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


use std::collections::HashMap;
use std::collections::hash_map::{Entry};
use std::hash::Hash;
use std::fmt;

/// An iterator adapter to filter out duplicate elements.
///
/// See [`.unique_by()`](../trait.Itertools.html#method.unique) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct UniqueBy<I: Iterator, V, F> {
    iter: I,
    // Use a hashmap for the entry API
    used: HashMap<V, ()>,
    f: F,
}

impl<I, V, F> fmt::Debug for UniqueBy<I, V, F>
    where I: Iterator + fmt::Debug,
          V: fmt::Debug + Hash + Eq,
{
    debug_fmt_fields!(UniqueBy, iter, used);
}

/// Create a new `UniqueBy` iterator.
pub fn unique_by<I, V, F>(iter: I, f: F) -> UniqueBy<I, V, F>
    where V: Eq + Hash,
          F: FnMut(&I::Item) -> V,
          I: Iterator,
{
    UniqueBy {
        iter: iter,
        used: HashMap::new(),
        f: f,
    }
}

// count the number of new unique keys in iterable (`used` is the set already seen)
fn count_new_keys<I, K>(mut used: HashMap<K, ()>, iterable: I) -> usize
    where I: IntoIterator<Item=K>,
          K: Hash + Eq,
{
    let iter = iterable.into_iter();
    let current_used = used.len();
    used.extend(iter.map(|key| (key, ())));
    used.len() - current_used
}

impl<I, V, F> Iterator for UniqueBy<I, V, F>
    where I: Iterator,
          V: Eq + Hash,
          F: FnMut(&I::Item) -> V
{
    type Item = I::Item;

    fn next(&mut self) -> Option<I::Item> {
        while let Some(v) = self.iter.next() {
            let key = (self.f)(&v);
            if self.used.insert(key, ()).is_none() {
                return Some(v);
            }
        }
        None
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        let (low, hi) = self.iter.size_hint();
        ((low > 0 && self.used.is_empty()) as usize, hi)
    }

    fn count(self) -> usize {
        let mut key_f = self.f;
        count_new_keys(self.used, self.iter.map(move |elt| key_f(&elt)))
    }
}

impl<I> Iterator for Unique<I>
    where I: Iterator,
          I::Item: Eq + Hash + Clone
{
    type Item = I::Item;

    fn next(&mut self) -> Option<I::Item> {
        while let Some(v) = self.iter.iter.next() {
            if let Entry::Vacant(entry) = self.iter.used.entry(v) {
                let elt = entry.key().clone();
                entry.insert(());
                return Some(elt);
            }
        }
        None
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        let (low, hi) = self.iter.iter.size_hint();
        ((low > 0 && self.iter.used.is_empty()) as usize, hi)
    }

    fn count(self) -> usize {
        count_new_keys(self.iter.used, self.iter.iter)
    }
}

/// An iterator adapter to filter out duplicate elements.
///
/// See [`.unique()`](../trait.Itertools.html#method.unique) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Unique<I: Iterator> {
    iter: UniqueBy<I, I::Item, ()>,
}

impl<I> fmt::Debug for Unique<I>
    where I: Iterator + fmt::Debug,
          I::Item: Hash + Eq + fmt::Debug,
{
    debug_fmt_fields!(Unique, iter);
}

pub fn unique<I>(iter: I) -> Unique<I>
    where I: Iterator,
          I::Item: Eq + Hash,
{
    Unique {
        iter: UniqueBy {
            iter: iter,
            used: HashMap::new(),
            f: (),
        }
    }
}