artsy 0.1.1

ART Tree data structure library.
Documentation 
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

use std::mem;

#[cfg(not(feature = "no-simd"))]
#[cfg(target_arch = "x86")]
use std::arch::x86::{
    _mm_cmpeq_epi8,
    _mm_loadu_si128,
    _mm_movemask_epi8,
    _mm_set1_epi8,
};

#[cfg(not(feature = "no-simd"))]
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::{
    _mm_cmpeq_epi8,
    _mm_loadu_si128,
    _mm_movemask_epi8,
    _mm_set1_epi8,
};

use super::{
    Child,
    NodeImpl,
};

#[cfg(feature = "node48")]
use crate::node48::Node48;

#[cfg(not(feature = "node48"))]
use crate::node256::Node256;

pub(crate) struct Node16<'a, T> {
    child_indices: [u8; 16],
    children: [Option<Box<Child<'a, T>>>; 16],
    nb_children: u8,
}

impl<'a, T> Default for Node16<'a, T> {
    fn default() -> Self {
        Node16 {
            child_indices: [0; 16],
            children: [
                None, None, None, None,
                None, None, None, None,
                None, None, None, None,
                None, None, None, None,
            ],
            nb_children: 0
        }
    }
}

impl<'a, T> Node16<'a, T> {
    #[cfg(feature = "node4")]
    pub fn new(child_indices: [u8; 16], children: [Option<Box<Child<'a, T>>>; 16], nb_children: u8) -> Self {
        Node16 { child_indices, children, nb_children }
    }

    #[cfg(feature = "node48")]
    fn upgrade_to_node48(mut self: Box<Self>) -> Box<Node48<'a, T>> {
        let mut child_indices = [48; 256];
        let mut children: [Option<Box<Child<'a, T>>>; 48] = [
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
            None, None, None, None, None, None,
        ];

        for i in 0..self.child_indices.len() {
            child_indices[self.child_indices[i] as usize] = i as u8;
            mem::swap(&mut self.children[i], &mut children[i]);
        }

        Box::new(Node48::new(child_indices, children, 16))
    }

    #[cfg(not(feature = "node48"))]
    fn upgrade_to_node256(mut self: Box<Self>) -> Box<Node256<'a, T>> {
        let mut children: [Option<Box<Child<'a, T>>>; 256] = [
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
            None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
        ];

        for i in 0..self.child_indices.len() {
            let key = self.child_indices[i] as usize;
            mem::swap(&mut children[key], &mut self.children[i]);
        }

        Box::new(Node256::new(children))
    }


    #[cfg(any(feature = "no-simd", all(not(target_arch = "x86"), not(target_arch = "x86_64"))))]
    fn find_child_index(&self, key: u8) -> Option<usize> {
        for i in 0..self.nb_children {
            if self.child_indices[i] == key {
                return Some(i);
            }
        }
        None
    }

    #[cfg(all(not(feature = "no-simd"), any(target_arch = "x86", target_arch = "x86_64")))]
    fn find_child_index(&self, key: u8) -> Option<usize> {
        // `key_vec` is 16 repeated copies of the searched-for byte, one for every possible
        // position in `child_indices` that needs to be searched.
        let key_vec = unsafe { _mm_set1_epi8(key as i8) };
        let indices_vec = unsafe { _mm_loadu_si128(self.child_indices.as_ptr() as *const _) };

        // Compare all `child_indices` in parallel. Don't worry if some of the keys
        // aren't valid, we'll mask the results to only consider the valid ones below.
        let matches = unsafe { _mm_cmpeq_epi8(key_vec, indices_vec) };

        // Apply a mask to select only the first `nb_children` values.
        let mask = (1 << self.nb_children) - 1;
        let match_bits = unsafe { _mm_movemask_epi8(matches) & mask };

        // The child's index is the first '1' in `match_bits`
        if match_bits != 0 {
            Some(match_bits.trailing_zeros() as usize)
        } else {
            None
        }
    }
}

impl<'a, T> NodeImpl<'a, T> for Node16<'a, T> {
    fn update_child(&mut self, key: u8, child: Child<'a, T>) -> Result<(), Child<'a, T>> {
        if let Some(_) = self.find_child_index(key) {
            return Ok(());
        } else {
            // If we're adding a new entry, there should be less than 16 entries.
            if self.nb_children < 16 {
                self.child_indices[self.nb_children as usize] = key;
                self.children[self.nb_children as usize] = Some(Box::new(child));
                self.nb_children += 1;
                return Ok(());
            }
        }

        Err(child)
    }

    fn insert_child(&mut self, key: u8, mut child: Child<'a, T>) -> Result<Option<Child<'a, T>>, Child<'a, T>> {
        if let Some(index) = self.find_child_index(key) {
            mem::swap(&mut child, self.children[index as usize].as_mut().unwrap());
            return Ok(Some(child));
        } else {
            // If we're adding a new entry, there should be less than 16 entries.
            if self.nb_children < 16 {
                self.child_indices[self.nb_children as usize] = key;
                self.children[self.nb_children as usize] = Some(Box::new(child));
                self.nb_children += 1;
                return Ok(None);
            }
        }

        Err(child)
    }

    fn upgrade(self: Box<Self>) -> Box<dyn NodeImpl<'a, T> + 'a> {
        #[cfg(feature = "node48")] {
            self.upgrade_to_node48()
        }

        #[cfg(not(feature = "node48"))] {
            self.upgrade_to_node256()
        }
    }

    fn find_child(&self, key: u8) -> Option<&Child<'a, T>> {
        if let Some(index) = self.find_child_index(key) {
            self.children[index as usize].as_ref().map(|x| &**x)
        } else {
            None
        }
    }
}