array[0]
            })
        } else {
            let next = self.prev as u8;
            self.prev >>= 8;
            Some(next)
        }
    }
    fn size_hint(&self) -> (usize,Option<usize>) {
        // Doesn't need to handle unlikely overflows correctly because
        // size_hint() cannot be relied upon anyway. (the trait isn't unsafe)
        let (min, max) = self.inner.size_hint();
        let add = 4 - (self.prev.leading_zeros() / 8) as usize;
        (min.wrapping_add(add), max.map(|max| max.wrapping_mul(4).wrapping_add(add) ))
    }
}
#[cfg(feature="std")]
impl<U:Borrow<Utf8Char>, I:Iterator<Item=U>> Read for Utf8CharSplitter<U,I> {
    /// Always returns `Ok`
    fn read(&mut self,  buf: &mut[u8]) -> Result<usize, ioError> {
        let mut i = 0;
        // write remaining bytes of previous codepoint
        while self.prev != 0  &&  i < buf.len() {
            buf[i] = self.prev as u8;
            self.prev >>= 8;
            i += 1;
        }
        // write whole characters
        while i < buf.len() {
            let bytes = match self.inner.next() {
                Some(u8c) => u8c.borrow().to_array().0,
                None => break
            };
            buf[i] = bytes[0];
            i += 1;
            if bytes[1] != 0 {
                let len = bytes[0].not().leading_zeros() as usize;
                let mut written = 1;
                while written < len {
                    if i < buf.len() {
                        buf[i] = bytes[written];
                        i += 1;
                        written += 1;
                    } else {
                        let bytes_as_u32 = unsafe{ u32::from_le(mem::transmute(bytes)) };
                        self.prev = bytes_as_u32 >> (8*written);
                        return Ok(i);
                    }
                }
            }
        }
        Ok(i)
    }
}



/// An iterator over the `Utf8Char` of a string slice, and their positions.
///
/// This struct is created by the `utf8char_indices() method from [`StrExt`] trait. See its documentation for more.
#[derive(Clone)]
pub struct Utf8CharIndices<'a>{
    str: &'a str,
    index: usize,
}
impl<'a> From<&'a str> for Utf8CharIndices<'a> {
    fn from(s: &str) -> Utf8CharIndices {
        Utf8CharIndices{str: s, index: 0}
    }
}
impl<'a> Utf8CharIndices<'a> {
    /// Extract the remainder of the source `str`.
    ///
    /// # Examples
    ///
    /// ```
    /// use encode_unicode::{StrExt, Utf8Char};
    /// let mut iter = "abc".utf8char_indices();
    /// assert_eq!(iter.next_back(), Some((2, Utf8Char::from('c'))));
    /// assert_eq!(iter.next(), Some((0, Utf8Char::from('a'))));
    /// assert_eq!(iter.as_str(), "b");
    /// ```
    pub fn as_str(&self) -> &'a str {
        &self.str[self.index..]
    }
}
impl<'a> Iterator for Utf8CharIndices<'a> {
    type Item = (usize,Utf8Char);
    fn next(&mut self) -> Option<(usize,Utf8Char)> {
        match Utf8Char::from_str_start(&self.str[self.index..]) {
            Ok((u8c, len)) => {
                let item = (self.index, u8c);
                self.index += len;
                Some(item)
            },
            Err(EmptyStrError) => None
        }
    }
    fn size_hint(&self) -> (usize,Option<usize>) {
        let len = self.str.len() - self.index;
        // For len+3 to overflow, the slice must fill all but two bytes of
        // addressable memory, and size_hint() doesn't need to be correct.
        (len.wrapping_add(3)/4, Some(len))
    }
}
impl<'a> DoubleEndedIterator for Utf8CharIndices<'a> {
    fn next_back(&mut self) -> Option<(usize,Utf8Char)> {
        // Cannot refactor out the unwrap without switching to ::from_slice()
        // since slicing the str panics if not on a boundary.
        if self.index < self.str.len() {
            let rev = self.str.bytes().rev();
            let len = 1 + rev.take_while(|b| b & 0b1100_0000 == 0b1000_0000 ).count();
            let starts = self.str.len() - len;
            let (u8c,_) = Utf8Char::from_str_start(&self.str[starts..]).unwrap();
            self.str = &self.str[..starts];
            Some((starts, u8c))
        } else {
            None
        }
    }
}
impl<'a> fmt::Debug for Utf8CharIndices<'a> {
    fn fmt(&self,  fmtr: &mut fmt::Formatter) -> fmt::Result {
        fmtr.debug_tuple("Utf8CharIndices")
            .field(&self.index)
            .field(&self.as_str())
            .finish()
    }
}


/// An iterator over the codepoints in a `str` represented as `Utf8Char`.
#[derive(Clone)]
pub struct Utf8Chars<'a>(Utf8CharIndices<'a>);
impl<'a> From<&'a str> for Utf8Chars<'a> {
    fn from(s: &str) -> Utf8Chars {
        Utf8Chars(Utf8CharIndices::from(s))
    }
}
impl<'a> Utf8Chars<'a> {
    /// Extract the remainder of the source `str`.
    ///
    /// # Examples
    ///
    /// ```
    /// use encode_unicode::{StrExt, Utf8Char};
    /// let mut iter = "abc".utf8chars();
    /// assert_eq!(iter.next(), Some(Utf8Char::from('a')));
    /// assert_eq!(iter.next_back(), Some(Utf8Char::from('c')));
    /// assert_eq!(iter.as_str(), "b");
    /// ```
    pub fn as_str(&self) -> &'a str {
        self.0.as_str()
    }
}
impl<'a> Iterator for Utf8Chars<'a> {
    type Item = Utf8Char;
    fn next(&mut self) -> Option<Utf8Char> {
        self.0.next().map(|(_,u8c)| u8c )
    }
    fn size_hint(&self) -> (usize,Option<usize>) {
        self.0.size_hint()
    }
}
impl<'a> DoubleEndedIterator for Utf8Chars<'a> {
    fn next_back(&mut self) -> Option<Utf8Char> {
        self.0.next_back().map(|(_,u8c)| u8c )
    }
}
impl<'a> fmt::Debug for Utf8Chars<'a> {
    fn fmt(&self,  fmtr: &mut fmt::Formatter) -> fmt::Result {
        fmtr.debug_tuple("Utf8CharIndices")
            .field(&self.as_str())
            .finish()
    }
}