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

// Copyright 2017 The UNIC Project Developers.
//
// See the COPYRIGHT file at the top-level directory of this distribution.
//
// 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.

use core::{char, ops};

use {step, CharRange};

const SURROGATE_RANGE: ops::Range<u32> = 0xD800..0xE000;

/// An iterator over a range of unicode code points.
///
/// Constructed via `CharRange::iter`. See `CharRange` for more information.
#[derive(Clone, Debug)]
pub struct CharIter {
    /// The lowest uniterated character (inclusive).
    ///
    /// Iteration is finished if this is higher than `high`.
    low: char,

    /// The highest uniterated character (inclusive).
    ///
    /// Iteration is finished if this is lower than `low`.
    high: char,
}

impl From<CharRange> for CharIter {
    fn from(range: CharRange) -> CharIter {
        CharIter {
            low: range.low,
            high: range.high,
        }
    }
}

impl From<CharIter> for CharRange {
    fn from(iter: CharIter) -> CharRange {
        CharRange {
            low: iter.low,
            high: iter.high,
        }
    }
}

impl CharIter {
    #[inline]
    #[allow(unsafe_code)]
    // When stepping `self.low` forward would go over `char::MAX`,
    // Set `self.high` to `'\0'` instead. It will have the same effect --
    // consuming the last element from the iterator and ending iteration.
    fn step_forward(&mut self) {
        if self.low == char::MAX {
            self.high = '\0'
        } else {
            self.low = unsafe { step::forward(self.low) }
        }
    }

    #[inline]
    #[allow(unsafe_code)]
    // When stepping `self.high` backward would cause underflow,
    // set `self.low` to `char::MAX` instead. It will have the same effect --
    // consuming the last element from the iterator and ending iteration.
    fn step_backward(&mut self) {
        if self.high == '\0' {
            self.low = char::MAX;
        } else {
            self.high = unsafe { step::backward(self.high) }
        }
    }

    #[inline]
    /// ExactSizeIterator::is_empty() for stable
    fn is_finished(&self) -> bool {
        self.low > self.high
    }
}

impl Iterator for CharIter {
    type Item = char;

    #[inline]
    fn next(&mut self) -> Option<char> {
        if self.is_finished() {
            return None;
        }

        let ch = self.low;
        self.step_forward();
        Some(ch)
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len();
        (len, Some(len))
    }

    fn last(self) -> Option<char> {
        if self.is_finished() {
            None
        } else {
            Some(self.high)
        }
    }

    fn max(self) -> Option<char> {
        self.last()
    }

    fn min(mut self) -> Option<char> {
        self.next()
    }
}

impl DoubleEndedIterator for CharIter {
    #[inline]
    fn next_back(&mut self) -> Option<Self::Item> {
        if self.is_finished() {
            None
        } else {
            let ch = self.high;
            self.step_backward();
            Some(ch)
        }
    }
}

impl ExactSizeIterator for CharIter {
    fn len(&self) -> usize {
        if self.is_finished() {
            return 0;
        }
        let naive_range = (self.low as u32)..(self.high as u32 + 1);
        if naive_range.start <= SURROGATE_RANGE.start && SURROGATE_RANGE.end <= naive_range.end {
            naive_range.len() - SURROGATE_RANGE.len()
        } else {
            naive_range.len()
        }
    }

    #[cfg(feature = "exact-size-is-empty")]
    fn is_empty(&self) -> bool {
        self.is_finished()
    }
}